# Enneagonal antitegum

The **enneagonal antitegum**, also known as the **enneagonal trapezohedron**, is an antitegum based on the enneagon, constructed as the dual of an enneagonal antiprism. It has 18 kites as faces, with 2 order–9 and 18 order–3 vertices.

Enneagonal antitegum | |
---|---|

Rank | 3 |

Type | Uniform dual |

Notation | |

Bowers style acronym | Eat |

Coxeter diagram | p2p18o () |

Conway notation | dA9 |

Elements | |

Faces | 18 kites |

Edges | 18+18 |

Vertices | 2+18 |

Vertex figure | 2 enneagons, 14 triangles |

Measures (edge length 1) | |

Dihedral angle | |

Central density | 1 |

Number of external pieces | 18 |

Level of complexity | 4 |

Related polytopes | |

Army | Eat |

Regiment | Eat |

Dual | Enneagonal antiprism |

Conjugate | Great enneagrammic concave antitegum |

Abstract & topological properties | |

Flag count | 144 |

Euler characteristic | 2 |

Surface | Sphere |

Orientable | Yes |

Genus | 0 |

Properties | |

Symmetry | (I_{2}(18)×A_{1})/2, order 36 |

Convex | Yes |

Nature | Tame |

Each face of this polyhedron is a kite with its longer edges times the length of its shorter edges.