World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0000001851
Reproduction Date:

Title: Antiprism  
Author: World Heritage Encyclopedia
Language: English
Subject: Octahedron, Johnson solid, Trapezohedron, Tetrahedron, Apeirogonal antiprism
Collection: Prismatoid Polyhedra, Uniform Polyhedra
Publisher: World Heritage Encyclopedia


Set of uniform antiprisms
Hexagonal antiprism
Type uniform polyhedron
Faces 2 n-gons, 2n triangles
Edges 4n
Vertices 2n
Vertex configuration 3.3.3.n
Schläfli symbol s{2,2n}
{ } {n}
Coxeter–Dynkin diagrams
Symmetry group Dnd, [2+,2n], (2*n), order 4n
Rotation group Dn, [2,n]+, (22n), order 2n
Dual polyhedron trapezohedron
Properties convex, semi-regular vertex-transitive

In geometry, an n-sided antiprism is a polyhedron composed of two parallel copies of some particular n-sided polygon, connected by an alternating band of triangles. Antiprisms are a subclass of the prismatoids.

Antiprisms are similar to prisms except the bases are twisted relative to each other, and that the side faces are triangles, rather than quadrilaterals.

In the case of a regular n-sided base, one usually considers the case where its copy is twisted by an angle 180°/n. Extra regularity is obtained by the line connecting the base centers being perpendicular to the base planes, making it a right antiprism. As faces, it has the two n-gonal bases and, connecting those bases, 2n isosceles triangles.


  • Uniform antiprism 1
    • Schlegel diagrams 1.1
  • Cartesian coordinates 2
  • Volume and surface area 3
  • Related polyhedra 4
  • Symmetry 5
  • Star antiprism 6
  • References 7
  • External links 8

Uniform antiprism

A uniform antiprism has, apart from the base faces, 2n equilateral triangles as faces. As a class, the uniform antiprisms form an infinite series of vertex-uniform polyhedra, as do the uniform prisms. For n = 2 we have as degenerate case the regular tetrahedron as a digonal antiprism, and for n = 3 the non-degenerate regular octahedron as a triangular antiprism.

The dual polyhedra of the antiprisms are the trapezohedra. Their existence was first discussed and their name was coined by Johannes Kepler.

Family of uniform antiprisms n.3.3.3
Config. V2.3.3.3 ...∞.3.3.3

Schlegel diagrams







Cartesian coordinates

Cartesian coordinates for the vertices of a right antiprism with n-gonal bases and isosceles triangles are

\left( \cos\frac{k\pi}{n}, \sin\frac{k\pi}{n}, (-1)^k h \right)

with k ranging from 0 to 2n−1; if the triangles are equilateral,


Volume and surface area

Let a be the edge-length of a uniform antiprism. Then the volume is

V = \frac{n \sqrt{4\cos^2\frac{\pi}{2n}-1}\sin \frac{3\pi}{2n} }{12\sin^2\frac{\pi}{n}} \; a^3

and the surface area is

A = \frac{n}{2} ( \cot{\frac{\pi}{n}} + \sqrt{3}) a^2.

Related polyhedra

There are an infinite set of truncated antiprisms, including a lower-symmetry form of the truncated octahedron (truncated triangular antiprism). These can be alternated to create snub antiprisms, two of which are Johnson solids, and the snub triangular antiprism is a lower symmetry form of the icosahedron.

Truncated antiprisms
ts{2,4} ts{2,6} ts{2,8} ts{2,10} ts{2,2n}
Snub antiprisms
J84 Icosahedron J85 Irregular...
ss{2,4} ss{2,6} ss{2,8} ss{2,10} ss{2,2n}


The symmetry group of a right n-sided antiprism with regular base and isosceles side faces is Dnd of order 4n, except in the case of a tetrahedron, which has the larger symmetry group Td of order 24, which has three versions of D2d as subgroups, and the octahedron, which has the larger symmetry group Oh of order 48, which has four versions of D3d as subgroups.

The symmetry group contains inversion if and only if n is odd.

The rotation group is Dn of order 2n, except in the case of a tetrahedron, which has the larger rotation group T of order 12, which has three versions of D2 as subgroups, and the octahedron, which has the larger rotation group O of order 24, which has four versions of D3 as subgroups.

Star antiprism





This shows all the non-star and star antiprisms up to 15 sides - together with those of a 29-gon.

Uniform star antiprisms are named by their star polygon bases, {p/q}, and exist in prograde and retrograde (crossed) solutions. Crossed forms have intersecting vertex figures, and are denoted by inverted fractions, p/(p-q) instead of p/q, like 5/3 versus 5/2.

In the retrograde forms but not in the prograde forms, the triangles joining the star bases intersect the axis of rotational symmetry.

Some retrograde star antiprisms with regular star polygon bases cannot be constructed with equal edge lengths, so are not uniform polyhedra. Star antiprism compounds also can be constructed where p and q have common factors; thus a 10/4 antiprism is the compound of two 5/2 star antiprisms.

Uniform star antiprisms by symmetry, up to 12
Symmetry group Star forms


  • Chapter 2: Archimedean polyhedra, prisma and antiprisms
  1. ^

External links

  • Weisstein, Eric W., "Antiprism", MathWorld.
  • Olshevsky, George, Antiprism at Glossary for Hyperspace.
    • Olshevsky, George, Prismatic polytopes at Glossary for Hyperspace.
  • Nonconvex Prisms and Antiprisms
  • Paper models of prisms and antiprisms
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.