### 12.13.9 Check if an object in space is an equilateral triangle: is_equilateral

See section 11.16.5 for checking for equilateral triangles in two-dimensional geometry.

The is_equilateral command takes as argument either three points or a geometric object.

is_equilateral returns 1 if the points are the vertices of an equilateral triangle or if the object is an equilateral triangle.

Input:

is_equilateral([2,0,0],[0,0,0],[1,sqrt(3),0])

Output:

1

Input:

T := triangle_equilateral([2,0,0],[0,0,0],[1,sqrt(3),0])

then:

is_equilateral(T)

Output:

1

Input:

is_equilateral([2,0,0],[0,2,0],[1,1,0])

Output:

0