Triangular-enneagonal duoprism

The triangular-enneagonal duoprism or tedip, also known as the 3-9 duoprism, is a uniform duoprism that consists of 3 enneagonal prisms and 9 triangular prisms, with two of each at each vertex. It can also be seen as a convex segmentochoron, being an enneagon atop an enneagonal prism.

This polychoron can be subsymmetrically faceted into a 9-3 step prism, although it cannot be made uniform.

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