Cyclic polygon

In geometry, a cyclic polygon is a polygon that has the property that when inscribed within a circumcircle all of its vertices lie upon the boundary of that circle. For example, a regular hexagon with sides n is a cyclic polygon for any circle with a radius n. The vertices of such polygons are said to be concyclic. All simple regular polygons are cyclic, although some types of complex polygon are cyclic. In addition, all triangles and all quadrilaterals containing four 90° angles are cyclic polygons.