Triangular-enneagrammic duoprism

The triangular-enneagrammic duoprism, also known as 3-9/2 duoprism, is a uniform duoprism that consists of 9 triangular prism s and 3 enneagrammic prism s, with 2 of each meeting at each vertex.

Coordinates
The coordinates of a triangular-enneagrammic duoprism, centered at the origin and with edge length 2sin(2π/9), are given by:


 * (0, 2sin(2π/9)*√3/3, 1, 0),
 * (0, 2sin(2π/9)*√3/3, cos(2π/9), ±sin(2π/9)),
 * (0, 2sin(2π/9)*√3/3, cos(4π/9), ±sin(4π/9)),
 * (0, 2sin(2π/9)*√3/3, –1/2, ±√3/2),
 * (0, 2sin(2π/9)*√3/3, cos(8π/9), ±sin(8π/9)),
 * (±sin(2π/9), –sin(2π/9)*√3/3, 1, 0),
 * (±sin(2π/9), –sin(2π/9)*√3/3, cos(2π/9), ±sin(2π/9)),
 * (±sin(2π/9), –sin(2π/9)*√3/3, cos(4π/9), ±sin(4π/9)),
 * (±sin(2π/9), –sin(2π/9)*√3/3, –1/2, ±√3/2),
 * (±sin(2π/9), –sin(2π/9)*√3/3, cos(8π/9), ±sin(8π/9)).