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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.
2757:. 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 4140: 1064: 3922: 804: 121: 4421:{\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}}} 317: 3507: 1587: 1363: 1188: 1355: 1347: 3917:{\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}}} 4951: 1577:
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
1638:(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 1101:
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
4445:. It was subspaces and subgroups of this space and group of mappings that were applied to produce early models of hyperbolic geometry by 1703: 5847: 1523:. A circle, that is, the intersection of a sphere with a secant plane, inverts into a circle, except that if the circle passes through 6099: 6074: 6051: 6033: 1965: 85: 5017:, and in fact, where the space has three or more dimensions, the mappings generated by inversion are the only conformal mappings. 5071:
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.
3185:{\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}}}} 5064: 1170: 6060: 6132: 5747: 1850:, green in the picture), then it will be mapped by the inversion at the unit sphere (red) onto the tangent plane at point 4008: 2172: 5571:{\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.} 2459:{\displaystyle x\mapsto R^{2}{\frac {x}{|x|^{2}}}=y\mapsto T^{2}{\frac {y}{|y|^{2}}}=\left({\frac {T}{R}}\right)^{2}x.} 6214: 5252:. The complex analytic inverse map is conformal and its conjugate, circle inversion, is anticonformal. In this case a 1077:
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
4058:{\textstyle {\frac {r}{\left|a^{*}a-r^{2}\right|}}} 2749:Reciprocation is key in transformation theory as a 1897:. The lines through the center of inversion (point 5713: 5570: 5397: 5154: 5109: 4945: 4685: 4657: 4628: 4564: 4420: 4126: 4106: 4057: 3997: 3939: 3916: 3493: 3473: 3430: 3400: 3349: 3318: 3256: 3207: 3184: 2978: 2955: 2912: 2878: 2809: 2789: 2737: 2666: 2637: 2557: 2507: 2458: 2269:{\displaystyle I={\frac {|x-y||w-z|}{|x-w||y-z|}}} 2268: 2158: 2107: 2087: 2060: 2033: 1909: 1889: 1842: 1822: 1781: 1692: 1630: 1610: 1503: 1128:of the intouch triangle is inverted into triangle 1010: 231: 5911:Transactions of the American Mathematical Society 1956:of inversive geometry has been interpreted as an 1266:Poles and polars have several useful properties: 830:, and vice versa; whereas a line passing through 5816: 5124: 4999:of each reflection and thus of the composition. 620:There is a construction of the inverse point to 280:(i.e. an involution). To make the inversion a 5866: 5864: 2474:When a point in the plane is interpreted as a 1374:in three dimensions. The inversion of a point 1223:that is perpendicular to the line containing 1072:click or hover over a circle to highlight it. 8: 4778: 4765: 4405: 4399: 4375: 4369: 4354: 4348: 4337: 4331: 4316: 4310: 4277: 4271: 4262: 4256: 4244: 4238: 4229: 4223: 4205: 4196: 892:, does so at inverse points with respect to 1358:Inversion of a spheroid (at the red sphere) 655:which may lie inside or outside the circle 232:{\displaystyle OP\cdot OP^{\prime }=r^{2}.} 5264:Inversive geometry and hyperbolic geometry 2765:of the whole plane and so are necessarily 1024:The points of intersection of two circles 6199:Visual Dictionary of Special Plane Curves 5931: 5783:Inversion of curves and surfaces (German) 5690: 5680: 5658: 5648: 5632: 5627: 5608: 5603: 5597: 5552: 5543: 5528: 5522: 5504: 5489: 5483: 5471: 5466: 5447: 5442: 5436: 5377: 5367: 5345: 5335: 5319: 5314: 5295: 5290: 5284: 5142: 5122: 5092: 5080: 4927: 4917: 4904: 4891: 4876: 4863: 4850: 4843: 4834: 4818: 4801: 4781: 4742: 4735: 4704: 4702: 4677: 4671: 4644: 4617: 4592: 4577: 4553: 4528: 4513: 4381: 4322: 4300: 4283: 4172: 4162: 4144: 4142: 4119: 4095: 4079: 4073: 4042: 4026: 4012: 4010: 3983: 3970: 3954: 3952: 3932: 3904: 3887: 3874: 3857: 3835: 3819: 3809: 3800: 3777: 3764: 3750: 3744: 3729: 3713: 3703: 3690: 3673: 3667: 3655: 3645: 3632: 3614: 3604: 3589: 3573: 3558: 3548: 3532: 3523: 3511: 3509: 3486: 3465: 3452: 3443: 3424: 3423: 3415: 3383: 3374: 3362: 3333: 3305: 3299: 3286: 3277: 3271: 3269: 3245: 3232: 3222: 3220: 3200: 3173: 3163: 3150: 3136: 3130: 3118: 3108: 3095: 3081: 3075: 3063: 3038: 3025: 3012: 3003: 2994: 2971: 2945: 2936: 2928: 2903: 2902: 2894: 2870: 2857: 2824: 2802: 2782: 2716: 2710: 2695: 2690: 2682: 2653: 2623: 2618: 2609: 2598: 2596: 2583: 2581: 2526: 2525: 2523: 2482: 2444: 2430: 2413: 2408: 2399: 2393: 2387: 2365: 2360: 2351: 2345: 2339: 2327: 2258: 2244: 2239: 2225: 2218: 2204: 2199: 2185: 2182: 2174: 2147: 2137: 2125: 2120: 2100: 2079: 2073: 2052: 2046: 2008: 1902: 1855: 1835: 1794: 1767: 1758: 1742: 1724: 1711: 1705: 1675: 1662: 1649: 1643: 1623: 1603: 1495: 1483: 1478: 1472: 1460: 1455: 1447: 1442: 1431: 1426: 1417: 1399: 960: 918: 542:. (Not labeled, it's the horizontal line) 220: 207: 189: 92: 27:Study of angle-preserving transformations 6169:Wilson Stother's inversive geometry page 5983:Joel C. Gibbons & Yushen Luo (2013) 4979:. When two hyperplanes intersect in an ( 3998:{\textstyle {\frac {a}{(aa^{*}-r^{2})}}} 3401:{\displaystyle w+w^{*}={\tfrac {1}{a}}.} 3319:{\textstyle {\frac {r}{|a^{2}-r^{2}|}}.