### 11.8.3 Right triangles in the plane: right_triangle

See section 12.7.3 for right triangles in space.

The right_triangle command takes three arguments and an optional fourth.
The three mandatory arguments are two points A and
B and a real nonzero number k.

right_triangle returns and draws the right triangle
ABC, with the right angle at A and with
AB = |k|·AC. If k > 0, then
AB to AC is counterclockwise; if k < 0
then AB to AC is clockwise.

Input:

right_triangle(i,-i,2)

Output:

Input:

right_triangle(i,-i,-2)

Output:

The optional argument needs to be a variable name
which is assigned to vertex C.

Input:

right_triangle(i, -i, 2, C)

Output:

Input:

affix(C)

Output:

4 + i