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Inversive geometry

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sphere maps the unit sphere to itself. It also maps the interior of the unit sphere to itself, with points outside the orthogonal sphere mapping inside, and vice versa; this defines the reflections of the Poincaré disc model if we also include with them the reflections through the diameters separating hemispheres of the unit sphere. These reflections generate the group of isometries of the model, which tells us that the isometries are conformal. Hence, the angle between two curves in the model is the same as the angle between two curves in the hyperbolic space.
1053: 2746:. The other generators are translation and rotation, both familiar through physical manipulations in the ambient 3-space. Introduction of reciprocation (dependent upon circle inversion) is what produces the peculiar nature of Möbius geometry, which is sometimes identified with inversive geometry (of the Euclidean plane). However, inversive geometry is the larger study since it includes the raw inversion in a circle (not yet made, with conjugation, into reciprocation). Inversive geometry also includes the 4129: 793: 110: 3911: 306: 1576: 1352: 4410:{\displaystyle {\begin{aligned}&aw+a^{*}w^{*}=1\Longleftrightarrow 2\operatorname {Re} \{aw\}=1\Longleftrightarrow \operatorname {Re} \{a\}\operatorname {Re} \{w\}-\operatorname {Im} \{a\}\operatorname {Im} \{w\}={\frac {1}{2}}\\\Longleftrightarrow {}&\operatorname {Im} \{w\}={\frac {\operatorname {Re} \{a\}}{\operatorname {Im} \{a\}}}\cdot \operatorname {Re} \{w\}-{\frac {1}{2\cdot \operatorname {Im} \{a\}}}.\end{aligned}}} 1177: 1344: 3496: 1336: 3906:{\displaystyle {\begin{aligned}&ww^{*}-{\frac {aw+a^{*}w^{*}}{(a^{*}a-r^{2})}}+{\frac {aa^{*}}{(aa^{*}-r^{2})^{2}}}={\frac {r^{2}}{(aa^{*}-r^{2})^{2}}}\\\Longleftrightarrow {}&\left(w-{\frac {a^{*}}{aa^{*}-r^{2}}}\right)\left(w^{*}-{\frac {a}{a^{*}a-r^{2}}}\right)=\left({\frac {r}{\left|aa^{*}-r^{2}\right|}}\right)^{2}\end{aligned}}} 4940: 1566:
A hyperboloid of one sheet, which is a surface of revolution contains a pencil of circles which is mapped onto a pencil of circles. A hyperboloid of one sheet contains additional two pencils of lines, which are mapped onto pencils of circles. The picture shows one such line (blue) and its inversion.
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Examples of inversion of circles A to J with respect to the red circle at O. Circles A to F, which pass through O, map to straight lines. Circles G to J, which do not, map to other circles. The reference circle and line L map to themselves. Circles intersect their inverses, if any, on the reference
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Since inversion in the unit sphere leaves the spheres orthogonal to it invariant, the inversion maps the points inside the unit sphere to the outside and vice versa. This is therefore true in general of orthogonal spheres, and in particular inversion in one of the spheres orthogonal to the unit
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by Robert C. Yates, National Council of Teachers of Mathematics, Inc., Washington, D.C., p. 127: "Geometrical inversion seems to be due to Jakob Steiner who indicated a knowledge of the subject in 1824. He was closely followed by Adolphe Quetelet (1825) who gave some examples. Apparently
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As mentioned above, zero, the origin, requires special consideration in the circle inversion mapping. The approach is to adjoin a point at infinity designated ∞ or 1/0 . In the complex number approach, where reciprocation is the apparent operation, this procedure leads to the
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to other circles or lines and that preserves the angles between crossing curves. Many difficult problems in geometry become much more tractable when an inversion is applied. Inversion seems to have been discovered by a number of people contemporaneously, including
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under inversion). In summary, for a point inside the circle, the nearer the point to the center, the further away its transformation. While for any point (inside or outside the circle), the nearer the point to the circle, the closer its transformation.
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The simplest surface (besides a plane) is the sphere. The first picture shows a non trivial inversion (the center of the sphere is not the center of inversion) of a sphere together with two orthogonal intersecting pencils of circles.
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which are invariant under inversion, orthogonal to the unit sphere, and have centers outside of the sphere. These together with the subspace hyperplanes separating hemispheres are the hypersurfaces of the
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A spheroid is a surface of revolution and contains a pencil of circles which is mapped onto a pencil of circles (see picture). The inverse image of a spheroid is a surface of degree 4.
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In the complex plane, the most obvious circle inversion map (i.e., using the unit circle centered at the origin) is the complex conjugate of the complex inverse map taking
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to the space obviates the distinction between hyperplane and hypersphere; higher dimensional inversive geometry is frequently studied then in the presumed context of an
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The inversion of a set of points in the plane with respect to a circle is the set of inverses of these points. The following properties make circle inversion useful.
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is a mechanical implementation of inversion in a circle. It provides an exact solution to the important problem of converting between linear and circular motion.
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in E can be used to generate dilations, translations, or rotations. Indeed, two concentric hyperspheres, used to produce successive inversions, result in a
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in 1831. Since then this mapping has become an avenue to higher mathematics. Through some steps of application of the circle inversion map, a student of
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It follows from the definition that the inversion of any point inside the reference circle must lie outside it, and vice versa, with the center and the
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mapping. Neither conjugation nor inversion-in-a-circle are in the Möbius group since they are non-conformal (see below). Möbius group elements are
1627:(south pole). This mapping can be performed by an inversion of the sphere onto its tangent plane. If the sphere (to be projected) has the equation 1090:
For a circle not passing through the center of inversion, the center of the circle being inverted and the center of its image under inversion are
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The circle inversion map is anticonformal, which means that at every point it preserves angles and reverses orientation (a map is called
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with negative determinant: in two dimensions the Jacobian must be a scalar times a reflection at every point. This means that if
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of mappings of that space. The significant properties of figures in the geometry are those that are invariant under this group.
3174:{\displaystyle ww^{*}-{\frac {a}{(a^{2}-r^{2})}}(w+w^{*})+{\frac {a^{2}}{(a^{2}-r^{2})^{2}}}={\frac {r^{2}}{(a^{2}-r^{2})^{2}}}} 372: 1839:, green in the picture), then it will be mapped by the inversion at the unit sphere (red) onto the tangent plane at point 3997: 2161: 5560:{\displaystyle x_{1}^{2}+\cdots +x_{n}^{2}+2{\frac {a_{1}}{c}}x_{1}+\cdots +2{\frac {a_{n}}{c}}x_{n}+{\frac {1}{c}}=0.} 2448:{\displaystyle x\mapsto R^{2}{\frac {x}{|x|^{2}}}=y\mapsto T^{2}{\frac {y}{|y|^{2}}}=\left({\frac {T}{R}}\right)^{2}x.} 5241:. The complex analytic inverse map is conformal and its conjugate, circle inversion, is anticonformal. In this case a 1066:
Inversion of a line is a circle containing the center of inversion; or it is the line itself if it contains the center
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independently discovered by Giusto Bellavitis in 1836, by Stubbs and Ingram in 1842–3, and by Lord Kelvin in 1845.)"
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For example, Smogorzhevsky develops several theorems of inversive geometry before beginning Lobachevskian geometry.
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was so overcome by this facility of mappings to identify geometrical phenomena that he delivered a manifesto, the
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If two tangent lines can be drawn from a pole to the circle, then its polar passes through both tangent points.
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Kasner, E. (1900). "The Invariant Theory of the Inversion Group: Geometry Upon a Quadric Surface".
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Inversion of a circle is another circle; or it is a line if the original circle contains the center
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Inversion with respect to a circle does not map the center of the circle to the center of its image
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Inversion leaves the measure of angles unaltered, but reverses the orientation of oriented angles.
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Brannan, David A.; Esplen, Matthew F.; Gray, Jeremy J. (1998), "Chapter 5: Inversive Geometry",
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When two parallel hyperplanes are used to produce successive reflections, the result is a
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it inverts into a line. This reduces to the 2D case when the secant plane passes through
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passes through two distinct points A and A' which are inverses with respect to a circle
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College Geometry: An Introduction to the Modern Geometry of the Triangle and the Circle
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is invariant under an inversion. In particular if O is the centre of the inversion and
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as the base space. The transformations of inversive geometry are often referred to as
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with the center of the reference circle. This fact can be used to prove that the
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According to Coxeter, the transformation by inversion in circle was invented by
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Consequently, the algebraic form of the inversion in a unit circle is given by
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of the reference sphere, then it inverts to a plane. Any plane passing through
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are a coordinate system for three-dimensional space obtained by inverting the
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If a point lies on the circle, its polar is the tangent through this point.
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of a triangle coincides with its OI line. The proof roughly goes as below:
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Any combination of reflections, translations, and rotations is called an
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The inverse, with respect to the red circle, of a circle going through
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angles). Algebraically, a map is anticonformal if at every point the
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The combination of two inversions in concentric circles results in a
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are orthogonal, then a straight line passing through the center O of
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changing positions, whilst any point on the circle is unaffected (is
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practice problems on how to use inversion for math olympiad problems
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M. Pieri (1911,12) "Nuovi principia di geometria della inversion",
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the circle transforms into the line parallel to the imaginary axis
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One of the first to consider foundations of inversive geometry was
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In addition, any two non-intersecting circles may be inverted into
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for the Möbius plane that comes from the Euclidean plane is the
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are distances to the ends of a line L, then length of the line
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wrote his thesis on "Invariant theory of the inversion group".
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circles, using circle of inversion centered at a point on the
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of the reference circle inverts to a line not passing through
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in 3D with respect to a reference sphere centered at a point
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Hence, it will be invariant under inversion if and only if
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To invert a number in arithmetic usually means to take its
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A simple property of isosceles triangles with applications
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Given a triangle OAB in which O is the center of a circle
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The inversion of a cylinder, cone, or torus results in a
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of the ratio of the radii of the two concentric circles.