} 1598:usually projects a sphere from a point 1585: 1361: 1353: 1345: 841:inverts to a circle not passing through 818:A circle that passes through the center 93:generalized to higher-dimensional spaces 6069:(2nd ed.), John Wiley & Sons, 5954: 5794: 1366:Inversion of a hyperboloid of one sheet 1350:Inversion of a sphere at the red sphere 755: 560:. (Not labeled. It's the vertical line) 6026:Inversion Theory and Conformal Mapping 5589: − 1)-spheres with equation 4465:in their plane geometry. Furthermore, 3431:{\displaystyle a\not \in \mathbb {R} } 1151:(usually denoted δ) is defined as the 5898:49:49–96 & 50:106–140 5155:{\displaystyle \det(J)=-{\sqrt {k}}.} 4636:found by inverting the length of the 3257:{\textstyle {\frac {a}{a^{2}-r^{2}}}} 2292:soon appreciates the significance of 1370:Circle inversion is generalizable to 1212: 793:(blue) is a circle not going through 443:. (Not labeled. It's the blue circle) 312:Compass and straightedge construction 7: 5896:Giornal di Matematiche di Battaglini 5839: 5837: 5428:, and on inversion gives the sphere 2956:{\displaystyle w={\frac {1}{z^{*}}}} 2879:{\displaystyle (z-a)(z-a)^{*}=r^{2}} 2300:, an outgrowth of certain models of 1693:{\displaystyle x^{2}+y^{2}+z^{2}=-z} 5882: 5870: 5828: 5162:Computing the Jacobian in the case 4987:, successive reflections produce a 4956:The transformation by inversion in 4629:{\displaystyle P=(p_{1},...,p_{n})} 4565:{\displaystyle O=(o_{1},...,o_{n})} 2966:it is straightforward to show that 1199:with respect to a circle of radius 769:(blue) is a line not going through 2920:Using the definition of inversion 2913:{\displaystyle a\in \mathbb {R} .} 2889:where without loss of generality, 1519:, inverts to a sphere touching at 983: 968: 935: 920: 250:. The inversion taking any point 25: 6174:IMO Compendium Training Materials 6160:Inversion: Reflection in a Circle 6028:, American Mathematical Society, 6004:Altshiller-Court, Nathan (1952), 5924:10.1090/S0002-9947-1900-1500550-1 4500:-dimensional Euclidean space, an 2773:Transforming circles into circles 1330:lies on its own polar line, then 1255:through one of the points is the 288:, it is necessary to introduce a 4972:about the hyperspheres' center. 4107:{\displaystyle a^{*}a\to r^{2},} 3474:{\displaystyle aa^{*}\neq r^{2}} 2558:{\displaystyle {\bar {z}}=x-iy,} 1219:; the polar is the line through 802: 778: 758: 91:The concept of inversion can be 5408:will have a positive radius if 5110:{\displaystyle J\cdot J^{T}=kI} 4572:is a map of an arbitrary point 3947:describes the circle of center 3215:describes the circle of center 1337:Each line has exactly one pole. 1036:, are inverses with respect to 853:Additional properties include: 6130:(1941) "The Inversive Plane", 5989:-sphere and inversive geometry 5133: 5127: 5051:Anticonformal mapping property 4924: 4897: 4882: 4856: 4811: 4760: 4748: 4715: 4623: 4585: 4559: 4521: 4297: 4214: 4184: 4088: 3989: 3960: 3726: 3710: 3680: 3652: 3622: 3595: 3566: 3338: 3306: 3278: 3170: 3143: 3115: 3088: 3069: 3050: 3044: 3018: 2854: 2841: 2838: 2826: 2700: 2658: 2619: 2610: 2603: 2531: 2409: 2400: 2380: 2361: 2352: 2332: 2259: 2245: 2240: 2226: 2219: 2205: 2200: 2186: 2159:{\displaystyle d/(r_{1}r_{2})} 2153: 2130: 1884: 1863: 1817: 1796: 1755: 1733: 1484: 1479: 1461: 1456: 1448: 1443: 1432: 1427: 1: 6133:American Mathematical Monthly 5748:Duality (projective geometry) 1937:Axiomatics and generalization 1083:Inversion of a parabola is a 837:A circle not passing through 2730: 2280:Relation to Erlangen program 1539:Examples in three dimensions 1390:' on the ray with direction 1089:Inversion of hyperbola is a 663:Take the intersection point 615: 296:and this point at infinity. 6092:Geometry: Euclid and Beyond 5803:Curves and Their Properties 1116:Invert with respect to the 567:be one of the points where 134:with respect to the circle. 111:with different translations 6231: 6114:Holt, Rinehart and Winston 6008:(2nd ed.), New York: 5966:A.S. Smogorzhevsky (1982) 5933:2027/miun.abv0510.0001.001 5021:is a classical theorem of 4991:where every point of the ( 2667:{\displaystyle z\mapsto w} 1890:{\displaystyle S=(0,0,-1)} 1823:{\displaystyle (0,0,-0.5)} 1180: 1171:Peaucellier–Lipkin linkage 1059:Examples in two dimensions 51:, a transformation of the 29: 5758:Limiting point (geometry) 2317:homothetic transformation 709:be the reflection of ray 624:with respect to a circle 504:To construct the inverse 320:To construct the inverse 284:that is also defined for 6066:Introduction to Geometry 6024:Blair, David E. (2000), 5743:Circle of antisimilitude 5729:of hyperbolic geometry. 1596:stereographic projection 1573:Hyperboloid of one sheet 1259:of the other point (the 1243:is the inverse of point 1164:circle of antisimilitude 797:(green), and vice versa. 773:(green), and vice versa. 