def is_ccw(A, B, C):
Vector_AB = Vector.from_start_end(A, B)
Vector_AC = Vector.from_start_end(A, C)
#Tests whether rotation from AB onto AC is ccw in the xy-plane
angle = Vector.angle_signed(Vector_AB, Vector_AC, (0, 0, 1))
if angle < 0:
return False
else:
return True
