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Finite geometry

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40: 3889: 2591: 1580: 20: 1274: 3901: 2617:, which states: "Fifteen schoolgirls walk each day in five groups of three. Arrange the girlsā€™ walk for a week so that in that time, each pair of girls walks together in a group just once." There are 35 different combinations for the girls to walk together. There are also 7 days of the week, and 3 girls in each group. Two of the seven non-isomorphic solutions to this problem can be stated in terms of structures in the Fano 3-space, PG(3,2), known as 3925: 3913: 1600: 2564: 1505:
2. (The order of an affine plane is the number of points on any line, see below.) Since no three are collinear, any pair of points determines a unique line, and so this plane contains six lines. It corresponds to a tetrahedron where non-intersecting edges are considered "parallel", or a square where
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for projective plane geometries, meaning that any true statement valid in all these geometries remains true if we exchange points for lines and lines for points. The smallest geometry satisfying all three axioms contains seven points. In this simplest of the projective planes, there are also seven
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of its points into disjoint lines, and a packing is a partition of the lines into disjoint spreads. In PG(3,2), a spread would be a partition of the 15 points into 5 disjoint lines (with 3 points on each line), thus corresponding to the arrangement of schoolgirls on a particular day. A packing of
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all finite division rings are fields. In this case, this construction produces a finite projective space. Furthermore, if the geometric dimension of a projective space is at least three then there is a division ring from which the space can be constructed in this manner. Consequently, all finite
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The last axiom eliminates reducible cases that can be written as a disjoint union of projective spaces together with 2-point lines joining any two points in distinct projective spaces. More abstractly, it can be defined as an
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to a projective space over a finite field (that is, the projectivization of a vector space over a finite field). However, dimension two has affine and projective planes that are not isomorphic to Galois geometries, namely the
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Finite affine plane of order 2, containing 4 "points" and 6 "lines". Lines of the same color are "parallel". The centre of the figure is not a "point" of this affine plane, hence the two green "lines" don't
1305:, by contrast, any two lines intersect at a unique point, so parallel lines do not exist. Both finite affine plane geometry and finite projective plane geometry may be described by fairly simple 1482: 3175: 1591:
An examination of the first two axioms shows that they are nearly identical, except that the roles of points and lines have been interchanged. This suggests the principle of
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are considered to be the points, would be a finite geometry. While there are many systems that could be called finite geometries, attention is mostly paid to the finite
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Every point is contained in 7 lines. Every pair of distinct points are contained in exactly one line and every pair of distinct planes intersects in exactly one line.
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that he developed, he considered a finite three dimensional space with 15 points, 35 lines and 15 planes (see diagram), in which each line had only three points on it.
3311: 1616:. If any of the lines is removed from the plane, along with the points on that line, the resulting geometry is the affine plane of order 2. The Fano plane is called 1397: 1357: 1765: 2299: 1442: 1377: 1498:
or too simple to be of interest, such as a single line with an arbitrary number of points on it), while the first two specify the nature of the geometry.
2579:. It has 15 points, 35 lines, and 15 planes. Each plane contains 7 points and 7 lines. Each line contains 3 points. As geometries, these planes are 2247:
projective spaces of geometric dimension at least three are defined over finite fields. A finite projective space defined over such a finite field has
2975: 2813:, pgs. 6ā€“7). Pasch was concerned with real projective space and was attempting to introduce order, which is not a concern of the Veblenā€“Young axiom. 2777: 2121: 1201:
is not finite, because a Euclidean line contains infinitely many points. A geometry based on the graphics displayed on a computer screen, where the
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the 2-dimensional (two independent generators) subspaces (closed under vector addition) of this vector space. Incidence is containment. If
3220: 2773: 1168: 1252:. Finite geometries can also be defined purely axiomatically. Most common finite geometries are Galois geometries, since any finite 3163: 2894: 268: 3712: 1592: 3857: 3342: 3185: 2862: 3929: 3247: 2947: 2711: 1294: 234: 1447: 3393: 1818:
The smallest integer that is not a prime power and not covered by the Bruckā€“Ryser theorem is 10; 10 is of the form
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The next smallest number to consider is 12, for which neither a positive nor a negative result has been proved.
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Collino, Alberto; Conte, Alberto; Verra, Alessandro (2013). "On the life and scientific work of Gino Fano".
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points on a line, so the two concepts of order coincide. Such a finite projective space is denoted by
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if that is the largest number for which there is a strictly ascending chain of subspaces of this form:
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Dimension 0 (no lines): The space is a single point and is so degenerate that it is usually ignored.
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because of their regularity and simplicity. Other significant types of finite geometry are finite
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PG(3,2) consists of seven disjoint spreads and so corresponds to a full week of arrangements.
3872: 3802: 3679: 3603: 3542: 3527: 3522: 3499: 3381: 397: 358: 317: 312: 165: 1402: 3852: 3732: 3727: 3651: 3552: 3014: 2957: 2904: 2455: 2436:{\displaystyle {{n+1} \choose {k+1}}_{q}=\prod _{i=0}^{k}{\frac {q^{n+1-i}-1}{q^{i+1}-1}},} 1663: 1647: 1382: 1342: 1065: 988: 836: 741: 263: 158: 72: 2477:
Dimension 2: There are at least 2 lines, and any two lines meet. A projective space for
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2 because it is unique (up to isomorphism). In general, the projective plane of order
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In any finite projective space, each line contains the same number of points and the
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For every two distinct points, there is exactly one line that contains both points.
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For every two distinct points, there is exactly one line that contains both points.