739:is the inverse point of 682:with an arbitrary point 173:, lying on the ray from 5778:Mohr-Mascheroni theorem 5237:, and additionally det( 4502:inversion in the sphere 4439:complex projective line 3350:{\displaystyle a\to r,} 2508:{\displaystyle z=x+iy,} 2290:transformation geometry 2034:{\displaystyle x,y,z,w} 1968:together with a single 1309:rotates about the pole 1091:lemniscate of Bernoulli 1032:orthogonal to a circle 743:with respect to circle 6108:Kay, David C. (1969), 5968:Lobachevskian Geometry 5843:Dutta, Surajit (2014) 5817:Altshiller-Court (1952 5715: 5572: 5399: 5274: − 1)-sphere 5256:is conformal while an 5156: 5111: 5075:is the Jacobian, then 5041:Möbius transformations 4947: 4687: 4659: 4630: 4566: 4508:centered at the point 4422: 4128: 4108: 4059: 3999: 3941: 3918: 3495: 3475: 3432: 3402: 3351: 3320: 3258: 3209: 3186: 2980: 2957: 2914: 2880: 2811: 2791: 2739: 2668: 2639: 2559: 2509: 2460: 2270: 2160: 2109: 2089: 2062: 2035: 1954:mathematical structure 1911: 1891: 1844: 1824: 1783: 1694: 1632: 1612: 1591: 1505: 1367: 1359: 1351: 1236: 1203:centered on the point 1073: 1012: 694:and from the point on 405:Draw the segment from 374: 233: 135: 112: 99:Inversion in a circle 5763:Möbius transformation 5716: 5573: 5400: 5157: 5112: 5067:is a scalar times an 4948: 4688: 4686:{\displaystyle r^{2}} 4660: 4631: 4567: 4423: 4129: 4109: 4060: 4000: 3942: 3919: 3496: 3476: 3433: 3403: 3352: 3321: 3259: 3210: 3187: 2981: 2958: 2915: 2881: 2812: 2792: 2740: 2669: 2640: 2560: 2510: 2461: 2271: 2161: 2110: 2090: 2088:{\displaystyle r_{2}} 2063: 2061:{\displaystyle r_{1}} 2036: 1931:Cartesian coordinates 1912: 1892: 1845: 1825: 1784: 1700:(alternately written 1695: 1633: 1613: 1589: 1553:Cylinder, cone, torus 1506: 1365: 1357: 1349: 1190: 1066: 1013: 636:is inside or outside 319: 234: 123: 106: 18:Inversion in a circle 5596: 5435: 5283: 5121: 5079: 4701: 4670: 4643: 4576: 4512: 4492:In higher dimensions 4141: 4118: 4072: 4009: 3951: 3931: 3508: 3485: 3442: 3414: 3361: 3332: 3268: 3219: 3199: 2993: 2970: 2927: 2893: 2823: 2801: 2781: 2681: 2652: 2580: 2522: 2481: 2326: 2173: 2119: 2099: 2072: 2045: 2007: 1927:6-sphere coordinates 1921:6-sphere coordinates 1901: 1854: 1834: 1793: 1704: 1642: 1622: 1602: 1398: 917: 616:Dutta's construction 457:be the points where 378:Point outside circle 188: 156:reference circle (Ø) 107:Inversion of lambda 30:For other uses, see 5856:Forum Geometricorum 5768:Projective geometry 5727:Poincaré disc model 5637: 5613: 5476: 5452: 5324: 5300: 5019:Liouville's theorem 4826: 4665:and multiplying by 4658:{\displaystyle P-O} 4638:displacement vector 4441:, often called the 2986:obeys the equation 2302:hyperbolic geometry 1976:, also known as an 1958:incidence structure 1843:{\displaystyle 0.5} 1342:In three dimensions 1301:moves along a line 865:, then the circles 500:Point inside circle 424:be the midpoint of 6215:Inversive geometry 6182:Weisstein, Eric W. 6010:Barnes & Noble 5850:2018-04-21 at the 5711: 5623: 5599: 5568: 5462: 5438: 5395: 5310: 5286: 5260:is anticonformal. 5152: 5107: 5028:The addition of a 5023:conformal geometry 4943: 4941: 4896: 4814: 4683: 4655: 4626: 4562: 4418: 4416: 4124: 4104: 4055: 3995: 3937: 3914: 3912: 3491: 3471: 3428: 3398: 3393: 3347: 3316: 3254: 3205: 3182: 2976: 2953: 2910: 2876: 2807: 2787: 2763:analytic functions 2735: 2664: 2635: 2555: 2505: 2456: 2266: 2156: 2105: 2085: 2058: 2031: 1962:incidence geometry 1952:More recently the 1945:in 1911 and 1912. 1907: 1887: 1840: 1820: 1779: 1777: 1752: 1690: 1628: 1608: 1592: 1501: 1368: 1360: 1352: 1286:lies on the polar 1237: 1149:inversive distance 1147:circles. Then the 1074: 1008: 678:Connect the point 643:Consider a circle 531:(center of circle 409:(center of circle 375: 343:. Right triangles 229: 154:with respect to a 136: 130:is the inverse of 116:Inverse of a point 113: 43:inversive geometry 6084:Hartshorne, Robin 5985:Colorings of the 5560: 5537: 5498: 5147: 5069:orthogonal matrix 5030:point at infinity 5013:All of these are 4934: 4887: 4788: 4409: 4358: 4291: 4127:{\displaystyle w} 4114:the equation for 4053: 3993: 3940:{\displaystyle w} 3927:showing that the 3898: 3842: 3784: 3720: 3662: 3599: 3494:{\displaystyle w} 3392: 3311: 3252: 3208:{\displaystyle w} 3180: 3125: 3048: 2979:{\displaystyle w} 2951: 2810:{\displaystyle a} 2797:around the point 2790:{\displaystyle r} 2733: 2724: 2705: 2703: 2630: 2606: 2591: 2534: 2517:complex conjugate 2438: 2420: 2372: 2264: 2108:{\displaystyle d} 2003:between 4 points 1970:point at infinity 1910:{\displaystyle N} 1776: 1751: 1631:{\displaystyle S} 1611:{\displaystyle N} 1334:is on the circle. 1153:natural logarithm 967: 963: 959: 888:and intersecting 593:perpendicular to 578:Draw the segment 556:perpendicular to 397:outside a circle 339:be the radius of 331:outside a circle 301:point at infinity 290:point at infinity 16:(Redirected from 6222: 6195: 6194: 6124: 6110:College Geometry 6104: 6079: 6056: 6038: 6020: 5991: 5981: 5975: 5964: 5958: 5957:, pp. 77–95 5952: 5946: 5945: 5935: 5905: 5899: 5892: 5886: 5880: 5874: 5868: 5859: 5841: 5832: 5826: 5820: 5814: 5808: 5799: 5720: 5718: 5717: 5712: 5695: 5694: 5685: 5684: 5663: 5662: 5653: 5652: 5636: 5631: 5612: 5607: 5577: 5575: 5574: 5569: 5561: 5553: 5548: 5547: 5538: 5533: 5532: 5523: 5509: 5508: 5499: 5494: 5493: 5484: 5475: 5470: 5451: 5446: 5424:is greater than 5404: 5402: 5401: 5396: 5382: 5381: 5372: 5371: 5350: 5349: 5340: 5339: 5323: 5318: 5299: 5294: 5236: 5234: 5223: 5213: 5196: 5188: 5186: 5161: 5159: 5158: 5153: 5148: 5143: 5116: 5114: 5113: 5108: 5097: 5096: 5059:if it preserves 4952: 4950: 4949: 4944: 4942: 4935: 4933: 4932: 4931: 4922: 4921: 4909: 4908: 4895: 4885: 4881: 4880: 4868: 4867: 4855: 4854: 4844: 4839: 4838: 4822: 4806: 4805: 4789: 4787: 4786: 4785: 4763: 4747: 4746: 