Tetrahedrons: tetrahedron pyramid

### 14.16.2 Tetrahedrons: tetrahedron pyramid

The tetrahedron creates tetrahedra.
pyramid is a synonym for tetrahedron.

- tetrahedron command takes three or four arguments:
  - A,B,C, three points.
  - Optionally D, another point.
- tetrahedron(A,B,C) returns and draws the regular tetrahedron given by:
  - One edge is AB.
  - One face is in the plane ABC, on the same side of line AB as is C.
  - The tetrahedron is on the side of plane ABC that makes the points A, B and C counterclockwise.
- tetrahedron(A,B,C,D) returns and draws the tetrahedron ABCD.

#### Examples.

- Input:
  tetrahedron([-2,0,0],[2,0,0],[0,2,0])
  or:
  pyramid([-2,0,0],[2,0,0],[0,2,0])
  Output:
- Input:
  tetrahedron([-2,0,0],[2,0,0],[0,2,0],[0,0,2])
  Output: