import math


def getAngle(a, b, c):
    """
    Helper function for filter_poly_angles()
    Find angle between three points ABC
    """
    ang = math.degrees(math.atan2(c[1]-b[1], c[0]-b[0]) \
                       - math.atan2(a[1]-b[1], a[0]-b[0]))
    return ang + 360 if ang < 0 else ang