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The first axiomatic treatment of finite projective geometry was developed by the
1722: 1286: 1249: 503: 366: 209: 133: 39: 3085:(1999). "Yea why try her raw wet hat: A tour of the smallest projective space". 1214: 1075: 1044: 978: 826: 771: 706: 3840: 3767: 3474: 2645: 2488:. These are much harder to classify, as not all of them are isomorphic with a 2188:{\displaystyle \varnothing =X_{-1}\subset X_{0}\subset \cdots \subset X_{n}=P.} 1233: 1218: 1131: 1039: 983: 948: 856: 766: 736: 696: 601: 3274: 3155: 3022: 1105: 716: 3945: 3628: 3560: 3512: 2998: 2769: 2527:
states in the finite case that every projective space of geometric dimension
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Dimension 1 (exactly one line): All points lie on the unique line, called a
2204: 1985: 1880: 1853:(1847) and the systematic development of finite projective geometry given by 1575:
There exists a set of four points, no three of which belong to the same line.
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There exists a set of four points, no three of which belong to the same line.
1110: 1095: 1024: 841: 801: 751: 526: 489: 456: 294: 290: 3256: 2825:, p. 28, where the formula is given, in terms of vector space dimension, by 2203:
A standard algebraic construction of systems satisfies these axioms. For a
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Fano, G. (1892), "Sui postulati fondamentali della geometria proiettiva",
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lines; each point is on three lines, and each line contains three points.
3772: 3436: 3359: 3321: 3229: 3180:, London Mathematical Society Student Texts, Cambridge University Press, 2858: 2680: 2580: 1714: 1257: 1085: 958: 776: 711: 639: 611: 586: 3126:, New York: Cambridge university Press, pp. 488ā€“499, archived from 2274:
is the size (order) of the finite field used to construct the geometry.
3757: 3636: 3431: 3098: 3048: 3006: 2584: 1635: + 1 points and the same number of lines; each line contains 1612: 1604: 1584: 1557:(whose elements are called "points"), along with a nonempty collection 1506:
not only opposite sides, but also diagonals are considered "parallel".
1321:(whose elements are called "points"), along with a nonempty collection 1222: 1190: 943: 922: 912: 902: 861: 806: 701: 691: 591: 442: 19: 1572:
The intersection of any two distinct lines contains exactly one point.
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The simplest affine plane contains only four points; it is called the
1273: 3211: 2602: 1943:) has many important applications in advanced mathematical theories. 1865: 1741:
elements. Planes not derived from finite fields also exist (e.g. for
1495: 953: 671: 634: 498: 470: 3040: 2989: 2222:(vector space dimension is the number of elements in a basis). Let 1731:), by using affine and projective planes over the finite field with 3661: 3580: 3507: 1931:
geometry and the geometry of higher-dimensional finite spaces, see
1868:. In his work on proving the independence of the set of axioms for 1861: 1728: 1659: 1186: 1034: 993: 963: 851: 846: 796: 521: 480: 428: 322: 285: 31: 3225: 2917: 1830:. The non-existence of a finite plane of order 10 was proven in a 3446: 2576: 2516:
and are projective planes over finite fields, but there are many
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Classification of finite projective spaces by geometric dimension
1725: 1662:ā‰ˆ PSL(3,2), which in this special case is also isomorphic to the 1650:
points (points on the same line) to collinear points is called a
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Finite affine plane of order 3, containing 9 points and 12 lines.
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The smallest 3-dimensional projective space is over the field
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Dimension at least 3: Two non-intersecting lines exist. The
1265:. Similar results hold for other kinds of finite geometries. 2572: 2563: 2104:). The full space and the empty space are always subspaces. 2085:
of the space is defined as one less than this common number.
1599: 1306: 1225:, and their higher-dimensional analogs such as higher finite 1202: 973: 897: 831: 676: 280: 275: 1646:
A permutation of the Fano plane's seven points that carries
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points (for an affine plane), or such that each line has
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This particular projective plane is sometimes called the
