# The Tetrahedron

A polyhedron bounded by four equilateral triangles; three meeting at each vertex.

The tetrahedron is one of the five platonic solids, and is the only regular polyhedron to be self-dual.

 VertexSymbol WythoffSymbol No. ofVertices No. ofEdges No. ofFaces SymmetryGroup Dual Polyhedron 33 3 | 2 3 4 6 4 S4 Tetrahedron

Edge ratios:

• e/r = 2 sqrt(6)
• e/rho = 2 sqrt(2)
• e/R = (2 sqrt(6))/3

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