Square-enneagonal duoprism

The square-enneagonal duoprism or sendip, also known as the 4-9 duoprism, is a uniform duoprism that consists of 4 enneagonal prisms and 9 cubes, with two of each joining at each vertex. It is also a convex segmentochoron, being the prism of the enneagonal prism.

Vertex coordinates
The coordinates of a square-enneagonal duoprism, centered at the origin and with edge length 2sin(π/9), are given by: where j = 2, 4, 8.
 * $$\left(±\sin\frac\pi9,±\sin\frac\pi9,1,0\right),$$
 * $$\left(±\sin\frac\pi9,±\sin\frac\pi9,\cos\left(\frac{j\pi}9\right),±\sin\left(\frac{j\pi}9\right)\right),$$
 * $$\left(±\sin\frac\pi9,±\sin\frac\pi9,-\frac12,±\frac{\sqrt3}2\right),$$

Representations
A square-enneagonal duoprism has the following Coxeter diagrams:
 * x4o x9o (full symmetry)
 * x x x9o (squares as rectangles)