4736: 4725: 4694: 4692: 4690: 4689: 4684: 4682: 4681: 4664: 4662: 4661: 4656: 4635: 4633: 4632: 4627: 4622: 4621: 4597: 4596: 4571: 4569: 4568: 4563: 4558: 4557: 4533: 4532: 4507: 4481:together with a 4471:Erlangen program 4427: 4425: 4424: 4419: 4417: 4410: 4408: 4382: 4359: 4357: 4340: 4323: 4301: 4292: 4284: 4177: 4176: 4167: 4166: 4147: 4133: 4131: 4130: 4125: 4113: 4111: 4110: 4105: 4100: 4099: 4084: 4083: 4064: 4062: 4061: 4056: 4054: 4052: 4048: 4047: 4046: 4031: 4030: 4013: 4004: 4002: 4001: 3996: 3994: 3992: 3988: 3987: 3975: 3974: 3955: 3946: 3944: 3943: 3938: 3923: 3921: 3920: 3915: 3913: 3909: 3908: 3903: 3899: 3897: 3893: 3892: 3891: 3879: 3878: 3858: 3848: 3844: 3843: 3841: 3840: 3839: 3824: 3823: 3810: 3805: 3804: 3790: 3786: 3785: 3783: 3782: 3781: 3769: 3768: 3755: 3754: 3745: 3730: 3721: 3719: 3718: 3717: 3708: 3707: 3695: 3694: 3678: 3677: 3668: 3663: 3661: 3660: 3659: 3650: 3649: 3637: 3636: 3620: 3619: 3618: 3605: 3600: 3598: 3594: 3593: 3578: 3577: 3564: 3563: 3562: 3553: 3552: 3533: 3528: 3527: 3514: 3500: 3498: 3497: 3492: 3480: 3478: 3477: 3472: 3470: 3469: 3457: 3456: 3437: 3435: 3434: 3429: 3427: 3407: 3405: 3404: 3399: 3394: 3385: 3379: 3378: 3356: 3354: 3353: 3348: 3325: 3323: 3322: 3317: 3312: 3310: 3309: 3304: 3303: 3291: 3290: 3281: 3272: 3263: 3261: 3260: 3255: 3253: 3251: 3250: 3249: 3237: 3236: 3223: 3214: 3212: 3211: 3206: 3191: 3189: 3188: 3183: 3181: 3179: 3178: 3177: 3168: 3167: 3155: 3154: 3141: 3140: 3131: 3126: 3124: 3123: 3122: 3113: 3112: 3100: 3099: 3086: 3085: 3076: 3068: 3067: 3049: 3047: 3043: 3042: 3030: 3029: 3013: 3008: 3007: 2985: 2983: 2982: 2977: 2962: 2960: 2959: 2954: 2952: 2950: 2949: 2937: 2919: 2917: 2916: 2911: 2906: 2885: 2883: 2882: 2877: 2875: 2874: 2862: 2861: 2816: 2814: 2813: 2808: 2796: 2794: 2793: 2788: 2744: 2742: 2741: 2736: 2734: 2729: 2725: 2717: 2711: 2706: 2704: 2696: 2691: 2673: 2671: 2670: 2665: 2644: 2642: 2641: 2636: 2631: 2629: 2628: 2627: 2622: 2613: 2607: 2599: 2597: 2592: 2584: 2564: 2562: 2561: 2556: 2536: 2535: 2527: 2514: 2512: 2511: 2506: 2465: 2463: 2462: 2457: 2449: 2448: 2443: 2439: 2431: 2421: 2419: 2418: 2417: 2412: 2403: 2394: 2392: 2391: 2373: 2371: 2370: 2369: 2364: 2355: 2346: 2344: 2343: 2298:Erlangen program 2275: 2273: 2272: 2267: 2265: 2263: 2262: 2248: 2243: 2229: 2223: 2222: 2208: 2203: 2189: 2183: 2165: 2163: 2162: 2157: 2152: 2151: 2142: 2141: 2129: 2114: 2112: 2111: 2106: 2094: 2092: 2091: 2086: 2084: 2083: 2067: 2065: 2064: 2059: 2057: 2056: 2040: 2038: 2037: 2032: 1916: 1914: 1913: 1908: 1896: 1894: 1893: 1888: 1849: 1847: 1846: 1841: 1829: 1827: 1826: 1821: 1788: 1786: 1785: 1780: 1778: 1769: 1763: 1762: 1753: 1744: 1729: 1728: 1716: 1715: 1699: 1697: 1696: 1691: 1680: 1679: 1667: 1666: 1654: 1653: 1637: 1635: 1634: 1629: 1617: 1615: 1614: 1609: 1510: 1508: 1507: 1502: 1500: 1499: 1487: 1482: 1477: 1476: 1464: 1459: 1451: 1446: 1435: 1430: 1422: 1421: 1372:sphere inversion 1278:, then the pole 1111:intouch triangle 1017: 1015: 1014: 1009: 1004: 996: 965: 964: 961: 957: 956: 948: 806: 782: 762: 737: 730: 690:(different from 671:with the circle 554: 540: 515:inside a circle 513: 493: 482: 473: 455: 431:Draw the circle 391: 371: 352: 325: 271: 264: 244:circle inversion 238: 236: 235: 230: 225: 224: 212: 211: 172: 129: 45:is the study of 32:Point reflection 21: 6230: 6229: 6225: 6224: 6223: 6221: 6220: 6219: 6205: 6204: 6180: 6179: 6156: 6142:10.2307/2303867 6128:Patterson, Boyd 6107: 6102: 6082: 6077: 6061:Coxeter, H.S.M. 6059: 6054: 6041: 6036: 6023: 6003: 6000: 5995: 5994: 5982: 5978: 5965: 5961: 5953: 5949: 5907: 5906: 5902: 5893: 5889: 5881: 5877: 5869: 5862: 5852:Wayback Machine 5842: 5835: 5827: 5823: 5815: 5811: 5800: 5796: 5791: 5739: 5686: 5676: 5654: 5644: 5594: 5593: 5539: 5524: 5500: 5485: 5433: 5432: 5423: 5414: 5373: 5363: 5341: 5331: 5281: 5280: 5266: 5258:anti-homography 5230: 5225: 5215: 5212: 5203: 5192: 5190: 5182: 5180: 5171: 5163: 5119: 5118: 5088: 5077: 5076: 5053: 4940: 4939: 4923: 4913: 4900: 4886: 4872: 4859: 4846: 4845: 4830: 4807: 4797: 4794: 4793: 4777: 4764: 4738: 4737: 4718: 4711: 4699: 4698: 4673: 4668: 4667: 4666: 4641: 4640: 4613: 4588: 4574: 4573: 4549: 4524: 4510: 4509: 4505: 4494: 4434: 4432:Higher geometry 4415: 4414: 4386: 4341: 4324: 4302: 4294: 4293: 4168: 4158: 4139: 4138: 4116: 4115: 4091: 4075: 4070: 4069: 4038: 4022: 4021: 4017: 4007: 4006: 3979: 3966: 3959: 3949: 3948: 3929: 3928: 3911: 3910: 3883: 3870: 3866: 3862: 3853: 3852: 3831: 3815: 3814: 3796: 3795: 3791: 3773: 3760: 3756: 3746: 3737: 3733: 3731: 3723: 3722: 3709: 3699: 3686: 3679: 3669: 3651: 3641: 3628: 3621: 3610: 3606: 3585: 3569: 3565: 3554: 3544: 3534: 3519: 3506: 3505: 3483: 3482: 3481:the result for 3461: 3448: 3440: 3439: 3412: 3411: 3370: 3359: 3358: 3330: 3329: 3295: 3282: 3276: 3266: 3265: 3241: 3228: 3227: 3217: 3216: 3197: 3196: 3195:and hence that 3169: 3159: 3146: 3142: 3132: 3114: 3104: 3091: 3087: 3077: 3059: 3034: 3021: 3017: 2999: 2991: 2990: 2968: 2967: 2941: 2925: 2924: 2891: 2890: 2866: 2853: 2821: 2820: 2799: 2798: 2779: 2778: 2775: 2712: 2679: 2678: 2650: 2649: 2617: 2608: 2578: 2577: 2520: 2519: 2479: 2478: 2472: 2426: 2425: 2407: 2398: 2383: 2359: 2350: 2335: 2324: 2323: 2309: 2282: 2224: 2184: 2171: 2170: 2143: 2133: 2117: 2116: 2097: 2096: 2075: 2070: 2069: 2048: 2043: 2042: 2005: 2004: 1997: 1978:inversive plane 1939: 1923: 1899: 1898: 1852: 1851: 1832: 1831: 1791: 1790: 1754: 1720: 1707: 1702: 1701: 1671: 1658: 1645: 1640: 1639: 1620: 1619: 1600: 1599: 1584: 1575: 1567: 1555: 1546: 1541: 1491: 1468: 1413: 1396: 1395: 1344: 1274:lies on a line 1247:then the lines 1213:inversion point 1191:The polar line 1185: 1179: 1126:medial triangle 1099: 1061: 997: 989: 962: and  949: 941: 915: 914: 876:If the circles 873:are orthogonal. 