Enneagonal antiprism

The enneagonal antiprism, or eap, is a prismatic uniform polyhedron. It consists of 18 triangles and 2 enneagons. Each vertex joins one enneagon and three triangles. As the name suggests, it is an antiprism based on an enneagon.

Vertex coordinates
The vertices of an enneagonal antiprism, centered at the origin and with edge length 2sin(π/9), are given by the following points, as well as their central inversions: where $$H=\sqrt{\frac{1+2\cos\frac\pi9}{2+2\cos\frac\pi9}}\sin\frac\pi9.$$
 * $$\left(1,\,0,\,H\right),$$
 * $$\left(\cos\left(\frac{2\pi}9\right),\,±\sin\left(\frac{2\pi}9\right),\,H\right),$$
 * $$\left(\cos\left(\frac{4\pi}9\right),\,±\sin\left(\frac{4\pi}9\right),\,H\right),$$
 * $$\left(-\frac12,\,±\frac{\sqrt3}2,\,H\right),$$
 * $$\left(\cos\left(\frac{8\pi}9\right),\,±\sin\left(\frac{8\pi}9\right),\,H\right),$$