What is a 'quadrilateral triangle'?

This can be interpreted in several ways. At first sight “quadri”(4) and “tri”(3) do not go together. However several triangles do exist related to a quadrilateral. The most well-known is the diagonal triangle. read more

However several triangles do exist related to a quadrilateral. The most well-known is the diagonal triangle. When a quadrilateral is defined as a configuration of 4 lines L1, L2, L3, L4, then the diagonal triangle is the triangle defined by the lines (L1^L2)^(L3^L4), (L1^L3)^(L2^L4), (L1^L4)^(L2^L3). read more

In Euclidean plane geometry, a quadrilateral is a polygon with four edges (or sides) and four vertices or corners. Sometimes, the term quadrangle is used, by analogy with triangle, and sometimes tetragon for consistency with pentagon (5-sided), hexagon (6-sided) and so on. read more