## The Octahedron

The Octahedron is a regular four-sided double pyramid. Its surface consists of eight equilateral triangles
and is therefore one of the five *Platonic solids*.

The following elements of a Octahedron 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 O

### Example:

Given:
Circumradius rc = 1
Results: Edge a = 1,4142136
Apothem h1 = 1,2247449
Altitude h2 = 2
Circumradius rc = 1
Inradius ri = 0,57735027
Volume V = 1,3333333
Surface S = 6,9282032

### See also:

Wikipedia: Platonic solid