# Square-enneagrammic duoprism

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Square-enneagrammic duoprism
Rank4
TypeUniform
SpaceSpherical
Bowers style acronymSastedip
Info
Coxeter diagramx4o x9/2o
SymmetryBC2×I2(9), order 144
ArmySemi-uniform sendip
RegimentSastedip
Elements
Vertex figureDigonal disphenoid, edge lengths 2cos(2π/9) (base 1) and 2 (base 2 and sides)
Cells9 cubes, 4 enneagrammic prisms
Faces9+36 squares, 4 enneagrammic prisms
Edges36+36
Vertices36
Measures (edge length 1)
Circumradius2+csc2(2π/9)/2 ≈ 1.05122
Hypervolume9/[4tan(2π/9)] ≈ 2.68145
Dichoral anglesCube–4–cube: 100°
Step–9/2–step: 90°
Cube–4–step: 90°
Central density2
Related polytopes
DualSquare-enneagrammic duotegum
ConjugatesSquare-enneagonal duoprism, Square-great enneagrammic duoprism
Properties
ConvexNo
OrientableYes
NatureTame

The square-enneagrammic duoprism, also known as sastedip or the 4-9/2 duoprism, is a uniform duoprism that consists of 9 cubes and 4 enneagrammic prisms, with 2 of each meeting at each vertex.

The name can also refer to the square-great enneagrammic duoprism, which uses a different stellation of the enneagon.

## Vertex coordinates

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

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