Theorem 1.3: (Coxeter [3]) Let 0 < k < n/2. The angle at the points of an {n/k} star is 180 - 360k/n.

proof: The {n/k} star is a set of points on a circle, and the angle at the point of the star is an inscribed angle whose central angle is 360 - 2(360k/n).