Dual polyhedron facts for kids

This diagram shows how the cube and octahedron are dual. Each vertex of the octahedron matches with a face of the cube, and each vertex of the cube matches with a face of the octahedron

In geometry, every polyhedron is related to a dual polyhedron, where the vertices (points) of one polyhedron match with the faces (flat surfaces) of the other, and the edges connecting vertices in one polyhedron match with the edges connecting faces of the other. Starting with any given polyhedron, the dual of its dual is the original polyhedron.

For the five platonic polyhedra, only the tetrahedron is dual to itself. The cube and octahedron are dual, and the dodecahedron and icosahedron are dual.

Duals of Platonic polyhedra

Polyhedron	Vertices	Edges	Faces	Dual
Tetrahedron	4	6	4	Tetrahedron
Cube	8	12	6	Octahedron
Octahedron	6	12	8	Cube
Dodecahedron	20	30	12	Icosahedron
Icosahedron	12	30	20	Dodecahedron

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Images for kids

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  The dual of a cube is an octahedron. Vertices of one correspond to faces of the other, and edges correspond to each other.

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  The dual of a Platonic solid can be constructed by connecting the face centers. In general this creates only a topological dual. Images from Kepler's Harmonices Mundi (1619)

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  Canonical dual compound of cuboctahedron (light) and rhombic dodecahedron (dark). Pairs of edges meet on their common midsphere.

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  The square tiling, {4,4}, is self-dual, as shown by these red and blue tilings

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  The Infinite-order apeirogonal tiling, {∞,∞} in red, and its dual position in blue