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The inverse, with respect to the red circle, of a circle
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If M and M' are inverse points with respect to a circle
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where the generalized circles are called "blocks": In
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Any two non-intersecting circles may be inverted into
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on two curves m and m', also inverses with respect to
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to the reference circle at the points of intersection.
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is inverted into itself (but not pointwise invariant).
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Consider, in the complex plane, the circle of radius
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Stereographic projection as the inversion of a sphere
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under an inversion with radius 1. The invariant is:
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Stereographic projection as an inversion of a sphere
4047:{\textstyle {\frac {r}{\left|a^{*}a-r^{2}\right|}}} 2738:Reciprocation is key in transformation theory as a 1886:. The lines through the center of inversion (point 6168: 5702: 5559: 5386: 5143: 5098: 4934: 4674: 4646: 4617: 4553: 4409: 4115: 4095: 4046: 3986: 3928: 3905: 3482: 3462: 3419: 3389: 3338: 3307: 3245: 3196: 3173: 2967: 2944: 2901: 2867: 2798: 2778: 2726: 2655: 2626: 2546: 2496: 2447: 2258:{\displaystyle I={\frac {|x-y||w-z|}{|x-w||y-z|}}} 2257: 2147: 2096: 2076: 2049: 2022: 1898: 1878: 1831: 1811: 1770: 1681: 1619: 1599: 1492: 1117:of the intouch triangle is inverted into triangle 999: 220: 6030: 5900:Transactions of the American Mathematical Society 5039: 1945:of inversive geometry has been interpreted as an 1255:Poles and polars have several useful properties: 819:, and vice versa; whereas a line passing through 6195: 5992: 5805: 5113: 4988:of each reflection and thus of the composition. 1925: 609:There is a construction of the inverse point to 2268: 1527: 269:(i.e. an involution). To make the inversion a 5855: 5853: 2463:When a point in the plane is interpreted as a 1363:in three dimensions. The inversion of a point 1212:that is perpendicular to the line containing 1061:click or hover over a circle to highlight it. 1047: 4767: 4754: 4394: 4388: 4364: 4358: 4343: 4337: 4326: 4320: 4305: 4299: 4266: 4260: 4251: 4245: 4233: 4227: 4218: 4212: 4194: 4185: 881:, does so at inverse points with respect to 5850: 1561: 1347:Inversion of a spheroid (at the red sphere) 644:which may lie inside or outside the circle 221:{\displaystyle OP\cdot OP^{\prime }=r^{2}.} 6071: 5253:Inversive geometry and hyperbolic geometry 2754:of the whole plane and so are necessarily 1013:The points of intersection of two circles 6188:Visual Dictionary of Special Plane Curves 5920: 5772:Inversion of curves and surfaces (German) 3413: 2892: 531:. (Not labeled, it's the horizontal line) 81: 16:Study of angle-preserving transformations 6158:Wilson Stother's inversive geometry page 5972:Joel C. Gibbons & Yushen Luo (2013) 4968:. When two hyperplanes intersect in an ( 3987:{\textstyle {\frac {a}{(aa^{*}-r^{2})}}} 3390:{\displaystyle w+w^{*}={\tfrac {1}{a}}.} 3308:{\textstyle {\frac {r}{|a^{2}-r^{2}|}}.} 1587:usually projects a sphere from a point 1574: 1541: 1350: 1342: 1334: 1175: 1051: 830:inverts to a circle not passing through 807:A circle that passes through the center 304: 108: 91: 87: 82:generalized to higher-dimensional spaces 6058:(2nd ed.), John Wiley & Sons, 6048: 5943: 4480: 1909: 1355:Inversion of a hyperboloid of one sheet 1339:Inversion of a sphere at the red sphere 604: 549:. (Not labeled. It's the vertical line) 366: 6196: 6015:Inversion Theory and Conformal Mapping 5896: 5578: − 1)-spheres with equation 4454:in their plane geometry. Furthermore, 3420:{\displaystyle a\not \in \mathbb {R} } 1330: 1140:(usually denoted δ) is defined as the 488: 6169: 6012: 5887:49:49–96 & 50:106–140 5144:{\displaystyle \det(J)=-{\sqrt {k}}.} 4625:found by inverting the length of the 3246:{\textstyle {\frac {a}{a^{2}-r^{2}}}} 2281:soon appreciates the significance of 1359:Circle inversion is generalizable to 1201: 782:(blue) is a circle not going through 432:. (Not labeled. It's the blue circle) 301:Compass and straightedge construction 104: 5885:Giornal di Matematiche di Battaglini 5828: 5826: 5417:, and on inversion gives the sphere 2945:{\displaystyle w={\frac {1}{z^{*}}}} 2868:{\displaystyle (z-a)(z-a)^{*}=r^{2}} 2289:, an outgrowth of certain models of 1682:{\displaystyle x^{2}+y^{2}+z^{2}=-z} 6096: 5871: 5859: 5817: 5151:Computing the Jacobian in the case 4976:, successive reflections produce a 4945:The transformation by inversion in 4618:{\displaystyle P=(p_{1},...,p_{n})} 4554:{\displaystyle O=(o_{1},...,o_{n})} 2955:it is straightforward to show that 1188:with respect to a circle of radius 758:(blue) is a line not going through 13: 4420: 2909:Using the definition of inversion 2902:{\displaystyle a\in \mathbb {R} .} 2878:where without loss of generality, 1508:, inverts to a sphere touching at 1462: 1407: 972: 957: 924: 909: 239:. The inversion taking any point 197: 14: 6215: 6163:IMO Compendium Training Materials 6149:Inversion: Reflection in a Circle 6142: 6017:, American Mathematical Society, 5993:Altshiller-Court, Nathan (1952), 5913:10.1090/S0002-9947-1900-1500550-1 5823: 4489:-dimensional Euclidean space, an 2762:Transforming circles into circles 1319:lies on its own polar line, then 1244:through one of the points is the 1165: 277:, it is necessary to introduce a 4961:about the hyperspheres' center. 4096:{\displaystyle a^{*}a\to r^{2},} 3463:{\displaystyle aa^{*}\neq r^{2}} 2547:{\displaystyle {\bar {z}}=x-iy,} 2458: 1208:; the polar is the line through 791: 767: 747: 80:The concept of inversion can be 5966: 5949: 5397:will have a positive radius if 5099:{\displaystyle J\cdot J^{T}=kI} 4561:is a map of an arbitrary point 3936:describes the circle of center 3204:describes the circle of center 1326:Each line has exactly one pole. 1025:, are inverses with respect to 842:Additional properties include: 6119:(1941) "The Inversive Plane", 5978:-sphere and inversive geometry 5937: 5890: 5877: 5865: 5811: 5799: 5784: 5122: 5116: 5040:Anticonformal mapping property 4913: 4886: 4871: 4845: 4800: 4749: 4737: 4704: 4612: 4574: 4548: 4510: 4286: 4203: 4173: 4077: 3978: 3949: 3715: 3699: 3669: 3641: 3611: 3584: 3555: 3327: 3295: 3267: 3159: 3132: 3104: 3077: 3058: 3039: 3033: 3007: 2843: 2830: 2827: 2815: 2689: 2647: 2608: 2599: 2592: 2520: 2398: 2389: 2369: 2350: 2341: 2321: 2248: 2234: 2229: 2215: 2208: 2194: 2189: 2175: 2148:{\displaystyle d/(r_{1}r_{2})} 2142: 2119: 1873: 1852: 1806: 1785: 1744: 1722: 1473: 1468: 1450: 1445: 1437: 1432: 1421: 1416: 1085: 1: 6122:American Mathematical Monthly 5986: 5737:Duality (projective geometry) 1926:Axiomatics and generalization 1072:Inversion of a parabola is a 826:A circle not passing through 740: 2719: 2269:Relation to Erlangen program 1983: 1528:Examples in three dimensions 1379:' on the ray with direction 1078:Inversion of hyperbola is a 652:Take the intersection point 285:and this point at infinity. 