Equilateral triangles in the plane: equilateral_triangle

### 13.8.4 Equilateral triangles in the plane: equilateral_triangle

See Section 14.7.4 for equilateral triangles in space.

The equilateral_triangle command creates equilateral triangles.

- equilateral_triangle takes two mandatory arguments and one optional argument:
  - A,B, two points.
  - Optionally, var, a variable name.
- equilateral_triangle(A,B ⟨var⟩) returns and draws the equilateral ABC, where AB to AC is counterclockwise.
  With the argument var, C will be assigned to var.

Examples.

- Input:
  equilateral_triangle(0,2)
  Output:
- Input:
  equilateral_triangle(0, 2, C)
  Output:
  Input:
  affix(C)
  Output:

  ⎛ ⎜ ⎝ | √ |
  3
  | i+1 | ⎞ ⎟ ⎠