Enneagonal-dodecagonal duoprism

The enneagonal-dodecagonal duoprism or etwadip, also known as the 9-12 duoprism, is a uniform duoprism that consists of 9 dodecagonal prisms and 12 enneagonal prisms, with two of each joining at each vertex.

This polychoron can be subsymmetrically faceted into a triangular-square triswirlprism, although it cannot be made uniform.

Vertex coordinates
The coordinates of an enneagonal-dodecagonal duoprism, centered at the origin and with edge length 2sin(π/9), are given by:
 * (1, 0, ±sin(π/9)(1+$\sqrt{2}$), ±sin(π/9)(1+$\sqrt{6}$)),
 * (1, 0, ±sin(π/9), ±sin(π/9)(2+$\sqrt{2}$)),
 * (1, 0, ±sin(π/9)(2+$\sqrt{3}$), ±sin(π/9)),
 * (cos(2π/9), ±sin(2π/9), ±sin(π/9)(1+$\sqrt{3}$), ±sin(π/9)(1+$\sqrt{3}$)),
 * (cos(2π/9), ±sin(2π/9), ±sin(π/9), ±sin(π/9)(2+$\sqrt{3}$)),
 * (cos(2π/9), ±sin(2π/9), ±sin(π/9)(2+$\sqrt{3}$), ±sin(π/9)),
 * (cos(4π/9), ±sin(4π/9), ±sin(π/9)(1+$\sqrt{3}$), ±sin(π/9)(1+$\sqrt{3}$)),
 * (cos(4π/9), ±sin(4π/9), ±sin(π/9), ±sin(π/9)(2+$\sqrt{3}$)),
 * (cos(4π/9), ±sin(4π/9), ±sin(π/9)(2+$\sqrt{3}$), ±sin(π/9)),
 * (–1/2, ±$\sqrt{3}$/2, ±sin(π/9)(1+$\sqrt{3}$), ±sin(π/9)(1+$\sqrt{3}$)),
 * (–1/2, ±$\sqrt{3}$/2, ±sin(π/9), ±sin(π/9)(2+$\sqrt{3}$)),
 * (–1/2, ±$\sqrt{3}$/2, ±sin(π/9)(2+$\sqrt{3}$), ±sin(π/9)),
 * (cos(8π/9), ±sin(8π/9), ±sin(π/9)(1+$\sqrt{3}$), ±sin(π/9)(1+$\sqrt{3}$)),
 * (cos(8π/9), ±sin(8π/9), ±sin(π/9), ±sin(π/9)(2+$\sqrt{3}$)),
 * (cos(8π/9), ±sin(8π/9), ±sin(π/9)(2+$\sqrt{3}$), ±sin(π/9)).

Representations
An enneagonal-dodecagonal duoprism has the following Coxeter diagrams:


 * x9o x12o (full symmetry)
 * x6x x9o (dodecagons as dihexagons)