### 11.9.2 Rhombuses in the plane: rhombus

See section 12.8.2 for rhombuses in space.

The rhombus command takes three mandatory arguments and one or two optional arguments. The three mandatory arguments are two points A and B and a real number a.

rhombus returns and draws the rhombus ABCD, where a is the counterclockwise angle from AB to AC.
Input:

rhombus(-2*i, sqrt(3) - i, pi/3)

Output:

The optional fourth and fifth arguments need to be variable names which will be assigned to vertices C and D.
Input:

rhombus(-2*i, sqrt(3) - i, pi/3, C, D)

Output:

Input:

affix(C), affix(D)

Output:

sqrt(3) + i, 0