bitangent plane

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• Bitangent — (black) has 28 real bitangents (red).This image shows 7 of them; the others are symmetric with respect to 90° rotations through the origin.] In mathematics, a bitangent to a curve C is a line L that touches C in two distinct points P and Q and… …   Wikipedia

• Plane curve — In mathematics, a plane curve is a curve in a Euclidean plane (cf. space curve). The most frequently studied cases are smooth plane curves (including piecewise smooth plane curves), and algebraic plane curves. A smooth plane curve is a curve in a …   Wikipedia

• Villarceau circles — In geometry, Villarceau circles (pronEng|viːlɑrˈsoʊ) are a pair of circles produced by cutting a torus diagonally through the center at the correct angle. Given an arbitrary point on a torus, four circles can be drawn through it. One is in the… …   Wikipedia

• Pseudotriangle — In Euclidean plane geometry, a pseudotriangle is the simply connected subset of the plane that lies between any three mutually tangent convex sets. A pseudotriangulation is a partition of a region of the plane into pseudotriangles, and a pointed… …   Wikipedia

• Trott curve — In real algebraic geometry, the Trott curve is the set of points ( x , y ) satisfying the degree four polynomial equation:displaystyle 144(x^4+y^4) 225(x^2+y^2)+350x^2y^2+81=0.These points form a nonsingular quartic plane curve that has genus… …   Wikipedia

• Riemann surface — For the Riemann surface of a subring of a field, see Zariski–Riemann space. Riemann surface for the function ƒ(z) = √z. The two horizontal axes represent the real and imaginary parts of z, while the vertical axis represents the real… …   Wikipedia

• K-set (geometry) — In discrete geometry, a k set of a finite point set S in the Euclidean plane is a subset of k elements of S that can be strictly separated from the remaining points by a line. More generally, in Euclidean space of higher dimensions, a k set of a… …   Wikipedia

• Genus–degree formula — In classical algebraic geometry, the genus–degree formula relates the degree d of a non singular plane curve with its arithmetic genus g via the formula: A singularity of order r decreases the genus by .[1] Proofs The proof follows immediately… …   Wikipedia

• Moduli of algebraic curves — In algebraic geometry, a moduli space of (algebraic) curves is a geometric space (typically a scheme or an algebraic stack) whose points represent isomorphism classes of algebraic curves. It is thus a special case of a moduli space. Depending on… …   Wikipedia

• De Franchis theorem — In mathematics, the de Franchis theorem is one of a number of closely related statements applying to compact Riemann surfaces, or, more generally, algebraic curves, X and Y, in the case of genus g > 1. The simplest is that the automorphism… …   Wikipedia

• Tangent lines to circles — In Euclidean plane geometry, tangent lines to circles form the subject of several theorems, and play an important role in many geometrical constructions and proofs. Since the tangent line to a circle at a point P is perpendicular to the radius to …   Wikipedia