The Compendium Geometry is an eBook providing facts, formulas and explanations about geometry.


A regular icosahedron is one of the Platonic solids having 20 equilateral triangular faces.

The volume V of the icosahedron is given by

its surface S is defined by

The radii of the circumscribed (rc) and inscribed (ri) spheres are

= a0.951056516295153572116439...,
= a0.75576131407617073048013...

Last Update: 2010-12-06