### 11.16.3 Check if four points are concyclic in the plane: is_concyclic

See section 12.13.7 for checking for concyclicity in three-dimensional geometry.

The is_concyclic command is a Boolean function which takes as argument a list or sequence of points.

is_concyclic returns 1 if the points are cyclic and returns 0 otherwise.
Input:

is_concyclic(1+i, -1+i, -1-i, 1-i)

Output:

1

Input:

is_concyclic(i, -1+i, -1-i, 1-i)

Output:

0