810: 807: 798: 783: 774: 763: 754: 735: 728: 618: 552: 538: 511: 502: 491: 480: 471: 453: 389: 380: 369: 350: 323: 314: 269: 262: 258:) to its image 248:plane inversion 242:This is called 216: 203: 186: 185: 170: 127: 118: 101: 53:Euclidean plane 35: 28: 23: 22: 15: 12: 11: 5: 6228: 6226: 6218: 6217: 6207: 6206: 6203: 6202: 6196: 6177: 6171: 6166: 6155: 6154:External links 6152: 6151: 6150: 6125: 6105: 6100: 6080: 6075: 6057: 6052: 6039: 6034: 6021: 5999: 5996: 5993: 5992: 5976: 5972:Mir Publishers 5959: 5947: 5918:(4): 430–498. 5900: 5887: 5885:, p. 269) 5875: 5873:, p. 265) 5860: 5833: 5831:, p. 264) 5821: 5819:, p. 230) 5809: 5793: 5792: 5790: 5787: 5786: 5785: 5780: 5775: 5773:Soddy's hexlet 5770: 5765: 5760: 5755: 5750: 5745: 5738: 5735: 5722: 5721: 5710: 5707: 5704: 5701: 5698: 5693: 5689: 5683: 5679: 5675: 5672: 5669: 5666: 5661: 5657: 5651: 5647: 5643: 5640: 5635: 5630: 5626: 5622: 5619: 5616: 5611: 5606: 5602: 5579: 5578: 5567: 5564: 5559: 5556: 5551: 5546: 5542: 5536: 5531: 5527: 5521: 5518: 5515: 5512: 5507: 5503: 5497: 5492: 5488: 5482: 5479: 5474: 5469: 5465: 5461: 5458: 5455: 5450: 5445: 5441: 5419: 5412: 5406: 5405: 5394: 5391: 5388: 5385: 5380: 5376: 5370: 5366: 5362: 5359: 5356: 5353: 5348: 5344: 5338: 5334: 5330: 5327: 5322: 5317: 5313: 5309: 5306: 5303: 5298: 5293: 5289: 5276:with equation 5265: 5262: 5208: 5201: 5176: 5167: 5151: 5146: 5141: 5138: 5135: 5132: 5129: 5126: 5106: 5103: 5100: 5095: 5091: 5087: 5084: 5052: 5049: 5015:conformal maps 4995:–2)-flat is a 4954: 4953: 4938: 4930: 4926: 4920: 4916: 4912: 4907: 4903: 4899: 4894: 4890: 4884: 4879: 4875: 4871: 4866: 4862: 4858: 4853: 4849: 4842: 4837: 4833: 4829: 4825: 4821: 4817: 4813: 4810: 4808: 4804: 4800: 4796: 4795: 4792: 4784: 4780: 4776: 4773: 4770: 4767: 4762: 4759: 4756: 4753: 4750: 4745: 4741: 4734: 4731: 4728: 4724: 4721: 4717: 4714: 4712: 4710: 4707: 4706: 4680: 4676: 4654: 4651: 4648: 4625: 4620: 4616: 4612: 4609: 4606: 4603: 4600: 4595: 4591: 4587: 4584: 4581: 4561: 4556: 4552: 4548: 4545: 4542: 4539: 4536: 4531: 4527: 4523: 4520: 4517: 4493: 4490: 4443:Riemann sphere 4433: 4430: 4429: 4428: 4413: 4407: 4404: 4401: 4398: 4395: 4392: 4389: 4385: 4380: 4377: 4374: 4371: 4368: 4365: 4362: 4356: 4353: 4350: 4347: 4344: 4339: 4336: 4333: 4330: 4327: 4321: 4318: 4315: 4312: 4309: 4306: 4303: 4299: 4296: 4295: 4290: 4287: 4282: 4279: 4276: 4273: 4270: 4267: 4264: 4261: 4258: 4255: 4252: 4249: 4246: 4243: 4240: 4237: 4234: 4231: 4228: 4225: 4222: 4219: 4216: 4213: 4210: 4207: 4204: 4201: 4198: 4195: 4192: 4189: 4186: 4183: 4180: 4175: 4171: 4165: 4161: 4157: 4154: 4151: 4148: 4146: 4123: 4103: 4098: 4094: 4090: 4087: 4082: 4078: 4051: 4045: 4041: 4037: 4034: 4029: 4025: 4020: 4016: 3991: 3986: 3982: 3978: 3973: 3969: 3965: 3962: 3958: 3936: 3925: 3924: 3907: 3902: 3896: 3890: 3886: 3882: 3877: 3873: 3869: 3865: 3861: 3856: 3851: 3847: 3838: 3834: 3830: 3827: 3822: 3818: 3813: 3808: 3803: 3799: 3794: 3789: 3780: 3776: 3772: 3767: 3763: 3759: 3753: 3749: 3743: 3740: 3736: 3732: 3728: 3725: 3724: 3716: 3712: 3706: 3702: 3698: 3693: 3689: 3685: 3682: 3676: 3672: 3666: 3658: 3654: 3648: 3644: 3640: 3635: 3631: 3627: 3624: 3617: 3613: 3609: 3603: 3597: 3592: 3588: 3584: 3581: 3576: 3572: 3568: 3561: 3557: 3551: 3547: 3543: 3540: 3537: 3531: 3526: 3522: 3518: 3515: 3513: 3490: 3468: 3464: 3460: 3455: 3451: 3447: 3426: 3422: 3419: 3397: 3391: 3388: 3382: 3377: 3373: 3369: 3366: 3346: 3343: 3340: 3337: 3315: 3308: 3302: 3298: 3294: 3289: 3285: 3280: 3275: 3248: 3244: 3240: 3235: 3231: 3226: 3204: 3193: 3192: 3176: 3172: 3166: 3162: 3158: 3153: 3149: 3145: 3139: 3135: 3129: 3121: 3117: 3111: 3107: 3103: 3098: 3094: 3090: 3084: 3080: 3074: 3071: 3066: 3062: 3058: 3055: 3052: 3046: 3041: 3037: 3033: 3028: 3024: 3020: 3016: 3011: 3006: 3002: 2998: 2975: 2964: 2963: 2948: 2944: 2940: 2935: 2932: 2909: 2905: 2901: 2898: 2887: 2886: 2873: 2869: 2865: 2860: 2856: 2852: 2849: 2846: 2843: 2840: 2837: 2834: 2831: 2828: 2806: 2786: 2774: 2771: 2747: 2746: 2732: 2728: 2723: 2720: 2715: 2709: 2702: 2699: 2694: 2689: 2686: 2663: 2660: 2657: 2646: 2645: 2634: 2626: 2621: 2616: 2612: 2605: 2602: 2595: 2590: 2587: 2554: 2551: 2548: 2545: 2542: 2539: 2533: 2530: 2504: 2501: 2498: 2495: 2492: 2489: 2486: 2476:complex number 2471: 2468: 2467: 2466: 2455: 2452: 2447: 2442: 2437: 2434: 2429: 2424: 2416: 2411: 2406: 2402: 2397: 2390: 2386: 2382: 2379: 2376: 2368: 2363: 2358: 2354: 2349: 2342: 2338: 2334: 2331: 2308: 2305: 2281: 2278: 2277: 2276: 2261: 2257: 2254: 2251: 2247: 2242: 2238: 2235: 2232: 2228: 2221: 2217: 2214: 2211: 2207: 2202: 2198: 2195: 2192: 2188: 2181: 2178: 2155: 2150: 2146: 2140: 2136: 2132: 2128: 2124: 2104: 2082: 2078: 2055: 2051: 2030: 2027: 2024: 2021: 2018: 2015: 2012: 1996: 1993: 1989:Riemann sphere 1938: 1935: 1922: 1919: 1906: 1886: 1883: 1880: 1877: 1874: 1871: 1868: 