## The Icosahedron

The surface of an Icosahedron consists of twenty equilateral triangles and is therefore one of the five
** Platonic solids**.

The following elements of a Icosahedron are calculated if one of them is given:

- Edge a
- Apothem h
_{1} - Altitude h
_{2} - Circumradius r
_{u} - Inradius r
_{i} - Volume V
- Surface S

### Example:

Given: ¯¯¯¯¯¯ Circumradius rc = 1 Results: ¯¯¯¯¯¯¯ Edge a = 1,0514622 Apothem h1 = 0,910593 Altitude h2 = 2 Inradius ri = 0,79465447 Volume V = 2,5361507 Surface S = 9,5745414

### See also:

Graphics 3DWikipedia: Platonic solid