Checking whether an object in space is an equilateral triangle

See Section 26.15.5 for checking for equilateral triangles in 2D geometry.

The is_equilateral command determines whether or not a geometric object is an equilateral triangle.

is_equilateral takes G, a geometric object or a sequence of three points assumed to be the vertices of a triangle.
is_equilateral(G) returns 1 if the object is an equilateral triangle and 0 otherwise.

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

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

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