# The Icosahedron

A polyhedron bounded by twenty equilateral triangles; five meeting at each vertex.

The icosahdedron is one of the five platonic solids.

 VertexSymbol WythoffSymbol No. ofVertices No. ofEdges No. ofFaces SymmetryGroup Dual Polyhedron 35 5 | 2 3 12 30 20 A5×C2 Dodecahedron

Edge ratios:

• e/r = sqrt(3) (3-sqrt(5))
• e/rho = sqrt(5)-1
• e/R = sqrt((10-2sqrt(5))/5)

where e is the edge length, r is the in-radius, rho is the inter-radius, and R is the circum-radius.