Hendecagram

The hendecagram, or henge, is a non-convex polygon with 11 sides. It's created by taking the second stellation of a hendecagon. A regular hendecagram has equal sides and equal angles.

It is one of four regular 11-sided star polygons, the other three being the small hendecagram, the great hendecagram, and the grand hendecagram. The name "hendecagram" is often used to describe any of these shapes.

Vertex coordinates
Coordinates for a hendecagram of edge length 2sin(3π/11), centered at the origin, are:


 * (1, 0),
 * (cos(2π/11), ±sin(2π/11)),
 * (cos(4π/11), ±sin(4π/11)),
 * (cos(6π/11), ±sin(6π/11)),
 * (cos(8π/11), ±sin(8π/11)),
 * (cos(10π/11), ±sin(10π/11)).