Isosceles triangles in the plane: isosceles_triangle

### 13.8.2 Isosceles triangles in the plane: isosceles_triangle

See Section 14.7.2 for isosceles triangles in space.

The isosceles_triangle command creates isosceles triangles.

- isosceles_triangle takes three mandatory arguments and one optional argument:
  - a,b, two points.
  - θ, an angle.
  - Optionally, var, a variable name.
- isosceles_triangle(a,b,θ ⟨var⟩) returns and draws the isosceles triangle abc, where ab and ac are equal sides and θ is the angle between ab and ac.
  With the argument var, c will be assigned to var.

Examples.

- Input:
  isosceles_triangle(i, 1, -3*pi/4)
  Output:
- Input:
  isosceles_triangle(i, 1, -3*pi/4,C)
  Output:
  Input:
  normal(affix(C))
  Output:

  − | √ |
  2
  | +i