1865: 1862: 1859: 1839: 1819: 1816: 1813: 1810: 1807: 1804: 1801: 1798: 1775: 1772: 1766: 1761: 1757: 1750: 1747: 1741: 1738: 1735: 1732: 1727: 1723: 1719: 1714: 1710: 1689: 1686: 1683: 1678: 1674: 1670: 1665: 1661: 1657: 1652: 1648: 1627: 1607: 1583: 1580: 1574: 1571: 1566: 1563: 1554: 1551: 1545: 1542: 1540: 1537: 1498: 1494: 1490: 1486: 1481: 1475: 1471: 1467: 1463: 1458: 1454: 1450: 1445: 1441: 1438: 1434: 1429: 1425: 1420: 1416: 1412: 1409: 1406: 1403: 1343: 1340: 1339: 1338: 1335: 1324: 1321: 1318: 1295: 1183:pole and polar 1181:Main article: 1178: 1177:Pole and polar 1175: 1098: 1095: 1094: 1093: 1087: 1081: 1078: 1060: 1057: 1056: 1055: 1052: 1041: 1021: 1020: 1019: 1018: 1007: 1003: 1000: 995: 992: 988: 985: 982: 979: 976: 973: 970: 955: 952: 947: 944: 940: 937: 934: 931: 928: 925: 922: 909: 908: 897: 874: 851: 850: 835: 812: 811: 808: 801: 799: 789:going through 784: 777: 775: 764: 757: 753: 750: 749: 748: 703: 686:on the circle 676: 617: 614: 613: 612: 598: 583: 576: 561: 543: 501: 498: 497: 496: 476: 466: 444: 439:going through 429: 418: 379: 376: 313: 310: 282:total function 278:self-inversion 240: 239: 228: 223: 219: 215: 210: 206: 202: 199: 196: 193: 117: 114: 109:Mandelbrot set 100: 97: 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 6227: 6216: 6213: 6212: 6210: 6200: 6197: 6192: 6191: 6186: 6183: 6178: 6175: 6172: 6170: 6167: 6165: 6161: 6158: 6157: 6153: 6149: 6146: 6143: 6139: 6135: 6134: 6129: 6126: 6123: 6119: 6115: 6111: 6106: 6103: 6101:0-387-98650-2 6097: 6093: 6089: 6085: 6081: 6078: 6076:0-471-18283-4 6072: 6068: 6067: 6062: 6058: 6055: 6053:0-521-59787-0 6049: 6045: 6040: 6037: 6035:0-8218-2636-0 6031: 6027: 6022: 6019: 6015: 6011: 6007: 6002: 6001: 5997: 5990: 5988: 5980: 5977: 5973: 5969: 5963: 5960: 5956: 5951: 5948: 5943: 5939: 5934: 5929: 5925: 5921: 5917: 5913: 5912: 5904: 5901: 5897: 5891: 5888: 5884: 5879: 5876: 5872: 5867: 5865: 5861: 5857: 5853: 5849: 5846: 5840: 5838: 5834: 5830: 5825: 5822: 5818: 5813: 5810: 5805: 5804: 5798: 5795: 5788: 5784: 5781: 5779: 5776: 5774: 5771: 5769: 5766: 5764: 5761: 5759: 5756: 5754: 5753:Inverse curve 5751: 5749: 5746: 5744: 5741: 5740: 5736: 5734: 5730: 5728: 5708: 5705: 5702: 5699: 5696: 5691: 5687: 5681: 5677: 5673: 5670: 5667: 5664: 5659: 5655: 5649: 5645: 5641: 5638: 5633: 5628: 5624: 5620: 5617: 5614: 5609: 5604: 5600: 5592: 5591: 5590: 5588: 5584: 5565: 5562: 5557: 5554: 5549: 5544: 5540: 5534: 5529: 5525: 5519: 5516: 5513: 5510: 5505: 5501: 5495: 5490: 5486: 5480: 5477: 5472: 5467: 5463: 5459: 5456: 5453: 5448: 5443: 5439: 5431: 5430: 5429: 5427: 5422: 5418: 5411: 5392: 5389: 5386: 5383: 5378: 5374: 5368: 5364: 5360: 5357: 5354: 5351: 5346: 5342: 5336: 5332: 5328: 5325: 5320: 5315: 5311: 5307: 5304: 5301: 5296: 5291: 5287: 5279: 5278: 5277: 5275: 5273: 5263: 5261: 5259: 5255: 5251: 5247: 5242: 5240: 5233: 5228: 5222: 5218: 5211: 5207: 5200: 5195: 5185: 5179: 5175: 5170: 5166: 5149: 5144: 5139: 5136: 5130: 5104: 5101: 5098: 5093: 5089: 5085: 5082: 5074: 5070: 5066: 5062: 5058: 5050: 5048: 5046: 5042: 5038: 5036: 5031: 5026: 5024: 5020: 5016: 5011: 5009: 5005: 5000: 4998: 4994: 4990: 4986: 4982: 4978: 4973: 4971: 4967: 4963: 4959: 4936: 4928: 4918: 4914: 4910: 4905: 4901: 4892: 4888: 4877: 4873: 4869: 4864: 4860: 4851: 4847: 4840: 4835: 4831: 4827: 4823: 4819: 4815: 4809: 4802: 4798: 4790: 4782: 4774: 4771: 4768: 4757: 4754: 4751: 4743: 4739: 4732: 4729: 4726: 4722: 4719: 4713: 4708: 4697: 4696: 4695: 4678: 4674: 4652: 4649: 4646: 4639: 4618: 4614: 4610: 4607: 4604: 4601: 4598: 4593: 4589: 4582: 4579: 4554: 4550: 4546: 4543: 4540: 4537: 4534: 4529: 4525: 4518: 4515: 4503: 4499: 4491: 4489: 4486: 4484: 4480: 4476: 4472: 4468: 4464: 4460: 4456: 4452: 4448: 4444: 4440: 4431: 4411: 4402: 4396: 4393: 4390: 4387: 4383: 4378: 4372: 4366: 4363: 4360: 4351: 4345: 4342: 4334: 4328: 4325: 4319: 4313: 4307: 4304: 4288: 4285: 4280: 4274: 4268: 4265: 4259: 4253: 4250: 4247: 4241: 4235: 4232: 4226: 4220: 4217: 4211: 4208: 4202: 4199: 4193: 4190: 4187: 4181: 4178: 4173: 4169: 4163: 4159: 4155: 4152: 4149: 4137: 4136: 4135: 4121: 4101: 4096: 4092: 4085: 4080: 4076: 4066: 4049: 4043: 4039: 4035: 4032: 4027: 4023: 4018: 4014: 3984: 3980: 3976: 3971: 3967: 3963: 3956: 3934: 3905: 3900: 3894: 3888: 3884: 3880: 3875: 3871: 3867: 3863: 3859: 3854: 3849: 3845: 3836: 3832: 3828: 3825: 3820: 3816: 3811: 3806: 3801: 3797: 3792: 3787: 3778: 3774: 3770: 3765: 3761: 3757: 3751: 3747: 3741: 3738: 3734: 3714: 3704: 3700: 3696: 3691: 3687: 3683: 3674: 3670: 3664: 3656: 3646: 3642: 3638: 3633: 3629: 3625: 3615: 3611: 3607: 3601: 3590: 3586: 3582: 3579: 3574: 3570: 3559: 3555: 3549: 3545: 3541: 3538: 3535: 3529: 3524: 3520: 3516: 3504: 3503: 3502: 3488: 3466: 3462: 3458: 3453: 3449: 3445: 3420: 3417: 3408: 3395: 3389: 3386: 3380: 3375: 3371: 3367: 3364: 3344: 3341: 3335: 3326: 3313: 3300: 3296: 3292: 3287: 3283: 3273: 3246: 3242: 3238: 3233: 3229: 3224: 3202: 3174: 3164: 3160: 3156: 3151: 3147: 3137: 3133: 3127: 3119: 3109: 3105: 3101: 3096: 3092: 3082: 3078: 3072: 3064: 3060: 3056: 3053: 3039: 3035: 3031: 3026: 3022: 3014: 3009: 3004: 3000: 2996: 2989: 2988: 2987: 2973: 2946: 2942: 2938: 2933: 2930: 2923: 2922: 2921: 2907: 2899: 2896: 2871: 2867: 2863: 2858: 2850: 2847: 2844: 2835: 2832: 2829: 2819: 2818: 2817: 2804: 2784: 2772: 2770: 2768: 2764: 