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Seven circles theorem — In geometry, the seven circles theorem states that, given a chain of six circles all tangent to a given circle and each tangent to its two neighbours, the three lines drawn between the tangent points of opposite circles on the chain with the… … Wikipedia
Miquel's theorem — A diagram showing circles passing through the vertices of a triangle ABC and points A´, B´ and C´ on the adjacent sides of the triangle intersecting at a common point, M. Miquel s theorem is a theorem in geometry, named after Auguste Miquel,… … Wikipedia
Malfatti circles — In geometry, the Malfatti circles are three circles inside a given triangle such that each circle is tangent to the other two and to two sides of the triangle. They are named after Gian Francesco Malfatti, who made early studies of the problem of … Wikipedia
Johnson circles — In geometry, a set of Johnson circles comprise three circles of equal radius r sharing one common point of intersection H . In such a configuration the circles usually have a total of four intersections (points where at least two of them meet):… … Wikipedia
Tangent circles — In geometry, tangent circles (also known as kissing circles) are circles that intersect in a single point. There are two types of tangency: internal and external. Many problems and constructions in geometry are related to tangent circles; such… … Wikipedia
Descartes' theorem — For other uses, see Descartes theorem (disambiguation). In geometry, Descartes theorem, named after René Descartes, establishes a relationship between four kissing, or mutually tangent, circles. The theorem can be used to construct a fourth… … 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
Nielsen–Schreier theorem — In group theory, a branch of mathematics, the Nielsen–Schreier theorem is the statement that every subgroup of a free group is itself free.[1][2][3] It is named after Jakob Nielsen and Otto Schreier. Contents … Wikipedia
Pascal's theorem — In projective geometry, Pascal s theorem (aka Hexagrammum Mysticum Theorem) states that if an arbitrary hexagon is inscribed in any conic section, and opposite pairs of sides are extended until they meet, the three intersection points will lie on … Wikipedia
Gershgorin circle theorem — In mathematics, the Gershgorin circle theorem may be used to bound the spectrum of a square matrix. It was first published by the Belarusian mathematician Semyon Aranovich Gershgorin in 1931. The spelling of S. A. Gershgorin s name has been… … Wikipedia
