Hexadecagram

The hexadecagram, or had, is a non-convex polygon with 16 sides. It's created by taking the fourth stellation of a hexadecagon. A regular hexadecagram has equal sides and equal angles.

It is one of three regular 16-sided star polygons, the other two being the small hexadecagram and the great hexadecagram.

It is the uniform quasitruncation of the octagram.

Vertex coordinates
The vertices of a regular small hexadecagram of edge length 1 are given by all permutations of:


 * $$\left(±\frac12,\,±\frac{1-\sqrt2+\sqrt{4-2\sqrt2}}{2}\right),$$
 * $$\left(±\frac{1-\sqrt{2-\sqrt2}}{2},\,±\frac{1-\sqrt2+\sqrt{2-\sqrt2}}{2}\right).$$