3201: 2550:-dimensional projective space over some finite field GF( 1922: 3293:
on canonical geometric properties of small finite sets.
3023:"The Search for a Finite Projective Plane of Order 10" 2880: 2810: 2789: 2558: 2226:
be the 1-dimensional (single generator) subspaces and
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Projective geometry: from foundations to applications
2302: 2124: 1747: 1450: 1430: 1405: 1385: 1365: 1345: 1285:. There are two main kinds of finite plane geometry: 1767:), but all known examples have order a prime power. 1697:
Is the order of a finite plane always a prime power?
2700:Laywine, Charles F.; Mullen, Gary L. (1998-09-17). 2613:PG(3,2) arises as the background for a solution of 1970:(the set of lines), satisfying these axioms : 2927: 2605:was the first to consider such a finite geometry. 2435: 2187: 1759: 1587:: Each point corresponds to a line and vice versa. 1476: 1436: 1416: 1391: 1371: 1351: 2976:Transactions of the American Mathematical Society 2910: 2778:Transactions of the American Mathematical Society 2745: 2336: 2307: 1939:. The study of these higher-dimensional spaces ( 3943: 2936:Ergebnisse der Mathematik und ihrer Grenzgebiete 2881:Beutelspacher, Albrecht; Rosenbaum, Ute (1998), 2642:ā€“ a generalization of a finite projective plane. 1849:Individual examples can be found in the work of 1658:is of order 168 and is isomorphic to the group 1565:(whose elements are called "lines"), such that: 1490:The last axiom ensures that the geometry is not 1329:(whose elements are called "lines"), such that: 2608: 2270:is the geometric dimension of the geometry and 2088:A subspace of the projective space is a subset 1516:More generally, a finite affine plane of order 16:Geometric system with a finite number of points 3177:Finite Geometry and Combinatorial Applications 2092:, such that any line containing two points of 1927:For some important differences between finite 1814:does not occur as the order of a finite plane. 1553:A projective plane geometry is a nonempty set 1477:{\displaystyle \ell \cap \ell '=\varnothing .} 1221:, which are examples of a general type called 3343: 3235:Essay on Finite Geometry by Michael Greenberg 2983:(2), American Mathematical Society: 229ā€“277, 2699: 1162: 2973:Hall, Marshall (1943), "Projective planes", 1639: + 1 points, and each point is on 1509:The affine plane of order 3 is known as the 3357: 2266:, where PG stands for projective geometry, 1907:-dimensional finite geometry is denoted PG( 1548: 1317:An affine plane geometry is a nonempty set 1281:The following remarks apply only to finite 3350: 3336: 3312:ā€œProblem 31: Kirkman's schoolgirl problemā€ 2069:projective space requires one more axiom: 2004:are distinct points and the lines through 1169: 1155: 38: 2988: 2925: 2916: 2822: 2760:Finite Geometries? an AMS Featured Column 2198: 2062:stating which points lie on which lines. 1962:(the set of points), together with a set 1232:Finite geometries may be constructed via 3280: 3275:Galois Geometry and Generalized Polygons 2703:Discrete Mathematics Using Latin Squares 2589: 2562: 1826:, but it is equal to the sum of squares 1598: 1578: 1272: 18: 3081: 3072: 2567:PG(3,2) but not all the lines are drawn 1946: 1806:is not equal to the sum of two integer 1770:The best general result to date is the 1312: 3944: 3263:Books by Hirschfeld on finite geometry 3056: 2857: 2757: 1958:can be defined axiomatically as a set 1705:Affine and projective planes of order 269:Straightedge and compass constructions 3331: 3202: 3145: 3113: 2023:Any line has at least 3 points on it. 1923:Finite spaces of 3 or more dimensions 1915:and has an associated transformation 3912: 3221:Incidence Geometry by Eric Moorhouse 3173: 2972: 2963: 2726: 3924: 3020: 2559:The smallest projective three-space 2012:meet, then so do the lines through 1835: 13: 3259:, researcher on finite geometries 2864:Combinatorics of Finite Geometries 2811:Beutelspacher & Rosenbaum 1998 2790:Beutelspacher & Rosenbaum 1998 2504:(those that are isomorphic with a 2311: 2100:(that is, completely contained in 1672: 14: 3968: 3195: 1468: 1256:of dimension three or greater is 235:Noncommutative algebraic geometry 3923: 3911: 3900: 3899: 3887: 3226:Algebraic Combinatorial Geometry 3075:Fundamental Concepts of Geometry 2966:A Survey of Geometry: Volume One 1702:This is conjectured to be true. 1399:, there exists exactly one line 1268: 3808:Computational complexity theory 3318: (archived August 17, 2010) 2746:Collino, Conte & Verra 2013 2218:-dimensional vector space over 1684:is one such that each line has 3281:Carnahan, Scott (2007-10-27), 3270:AMS Column: Finite Geometries? 