# Regular Icosahedron ( midscribed sphere radius)

## Description

An icosahedron is a polyhedron with 20 triangular faces, 30 edges and 12 vertices. A regular icosahedron has 20 identical equilateral faces, with five of the triangular faces meeting at each vertex. If the edge length of a regular icosahedron is “a”, the radius of a midscribed sphere ( which touches the middle of each edge, ) is related with the length of the edge of the triangle face and the “golden ratio”

Related formulas## Variables

r_{m} | Radius of the midscribed sphere (m) |

a | Length of the edge of the triangle face (m) |