Quadrilaterals

In geometry, a quadrilateral is a four-sided polygon, having four edges (sides) and four corners (vertices). The word is derived from the Latin words quadri, a variant of four, and latus, meaning "side". It is also called a tetragon, derived from Greek "tetra" meaning "four" and "gon" meaning "corner" or "angle", in analogy to other polygons (e.g. pentagon). Since "gon" means "angle", it is analogously called a quadrangle, or 4-angle. A quadrilateral with vertices A, B, C and D is sometimes denoted as \square ABCD.

product of some integer with itself

subclass of centered polygonal number

problem about proving that five points in the plane will have a subset forming the vertices of a convex quadrilateral

positive integer that can be written as the sum of two or more consecutive positive integers