3087:The Mathematical Intelligencer 3077:, New York: Dover Publications 2968:, Boston: Allyn and Bacon Inc. 2867:, Cambridge University Press, 2816: 2795: 2783: 2763: 2751: 2739: 2720: 2693: 1903:+ 1 coordinates are used, the 628:- / other-dimensional 1: 3028:American Mathematical Monthly 2938:, Band 44, Berlin, New York: 2851: 2448:Gaussian binomial coefficient 2234:is finite then it must be a 1834:that finished in 1989 ā€“ see ( 1538:points, and each point is on 3322:Projective Plane of Order 12 2774:Finite Projective Geometries 2615:Kirkman's schoolgirl problem 2609:Kirkman's schoolgirl problem 2594:Square model of Fano 3-space 7: 2633: 2625:of a projective space is a 2244:Wedderburn's little theorem 2111:of the space is said to be 1883:and W. H. Bussey described 10: 3973: 3858:Films about mathematicians 3303:: CS1 maint: postscript ( 3277:, intensive course in 1998 3150:, Universitext, Springer, 3073:Meserve, Bruce E. (1983), 2887:Cambridge University Press 2281:-dimensional subspaces of 2277:In general, the number of 1933:axiomatic projective space 1844: 1534:lines; each line contains 1248:so constructed are called 1215:Mƶbius or inversive planes 3881: 3831: 3788: 3698: 3660: 3627: 3579: 3551: 3498: 3445: 3427:Philosophy of mathematics 3402: 3367: 3245:Finite Geometry Resources 3156:10.1007/978-3-642-15627-4 3146:Shult, Ernest E. (2011), 2926:Dembowski, Peter (1968), 2706:. John Wiley & Sons. 2293:is given by the product: 1974:Each two distinct points 1621:projective plane of order 3863:Recreational mathematics 3240:Finite geometry (Script) 2801:also referred to as the 2686: 1982:are in exactly one line. 1851:Thomas Penyngton Kirkman 1549:Finite projective planes 124:Non-Archimedean geometry 3748:Mathematical statistics 3738:Mathematical psychology 3708:Engineering mathematics 3642:Algebraic number theory 3287:Secret Blogging Seminar 2729:Giornale di Matematiche 2666:Linear space (geometry) 2518:non-Desarguesian planes 1889:homogeneous coordinates 1832:computer-assisted proof 1774:of 1949, which states: 1654:of the plane. The full 1263:non-Desarguesian planes 1189:system that has only a 230:Noncommutative geometry 3894:Mathematics portal 3743:Mathematical sociology 3723:Mathematical economics 3718:Mathematical chemistry 3647:Analytic number theory 3528:Differential equations 3021:Lam, C. W. H. (1991), 2805:and mistakenly as the 2595: 2568: 2437: 2371: 2199:Algebraic construction 2189: 1891:with entries from the 1761: 1643: + 1 lines. 1607: 1588: 1478: 1438: 1418: 1417:{\displaystyle \ell '} 1393: 1373: 1353: 1297:, the normal sense of 1278: 198:Discrete/Combinatorial 25: 3873:Mathematics education 3803:Theory of computation 3523:Hypercomplex analysis 3289:, notes on a talk by 3174:Ball, Simeon (2015), 2964:Eves, Howard (1963), 2859:Batten, Lynn Margaret 2593: 2566: 2534:is isomorphic with a 2438: 2351: 2190: 1762: 1602: 1582: 1503:affine plane of order 1479: 1439: 1419: 1394: 1392:{\displaystyle \ell } 1374: 1354: 1352:{\displaystyle \ell } 1276: 181:Discrete differential 22: 3853:Informal mathematics 3733:Mathematical physics 3728:Mathematical finance 3713:Mathematical biology 3652:Diophantine geometry 3120:On Galois Geometries 3059:"Finite Geometries?" 2525:Veblenā€“Young theorem 2456:binomial coefficient 2300: 2122: 2047:consisting of a set 1947:Axiomatic definition 1745: 1664:general linear group 1448: 1428: 1403: 1383: 1363: 1343: 1313:Finite affine planes 1301:lines applies. In a 1227:inversive geometries 3868:Mathematics and art 3778:Operations research 3533:Functional analysis 3283:"Small finite sets" 3257:J. W. P. Hirschfeld 2656:Generalized polygon 2514:Desargues's theorem 2502:Desarguesian planes 2109:geometric dimension 2030:incidence structure 1885:projective geometry 1772:Bruckā€“Ryser theorem 1760:{\displaystyle n=9} 1511:Hesse configuration 448:Pythagorean theorem 3813:Numerical analysis 3422:Mathematical logic 3417:Information theory 3250:2011-09-27 at the 3204:Weisstein, Eric W. 3099:10.1007/BF03024845 2803:Veblenā€“Young axiom 2661:Incidence geometry 2596: 2575:and is denoted by 2569: 2433: 2185: 2073:The set of points 2057:incidence relation 1913:synthetic geometry 1757: 1677:A finite plane of 1667:GL(3,2) ā‰ˆ PGL(3,2) 1656:collineation group 1608: 1589: 1474: 1434: 1414: 1389: 1369: 1349: 1279: 1199:Euclidean geometry 26: 3939: 3938: 3538:Harmonic analysis 3291:Jean-Pierre Serre 3207:"finite geometry" 3165:978-3-642-15626-7 3057:Malkevitch, Joe. 2930:Finite geometries 2896:978-0-521-48364-3 2428: 2334: 2055:of lines, and an 2051:of points, a set 1937:J.W.P. Hirschfeld 1437:{\displaystyle p} 1372:{\displaystyle p} 1250:Galois geometries 1246:projective planes 1244:; the affine and 1179: 1178: 1144: 1143: 867:List of geometers 550:Three-dimensional 539: 538: 3964: 3927: 3926: 3915: 3914: 3903: 3902: 3892: 3891: 3823:Computer algebra 3798:Computer science 3518:Complex analysis 3352: 3345: 3338: 3329: 3328: 3324:on MathOverflow. 