# Bifrustum

An *n*-agonal **bifrustum** is a polyhedron composed of three parallel planes of *n*-agons, with the middle plane largest and usually the top and bottom congruent.

Set of bifrusta | |
---|---|

Example hexagonal bifrustum | |

Faces | 2 n-gons, 2n trapezoids |

Edges | 5n |

Vertices | 3n |

Symmetry group | D_{nh}, [n,2], (*n22) |

Dual polyhedron | Elongated bipyramids |

Properties | convex |

It can be constructed as two congruent frusta combined across a plane of symmetry, and also as a bipyramid with the two polar vertices truncated.

They are duals to the family of elongated bipyramids.

## Forms

Three bifrustums are duals to three Johnson solids, J14-16. In general, a **n-agonal bifrustum** has 2n trapezoids, 2 n-agons, and is dual to the elongated dipyramids.

Triangular bifrustum | Square bifrustum | Pentagonal bifrustum |
---|---|---|

6 trapezoids, 2 triangles. Dual to elongated triangular bipyramid, J14 | 8 trapezoids, 2 squares. Dual to elongated square bipyramid, J15 | 10 trapezoids, 2 pentagons. Dual to elongated pentagonal bipyramid, J16 |

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