7: 6081:Geometry: Euclid and Beyond 5792:Curves and Their Properties 5725: 2295: 1553: 1105:Invert with respect to the 556:be one of the points where 123:with respect to the circle. 100:with different translations 10: 6220: 6103:Holt, Rinehart and Winston 5997:(2nd ed.), New York: 5955:A.S. Smogorzhevsky (1982) 5922:2027/miun.abv0510.0001.001 5010:is a classical theorem of 4980:where every point of the ( 2656:{\displaystyle z\mapsto w} 1879:{\displaystyle S=(0,0,-1)} 1812:{\displaystyle (0,0,-0.5)} 1169: 1160:Peaucellier–Lipkin linkage 1048:Examples in two dimensions 40:, a transformation of the 18: 5747:Limiting point (geometry) 2306:homothetic transformation 1532: 698:be the reflection of ray 613:with respect to a circle 493:To construct the inverse 309:To construct the inverse 273:that is also defined for 6055:Introduction to Geometry 6013:Blair, David E. (2000), 5777: 5732:Circle of antisimilitude 5718:of hyperbolic geometry. 1585:stereographic projection 1562:Hyperboloid of one sheet 1248:of the other point (the 1232:is the inverse of point 1153:circle of antisimilitude 786:(green), and vice versa. 762:(green), and vice versa. 728:is the inverse point of 671:with an arbitrary point 162:, lying on the ray from 5767:Mohr-Mascheroni theorem 5226:, and additionally det( 4491:inversion in the sphere 4428:complex projective line 3339:{\displaystyle a\to r,} 2497:{\displaystyle z=x+iy,} 2279:transformation geometry 2023:{\displaystyle x,y,z,w} 1957:together with a single 1298:rotates about the pole 1080:lemniscate of Bernoulli 1021:orthogonal to a circle 732:with respect to circle 6097:Kay, David C. (1969), 5957:Lobachevskian Geometry 5832:Dutta, Surajit (2014) 5806:Altshiller-Court (1952 5704: 5561: 5388: 5263: − 1)-sphere 5245:is conformal while an 5145: 5100: 5064:is the Jacobian, then 5030:Möbius transformations 4936: 4676: 4648: 4619: 4555: 4497:centered at the point 4411: 4117: 4097: 4048: 3988: 3930: 3907: 3484: 3464: 3421: 3391: 3340: 3309: 3247: 3198: 3175: 2969: 2946: 2903: 2869: 2800: 2780: 2728: 2657: 2628: 2548: 2498: 2449: 2259: 2149: 2098: 2078: 2051: 2024: 1943:mathematical structure 1900: 1880: 1833: 1813: 1772: 1683: 1621: 1601: 1580: 1494: 1356: 1348: 1340: 1225: 1192:centered on the point 1062: 1001: 683:and from the point on 394:Draw the segment from 363: 222: 124: 101: 88:Inversion in a circle 5752:Möbius transformation 5705: 5562: 5389: 5146: 5101: 5056:is a scalar times an 4937: 4677: 4675:{\displaystyle r^{2}} 4649: 4620: 4556: 4412: 4118: 4098: 4049: 3989: 3931: 3908: 3485: 3465: 3422: 3392: 3341: 3310: 3248: 3199: 3176: 2970: 2947: 2904: 2870: 2801: 2781: 2729: 2658: 2629: 2549: 2499: 2450: 2260: 2150: 2099: 2079: 2077:{\displaystyle r_{2}} 2052: 2050:{\displaystyle r_{1}} 2025: 1920:Cartesian coordinates 1901: 1881: 1834: 1814: 1773: 1689:(alternately written 1684: 1622: 1602: 1578: 1542:Cylinder, cone, torus 1495: 1354: 1346: 1338: 1179: 1055: 1002: 625:is inside or outside 308: 223: 112: 95: 5585: 5424: 5272: 5110: 5068: 4690: 4659: 4632: 4565: 4501: 4481:In higher dimensions 4130: 4107: 4061: 3998: 3940: 3920: 3497: 3474: 3431: 3403: 3350: 3321: 3257: 3208: 3188: 2982: 2959: 2916: 2882: 2812: 2790: 2770: 2670: 2641: 2569: 2511: 2470: 2315: 2162: 2108: 2088: 2061: 2034: 1996: 1916:6-sphere coordinates 1910:6-sphere coordinates 1890: 1843: 1823: 1782: 1693: 1631: 1611: 1591: 1387: 906: 605:Dutta's construction 446:be the points where 367:Point outside circle 177: 145:reference circle (Ø) 96:Inversion of lambda 19:For other uses, see 5845:Forum Geometricorum 5757:Projective geometry 5716:Poincaré disc model 5626: 5602: 5465: 5441: 5313: 5289: 5008:Liouville's theorem 4815: 4654:and multiplying by 4647:{\displaystyle P-O} 4627:displacement vector 4430:, often called the 2975:obeys the equation 2291:hyperbolic geometry 1965:, also known as an 1947:incidence structure 1832:{\displaystyle 0.5} 1331:In three dimensions 1290:moves along a line 854:, then the circles 489:Point inside circle 413:be the midpoint of 6204:Inversive geometry 6171:Weisstein, Eric W. 5999:Barnes & Noble 5839:2018-04-21 at the 5700: 5612: 5588: 5557: 5451: 5427: 5384: 5299: 5275: 5249:is anticonformal. 5141: 5096: 5017:The addition of a 5012:conformal geometry 4932: 4930: 4885: 4803: 4672: 4644: 4615: 4551: 4407: 4405: 4113: 4093: 4044: 3984: 3926: 3903: 3901: 3480: 3460: 3417: 3387: 3382: 3336: 3305: 3243: 3194: 3171: 2965: 2942: 2899: 2865: 2796: 2776: 2752:analytic functions 2724: 2653: 2624: 2544: 2494: 2445: 2255: 2145: 2094: 2074: 2047: 2020: 1951:incidence geometry 1941:More recently the 1934:in 1911 and 1912. 1896: 1876: 1829: 1809: 1768: 1766: 1741: 1679: 1617: 1597: 1581: 1490: 1357: 1349: 1341: 1275:lies on the polar 1226: 1138:inversive distance 1136:circles. Then the 1063: 997: 667:Connect the point 632:Consider a circle 520:(center of circle 398:(center of circle 364: 332:. Right triangles 218: 143:with respect to a 125: 119:is the inverse of 105:Inverse of a point 102: 32:inversive geometry 6073:Hartshorne, Robin 5974:Colorings of the 5549: 5526: 5487: 5136: 5058:orthogonal matrix 5019:point at infinity 5002:All of these are 4923: 4876: 4777: 4398: 4347: 4280: 4116:{\displaystyle w} 4103:the equation for 4042: 3982: 3929:{\displaystyle w} 3916:showing that the 3887: 3831: 3773: 3709: 3651: 3588: 3483:{\displaystyle w} 3381: 3300: 3241: 3197:{\displaystyle w} 3169: 3114: 3037: 2968:{\displaystyle w} 2940: 2799:{\displaystyle a} 2786:around the point 2779:{\displaystyle r} 2722: 2713: 2694: 2692: 2619: 2595: 2580: 2523: 2506:complex conjugate 2427: 2409: 2361: 2253: 2097:{\displaystyle d} 1992:between 4 points 1959:point at infinity 1899:{\displaystyle N} 1765: 1740: 1620:{\displaystyle S} 1600:{\displaystyle N} 1323:is on the circle. 1142:natural logarithm 956: 952: 948: 877:and intersecting 582:perpendicular to 567:Draw the segment 545:perpendicular to 386:outside a circle 328:be the radius of 320:outside a circle 290:point at infinity 279:point at infinity 6211: 6184: 6183: 6113: 6099:College Geometry 6093: 6068: 6045: 6027: 6009: 5980: 5970: 5964: 5953: 5947: 5946:, pp. 77–95 5941: 5935: 5934: 5924: 5894: 5888: 5881: 5875: 5869: 5863: 5857: 5848: 5830: 5821: 5815: 5809: 5803: 5797: 5788: 5709: 5707: 5706: 5701: 5684: 5683: 5674: 5673: 5652: 5651: 5642: 5641: 5625: 5620: 5601: 5596: 5566: 5564: 5563: 5558: 5550: 5542: 5537: 5536: 5527: 5522: 5521: 5512: 5498: 5497: 5488: 5483: 5482: 5473: 5464: 5459: 5440: 5435: 5413:is greater than 5393: 5391: 5390: 5385: 5371: 5370: 5361: 5360: 5339: 5338: 5329: 5328: 5312: 5307: 5288: 5283: 5225: 5223: 5212: 5202: 5185: 5177: 5175: 5150: 5148: 5147: 5142: 5137: 5132: 5105: 5103: 5102: 5097: 5086: 5085: 5048:if it preserves 4941: 4939: 4938: 4933: 4931: 4924: 4922: 4921: 4920: 4911: 4910: 4898: 4897: 4884: 4874: 4870: 4869: 4857: 4856: 4844: 4843: 4833: 4828: 4827: 4811: 4795: 4794: 4778: 4776: 4775: 4774: 4752: 4736: 4735: 4725: 4714: 4683: 4681: 4679: 4678: 4673: 4671: 4670: 4653: 4651: 4650: 4645: 4624: 4622: 4621: 4616: 4611: 4610: 4586: 4585: 4560: 4558: 4557: 4552: 4547: 4546: 4522: 4521: 4496: 4470:together with a 4460:Erlangen program 4416: 4414: 4413: 4408: 4406: 4399: 4397: 4371: 4348: 4346: 4329: 4312: 4290: 4281: 4273: 4166: 4165: 4156: 4155: 4136: 4122: 4120: 4119: 4114: 4102: 4100: 4099: 4094: 4089: 4088: 4073: 4072: 4053: 4051: 4050: 4045: 4043: 4041: 4037: 4036: 4035: 4020: 4019: 4002: 3993: 3991: 3990: 3985: 3983: 3981: 3977: 3976: 3964: 3963: 3944: 3935: 3933: 3932: 3927: 3912: 3910: 3909: 3904: 3902: 3898: 3897: 3892: 3888: 3886: 3882: 3881: 3880: 3868: 3867: 3847: 3837: 3833: 3832: 3830: 3829: 3828: 3813: 3812: 3799: 3794: 3793: 3779: 3775: 3774: 3772: 3771: 3770: 3758: 3757: 3744: 3743: 3734: 3719: 3710: 3708: 3707: 3706: 3697: 3696: 3684: 3683: 3667: 3666: 3657: 3652: 3650: 3649: 3648: 3639: 3638: 3626: 3625: 3609: 3608: 3607: 3594: 3589: 3587: 3583: 3582: 3567: 3566: 3553: 3552: 3551: 3542: 3541: 3522: 3517: 3516: 3503: 3489: 3487: 3486: 3481: 3469: 3467: 3466: 3461: 3459: 3458: 3446: 3445: 3426: 3424: 3423: 3418: 3416: 3396: 3394: 3393: 3388: 3383: 3374: 3368: 3367: 3345: 3343: 3342: 3337: 3314: 3312: 3311: 3306: 3301: 3299: 3298: 3293: 3292: 3280: 3279: 3270: 3261: 3252: 3250: 3249: 3244: 3242: 3240: 3239: 3238: 3226: 3225: 3212: 3203: 3201: 3200: 3195: 3180: 3178: 3177: 3172: 3170: 3168: 3167: 3166: 3157: 3156: 3144: 3143: 3130: 3129: 3120: 3115: 3113: 3112: 3111: 3102: 3101: 3089: 3088: 3075: 3074: 3065: 3057: 3056: 3038: 3036: 3032: 3031: 3019: 3018: 3002: 2997: 2996: 2974: 2972: 2971: 2966: 2951: 2949: 2948: 2943: 2941: 2939: 2938: 2926: 2908: 2906: 2905: 2900: 2895: 2874: 2872: 2871: 2866: 2864: 2863: 2851: 2850: 2805: 2803: 2802: 2797: 2785: 2783: 2782: 2777: 2733: 2731: 2730: 2725: 2723: 2718: 2714: 2706: 2700: 2695: 2693: 2685: 2680: 2662: 2660: 2659: 2654: 2633: 2631: 2630: 2625: 2620: 2618: 2617: 2616: 2611: 2602: 2596: 2588: 2586: 2581: 2573: 2553: 2551: 2550: 2545: 2525: 2524: 2516: 2503: 2501: 2500: 2495: 2454: 2452: 2451: 2446: 2438: 2437: 2432: 2428: 2420: 2410: 2408: 2407: 2406: 2401: 2392: 2383: 2381: 2380: 2362: 2360: 2359: 2358: 2353: 2344: 2335: 2333: 2332: 2287:Erlangen program 2264: 2262: 2261: 2256: 2254: 2252: 2251: 2237: 2232: 2218: 2212: 2211: 2197: 2192: 2178: 2172: 2154: 2152: 2151: 2146: 2141: 2140: 2131: 2130: 2118: 2103: 2101: 2100: 2095: 2083: 2081: 2080: 2075: 2073: 2072: 2056: 2054: 2053: 2048: 2046: 2045: 2029: 2027: 2026: 2021: 1905: 1903: 1902: 1897: 1885: 1883: 1882: 1877: 1838: 1836: 1835: 1830: 1818: 1816: 1815: 1810: 1777: 1775: 1774: 1769: 1767: 1758: 1752: 1751: 1742: 1733: 1718: 1717: 1705: 1704: 1688: 1686: 1685: 1680: 1669: 1668: 1656: 1655: 1643: 1642: 1626: 1624: 1623: 1618: 1606: 1604: 1603: 1598: 1499: 1497: 1496: 1491: 1489: 1488: 1476: 1471: 1466: 1465: 1453: 1448: 1440: 1435: 1424: 1419: 1411: 1410: 1361:sphere inversion 1267:, then the pole 1100:intouch triangle 1006: 1004: 1003: 998: 993: 985: 954: 953: 950: 946: 945: 937: 795: 771: 751: 726: 719: 679:(different from 660:with the circle 543: 529: 504:inside a circle 502: 482: 471: 462: 444: 420:Draw the circle 380: 360: 341: 314: 260: 253: 233:circle inversion 227: 225: 224: 219: 214: 213: 201: 200: 161: 118: 34:is the study of 21:Point reflection 6219: 6218: 6214: 6213: 6212: 6210: 6209: 6208: 6194: 6193: 6145: 6131:10.2307/2303867 6117:Patterson, Boyd 6091: 6066: 6050:Coxeter, H.S.M. 6043: 6025: 5989: 5984: 5983: 5971: 5967: 5954: 5950: 5942: 5938: 5895: 5891: 5882: 5878: 5870: 5866: 5858: 5851: 5841:Wayback Machine 5831: 5824: 5816: 5812: 5804: 5800: 5789: 5785: 5780: 5728: 5679: 5675: 5669: 5665: 5647: 5643: 5637: 5633: 5621: 5616: 5597: 5592: 5586: 5583: 5582: 5541: 5532: 5528: 5517: 5513: 5511: 5493: 5489: 5478: 5474: 5472: 5460: 5455: 5436: 5431: 5425: 5422: 5421: 5412: 5403: 5366: 5362: 5356: 5352: 5334: 5330: 5324: 5320: 5308: 5303: 5284: 5279: 5273: 5270: 5269: 5255: 5247:anti-homography 5219: 5214: 5204: 5201: 5192: 5181: 5179: 5171: 5169: 5160: 5152: 5131: 5111: 5108: 5107: 5081: 5077: 5069: 5066: 5065: 5042: 4929: 4928: 4916: 4912: 4906: 4902: 4893: 4889: 4880: 4875: 4865: 4861: 4852: 4848: 4839: 4835: 4834: 4832: 4823: 4819: 4807: 4796: 4790: 4786: 4783: 4782: 4770: 4766: 4753: 4731: 4727: 4726: 4724: 4707: 4700: 4693: 4691: 4688: 4687: 4666: 4662: 4660: 4657: 4656: 4655: 4633: 4630: 4629: 4606: 4602: 4581: 4577: 4566: 4563: 4562: 4542: 4538: 4517: 4513: 4502: 4499: 4498: 4494: 4483: 4423: 4421:Higher geometry 4404: 4403: 4375: 4370: 4330: 4313: 4311: 4291: 4289: 4283: 4282: 4272: 4161: 4157: 4151: 4147: 4133: 4131: 4128: 4127: 4108: 4105: 4104: 4084: 4080: 4068: 4064: 4062: 4059: 4058: 4031: 4027: 4015: 4011: 4010: 4006: 4001: 3999: 3996: 3995: 3972: 3968: 3959: 3955: 3948: 3943: 3941: 3938: 3937: 3921: 3918: 3917: 3900: 3899: 3893: 3876: 3872: 3863: 3859: 3855: 3851: 3846: 3842: 3841: 3824: 3820: 3808: 3804: 3803: 3798: 3789: 3785: 3784: 3780: 3766: 3762: 3753: 3749: 3745: 3739: 3735: 3733: 3726: 3722: 3720: 3718: 3712: 3711: 3702: 3698: 3692: 3688: 3679: 3675: 3668: 3662: 3658: 3656: 3644: 3640: 3634: 3630: 3621: 3617: 3610: 3603: 3599: 3595: 3593: 3578: 3574: 3562: 3558: 3554: 3547: 3543: 3537: 3533: 3523: 3521: 3512: 3508: 3500: 3498: 3495: 3494: 3475: 3472: 3471: 3470:the result for 3454: 3450: 3441: 3437: 3432: 3429: 3428: 3412: 3404: 3401: 3400: 3372: 3363: 3359: 3351: 3348: 3347: 3322: 3319: 3318: 3294: 3288: 3284: 3275: 3271: 3266: 3265: 3260: 3258: 3255: 3254: 3234: 3230: 3221: 3217: 3216: 3211: 3209: 3206: 3205: 3189: 3186: 3185: 3184:and hence that 3162: 3158: 3152: 3148: 3139: 3135: 3131: 