Compute the angle (in degrees) between the line from this point to
p1 and the line from this point to
The ordering of points
p2 is important. The function returns a value between 0 and 180 when the angle (in the direction from
p2) is clockwise, and a value between 180 and 360 when the angle is counterclockwise. The function returns
NaN if either of the points
p2 is coincident with this point.