## The Tetrahedron

The Tetrahedron is a regular three-sided Pyramid. Its surface consists of four equilateral triangles and is therefore one of the five
*Platonic solids*.

The following elements of a tetrahedron 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 = 1,6329932
Apothem h1 = 1,4142136
Altitude h2 = 1,3333333
Inradius ri = 0,33333333
Volume V = 0,51320024
Surface S = 4,6188022