3125: 3121: 3119: 3107: 3103: 3097: 3093: 3084: 3080: 3076: 3070: 3066: 3064: 3052: 3048: 3027: 3023: 3014: 3010: 3006: 3001: 2992: 2988: 2983: 2980: 2979: 2960: 2957: 2956: 2934: 2930: 2925: 2917: 2914: 2913: 2891: 2883: 2880: 2879: 2859: 2855: 2846: 2842: 2813: 2810: 2809: 2791: 2788: 2787: 2771: 2768: 2767: 2764: 2705: 2701: 2699: 2684: 2679: 2671: 2668: 2667: 2642: 2639: 2638: 2612: 2607: 2606: 2598: 2597: 2587: 2585: 2572: 2570: 2567: 2566: 2515: 2514: 2512: 2509: 2508: 2471: 2468: 2467: 2461: 2433: 2419: 2415: 2414: 2402: 2397: 2396: 2388: 2387: 2382: 2376: 2372: 2354: 2349: 2348: 2340: 2339: 2334: 2328: 2324: 2316: 2313: 2312: 2298: 2271: 2247: 2233: 2228: 2214: 2213: 2207: 2193: 2188: 2174: 2173: 2171: 2163: 2160: 2159: 2136: 2132: 2126: 2122: 2114: 2109: 2106: 2105: 2089: 2086: 2085: 2068: 2064: 2062: 2059: 2058: 2041: 2037: 2035: 2032: 2031: 1997: 1994: 1993: 1986: 1967:inversive plane 1928: 1912: 1891: 1888: 1887: 1844: 1841: 1840: 1824: 1821: 1820: 1783: 1780: 1779: 1756: 1747: 1743: 1731: 1713: 1709: 1700: 1696: 1694: 1691: 1690: 1664: 1660: 1651: 1647: 1638: 1634: 1632: 1629: 1628: 1612: 1609: 1608: 1592: 1589: 1588: 1573: 1564: 1556: 1544: 1535: 1530: 1484: 1480: 1472: 1467: 1461: 1457: 1449: 1444: 1436: 1431: 1420: 1415: 1406: 1402: 1388: 1385: 1384: 1333: 1263:lies on a line 1236:then the lines 1202:inversion point 1180:The polar line 1174: 1168: 1115:medial triangle 1088: 1050: 986: 978: 951: and  949: 938: 930: 907: 904: 903: 865:If the circles 862:are orthogonal. 799: 796: 787: 772: 763: 752: 743: 724: 717: 607: 541: 527: 500: 491: 480: 469: 460: 442: 378: 369: 358: 339: 312: 303: 258: 251: 247:) to its image 237:plane inversion 231:This is called 209: 205: 196: 192: 178: 175: 174: 159: 116: 107: 90: 42:Euclidean plane 24: 17: 12: 11: 5: 6217: 6207: 6206: 6192: 6191: 6185: 6166: 6160: 6155: 6144: 6143:External links 6141: 6140: 6139: 6114: 6094: 6089: 6069: 6064: 6046: 6041: 6028: 6023: 6010: 5988: 5985: 5982: 5981: 5965: 5961:Mir Publishers 5948: 5936: 5907:(4): 430–498. 5889: 5876: 5874:, p. 269) 5864: 5862:, p. 265) 5849: 5822: 5820:, p. 264) 5810: 5808:, p. 230) 5798: 5782: 5781: 5779: 5776: 5775: 5774: 5769: 5764: 5762:Soddy's hexlet 5759: 5754: 5749: 5744: 5739: 5734: 5727: 5724: 5711: 5710: 5699: 5696: 5693: 5690: 5687: 5682: 5678: 5672: 5668: 5664: 5661: 5658: 5655: 5650: 5646: 5640: 5636: 5632: 5629: 5624: 5619: 5615: 5611: 5608: 5605: 5600: 5595: 5591: 5568: 5567: 5556: 5553: 5548: 5545: 5540: 5535: 5531: 5525: 5520: 5516: 5510: 5507: 5504: 5501: 5496: 5492: 5486: 5481: 5477: 5471: 5468: 5463: 5458: 5454: 5450: 5447: 5444: 5439: 5434: 5430: 5408: 5401: 5395: 5394: 5383: 5380: 5377: 5374: 5369: 5365: 5359: 5355: 5351: 5348: 5345: 5342: 5337: 5333: 5327: 5323: 5319: 5316: 5311: 5306: 5302: 5298: 5295: 5292: 5287: 5282: 5278: 5265:with equation 5254: 5251: 5197: 5190: 5165: 5156: 5140: 5135: 5130: 5127: 5124: 5121: 5118: 5115: 5095: 5092: 5089: 5084: 5080: 5076: 5073: 5041: 5038: 5004:conformal maps 4984:–2)-flat is a 4943: 4942: 4927: 4919: 4915: 4909: 4905: 4901: 4896: 4892: 4888: 4883: 4879: 4873: 4868: 4864: 4860: 4855: 4851: 4847: 4842: 4838: 4831: 4826: 4822: 4818: 4814: 4810: 4806: 4802: 4799: 4797: 4793: 4789: 4785: 4784: 4781: 4773: 4769: 4765: 4762: 4759: 4756: 4751: 4748: 4745: 4742: 4739: 4734: 4730: 4723: 4720: 4717: 4713: 4710: 4706: 4703: 4701: 4699: 4696: 4695: 4669: 4665: 4643: 4640: 4637: 4614: 4609: 4605: 4601: 4598: 4595: 4592: 4589: 4584: 4580: 4576: 4573: 4570: 4550: 4545: 4541: 4537: 4534: 4531: 4528: 4525: 4520: 4516: 4512: 4509: 4506: 4482: 4479: 4432:Riemann sphere 4422: 4419: 4418: 4417: 4402: 4396: 4393: 4390: 4387: 4384: 4381: 4378: 4374: 4369: 4366: 4363: 4360: 4357: 4354: 4351: 4345: 4342: 4339: 4336: 4333: 4328: 4325: 4322: 4319: 4316: 4310: 4307: 4304: 4301: 4298: 4295: 4292: 4288: 4285: 4284: 4279: 4276: 4271: 4268: 4265: 4262: 4259: 4256: 4253: 4250: 4247: 4244: 4241: 4238: 4235: 4232: 4229: 4226: 4223: 4220: 4217: 4214: 4211: 4208: 4205: 4202: 4199: 4196: 4193: 4190: 4187: 4184: 4181: 4178: 4175: 4172: 4169: 4164: 4160: 4154: 4150: 4146: 4143: 4140: 4137: 4135: 4112: 4092: 4087: 4083: 4079: 4076: 4071: 4067: 4040: 4034: 4030: 4026: 4023: 4018: 4014: 4009: 4005: 3980: 3975: 3971: 3967: 3962: 3958: 3954: 3951: 3947: 3925: 3914: 3913: 3896: 3891: 3885: 3879: 3875: 3871: 3866: 3862: 3858: 3854: 3850: 3845: 3840: 3836: 3827: 3823: 3819: 3816: 3811: 3807: 3802: 3797: 3792: 3788: 3783: 3778: 3769: 3765: 3761: 3756: 3752: 3748: 3742: 3738: 3732: 3729: 3725: 3721: 3717: 3714: 3713: 3705: 3701: 3695: 3691: 3687: 3682: 3678: 3674: 3671: 3665: 3661: 3655: 3647: 3643: 3637: 3633: 3629: 3624: 3620: 3616: 3613: 3606: 3602: 3598: 3592: 3586: 3581: 3577: 3573: 3570: 3565: 3561: 3557: 3550: 3546: 3540: 3536: 3532: 3529: 3526: 3520: 3515: 3511: 3507: 3504: 3502: 3479: 3457: 3453: 3449: 3444: 3440: 3436: 3415: 3411: 3408: 3386: 3380: 3377: 3371: 3366: 3362: 3358: 3355: 3335: 3332: 3329: 3326: 3304: 3297: 3291: 3287: 3283: 3278: 3274: 3269: 3264: 3237: 3233: 3229: 3224: 3220: 3215: 3193: 3182: 3181: 3165: 3161: 3155: 3151: 3147: 3142: 3138: 3134: 3128: 3124: 3118: 3110: 3106: 3100: 3096: 3092: 3087: 3083: 3079: 3073: 3069: 3063: 3060: 3055: 3051: 3047: 3044: 3041: 3035: 3030: 3026: 3022: 3017: 3013: 3009: 3005: 3000: 2995: 2991: 2987: 2964: 2953: 2952: 2937: 2933: 2929: 2924: 2921: 2898: 2894: 2890: 2887: 2876: 2875: 2862: 2858: 2854: 2849: 2845: 2841: 2838: 2835: 2832: 2829: 2826: 2823: 2820: 2817: 2795: 2775: 2763: 2760: 2736: 2735: 2721: 2717: 2712: 2709: 2704: 2698: 2691: 2688: 2683: 2678: 2675: 2652: 2649: 2646: 2635: 2634: 2623: 2615: 2610: 2605: 2601: 2594: 2591: 2584: 2579: 2576: 2543: 2540: 2537: 2534: 2531: 2528: 2522: 2519: 2493: 2490: 2487: 2484: 2481: 2478: 2475: 2465:complex number 2460: 2457: 2456: 2455: 2444: 2441: 2436: 2431: 2426: 2423: 2418: 2413: 2405: 2400: 2395: 2391: 2386: 2379: 2375: 2371: 2368: 2365: 2357: 2352: 2347: 2343: 2338: 2331: 2327: 2323: 2320: 2297: 2294: 2270: 2267: 2266: 2265: 2250: 2246: 2243: 2240: 2236: 2231: 2227: 2224: 2221: 2217: 2210: 2206: 2203: 2200: 2196: 2191: 2187: 2184: 2181: 2177: 2170: 2167: 2144: 2139: 2135: 2129: 2125: 2121: 2117: 2113: 2093: 2071: 2067: 2044: 2040: 2019: 2016: 2013: 2010: 2007: 2004: 2001: 1985: 1982: 1978:Riemann sphere 1927: 1924: 1911: 1908: 1895: 1875: 1872: 1869: 1866: 1863: 1860: 1857: 1854: 1851: 1848: 1828: 1808: 1805: 1802: 1799: 1796: 1793: 1790: 1787: 1764: 1761: 1755: 1750: 1746: 1739: 1736: 1730: 1727: 1724: 1721: 1716: 1712: 1708: 1703: 1699: 1678: 1675: 1672: 1667: 1663: 1659: 1654: 1650: 1646: 1641: 1637: 1616: 1596: 1572: 1569: 1563: 1560: 1555: 1552: 1543: 1540: 