### 12.8.2 Isosceles triangles in the plane: isosceles_triangle

See section 13.7.2 for isosceles triangles in space.

The isosceles_triangle command takes three arguments and an optional fourth. The three mandatory arguments are two points A and B and an angle θ.

isosceles_triangle returns and draws the isosceles triangle ABC, where AB and AC are equal sides and θ is the angle from AB to AC.
Input:

isosceles_triangle(i, 1, -3*pi/4)

Output:

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

isosceles_triangle(i, 1, -3*pi/4,C)

Output:

Input:

normal(affix(C))

Output:

-sqrt(2) + i