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  2. List of theorems - Wikipedia

    en.wikipedia.org/wiki/List_of_theorems

    Jacobson–Morozov theorem (Lie algebra) Japanese theorem for concyclic polygons (Euclidean geometry) Japanese theorem for concyclic quadrilaterals (Euclidean geometry) John ellipsoid ; Jordan curve theorem ; Jordan–Hölder theorem (group theory) Jordan–Schönflies theorem (geometric topology) Jordan–Schur theorem (group theory)

  3. Ptolemy's theorem - Wikipedia

    en.wikipedia.org/wiki/Ptolemy's_theorem

    In Euclidean geometry, Ptolemy's theorem is a relation between the four sides and two diagonals of a cyclic quadrilateral (a quadrilateral whose vertices lie on a common circle). The theorem is named after the Greek astronomer and mathematician Ptolemy (Claudius Ptolemaeus). [ 1 ]

  4. List of mathematical logic topics - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_logic...

    Ax–Grothendieck theorem; Ax–Kochen theorem; Peano axioms; Non-standard model of arithmetic; First-order arithmetic; Second-order arithmetic; Presburger arithmetic; Wilkie's theorem; Functional predicate; T-schema; Back-and-forth method; Barwise compactness theorem; Skolemization; Lindenbaum–Tarski algebra; Löb's theorem; Arithmetical set ...

  5. Hierarchy (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Hierarchy_(mathematics)

    The term hierarchy is used to stress a hierarchical relation among the elements. Sometimes, a set comes equipped with a natural hierarchical structure. For example, the set of natural numbers N is equipped with a natural pre-order structure, where n ≤ n ′ {\displaystyle n\leq n'} whenever we can find some other number m {\displaystyle m} so ...

  6. Euler's quadrilateral theorem - Wikipedia

    en.wikipedia.org/wiki/Euler's_quadrilateral_theorem

    Euler's quadrilateral theorem or Euler's law on quadrilaterals, named after Leonhard Euler (1707–1783), describes a relation between the sides of a convex quadrilateral and its diagonals. It is a generalisation of the parallelogram law which in turn can be seen as generalisation of the Pythagorean theorem .

  7. Ptolemy's inequality - Wikipedia

    en.wikipedia.org/wiki/Ptolemy's_inequality

    For four points in order around a circle, Ptolemy's inequality becomes an equality, known as Ptolemy's theorem: ¯ ¯ + ¯ ¯ = ¯ ¯. In the inversion-based proof of Ptolemy's inequality, transforming four co-circular points by an inversion centered at one of them causes the other three to become collinear, so the triangle equality for these three points (from which Ptolemy's inequality may ...

  8. Quadrilateral - Wikipedia

    en.wikipedia.org/wiki/Quadrilateral

    A Watt quadrilateral is a quadrilateral with a pair of opposite sides of equal length. [6] A quadric quadrilateral is a convex quadrilateral whose four vertices all lie on the perimeter of a square. [7] A diametric quadrilateral is a cyclic quadrilateral having one of its sides as a diameter of the circumcircle. [8]

  9. Complete quadrangle - Wikipedia

    en.wikipedia.org/wiki/Complete_quadrangle

    A complete quadrangle (at left) and a complete quadrilateral (at right).. In mathematics, specifically in incidence geometry and especially in projective geometry, a complete quadrangle is a system of geometric objects consisting of any four points in a plane, no three of which are on a common line, and of the six lines connecting the six pairs of points.