2760: 2756: 2752: 2726: 2721: 2718: 2713: 2707: 2697: 2692: 2687: 2684: 2677: 2676: 2675: 2661: 2655: 2632: 2624: 2614: 2600: 2593: 2588: 2585: 2576: 2575: 2574: 2572: 2568: 2552: 2549: 2546: 2543: 2540: 2537: 2528: 2518: 2502: 2499: 2496: 2493: 2490: 2487: 2484: 2477: 2470:Reciprocation 2469: 2453: 2450: 2445: 2440: 2435: 2432: 2427: 2422: 2414: 2404: 2395: 2388: 2384: 2377: 2374: 2366: 2356: 2347: 2340: 2336: 2329: 2322: 2321: 2320: 2318: 2314: 2306: 2304: 2303: 2299: 2295: 2291: 2287: 2279: 2255: 2252: 2249: 2236: 2233: 2230: 2215: 2212: 2209: 2196: 2193: 2190: 2179: 2176: 2169: 2168: 2167: 2148: 2144: 2138: 2134: 2126: 2122: 2102: 2080: 2076: 2053: 2049: 2028: 2025: 2022: 2019: 2016: 2013: 2010: 2002: 1994: 1992: 1990: 1986: 1981: 1979: 1975: 1971: 1967: 1963: 1959: 1955: 1950: 1948: 1947:Edward Kasner 1944: 1936: 1934: 1932: 1928: 1920: 1918: 1904: 1881: 1878: 1875: 1872: 1869: 1866: 1860: 1857: 1837: 1814: 1811: 1808: 1805: 1802: 1799: 1773: 1770: 1764: 1759: 1748: 1745: 1739: 1736: 1730: 1725: 1721: 1717: 1712: 1708: 1687: 1684: 1681: 1676: 1672: 1668: 1663: 1659: 1655: 1650: 1646: 1625: 1605: 1597: 1588: 1581: 1579: 1572: 1570: 1564: 1562: 1560: 1559:Dupin cyclide 1552: 1550: 1543: 1538: 1536: 1534: 1530: 1526: 1522: 1518: 1514: 1496: 1492: 1488: 1469: 1465: 1452: 1439: 1436: 1423: 1414: 1410: 1407: 1404: 1401: 1393: 1389: 1385: 1381: 1377: 1373: 1364: 1356: 1348: 1341: 1336: 1333: 1329: 1325: 1322: 1319: 1316: 1312: 1308: 1304: 1300: 1296: 1293: 1289: 1285: 1281: 1277: 1273: 1269: 1268: 1267: 1264: 1262: 1258: 1254: 1250: 1249:perpendicular 1246: 1242: 1234: 1230: 1226: 1222: 1218: 1214: 1210: 1207:. The point 1206: 1202: 1198: 1194: 1189: 1184: 1176: 1174: 1172: 1167: 1165: 1161: 1156: 1154: 1150: 1146: 1141: 1139: 1135: 1131: 1127: 1123: 1119: 1114: 1112: 1108: 1104: 1096: 1092: 1088: 1086: 1082: 1079: 1076: 1075: 1071: 1070:the SVG file, 1065: 1058: 1053: 1050: 1046: 1042: 1039: 1035: 1031: 1027: 1023: 1022: 1005: 1001: 998: 993: 990: 986: 980: 977: 974: 971: 953: 950: 945: 942: 938: 932: 929: 926: 923: 913: 912: 911: 910: 906: 902: 898: 895: 891: 887: 883: 879: 875: 872: 868: 864: 860: 856: 855: 854: 848: 844: 840: 836: 833: 829: 825: 821: 817: 816: 815: 805: 800: 796: 792: 788: 781: 776: 772: 768: 761: 756: 751: 746: 742: 738: 731: 724: 720: 716: 712: 708: 704: 701: 698:antipodal to 697: 693: 689: 685: 681: 677: 674: 670: 666: 662: 661: 660: 658: 654: 650: 646: 641: 639: 635: 631: 627: 623: 610: 606: 603:is where ray 602: 599: 596: 592: 588: 584: 581: 577: 574: 570: 566: 562: 559: 555: 548: 544: 541: 534: 530: 526: 522: 521: 520: 518: 514: 507: 499: 494: 487: 483: 477: 474: 468:Draw segment 467: 464: 460: 456: 449: 445: 442: 438: 434: 430: 428:. (Not shown) 427: 423: 419: 416: 412: 408: 404: 403: 402: 400: 396: 392: 385: 377: 372: 365: 361: 357: 354:are similar. 353: 346: 342: 338: 334: 330: 326: 318: 311: 309: 306: 302: 297: 295: 291: 287: 283: 279: 275: 268: 261: 257: 253: 249: 245: 226: 221: 217: 213: 204: 200: 197: 194: 191: 184: 183: 182: 180: 176: 169: 165: 161: 157: 153: 149: 145: 141: 133: 126: 122: 115: 110: 105: 98: 96: 94: 89: 87: 84:(1842–3) and 83: 79: 75: 71: 67: 62: 58: 54: 50: 49: 44: 40: 33: 19: 6188: 6164:cut-the-knot 6136:48: 589–99, 6131: 6112:, New York: 6109: 6094:, Springer, 6091: 6065: 6043: 6025: 6005: 5986: 5979: 5967: 5962: 5955:Coxeter 1969 5950: 5915: 5909: 5903: 5895: 5890: 5878: 5824: 5812: 5801: 5797: 5731: 5723: 5586: 5582: 5580: 5425: 5420: 5416: 5409: 5407: 5271: 5267: 5249: 5245: 5243: 5238: 5231: 5229:= 1/‖ 5226: 5220: 5216: 5209: 5205: 5198: 5193: 5183: 5177: 5173: 5168: 5164: 5072: 5060: 5054: 5044: 5034: 5027: 5012: 5001: 4992: 4980: 4974: 4962:hyperspheres 4955: 4501: 4497: 4495: 4487: 4474: 4435: 4067: 3926: 3409: 3327: 3194: 2965: 2888: 2776: 2755:Möbius group 2748: 2647: 2570: 2473: 2310: 2286:L. I. Magnus 2283: 2115:will become 1998: 1982: 1977: 1974:Möbius plane 1966:affine plane 1951: 1940: 1924: 1593: 1576: 1568: 1556: 1547: 1532: 1528: 1524: 1520: 1516: 1512: 1391: 1387: 1383: 1382:with radius 1379: 1375: 1369: 1331: 1327: 1314: 1313:of the line 1310: 1306: 1305:, its polar 1302: 1298: 1291: 1287: 1283: 1282:of the line 1279: 1275: 1271: 1265: 1252: 1251:to the line 1244: 1240: 1238: 1232: 1228: 1224: 1220: 1216: 1208: 1204: 1200: 1196: 1192: 1168: 1157: 1142: 1133: 1129: 1121: 1120:of triangle 1115: 1100: 1048: 1044: 1037: 1033: 1029: 1025: 904: 900: 893: 889: 885: 881: 877: 870: 866: 862: 858: 857:If a circle 852: 842: 838: 831: 827: 823: 819: 813: 794: 790: 786: 770: 766: 744: 740: 733: 726: 722: 718: 714: 710: 706: 699: 695: 691: 687: 683: 679: 672: 668: 664: 656: 652: 651:and a point 648: 647:with center 644: 642: 637: 633: 629: 625: 621: 619: 608: 604: 600: 594: 590: 586: 579: 572: 568: 564: 557: 550: 546: 536: 532: 528: 524: 516: 509: 505: 503: 489: 485: 478: 469: 462: 458: 451: 447: 440: 436: 435:with center 432: 425: 421: 414: 410: 406: 398: 394: 387: 386:the inverse 381: 367: 363: 359: 355: 348: 344: 340: 336: 332: 328: 321: 304: 298: 293: 285: 273: 266: 259: 255: 254:(other than 251: 247: 243: 241: 178: 174: 167: 163: 159: 158:with center 155: 151: 147: 137: 131: 124: 90: 46: 42: 36: 6185:"Inversion" 5858:14: 237–240 5197:‖ = 4997:fixed point 4977:translation 4958:hyperplanes 4467:Felix Klein 4459:Lobachevsky 4005:and radius 3264:and radius 2759:conjugation 2294:Felix Klein 2001:cross-ratio 1943:Mario Pieri 1386:is a point 1326:If a point 1297:If a point 1270:If a point 1195:to a point 1097:Application 1068:circle. In 725:in a point 667:of the ray 632:of whether 630:independent 508:of a point 393:of a point 327:of a point 265:also takes 166:is a point 162:and radius 150:of a point 5998:References 5254:homography 5008:similarity 4504:of radius 4496:In a real 2567:reciprocal 2313:similarity 1394:such that 1145:concentric 1107:Euler line 847:orthogonal 752:Properties 611:intersect. 