Dodecahedron

The dodecahedron, or doe, is one of the five Platonic solids. It has 12 pentagons as faces, joining 3 to a vertex.

It is the only Platonic solid that does not appear as the vertex figure in one of the convex regular polychora. It does, however, appear as the vertex figure of the hyperbolic icosahedral honeycomb. It also appears as a cell of the hecatonicosachoron.

Vertex coordinates
The vertices of a dodecahedron of edge length 1, centered at the origin, are given by:


 * $$\left(±\frac{1+\sqrt{5}}{4},\,±\frac{1+\sqrt{5}}{4},\,±\frac{1+\sqrt{5}}{4}\right),$$

along with all even permutations of:


 * $$\left(±\frac{3+\sqrt{5}}{4},\,±\frac{1}{2},\,0\right).$$

The first set of vertices corresponds to a cube of edge length (1+$\sqrt{5}$)/2 which can be inscribed into the dodecahedron's vertices.

Representations
A regular dodecahedron has the following Coxeter diagrams:


 * x5o3o (full symmetry)
 * x4oo5oo4x&#xt (H2 axial, face-first)
 * ofxfoo3oofxfo&#xt (A2 axial, vertex-first)
 * xfoFofx ofFxFxo&#xt (A1×A1 axial, edge-first)
 * oxfF xFfo Fofx&#zx (A1×A1×A1 symmetry)

Related polyhedra
Several Johnson solids can be formed by augmenting the faces of the dodecahedron with pentagonal pyramids:


 * Augmented dodecahedron - One face is augmented
 * Parabiaugmented dodecahedron - Two opposite faces are augmented
 * Metabiaugmented dodecahedron - Two non-adjacent, non-opposite faces are augmented
 * Triaugmented dodecahedron - Three mutually non-adjacent faces are augmented

The dodecahedron has three stellations, namely the small stellated dodecahedron, the great dodecahedron, and the great stellated dodecahedron.