Icosahedron

A regular icosahedra is a regular polyhedron formed by $20$ equal equilateral triangles.

If we develop the icosahedra, we obtain the following figure:

The properties of the octahedron are:

• Number of faces: $20$
• Number of vertexes: $12$
• Number of edges: $30$
• Number of edges meeting in each vertexes: $5$