Polyhedron with twenty faces.

### Properties

- A regular icosahedron is a Platonic solid. It is made up of 20 congruent equilateral triangles.
- Therefore, it has 20 faces, 12 vertices and 30 edges.
- Five faces meet at each vertex.
- Its area
*A*and its volume*V*can be calculated as a function of its edge length*a:*

\(A=5\sqrt{3}a^{2}\)

\(V=\frac{5\sqrt{14+6\sqrt{5}}}{12}a^{3}\)