### 11.11.7 The power of a point relative to a circle: powerpc

Given a circle C of radius r and a point A at a distance of d
from the center of C, the power of A relative to C is d^{2} − r^{2}.

The powerpc command takes as arguments a circle and a point.

powerpc returns the power of the point relative to the circle.

Input:

powerpc(circle(0, 1+i), 3+i)

Output:

8