Heptagonal-great enneagrammic duoprism

The heptagonal-great enneagrammic duoprism, also known as hegstedip or the 7-9/4 duoprism, is a uniform duoprism that consists of 9 heptagonal prisms and 7 great enneagrammic prisms, with 2 of each at each vertex.

Vertex coordinates
The coordinates of a heptagonal-great enneagrammic duoprism, centered at the origin and with edge length 4sin(π/7)sin(4π/9), are given by: where j = 2, 4, 6 and k = 2, 4, 8.
 * $$\left(2\sin\frac{4\pi}9,\,0,\,2\sin\frac{\pi}7,\,0\right),$$
 * $$\left(2\sin\frac{4\pi}9,\,0,\,2\sin\frac{\pi}7\cos\left(\frac{k\pi}9\right),\,±2\sin\frac{\pi}7\sin\left(\frac{k\pi}9\right)\right),$$
 * $$\left(2\sin\frac{4\pi}9,\,0,\,-\sin\frac{\pi}7,\,±\sqrt3\sin\frac{\pi}7\right),$$
 * $$\left(2\sin\frac{4\pi}9\cos\left(\frac{j\pi}7\right),\,±2\sin\frac{4\pi}9\sin\left(\frac{j\pi}7\right),\,2\sin\frac{\pi}7,\,0\right),$$
 * $$\left(2\sin\frac{4\pi}9\cos\left(\frac{j\pi}7\right),\,±2\sin\frac{4\pi}9\sin\left(\frac{j\pi}7\right),\,2\sin\frac{\pi}7\cos\left(\frac{k\pi}9\right),\,±2\sin\frac{\pi}7\sin\left(\frac{k\pi}9\right)\right),$$
 * $$\left(2\sin\frac{4\pi}9\cos\left(\frac{j\pi}7\right),\,±2\sin\frac{4\pi}9\sin\left(\frac{j\pi}7\right),\,-\sin\frac{\pi}7,\,±\sqrt3\sin\frac{\pi}7\right),$$