3308: 3302: 3294: 3217: 3216: 3190: 3168: 3148:Points and Lines 3140: 3139: 3138: 3132: 3125: 3115:Segre, Beniamino 3110: 3083:Polster, Burkard 3078: 3069: 3067: 3065: 3051: 3017: 2992: 2969: 2960: 2933: 2922: 2920: 2907: 2877: 2845: 2843: 2820: 2814: 2799: 2793: 2787: 2781: 2767: 2761: 2755: 2749: 2743: 2737: 2736: 2724: 2718: 2717: 2697: 2676:Partial geometry 2545: 2533: 2511: 2499: 2486:projective plane 2483: 2442: 2440: 2439: 2434: 2429: 2427: 2420: 2419: 2403: 2396: 2395: 2373: 2370: 2365: 2347: 2346: 2341: 2340: 2339: 2333: 2322: 2310: 2292: 2265: 2253: 2217: 2194: 2192: 2191: 2186: 2175: 2174: 2156: 2155: 2143: 2142: 2077:is a finite set. 2046: 1953:projective space 1942: 1911:). It arises in 1829: 1825: 1801: 1793: 1784:positive integer 1766: 1764: 1763: 1758: 1740: 1668: 1544: 1533: 1483: 1481: 1480: 1475: 1464: 1443: 1441: 1440: 1435: 1423: 1421: 1420: 1415: 1413: 1398: 1396: 1395: 1390: 1378: 1376: 1375: 1370: 1358: 1356: 1355: 1350: 1337:Playfair's axiom 1303:projective plane 1254:projective space 1236:, starting from 1171: 1164: 1157: 885: 884: 404: 403: 337:Zero-dimensional 42: 28: 27: 3972: 3971: 3967: 3966: 3965: 3963: 3962: 3961: 3952:Finite geometry 3942: 3941: 3940: 3935: 3886: 3877: 3827: 3784: 3763:Systems science 3694: 3690:Homotopy theory 3656: 3623: 3575: 3547: 3494: 3441: 3412:Category theory 3398: 3363: 3356: 3316:Wayback Machine 3296: 3295: 3252:Wayback Machine 3198: 3188: 3166: 3136: 3134: 3130: 3123: 3063: 3061: 3041:10.2307/2323798 2990:10.2307/1990331 2950: 2940:Springer-Verlag 2897: 2875: 2854: 2849: 2848: 2833: 2826: 2821: 2817: 2800: 2796: 2788: 2784: 2768: 2764: 2756: 2752: 2744: 2740: 2725: 2721: 2714: 2698: 2694: 2689: 2636: 2611: 2561: 2535: 2528: 2505: 2489: 2478: 2472:projective line 2464: 2409: 2405: 2404: 2379: 2375: 2374: 2372: 2366: 2355: 2342: 2335: 2323: 2312: 2306: 2305: 2304: 2303: 2301: 2298: 2297: 2282: 2255: 2248: 2211: 2201: 2170: 2166: 2151: 2147: 2135: 2131: 2123: 2120: 2119: 2096:is a subset of 2032: 1949: 1940: 1925: 1847: 1838:) for details. 1827: 1819: 1795: 1787: 1746: 1743: 1742: 1732: 1709:exist whenever 1675: 1673:Order of planes 1666: 1583:Duality in the 1551: 1539: 1525: 1457: 1449: 1446: 1445: 1429: 1426: 1425: 1406: 1404: 1401: 1400: 1384: 1381: 1380: 1364: 1361: 1360: 1344: 1341: 1340: 1339:: Given a line 1315: 1271: 1219:Laguerre planes 1197:. The familiar 1183:finite geometry 1175: 1146: 1145: 882: 881: 872: 871: 662: 661: 645: 644: 630: 629: 617: 616: 553: 552: 541: 540: 401: 400: 398:Two-dimensional 389: 388: 362: 361: 359:One-dimensional 350: 349: 340: 339: 328: 327: 261: 260: 259: 242: 241: 90: 89: 78: 55: 17: 12: 11: 5: 3970: 3960: 3959: 3954: 3937: 3936: 3934: 3933: 3921: 3909: 3897: 3882: 3879: 3878: 3876: 3875: 3870: 3865: 3860: 3855: 3850: 3849: 3848: 3841:Mathematicians 3837: 3835: 3833:Related topics 3829: 3828: 3826: 3825: 3820: 3815: 3810: 3805: 3800: 3794: 3792: 3786: 3785: 3783: 3782: 3781: 3780: 3775: 3770: 3768:Control theory 3760: 3755: 3750: 3745: 3740: 3735: 3730: 3725: 3720: 3715: 3710: 3704: 3702: 3696: 3695: 3693: 3692: 3687: 3682: 3677: 3672: 3666: 3664: 3658: 3657: 3655: 3654: 3649: 3644: 3639: 3633: 3631: 3625: 3624: 3622: 3621: 3616: 3611: 3606: 3601: 3596: 3591: 3585: 3583: 3577: 3576: 3574: 3573: 3568: 3563: 3557: 3555: 3549: 3548: 3546: 3545: 3543:Measure theory 3540: 3535: 3530: 3525: 3520: 3515: 3510: 3504: 3502: 3496: 3495: 3493: 3492: 3487: 3482: 3477: 3472: 3467: 3462: 3457: 3451: 3449: 3443: 3442: 3440: 3439: 3434: 3429: 3424: 3419: 3414: 3408: 3406: 3400: 3399: 3397: 3396: 3391: 3386: 3385: 3384: 3379: 3368: 3365: 3364: 3355: 3354: 3347: 3340: 3332: 3326: 3325: 3319: 3309: 3278: 3272: 3267: 3266: 3265: 3254: 3242: 3237: 3232: 3223: 3218: 3197: 3196:External links 3194: 3193: 3192: 3187:978-1107518438 3186: 3170: 3169: 3164: 3142: 3141: 3111: 3079: 3070: 3053: 3052: 3035:(4): 305ā€“318, 3018: 2970: 2961: 2948: 2923: 2908: 2895: 2878: 2873: 2853: 2850: 2847: 2846: 2828: 2823:Dembowski 1968 2815: 2807:axiom of Pasch 2794: 2782: 2762: 2750: 2738: 2719: 2712: 2691: 2690: 2688: 2685: 2684: 2683: 2678: 2673: 2668: 2663: 2658: 2653: 2648: 2646:Discrete space 2643: 2635: 2632: 2610: 2607: 2560: 2557: 2556: 2555: 2521: 2475: 2468: 2463: 2460: 2454:analogue of a 2444: 