1534: 1531: 1529: 1526: 1487: 1483: 1479: 1475: 1470: 1464: 1460: 1456: 1452: 1447: 1443: 1439: 1434: 1430: 1427: 1423: 1418: 1414: 1409: 1405: 1401: 1398: 1395: 1392: 1332: 1329: 1328: 1327: 1324: 1313: 1310: 1307: 1284: 1172:pole and polar 1170:Main article: 1167: 1166:Pole and polar 1164: 1087: 1084: 1083: 1082: 1076: 1070: 1067: 1049: 1046: 1045: 1044: 1041: 1030: 1010: 1009: 1008: 1007: 996: 992: 989: 984: 981: 977: 974: 971: 968: 965: 962: 959: 944: 941: 936: 933: 929: 926: 923: 920: 917: 914: 911: 898: 897: 886: 863: 840: 839: 824: 801: 800: 797: 790: 788: 778:going through 773: 766: 764: 753: 746: 742: 739: 738: 737: 692: 675:on the circle 665: 606: 603: 602: 601: 587: 572: 565: 550: 532: 490: 487: 486: 485: 465: 455: 433: 428:going through 418: 407: 368: 365: 302: 299: 271:total function 267:self-inversion 229: 228: 217: 212: 208: 204: 199: 195: 191: 188: 185: 182: 106: 103: 98:Mandelbrot set 89: 86: 15: 9: 6: 4: 3: 2: 6216: 6205: 6202: 6201: 6199: 6189: 6186: 6181: 6180: 6175: 6172: 6167: 6164: 6161: 6159: 6156: 6154: 6150: 6147: 6146: 6138: 6135: 6132: 6128: 6124: 6123: 6118: 6115: 6112: 6108: 6104: 6100: 6095: 6092: 6090:0-387-98650-2 6086: 6082: 6078: 6074: 6070: 6067: 6065:0-471-18283-4 6061: 6057: 6056: 6051: 6047: 6044: 6042:0-521-59787-0 6038: 6034: 6029: 6026: 6024:0-8218-2636-0 6020: 6016: 6011: 6008: 6004: 6000: 5996: 5991: 5990: 5979: 5977: 5969: 5962: 5958: 5952: 5945: 5940: 5932: 5928: 5923: 5918: 5914: 5910: 5906: 5902: 5901: 5893: 5886: 5880: 5873: 5868: 5861: 5856: 5854: 5846: 5842: 5838: 5835: 5829: 5827: 5819: 5814: 5807: 5802: 5794: 5793: 5787: 5783: 5773: 5770: 5768: 5765: 5763: 5760: 5758: 5755: 5753: 5750: 5748: 5745: 5743: 5742:Inverse curve 5740: 5738: 5735: 5733: 5730: 5729: 5723: 5719: 5717: 5697: 5694: 5691: 5688: 5685: 5680: 5676: 5670: 5666: 5662: 5659: 5656: 5653: 5648: 5644: 5638: 5634: 5630: 5627: 5622: 5617: 5613: 5609: 5606: 5603: 5598: 5593: 5589: 5581: 5580: 5579: 5577: 5573: 5554: 5551: 5546: 5543: 5538: 5533: 5529: 5523: 5518: 5514: 5508: 5505: 5502: 5499: 5494: 5490: 5484: 5479: 5475: 5469: 5466: 5461: 5456: 5452: 5448: 5445: 5442: 5437: 5432: 5428: 5420: 5419: 5418: 5416: 5411: 5407: 5400: 5381: 5378: 5375: 5372: 5367: 5363: 5357: 5353: 5349: 5346: 5343: 5340: 5335: 5331: 5325: 5321: 5317: 5314: 5309: 5304: 5300: 5296: 5293: 5290: 5285: 5280: 5276: 5268: 5267: 5266: 5264: 5262: 5250: 5248: 5244: 5240: 5236: 5231: 5229: 5222: 5217: 5211: 5207: 5200: 5196: 5189: 5184: 5174: 5168: 5164: 5159: 5155: 5138: 5133: 5128: 5125: 5119: 5093: 5090: 5087: 5082: 5078: 5074: 5071: 5063: 5059: 5055: 5051: 5047: 5037: 5035: 5031: 5027: 5025: 5020: 5015: 5013: 5009: 5005: 5000: 4998: 4994: 4989: 4987: 4983: 4979: 4975: 4971: 4967: 4962: 4960: 4956: 4952: 4948: 4925: 4917: 4907: 4903: 4899: 4894: 4890: 4881: 4877: 4866: 4862: 4858: 4853: 4849: 4840: 4836: 4829: 4824: 4820: 4816: 4812: 4808: 4804: 4798: 4791: 4787: 4779: 4771: 4763: 4760: 4757: 4746: 4743: 4740: 4732: 4728: 4721: 4718: 4715: 4711: 4708: 4702: 4697: 4686: 4685: 4684: 4667: 4663: 4641: 4638: 4635: 4628: 4607: 4603: 4599: 4596: 4593: 4590: 4587: 4582: 4578: 4571: 4568: 4543: 4539: 4535: 4532: 4529: 4526: 4523: 4518: 4514: 4507: 4504: 4492: 4488: 4478: 4475: 4473: 4469: 4465: 4461: 4457: 4453: 4449: 4445: 4441: 4437: 4433: 4429: 4400: 4391: 4385: 4382: 4379: 4376: 4372: 4367: 4361: 4355: 4352: 4349: 4340: 4334: 4331: 4323: 4317: 4314: 4308: 4302: 4296: 4293: 4277: 4274: 4269: 4263: 4257: 4254: 4248: 4242: 4239: 4236: 4230: 4224: 4221: 4215: 4209: 4206: 4200: 4197: 4191: 4188: 4182: 4179: 4176: 4170: 4167: 4162: 4158: 4152: 4148: 4144: 4141: 4138: 4126: 4125: 4124: 4110: 4090: 4085: 4081: 4074: 4069: 4065: 4055: 4038: 4032: 4028: 4024: 4021: 4016: 4012: 4007: 4003: 3973: 3969: 3965: 3960: 3956: 3952: 3945: 3923: 3894: 3889: 3883: 3877: 3873: 3869: 3864: 3860: 3856: 3852: 3848: 3843: 3838: 3834: 3825: 3821: 3817: 3814: 3809: 3805: 3800: 3795: 3790: 3786: 3781: 3776: 3767: 3763: 3759: 3754: 3750: 3746: 3740: 3736: 3730: 3727: 3723: 3703: 3693: 3689: 3685: 3680: 3676: 3672: 3663: 3659: 3653: 3645: 3635: 3631: 3627: 3622: 3618: 3614: 3604: 3600: 3596: 3590: 3579: 3575: 3571: 3568: 3563: 3559: 3548: 3544: 3538: 3534: 3530: 3527: 3524: 3518: 3513: 3509: 3505: 3493: 3492: 3491: 3477: 3455: 3451: 3447: 3442: 3438: 3434: 3409: 3406: 3397: 3384: 3378: 3375: 3369: 3364: 3360: 3356: 3353: 3333: 3330: 3324: 3315: 3302: 3289: 3285: 3281: 3276: 3272: 3262: 3235: 3231: 3227: 3222: 3218: 3213: 3191: 3163: 3153: 3149: 3145: 3140: 3136: 3126: 3122: 3116: 3108: 3098: 3094: 3090: 3085: 3081: 3071: 3067: 3061: 3053: 3049: 3045: 3042: 3028: 3024: 3020: 3015: 3011: 3003: 2998: 2993: 2989: 2985: 2978: 2977: 2976: 2962: 2935: 2931: 2927: 2922: 2919: 2912: 2911: 2910: 2896: 2888: 2885: 2860: 2856: 2852: 2847: 2839: 2836: 2833: 2824: 2821: 2818: 2808: 2807: 2806: 2793: 2773: 2759: 2757: 2753: 2749: 2745: 2741: 2715: 2710: 2707: 2702: 2696: 2686: 2681: 2676: 2673: 2666: 2665: 2664: 2650: 2644: 2621: 2613: 2603: 2589: 2582: 2577: 2574: 2565: 2564: 2563: 2561: 2557: 2541: 2538: 2535: 2532: 2529: 2526: 2517: 2507: 2491: 2488: 2485: 2482: 2479: 2476: 2473: 2466: 2459:Reciprocation 2442: 2439: 2434: 2429: 2424: 2421: 2416: 2411: 2403: 2393: 2384: 2377: 2373: 2366: 2363: 2355: 2345: 2336: 2329: 2325: 2318: 2311: 2310: 2309: 2307: 2303: 2293: 2292: 2288: 2284: 2280: 2276: 2244: 2241: 2238: 2225: 2222: 2219: 2204: 2201: 2198: 2185: 2182: 2179: 2168: 2165: 2158: 2157: 2156: 2137: 2133: 2127: 2123: 2115: 2111: 2091: 2069: 2065: 2042: 2038: 2017: 2014: 2011: 2008: 2005: 2002: 1999: 1991: 1981: 1979: 1975: 1970: 1968: 1964: 1960: 1956: 1952: 1948: 1944: 1939: 1937: 1936:Edward Kasner 1933: 1923: 1921: 1917: 1907: 1893: 1870: 1867: 1864: 1861: 1858: 1855: 1849: 1846: 1826: 1803: 1800: 1797: 1794: 1791: 1788: 1762: 1759: 1753: 1748: 1737: 1734: 1728: 1725: 1719: 1714: 1710: 1706: 1701: 1697: 1676: 1673: 1670: 1665: 1661: 1657: 1652: 1648: 1644: 1639: 1635: 1614: 1594: 1586: 1577: 1568: 1559: 1551: 1549: 1548:Dupin cyclide 1539: 1525: 1523: 1519: 1515: 1511: 1507: 1503: 1485: 1481: 1477: 1458: 1454: 1441: 1428: 1425: 1412: 1403: 1399: 1396: 1393: 1390: 1382: 1378: 1374: 1370: 1366: 1362: 1353: 1345: 1337: 1325: 1322: 1318: 1314: 1311: 1308: 1305: 1301: 1297: 1293: 1289: 1285: 1282: 1278: 1274: 1270: 1266: 1262: 1258: 1257: 1256: 1253: 1251: 1247: 1243: 1239: 1238:perpendicular 1235: 1231: 1223: 1219: 1215: 1211: 1207: 1203: 1199: 1196:. The point 1195: 1191: 1187: 1183: 1178: 1173: 1163: 1161: 1156: 1154: 1150: 1145: 1143: 1139: 1135: 1130: 1128: 1124: 1120: 1116: 1112: 1108: 1103: 1101: 1097: 1093: 1081: 1077: 1075: 1071: 1068: 1065: 1064: 1060: 1059:the SVG file, 1054: 1042: 1039: 1035: 1031: 1028: 1024: 1020: 1016: 1012: 1011: 994: 990: 987: 982: 979: 975: 969: 966: 963: 960: 942: 939: 934: 931: 927: 921: 918: 915: 912: 902: 901: 900: 899: 895: 891: 887: 884: 880: 876: 872: 868: 864: 861: 857: 853: 849: 845: 844: 843: 837: 833: 829: 825: 822: 818: 814: 810: 806: 805: 804: 794: 789: 785: 781: 777: 770: 765: 761: 757: 750: 745: 744: 735: 731: 727: 720: 713: 709: 705: 701: 697: 693: 690: 687:antipodal to 686: 682: 678: 674: 670: 666: 663: 659: 655: 651: 650: 649: 647: 643: 639: 635: 630: 628: 624: 620: 616: 612: 599: 595: 592:is where ray 591: 588: 585: 581: 577: 573: 570: 566: 563: 559: 555: 551: 548: 544: 537: 533: 530: 523: 519: 515: 511: 510: 509: 507: 503: 496: 483: 476: 472: 466: 463: 457:Draw segment 456: 453: 449: 445: 438: 434: 431: 427: 423: 419: 417:. (Not shown) 416: 412: 408: 405: 401: 397: 393: 392: 391: 389: 385: 381: 374: 361: 354: 350: 346: 343:are similar. 