585:Draw line 575:intersect. 545:Draw line 535:) through 495:intersect. 465:intersect. 181:such that 140:reciprocal 74:Bellavitis 55:that maps 6190:MathWorld 6063:(1969) , 5883:Kay (1969 5871:Kay (1969 5829:Kay (1969 5668:⋯ 5618:⋯ 5514:⋯ 5457:⋯ 5355:⋯ 5305:⋯ 5181:/‖ 5140:− 5086:⋅ 5057:conformal 5047:-sphere. 4970:homothety 4911:− 4889:∑ 4870:− 4812:↦ 4779:‖ 4772:− 4766:‖ 4755:− 4716:↦ 4650:− 4397:⁡ 4391:⋅ 4379:− 4367:⁡ 4361:⋅ 4346:⁡ 4329:⁡ 4308:⁡ 4298:⟺ 4269:⁡ 4254:⁡ 4248:− 4236:⁡ 4221:⁡ 4215:⟺ 4194:⁡ 4185:⟺ 4174:∗ 4164:∗ 4089:→ 4081:∗ 4036:− 4028:∗ 3977:− 3972:∗ 3881:− 3876:∗ 3829:− 3821:∗ 3807:− 3802:∗ 3771:− 3766:∗ 3752:∗ 3742:− 3727:⟺ 3697:− 3692:∗ 3639:− 3634:∗ 3616:∗ 3583:− 3575:∗ 3560:∗ 3550:∗ 3530:− 3525:∗ 3459:≠ 3454:∗ 3376:∗ 3339:→ 3293:− 3239:− 3157:− 3102:− 3065:∗ 3032:− 3010:− 3005:∗ 2947:∗ 2900:∈ 2859:∗ 2848:− 2833:− 2767:conformal 2751:generator 2731:¯ 2701:¯ 2659:↦ 2604:¯ 2565:then the 2544:− 2532:¯ 2381:↦ 2333:↦ 2253:− 2234:− 2213:− 2194:− 1995:Invariant 1879:− 1830:, radius 1812:− 1789:; center 1685:− 1474:′ 1453:⋅ 1419:′ 1408:⋅ 1290:of point 1239:If point 1160:congruent 1138:collinear 1103:collinear 984:∠ 969:∠ 936:∠ 921:∠ 721:cuts ray 607:and line 523:Draw ray 484:is where 384:construct 305:invariant 209:′ 198:⋅ 48:inversion 6209:Category 6122:69-12075 6086:(2000), 6044:Geometry 6018:52-13504 5974:, Moscow 5848:Archived 5737:See also 5415:+ ... + 5235:‖ 5204:+ ... + 5191:‖ 5189:, where 5187:‖ 5065:Jacobian 5061:oriented 5004:isometry 4989:rotation 4966:dilation 4824:′ 4723:′ 4475:geometry 4447:Beltrami 4134:becomes 3421:∉ 2307:Dilation 1972:forms a 1565:Spheroid 1118:incircle 1085:cardioid 1002:′ 994:′ 954:′ 946:′ 713:in line 628:that is 589:through 549:through 272:back to 177:through 88:(1845). 76:(1836), 72:(1825), 70:Quetelet 68:(1824), 39:geometry 6201:Xah Lee 6148:0006034 5942:1986367 5224:, with 5037:-sphere 2753:of the 2674:where: 1211:is the 1109:of the 717:. Then 335:: Let 148:inverse 66:Steiner 57:circles 6120:  6098:  6073:  6050:  6032:  6016:  5940:  5214:gives 4477:for a 4463:Bolyai 4453:, and 4451:Cayley 1964:, any 1544:Sphere 1124:. The 966:  958:  907:, then 366:is to 358:is to 146:, the 86:Kelvin 82:Ingram 78:Stubbs 5938:JSTOR 5789:Notes 5248:to 1/ 4483:group 4479:space 4455:Klein 4068:When 3328:When 2515:with 1985:model 1257:polar 736:' 729:' 553:' 539:' 527:from 512:' 492:' 481:' 472:' 454:' 413:) to 390:' 370:' 351:' 324:' 270:' 263:' 171:' 144:plane 128:' 61:lines 6118:LCCN 6096:ISBN 6071:ISBN 6048:ISBN 6030:ISBN 6014:LCCN 5268:The 5117:and 4985:flat 4983:–2)- 4461:and 3438:and 3410:For 2068:and 1999:The 1925:The 1261:pole 1231:and 1169:The 1136:are 1028:and 880:and 869:and 705:Let 571:and 563:Let 488:and 461:and 450:and 446:Let 420:Let 347:and 80:and 6162:at 6138:doi 5928:hdl 5920:doi 5125:det 4968:or 4960:or 3501:is 2573:is 2569:of 2296:'s 1838:0.5 1815:0.5 1263:). 1215:of 1134:ABC 1130:ABC 1122:ABC 787:not 382:To 362:as 349:ONP 345:OPN 246:or 59:or 37:In 6211:: 6187:. 6145:MR 6116:, 6090:, 6012:, 5970:, 5936:. 5926:. 5914:. 5863:^ 5854:, 5836:^ 5566:0. 5221:kI 5219:= 5217:JJ 5172:= 5025:. 5010:. 4449:, 4394:Im 4364:Re 4343:Im 4326:Re 4305:Im 4266:Im 4251:Im 4233:Re 4218:Re 4191:Re 4065:. 2769:. 2315:, 1991:. 1983:A 1933:. 1594:A 1561:. 1535:. 1392:OP 1253:PR 1227:, 1166:. 1140:. 732:. 723:OC 715:BC 711:BA 669:OA 659:. 640:. 595:ON 580:ON 519:: 490:NN 486:OP 470:NN 426:OP 401:: 368:OP 356:OP 95:. 41:, 6193:. 6140:: 5987:n 5944:. 5930:: 5922:: 5916:1 5709:, 5706:0 5703:= 5700:1 5697:+ 5692:n 5688:x 5682:n 5678:a 5674:2 5671:+ 5665:+ 5660:1 5656:x 5650:1 5646:a 5642:2 5639:+ 5634:2 5629:n 5625:x 5621:+ 5615:+ 5610:2 5605:1 5601:x 5587:n 5583:c 5563:= 5558:c 5555:1 5550:+ 5545:n 5541:x 5535:c 5530:n 5526:a 5520:2 5517:+ 5511:+ 5506:1 5502:x 5496:c 5491:1 5487:a 5481:2 5478:+ 5473:2 5468:n 5464:x 5460:+ 5454:+ 5449:2 5444:1 5440:x 5426:c 5421:n 5417:a 5413:1 5410:a 5393:0 5390:= 5387:c 5384:+ 5379:n 5375:x 5369:n 5365:a 5361:2 5358:+ 5352:+ 5347:1 5343:x 5337:1 5333:a 5329:2 5326:+ 5321:2 5316:n 5312:x 5308:+ 5302:+ 5297:2 5292:1 5288:x 5272:n 5270:( 5250:z 5246:z 5239:J 5232:x 5227:k 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638:P 634:A 626:P 622:A 609:t 605:r 601:P 597:. 591:N 587:t 582:. 573:s 569:Ø 565:N 558:r 551:P 547:s 537:P 533:Ø 529:O 525:r 517:Ø 510:P 506:P 479:P 475:. 463:c 459:Ø 452:N 448:N 441:P 437:M 433:c 422:M 417:. 415:P 411:Ø 407:O 399:Ø 395:P 388:P 373:. 364:r 360:r 341:Ø 337:r 333:Ø 329:P 322:P 294:O 286:O 274:P 267:P 260:P 256:O 252:P 227:. 222:2 218:r 214:= 205:P 201:O 195:P 192:O 179:P 175:O 168:P 164:r 160:O 152:P 132:P 125:P 34:. 20:)

Index

Inversion in a circle
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

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