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:
 * (±sin(π/9), ±sin(π/9), 1, 0),
 * (±sin(π/9), ±sin(π/9), cos(2π/9), ±sin(2π/9)),
 * (±sin(π/9), ±sin(π/9), cos(4π/9), ±sin(4π/9)),
 * (±sin(π/9), ±sin(π/9), –1/2, ±$\sqrt{2}$/2),
 * (±sin(π/9), ±sin(π/9), cos(8π/9), ±sin(8π/9)).

Representations
A square-enneagonal duoprism has the following Coxeter diagrams:


 * x4o x9o (full symmetry)
 * x x x9o (squares as rectangles)