Category

Theorems about quadrilaterals

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parallelogram law

mathematical theorem

Bretschneider's formula

Varignon's theorem

theorem that the midpoints of the sides of an arbitrary quadrilateral form a parallelogram

van Aubel's theorem

theorem that, given a convex quadrilateral, if one constructs a square—external to the quadrilateral—on each side, the 2 line segments between the centers of opposite squares have equal lengths and are orthogonal

Euler's quadrilateral theorem

British flag theorem

on distances from opposite corners to a point inside a rectangle

Thébault's theorem

one of three theorems in geometry proved by French mathematician Victor Thébault

theorem in Euclidean geometry

Finsler–Hadwiger theorem

describes a third square derived from any two squares that share a vertex

Petr–Douglas–Neumann theorem

Theorem of the gnomon

certain parallelograms occurring in a gnomon have areas of equal size