342: 335: 331: 327: 323: 319: 315: 307: 298: 295: 291: 286: 284: 280: 276: 272: 268: 264: 257: 250: 246: 242: 238: 234: 215: 210: 206: 202: 193: 189: 186: 183: 180: 173: 172: 171: 169: 165: 158: 154: 150: 146: 142: 138: 134: 130: 122: 115: 111: 99: 94: 85: 83: 78: 76: 73:(1842–3) and 72: 68: 64: 60: 56: 51: 47: 43: 39: 38: 33: 29: 22: 6177: 6153:cut-the-knot 6125:48: 589–99, 6120: 6101:, New York: 6098: 6083:, Springer, 6080: 6054: 6032: 6014: 5994: 5975: 5968: 5956: 5951: 5944:Coxeter 1969 5939: 5904: 5898: 5892: 5884: 5879: 5867: 5813: 5801: 5790: 5786: 5720: 5712: 5575: 5571: 5569: 5414: 5409: 5405: 5398: 5396: 5260: 5256: 5238: 5234: 5232: 5227: 5220: 5218:= 1/‖ 5215: 5209: 5205: 5198: 5194: 5187: 5182: 5172: 5166: 5162: 5157: 5153: 5061: 5049: 5043: 5033: 5023: 5016: 5001: 4990: 4981: 4969: 4963: 4951:hyperspheres 4944: 4490: 4486: 4484: 4476: 4463: 4424: 4056: 3915: 3398: 3316: 3183: 2954: 2877: 2765: 2744:Möbius group 2737: 2636: 2559: 2462: 2299: 2275:L. I. Magnus 2272: 2104:will become 1987: 1971: 1966: 1963:Möbius plane 1955:affine plane 1940: 1929: 1913: 1582: 1565: 1557: 1545: 1536: 1521: 1517: 1513: 1509: 1505: 1501: 1380: 1376: 1372: 1371:with radius 1368: 1364: 1358: 1320: 1316: 1303: 1302:of the line 1299: 1295: 1294:, its polar 1291: 1287: 1280: 1276: 1272: 1271:of the line 1268: 1264: 1260: 1254: 1241: 1240:to the line 1233: 1229: 1227: 1221: 1217: 1213: 1209: 1205: 1197: 1193: 1189: 1185: 1181: 1157: 1146: 1131: 1122: 1118: 1110: 1109:of triangle 1104: 1089: 1037: 1033: 1026: 1022: 1018: 1014: 893: 889: 882: 878: 874: 870: 866: 859: 855: 851: 847: 846:If a circle 841: 831: 827: 820: 816: 812: 808: 802: 783: 779: 775: 759: 755: 733: 729: 722: 715: 711: 707: 703: 699: 695: 688: 684: 680: 676: 672: 668: 661: 657: 653: 645: 641: 640:and a point 637: 636:with center 633: 631: 626: 622: 618: 614: 610: 608: 597: 593: 589: 583: 579: 575: 568: 561: 557: 553: 546: 539: 535: 525: 521: 517: 513: 505: 498: 494: 492: 478: 474: 467: 458: 451: 447: 440: 436: 429: 425: 424:with center 421: 414: 410: 403: 399: 395: 387: 383: 376: 375:the inverse 370: 356: 352: 348: 344: 337: 333: 329: 325: 321: 317: 310: 293: 287: 282: 274: 262: 255: 248: 244: 243:(other than 240: 236: 232: 230: 167: 163: 156: 152: 148: 147:with center 144: 140: 136: 126: 120: 113: 79: 35: 31: 25: 6174:"Inversion" 5847:14: 237–240 5186:‖ = 4986:fixed point 4966:translation 4947:hyperplanes 4456:Felix Klein 4448:Lobachevsky 3994:and radius 3253:and radius 2748:conjugation 2283:Felix Klein 1990:cross-ratio 1932:Mario Pieri 1375:is a point 1315:If a point 1286:If a point 1259:If a point 1184:to a point 1086:Application 1057:circle. In 714:in a point 656:of the ray 621:of whether 619:independent 497:of a point 382:of a point 316:of a point 254:also takes 155:is a point 151:and radius 139:of a point 5987:References 5243:homography 4997:similarity 4493:of radius 4485:In a real 2556:reciprocal 2302:similarity 1383:such that 1134:concentric 1096:Euler line 836:orthogonal 741:Properties 600:intersect. 574:Draw line 564:intersect. 534:Draw line 524:) through 484:intersect. 454:intersect. 170:such that 129:reciprocal 63:Bellavitis 44:that maps 6179:MathWorld 6052:(1969) , 5872:Kay (1969 5860:Kay (1969 5818:Kay (1969 5657:⋯ 5607:⋯ 5503:⋯ 5446:⋯ 5344:⋯ 5294:⋯ 5170:/‖ 5129:− 5075:⋅ 5046:conformal 5036:-sphere. 4959:homothety 4900:− 4878:∑ 4859:− 4801:↦ 4768:‖ 4761:− 4755:‖ 4744:− 4705:↦ 4639:− 4386:⁡ 4380:⋅ 4368:− 4356:⁡ 4350:⋅ 4335:⁡ 4318:⁡ 4297:⁡ 4287:⟺ 4258:⁡ 4243:⁡ 4237:− 4225:⁡ 4210:⁡ 4204:⟺ 4183:⁡ 4174:⟺ 4163:∗ 4153:∗ 4078:→ 4070:∗ 4025:− 4017:∗ 3966:− 3961:∗ 3870:− 3865:∗ 3818:− 3810:∗ 3796:− 3791:∗ 3760:− 3755:∗ 3741:∗ 3731:− 3716:⟺ 3686:− 3681:∗ 3628:− 3623:∗ 3605:∗ 3572:− 3564:∗ 3549:∗ 3539:∗ 3519:− 3514:∗ 3448:≠ 3443:∗ 3365:∗ 3328:→ 3282:− 3228:− 3146:− 3091:− 3054:∗ 3021:− 2999:− 2994:∗ 2936:∗ 2889:∈ 2848:∗ 2837:− 2822:− 2756:conformal 2740:generator 2720:¯ 2690:¯ 2648:↦ 2593:¯ 2554:then the 2533:− 2521:¯ 2370:↦ 2322:↦ 2242:− 2223:− 2202:− 2183:− 1984:Invariant 1868:− 1819:, radius 1801:− 1778:; center 1674:− 1463:′ 1442:⋅ 1408:′ 1397:⋅ 1279:of point 1228:If point 1149:congruent 1127:collinear 1092:collinear 973:∠ 958:∠ 925:∠ 910:∠ 710:cuts ray 596:and line 512:Draw ray 473:is where 373:construct 294:invariant 198:′ 187:⋅ 37:inversion 6198:Category 6111:69-12075 6075:(2000), 6033:Geometry 6007:52-13504 5963:, Moscow 5837:Archived 5726:See also 5404:+ ... + 5224:‖ 5193:+ ... + 5180:‖ 5178:, where 5176:‖ 5054:Jacobian 5050:oriented 4993:isometry 4978:rotation 4955:dilation 4813:′ 4712:′ 4464:geometry 4436:Beltrami 4123:becomes 3410:∉ 2296:Dilation 1961:forms a 1554:Spheroid 1107:incircle 1074:cardioid 991:′ 983:′ 943:′ 935:′ 702:in line 617:that is 578:through 538:through 261:back to 166:through 77:(1845). 65:(1836), 61:(1825), 59:Quetelet 57:(1824), 28:geometry 6190:Xah Lee 6137:0006034 5931:1986367 5213:, with 5026:-sphere 2742:of the 2663:where: 1200:is the 1098:of the 706:. Then 324:: Let 137:inverse 55:Steiner 46:circles 6109:  6087:  6062:  6039:  6021:  6005:  5929:  5203:gives 4466:for a 4452:Bolyai 4442:, and 4440:Cayley 1953:, any 1533:Sphere 1113:. The 955:  947:  896:, then 355:is to 347:is to 135:, the 75:Kelvin 71:Ingram 67:Stubbs 5927:JSTOR 5778:Notes 5237:to 1/ 4472:group 4468:space 4444:Klein 4057:When 3317:When 2504:with 1974:model 1246:polar 725:' 718:' 542:' 528:' 516:from 501:' 481:' 470:' 461:' 443:' 402:) to 379:' 359:' 340:' 313:' 259:' 252:' 160:' 133:plane 117:' 50:lines 6107:LCCN 6085:ISBN 6060:ISBN 6037:ISBN 6019:ISBN 6003:LCCN 5257:The 5106:and 4974:flat 4972:–2)- 4450:and 3427:and 3399:For 2057:and 1988:The 1914:The 1250:pole 1220:and 1158:The 1125:are 1017:and 869:and 858:and 694:Let 560:and 552:Let 477:and 450:and 439:and 435:Let 409:Let 336:and 69:and 6151:at 6127:doi 5917:hdl 5909:doi 5114:det 4957:or 4949:or 3490:is 2562:is 2558:of 2285:'s 1827:0.5 1804:0.5 1252:). 