# Enneagonal prism

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Enneagonal prism | |
---|---|

Rank | 3 |

Type | Uniform |

Notation | |

Bowers style acronym | Ep |

Coxeter diagram | |

Conway notation | P9 |

Elements | |

Faces | 9 squares, 2 enneagons |

Edges | 9+18 |

Vertices | 18 |

Vertex figure | Isosceles triangle, edge lengths √2, √2, 2cos(π/9) |

Measures (edge length 1) | |

Circumradius | |

Volume | |

Dihedral angles | 4–4: 140° |

4–9: 90° | |

Height | 1 |

Central density | 1 |

Number of external pieces | 11 |

Level of complexity | 3 |

Related polytopes | |

Army | Ep |

Regiment | Ep |

Dual | Enneagonal tegum |

Conjugates | Enneagrammic prism, Great enneagrammic prism |

Abstract & topological properties | |

Flag count | 108 |

Euler characteristic | 2 |

Surface | Sphere |

Orientable | Yes |

Genus | 0 |

Skeleton | GP(9,1) |

Properties | |

Symmetry | I_{2}(9)×A_{1}, order 36 |

Convex | Yes |

Nature | Tame |

The **enneagonal prism**, **nonagonal prism**, or **ep**, is a prismatic uniform polyhedron. It consists of 2 enneagons and 9 squares. Each vertex joins one enneagon and two squares. As the name suggests, it is a prism based on an enneagon.

## Vertex coordinates[edit | edit source]

The coordinates of an enneagonal prism, centered at the origin and with edge length 2sin(π/9), are given by:

- ,
- ,
- ,
- ,
- .

## External links[edit | edit source]

- Wikipedia contributors. "Enneagonal prism".