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  2. Varignon's theorem - Wikipedia

    en.wikipedia.org/wiki/Varignon's_theorem

    An arbitrary quadrilateral and its diagonals. Bases of similar triangles are parallel to the blue diagonal. Ditto for the red diagonal. The base pairs form a parallelogram with half the area of the quadrilateral, A q, as the sum of the areas of the four large triangles, A l is 2 A q (each of the two pairs reconstructs the quadrilateral) while that of the small triangles, A s is a quarter of A ...

  3. Newton's theorem (quadrilateral) - Wikipedia

    en.wikipedia.org/wiki/Newton's_theorem...

    Newton's theorem can easily be derived from Anne's theorem considering that in tangential quadrilaterals the combined lengths of opposite sides are equal (Pitot theorem: a + c = b + d). According to Anne's theorem, showing that the combined areas of opposite triangles PAD and PBC and the combined areas of triangles PAB and PCD are equal is ...

  4. Newton–Gauss line - Wikipedia

    en.wikipedia.org/wiki/Newton–Gauss_line

    Labels used in proof concerning complete quadrilateral It is a well-known theorem that the three midpoints of the diagonals of a complete quadrilateral are collinear . [ 2 ] There are several proofs of the result based on areas [ 2 ] or wedge products [ 3 ] or, as the following proof, on Menelaus's theorem , due to Hillyer and published in 1920.

  5. Ptolemy's theorem - Wikipedia

    en.wikipedia.org/wiki/Ptolemy's_theorem

    Ptolemy's theorem is a relation among these lengths in a cyclic quadrilateral. = + 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).

  6. List of theorems - Wikipedia

    en.wikipedia.org/wiki/List_of_theorems

    Berger–Kazdan comparison theorem (Riemannian geometry) Bernstein's theorem (approximation theory) Bernstein's theorem (functional analysis) Berry–Esséen theorem (probability theory) Bertini's theorem (algebraic geometry) Bertrand–Diquet–Puiseux theorem (differential geometry) Bertrand's ballot theorem (probability theory, combinatorics)

  7. Lisa Piccirillo - Wikipedia

    en.wikipedia.org/wiki/Lisa_Piccirillo

    She works in the fields of geometry and low-dimensional topology. In 2020, Piccirillo published a mathematical proof in the journal Annals of Mathematics determining that the Conway knot is not a smoothly slice knot, [3] [4] answering an unsolved problem in knot theory first proposed over fifty years prior by English mathematician John Horton ...

  8. Happy ending problem - Wikipedia

    en.wikipedia.org/wiki/Happy_ending_problem

    The happy ending problem: every set of five points in general position contains the vertices of a convex quadrilateral In mathematics , the " happy ending problem " (so named by Paul Erdős because it led to the marriage of George Szekeres and Esther Klein [ 1 ] ) is the following statement:

  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.