2443: 2432: 2426: 2423: 2418: 2415: 2412: 2408: 2402: 2399: 2394: 2391: 2388: 2385: 2382: 2378: 2369: 2364: 2361: 2358: 2354: 2350: 2345: 2338: 2332: 2329: 2326: 2321: 2318: 2315: 2309: 2200: 2197: 2196: 2195: 2184: 2181: 2178: 2173: 2169: 2165: 2162: 2159: 2154: 2150: 2146: 2141: 2138: 2134: 2130: 2127: 2079: 2078: 2025: 2024: 2021: 1988:'s axiom: If 1983: 1966:of subsets of 1948: 1945: 1924: 1921: 1864:mathematician 1846: 1843: 1816: 1815: 1756: 1753: 1750: 1700: 1699: 1674: 1671: 1577: 1576: 1573: 1570: 1561:of subsets of 1550: 1547: 1488: 1487: 1484: 1473: 1470: 1467: 1463: 1460: 1456: 1453: 1433: 1412: 1409: 1388: 1368: 1348: 1334: 1325:of subsets of 1314: 1311: 1270: 1267: 1234:linear algebra 1177: 1176: 1174: 1173: 1166: 1159: 1151: 1148: 1147: 1142: 1141: 1140: 1139: 1134: 1126: 1125: 1121: 1120: 1119: 1118: 1113: 1108: 1103: 1098: 1093: 1088: 1083: 1078: 1073: 1068: 1060: 1059: 1055: 1054: 1053: 1052: 1047: 1042: 1037: 1032: 1027: 1022: 1017: 1009: 1008: 1004: 1003: 1002: 1001: 996: 991: 986: 981: 976: 971: 966: 961: 956: 951: 946: 938: 937: 933: 932: 931: 930: 925: 920: 915: 910: 905: 900: 892: 891: 883: 879: 878: 877: 874: 873: 870: 869: 864: 859: 854: 849: 844: 839: 834: 829: 824: 819: 814: 809: 804: 799: 794: 789: 784: 779: 774: 769: 764: 759: 754: 749: 744: 739: 734: 729: 724: 719: 714: 709: 704: 699: 694: 689: 684: 679: 674: 669: 663: 659: 658: 657: 654: 653: 647: 646: 643: 642: 637: 631: 624: 623: 622: 619: 618: 615: 614: 609: 604: 602:Platonic Solid 599: 594: 589: 584: 579: 574: 573: 572: 561: 560: 554: 548: 547: 546: 543: 542: 537: 536: 535: 534: 529: 524: 516: 515: 509: 508: 507: 506: 501: 493: 492: 486: 485: 484: 483: 478: 473: 468: 460: 459: 453: 452: 451: 450: 445: 440: 432: 431: 425: 424: 423: 422: 417: 412: 402: 396: 395: 394: 391: 390: 387: 386: 381: 380: 379: 374: 363: 357: 356: 355: 352: 351: 348: 347: 341: 335: 334: 333: 330: 329: 326: 325: 320: 315: 309: 308: 303: 298: 288: 283: 278: 272: 271: 262: 258: 257: 254: 250: 249: 248: 247: 244: 243: 240: 239: 238: 237: 227: 222: 217: 212: 207: 206: 205: 195: 190: 185: 184: 183: 178: 173: 163: 162: 161: 156: 146: 141: 136: 131: 126: 121: 120: 119: 114: 113: 112: 97: 91: 85: 84: 83: 80: 79: 77: 76: 66: 60: 57: 56: 43: 35: 34: 15: 9: 6: 4: 3: 2: 3969: 3958: 3957:Combinatorics 3955: 3953: 3950: 3949: 3947: 3932: 3931: 3922: 3920: 3919: 3910: 3908: 3907: 3898: 3896: 3895: 3890: 3884: 3883: 3880: 3874: 3871: 3869: 3866: 3864: 3861: 3859: 3856: 3854: 3851: 3847: 3844: 3843: 3842: 3839: 3838: 3836: 3834: 3830: 3824: 3821: 3819: 3816: 3814: 3811: 3809: 3806: 3804: 3801: 3799: 3796: 3795: 3793: 3791: 3790:Computational 3787: 3779: 3776: 3774: 3771: 3769: 3766: 3765: 3764: 3761: 3759: 3756: 3754: 3751: 3749: 3746: 3744: 3741: 3739: 3736: 3734: 3731: 3729: 3726: 3724: 3721: 3719: 3716: 3714: 3711: 3709: 3706: 3705: 3703: 3701: 3697: 3691: 3688: 3686: 3683: 3681: 3678: 3676: 3673: 3671: 3668: 3667: 3665: 3663: 3659: 3653: 3650: 3648: 3645: 3643: 3640: 3638: 3635: 3634: 3632: 3630: 3629:Number theory 3626: 3620: 3617: 3615: 3612: 3610: 3607: 3605: 3602: 3600: 3597: 3595: 3592: 3590: 3587: 3586: 3584: 3582: 3578: 3572: 3569: 3567: 3564: 3562: 3561:Combinatorics 3559: 3558: 3556: 3554: 3550: 3544: 3541: 3539: 3536: 3534: 3531: 3529: 3526: 3524: 3521: 3519: 3516: 3514: 3513:Real analysis 3511: 3509: 3506: 3505: 3503: 3501: 3497: 3491: 3488: 3486: 3483: 3481: 3478: 3476: 3473: 3471: 3468: 3466: 3463: 3461: 3458: 3456: 3453: 3452: 3450: 3448: 3444: 3438: 3435: 3433: 3430: 3428: 3425: 3423: 3420: 3418: 3415: 3413: 3410: 3409: 3407: 3405: 3401: 3395: 3392: 3390: 3387: 3383: 3380: 3378: 3375: 3374: 3373: 3370: 3369: 3366: 3361: 3353: 3348: 3346: 3341: 3339: 3334: 3333: 3330: 3323: 3320: 3317: 3313: 3310: 3306: 3300: 3292: 3288: 3284: 3279: 3276: 3273: 3271: 3268: 3264: 3261: 3260: 3258: 3255: 3253: 3249: 3246: 3243: 3241: 3238: 3236: 3233: 3231: 3227: 3224: 3222: 3219: 3214: 3213: 3208: 3205: 3200: 3199: 3189: 3183: 3179: 3178: 3172: 3171: 3167: 3161: 3157: 3153: 3149: 3144: 3143: 3133:on 2015-03-30 3129: 3122: 3121: 3116: 3112: 3108: 3104: 3100: 3096: 3092: 3088: 3084: 3080: 3076: 3071: 3060: 3055: 3054: 3050: 3046: 3042: 3038: 3034: 3030: 3029: 3024: 3019: 3016: 3012: 3008: 3004: 3000: 2996: 2991: 2986: 2982: 2978: 2977: 2971: 2967: 2962: 2959: 2955: 2951: 2949:3-540-61786-8 2945: 2941: 2937: 2932: 2931: 2924: 2919: 2914: 2909: 2906: 2902: 2898: 2892: 2888: 2884: 2879: 2876: 2870: 2866: 2865: 2860: 2856: 2855: 2841: 2837: 2831: 2824: 2819: 2812: 2808: 2804: 2798: 2791: 2786: 2779: 2775: 2771: 2770:Oswald Veblen 2766: 2759: 2754: 2747: 2742: 2734: 2730: 2723: 2715: 