1204:of 1123:ABC 1119:ABC 1111:ABC 776:not 371:To 351:as 338:ONP 334:OPN 235:or 48:or 26:In 6200:: 6176:. 6134:MR 6105:, 6079:, 6001:, 5959:, 5925:. 5915:. 5903:. 5852:^ 5843:, 5825:^ 5555:0. 5210:kI 5208:= 5206:JJ 5161:= 5014:. 4999:. 4438:, 4383:Im 4353:Re 4332:Im 4315:Re 4294:Im 4255:Im 4240:Im 4222:Re 4207:Re 4180:Re 4054:. 2758:. 2304:, 1980:. 1972:A 1922:. 1583:A 1550:. 1524:. 1381:OP 1242:PR 1216:, 1155:. 1129:. 721:. 712:OC 704:BC 700:BA 658:OA 648:. 629:. 584:ON 569:ON 508:: 479:NN 475:OP 459:NN 415:OP 390:: 357:OP 345:OP 84:. 30:, 6182:. 6129:: 5976:n 5933:. 5919:: 5911:: 5905:1 5698:, 5695:0 5692:= 5689:1 5686:+ 5681:n 5677:x 5671:n 5667:a 5663:2 5660:+ 5654:+ 5649:1 5645:x 5639:1 5635:a 5631:2 5628:+ 5623:2 5618:n 5614:x 5610:+ 5604:+ 5599:2 5594:1 5590:x 5576:n 5572:c 5552:= 5547:c 5544:1 5539:+ 5534:n 5530:x 5524:c 5519:n 5515:a 5509:2 5506:+ 5500:+ 5495:1 5491:x 5485:c 5480:1 5476:a 5470:2 5467:+ 5462:2 5457:n 5453:x 5449:+ 5443:+ 5438:2 5433:1 5429:x 5415:c 5410:n 5406:a 5402:1 5399:a 5382:0 5379:= 5376:c 5373:+ 5368:n 5364:x 5358:n 5354:a 5350:2 5347:+ 5341:+ 5336:1 5332:x 5326:1 5322:a 5318:2 5315:+ 5310:2 5305:n 5301:x 5297:+ 5291:+ 5286:2 5281:1 5277:x 5261:n 5259:( 5239:z 5235:z 5228:J 5221:x 5216:k 5199:n 5195:x 5191:1 5188:x 5183:x 5173:x 5167:i 5163:x 5158:i 5154:z 5139:. 5134:k 5126:= 5123:) 5120:J 5117:( 5094:I 5091:k 5088:= 5083:T 5079:J 5072:J 5062:J 5034:n 5024:n 4982:n 4970:n 4926:. 4918:2 4914:) 4908:k 4904:o 4895:k 4891:p 4887:( 4882:k 4872:) 4867:j 4863:o 4854:j 4850:p 4846:( 4841:2 4837:r 4830:+ 4825:j 4821:o 4817:= 4809:j 4805:p 4792:j 4788:p 4780:, 4772:2 4764:O 4758:P 4750:) 4747:O 4741:P 4738:( 4733:2 4729:r 4722:+ 4719:O 4716:= 4709:P 4698:P 4682:: 4668:2 4664:r 4642:O 4636:P 4613:) 4608:n 4604:p 4600:, 4597:. 4594:. 4591:. 4588:, 4583:1 4579:p 4575:( 4572:= 4569:P 4549:) 4544:n 4540:o 4536:, 4533:. 4530:. 4527:. 4524:, 4519:1 4515:o 4511:( 4508:= 4505:O 4495:r 4487:n 4401:. 4395:} 4392:a 4389:{ 4377:2 4373:1 4365:} 4362:w 4359:{ 4344:} 4341:a 4338:{ 4327:} 4324:a 4321:{ 4309:= 4306:} 4303:w 4300:{ 4278:2 4275:1 4270:= 4267:} 4264:w 4261:{ 4252:} 4249:a 4246:{ 4234:} 4231:w 4228:{ 4219:} 4216:a 4213:{ 4201:1 4198:= 4195:} 4192:w 4189:a 4186:{ 4177:2 4171:1 4168:= 4159:w 4149:a 4145:+ 4142:w 4139:a 4111:w 4091:, 4086:2 4082:r 4075:a 4066:a 4039:| 4033:2 4029:r 4022:a 4013:a 4008:| 4004:r 3979:) 3974:2 3970:r 3957:a 3953:a 3950:( 3946:a 3924:w 3895:2 3890:) 3884:| 3878:2 3874:r 3861:a 3857:a 3853:| 3849:r 3844:( 3839:= 3835:) 3826:2 3822:r 3815:a 3806:a 3801:a 3787:w 3782:( 3777:) 3768:2 3764:r 3751:a 3747:a 3737:a 3728:w 3724:( 3704:2 3700:) 3694:2 3690:r 3677:a 3673:a 3670:( 3664:2 3660:r 3654:= 3646:2 3642:) 3636:2 3632:r 3619:a 3615:a 3612:( 3601:a 3597:a 3591:+ 3585:) 3580:2 3576:r 3569:a 3560:a 3556:( 3545:w 3535:a 3531:+ 3528:w 3525:a 3510:w 3506:w 3478:w 3456:2 3452:r 3439:a 3435:a 3414:R 3407:a 3385:. 3379:a 3376:1 3370:= 3361:w 3357:+ 3354:w 3334:, 3331:r 3325:a 3303:. 3296:| 3290:2 3286:r 3277:2 3273:a 3268:| 3263:r 3236:2 3232:r 3223:2 3219:a 3214:a 3192:w 3164:2 3160:) 3154:2 3150:r 3141:2 3137:a 3133:( 3127:2 3123:r 3117:= 3109:2 3105:) 3099:2 3095:r 3086:2 3082:a 3078:( 3072:2 3068:a 3062:+ 3059:) 3050:w 3046:+ 3043:w 3040:( 3034:) 3029:2 3025:r 3016:2 3012:a 3008:( 3004:a 2990:w 2986:w 2963:w 2932:z 2928:1 2923:= 2920:w 2897:. 2893:R 2886:a 2861:2 2857:r 2853:= 2844:) 2840:a 2834:z 2831:( 2828:) 2825:a 2819:z 2816:( 2794:a 2774:r 2734:. 2716:) 2711:z 2708:1 2703:( 2697:= 2687:z 2682:1 2677:= 2674:w 2651:w 2645:z 2622:. 2614:2 2609:| 2604:z 2600:| 2590:z 2583:= 2578:z 2575:1 2560:z 2542:, 2539:y 2536:i 2530:x 2527:= 2518:z 2492:, 2489:y 2486:i 2483:+ 2480:x 2477:= 2474:z 2443:. 2440:x 2435:2 2430:) 2425:R 2422:T 2417:( 2412:= 2404:2 2399:| 2394:y 2390:| 2385:y 2378:2 2374:T 2367:y 2364:= 2356:2 2351:| 2346:x 2342:| 2337:x 2330:2 2326:R 2319:x 2249:| 2245:z 2239:y 2235:| 2230:| 2226:w 2220:x 2216:| 2209:| 2205:z 2199:w 2195:| 2190:| 2186:y 2180:x 2176:| 2169:= 2166:I 2143:) 2138:2 2134:r 2128:1 2124:r 2120:( 2116:/ 2112:d 2092:d 2070:2 2066:r 2043:1 2039:r 2018:w 2015:, 2012:z 2009:, 2006:y 2003:, 2000:x 1894:N 1874:) 1871:1 1865:, 1862:0 1859:, 1856:0 1853:( 1850:= 1847:S 1807:) 1798:, 1795:0 1792:, 1789:0 1786:( 1763:4 1760:1 1754:= 1749:2 1745:) 1738:2 1735:1 1729:+ 1726:z 1723:( 1720:+ 1715:2 1711:y 1707:+ 1702:2 1698:x 1677:z 1671:= 1666:2 1662:z 1658:+ 1653:2 1649:y 1645:+ 1640:2 1636:x 1615:S 1595:N 1522:O 1518:O 1514:O 1510:O 1506:O 1502:O 1486:2 1482:R 1478:= 1474:| 1469:| 1459:P 1455:O 1451:| 1446:| 1438:| 1433:| 1429:P 1426:O 1422:| 1417:| 1413:= 1404:P 1400:O 1394:P 1391:O 1377:P 1373:R 1369:O 1365:P 1321:P 1317:P 1306:. 1304:l 1300:L 1296:p 1292:l 1288:P 1283:. 1281:P 1277:p 1273:l 1269:L 1265:l 1261:P 1234:P 1230:R 1224:. 1222:Q 1218:P 1214:O 1210:P 1206:Q 1198:P 1194:O 1190:r 1186:Q 1182:q 1038:k 1034:k 1029:. 1027:k 1023:k 1019:q 1015:p 995:. 988:B 980:A 976:O 970:= 967:A 964:B 961:O 940:A 932:B 928:O 922:= 919:B 916:A 913:O 894:k 890:k 885:. 883:k 879:q 875:k 871:q 867:k 860:q 856:k 852:k 848:q 832:O 828:O 821:O 817:O 813:O 809:O 784:O 780:O 760:O 756:O 736:. 734:P 730:A 723:A 716:A 708:h 696:h 691:) 689:C 685:P 681:C 677:P 673:B 669:C 664:. 662:P 654:C 646:P 642:A 638:O 634:P 627:P 623:A 615:P 611:A 598:t 594:r 590:P 586:. 580:N 576:t 571:. 562:s 558:Ø 554:N 547:r 540:P 536:s 526:P 522:Ø 518:O 514:r 506:Ø 499:P 495:P 468:P 464:. 452:c 448:Ø 441:N 437:N 430:P 426:M 422:c 411:M 406:. 404:P 400:Ø 396:O 388:Ø 384:P 377:P 362:. 353:r 349:r 330:Ø 326:r 322:Ø 318:P 311:P 283:O 275:O 263:P 256:P 249:P 245:O 241:P 216:. 211:2 207:r 203:= 194:P 190:O 184:P 181:O 168:P 164:O 157:P 153:r 149:O 141:P 121:P 114:P 23:.

Index

Point reflection
geometry
inversion
Euclidean plane
circles
lines
Steiner
Quetelet
Bellavitis
Stubbs
Ingram
Kelvin
generalized to higher-dimensional spaces

Mandelbrot set

reciprocal
plane
self-inversion
total function
point at infinity
point at infinity

construct
The inverse, with respect to the red circle, of a circle going through O (blue) is a line not going through O (green), and vice versa.
The inverse, with respect to the red circle, of a circle not going through O (blue) is a circle not going through O (green), and vice versa.
Inversion with respect to a circle does not map the center of the circle to the center of its image
orthogonal

the SVG file,

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