Star polygon

Common card · No. 212977

In geometry, a star polygon is a type of non-convex polygon. Regular star polygons have been studied in depth; while star polygons in general appear not to have been formally defined, certain notable ones can arise through truncation operations on regular simple or star polygons. Branko Grünbaum identified two primary usages of this terminology by Johannes Kepler, one corresponding to the regular star polygons with intersecting edges that do not generate new vertices, and the other one to the isotoxal concave simple polygons. Polygrams include polygons like the pentagram, but also compound figures like the hexagram. One definition of a star polygon, used in turtle graphics, is a polygon having q ≥ 2 turns (q is called the turning number or density), like in spirolaterals.

Read on Wikipedia · Image Originally uploaded May 14, 2007, by Berig on English Wikipedia[1], Public domain