2713:9780471240648 2709: 2705: 2704: 2696: 2692: 2682: 2679: 2677: 2674: 2672: 2669: 2667: 2664: 2662: 2659: 2657: 2654: 2652: 2649: 2647: 2644: 2641: 2638: 2637: 2631: 2628: 2624: 2620: 2616: 2606: 2604: 2599: 2592: 2588: 2586: 2582: 2578: 2574: 2565: 2553: 2549: 2543: 2539: 2531: 2526: 2522: 2519: 2515: 2509: 2503: 2497: 2493: 2487: 2481: 2476: 2473: 2469: 2466: 2465: 2459: 2457: 2453: 2449: 2430: 2424: 2421: 2416: 2413: 2410: 2406: 2400: 2397: 2392: 2389: 2386: 2383: 2380: 2376: 2367: 2362: 2359: 2356: 2352: 2348: 2343: 2330: 2327: 2324: 2319: 2316: 2313: 2296: 2295: 2294: 2290: 2286: 2280: 2275: 2273: 2269: 2263: 2259: 2251: 2245: 2241: 2237: 2233: 2229: 2225: 2221: 2215: 2210:construct an 2209: 2206: 2205:division ring 2182: 2179: 2176: 2171: 2167: 2163: 2160: 2157: 2152: 2148: 2144: 2139: 2136: 2132: 2128: 2125: 2118: 2117: 2116: 2114: 2110: 2105: 2103: 2099: 2095: 2091: 2086: 2084: 2076: 2072: 2071: 2070: 2068: 2063: 2061: 2058: 2054: 2050: 2044: 2040: 2036: 2031: 2022: 2019: 2015: 2011: 2007: 2003: 1999: 1995: 1991: 1987: 1984: 1981: 1977: 1973: 1972: 1971: 1969: 1965: 1961: 1957: 1954: 1944: 1938: 1934: 1930: 1920: 1918: 1914: 1910: 1906: 1902: 1898: 1894: 1890: 1886: 1882: 1881:Oswald Veblen 1877: 1875: 1873: 1867: 1863: 1858: 1856: 1852: 1842: 1839: 1837: 1833: 1823: 1813: 1809: 1805: 1799: 1791: 1785: 1781: 1777: 1776: 1775: 1773: 1768: 1754: 1751: 1748: 1739: 1735: 1730: 1727: 1724: 1720: 1716: 1712: 1708: 1703: 1698: 1695: 1694: 1693: 1691: 1687: 1683: 1680: 1670: 1665: 1661: 1657: 1653: 1649: 1644: 1642: 1638: 1634: 1631: +  1630: 1626: 1622: 1619: 1615: 1614: 1606: 1601: 1597: 1594: 1586: 1581: 1574: 1571: 1568: 1567: 1566: 1564: 1560: 1556: 1546: 1542: 1537: 1532: 1528: 1523: 1519: 1514: 1512: 1507: 1504: 1499: 1497: 1493: 1485: 1471: 1465: 1461: 1458: 1454: 1451: 1431: 1410: 1407: 1386: 1366: 1346: 1338: 1335: 1332: 1331: 1330: 1328: 1324: 1320: 1310: 1308: 1304: 1300: 1296: 1292: 1288: 1284: 1275: 1269:Finite planes 1266: 1264: 1259: 1255: 1251: 1247: 1243: 1239: 1238:vector spaces 1235: 1230: 1228: 1224: 1220: 1216: 1212: 1211:affine spaces 1208: 1204: 1200: 1196: 1192: 1188: 1184: 1172: 1167: 1165: 1160: 1158: 1153: 1152: 1150: 1149: 1138: 1135: 1133: 1130: 1129: 1128: 1127: 1123: 1122: 1117: 1114: 1112: 1109: 1107: 1104: 1102: 1099: 1097: 1094: 1092: 1089: 1087: 1084: 1082: 1079: 1077: 1074: 1072: 1069: 1067: 1064: 1063: 1062: 1061: 1057: 1056: 1051: 1048: 1046: 1043: 1041: 1038: 1036: 1033: 1031: 1028: 1026: 1023: 1021: 1018: 1016: 1013: 1012: 1011: 1010: 1006: 1005: 1000: 997: 995: 992: 990: 987: 985: 982: 980: 977: 975: 972: 970: 967: 965: 962: 960: 957: 955: 952: 950: 947: 945: 942: 941: 940: 939: 935: 934: 929: 926: 924: 921: 919: 916: 914: 911: 909: 906: 904: 901: 899: 896: 895: 894: 893: 890: 887: 886: 876: 875: 868: 865: 863: 860: 858: 855: 853: 850: 848: 845: 843: 840: 838: 835: 833: 830: 828: 825: 823: 820: 818: 815: 813: 810: 808: 805: 803: 800: 798: 795: 793: 790: 788: 785: 783: 780: 778: 775: 773: 770: 768: 765: 763: 760: 758: 755: 753: 750: 748: 745: 743: 740: 738: 735: 733: 730: 728: 725: 723: 720: 718: 715: 713: 710: 708: 705: 703: 700: 698: 695: 693: 690: 688: 685: 683: 680: 678: 675: 673: 670: 668: 665: 664: 656: 655: 652: 649: 648: 641: 638: 636: 633: 632: 627: 621: 620: 613: 610: 608: 605: 603: 600: 598: 595: 593: 590: 588: 585: 583: 580: 578: 575: 571: 568: 567: 566: 563: 562: 559: 556: 555: 551: 545: 544: 533: 530: 528: 527:Circumference 525: 523: 520: 519: 518: 517: 514: 511: 510: 505: 502: 500: 497: 496: 495: 494: 491: 490:Quadrilateral 488: 487: 482: 479: 477: 474: 472: 469: 467: 464: 463: 462: 461: 458: 457:Parallelogram 455: 454: 449: 446: 444: 441: 439: 436: 435: 434: 433: 430: 427: 426: 421: 418: 416: 413: 411: 408: 407: 406: 405: 399: 393: 392: 385: 382: 378: 375: 373: 370: 369: 368: 365: 364: 360: 354: 353: 346: 343: 342: 338: 332: 331: 324: 321: 319: 316: 314: 311: 310: 307: 304: 302: 299: 296: 295:Perpendicular 292: 291:Orthogonality 289: 287: 284: 282: 279: 277: 274: 273: 270: 267: 266: 265: 255: 252: 251: 246: 245: 236: 233: 232: 231: 228: 226: 223: 221: 218: 216: 215:Computational 213: 211: 208: 204: 201: 200: 199: 196: 194: 191: 189: 186: 182: 179: 177: 174: 172: 169: 168: 167: 164: 160: 157: 155: 152: 151: 150: 147: 145: 142: 140: 137: 135: 132: 130: 127: 125: 122: 118: 115: 111: 108: 107: 106: 103: 102: 101: 100:Non-Euclidean 98: 96: 93: 92: 88: 82: 81: 74: 70: 67: 65: 62: 61: 59: 58: 54: 50: 46: 41: 37: 36: 33: 30: 29: 21: 3928: 3916: 3904: 3885: 3818:Optimization 3680:Differential 3618: 3604:Differential 3571:Order theory 3566:Graph theory 3470:Group theory 3286: 3210: 3176: 3147: 3135:, retrieved 3128:the original 3119: 3093:(2): 38ā€“43. 3090: 3086: 3074: 3062:. Retrieved 3032: 3026: 2980: 2974: 2965: 2929: 2882: 2863: 2839: 2835: 2829: 2818: 2802: 2797: 2785: 2765: 2753: 2741: 2732: 2728: 2722: 2702: 2695: 2671:Near polygon 2651:Finite space 2640:Block design 2618: 2612: 2600: 2597: 2570: 2551: 2547: 2541: 2537: 2529: 2507: 2495: 2491: 2479: 2471: 2451: 2445: 2288: 2284: 2278: 2276: 2271: 2267: 2261: 2257: 2249: 2242:), since by 2239: 2236:finite field 2231: 2227: 2223: 2219: 2213: 2207: 2202: 2112: 2108: 2106: 2101: 2097: 2093: 2089: 2087: 2082: 2080: 2074: 2066: 2065:Obtaining a 2064: 2059: 2052: 2048: 2042: 2038: 2034: 2026: 2017: 2013: 2009: 2005: 2001: 1997: 1993: 1989: 1979: 1975: 1967: 1963: 1959: 1955: 1952: 1950: 1928: 1926: 1908: 1904: 1900: 1896: 1893:Galois field 1878: 1871: 1859: 1848: 1840: 1821: 1817: 1811: 1803: 1797: 1789: 1786:of the form 1779: 1769: 1737: 1733: 1721:raised to a 1719:prime number 1710: 1706: 1704: 1701: 1696: 1689: 1685: 1681: 1678: 1676: 1652:collineation 1645: 1640: 1636: 1632: 1628: 1624: 1620: 1617: 1611: 1609: 1590: 1562: 1558: 1554: 1552: 1540: 1535: 1530: 1526: 1521: 1517: 1515: 1508: 1502: 1500: 1491: 1489: 1359:and a point 1326: 1322: 1318: 1316: 1295:affine plane 1282: 1280: 1242:finite field 1231: 1182: 1180: 999:Parameshvara 812:Parameshvara 582:Dodecahedron 192: 166:Differential 24:"intersect". 3930:WikiProject 3773:Game theory 3753:Probability 3490:Homological 3480:Multilinear 3460:Commutative 3437:Type theory 3404:Foundations 3360:mathematics 3230:Terence Tao 2681:Polar space 2446:which is a 1870:projective 1715:prime power 1524:points and 1424:containing 1223:Benz planes 1124:Present day 1071:Lobachevsky 1058:1700sā€“1900s 1015:Jyeį¹£į¹­hadeva 1007:1400sā€“1700s 959:Brahmagupta 782:Lobachevsky 762:Jyeį¹£į¹­hadeva 712:Brahmagupta 640:Hypersphere 612:Tetrahedron 587:Icosahedron 159:Diophantine 3946:Categories 3758:Statistics 3637:Arithmetic 3599:Arithmetic 3465:Elementary 3432:Set theory 3137:2015-07-02 2874:0521590140 2852:References 2758:Malkevitch 2585:Fano plane 2581:isomorphic 2512:) satisfy 1855:von Staudt 1613:Fano plane 1605:Fano plane 1585:Fano plane 1444:such that 1291:projective 1258:isomorphic 1207:projective 1193:number of 984:al-Yasamin 928:Apollonius 923:Archimedes 913:Pythagoras 903:Baudhayana 857:al-Yasamin 807:Pythagoras 702:Baudhayana 692:Archimedes 687:Apollonius 592:Octahedron 443:Hypotenuse 318:Similarity 313:Congruence 225:Incidence 176:Symplectic 171:Riemannian 154:Arithmetic 129:Projective 117:Hyperbolic 45:Projecting 3685:Geometric 3675:Algebraic 3614:Euclidean 3589:Algebraic 3485:Universal 3212:MathWorld 3107:122352568 2999:0002-9947 2918:1311.7177 2792:, pp. 6ā€“7 2780:7: 241ā€“59 2735:: 106ā€“132 2627:partition 2603:Gino Fano 2601:In 1892, 2422:− 2398:− 2390:− 2353:∏ 2164:⊂ 2161:⋯ 2158:⊂ 2145:⊂ 2137:− 2126:∅ 1866:Gino Fano 1648:collinear 1469:∅ 1459:ℓ 1455:∩ 1452:ℓ 1408:ℓ 1387:ℓ 1347:ℓ 1187:geometric 1101:Minkowski 1020:Descartes 954:Aryabhata 949:Kātyāyana 880:by period 792:Minkowski 767:Kātyāyana 727:Descartes 672:Aryabhata 651:Geometers 635:Tesseract 499:Trapezoid 471:Rectangle 264:Dimension 149:Algebraic 139:Synthetic 110:Spherical 95:Euclidean 3906:Category 3662:Topology 3609:Discrete 3594:Analytic 3581:Geometry 3553:Discrete 3508:Calculus 3500:Analysis 3455:Abstract 3394:Glossary 3377:Timeline 3299:citation 3248:Archived 3117:(1960), 2861:(1997), 2634:See also 2619:packings 1899:). When 1879:In 1906 1857:(1856). 1836:Lam 1991 1729:exponent 1723:positive 1660:PSL(2,7) 1494:(either 1462:′ 1411:′ 1299:parallel 1293:. In an 1091:PoincarĆ© 1035:Minggatu 994:Yang Hui 964:Virasena 852:Yang Hui 847:Virasena 817:PoincarĆ© 797:Minggatu 577:Cylinder 522:Diameter 481:Rhomboid 438:Altitude 429:Triangle 323:Symmetry 301:Parallel 286:Diagonal 256:Features 253:Concepts 144:Analytic 105:Elliptic 87:Branches 73:Timeline 32:Geometry 3918:Commons 3700:Applied 3670:General 3447:Algebra 3372:History 3314:at the 3049:2323798 3015:0008892 3007:1990331 2958:0233275 2905:1629468 2772:(1906) 2583:to the 2577:PG(3,2) 2500:. 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Index


Geometry
Stereographic projection from the top of a sphere onto a plane beneath it
Projecting
sphere
plane
Outline
History
Timeline
Branches
Euclidean
Non-Euclidean
Elliptic
Spherical
Hyperbolic
Non-Archimedean geometry
Projective
Affine
Synthetic
Analytic
Algebraic
Arithmetic
Diophantine
Differential
Riemannian
Symplectic
Discrete differential
Complex
Finite
Discrete/Combinatorial

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