code: def _polar_to_cartesian(cx, cy, r, theta):
          
          return cx - r * math.sin(theta), cy - r * math.cos(theta)
docs: :param cx: X coord of circle
          :param cy: Y coord of circle
          :param r: Radius of circle
          :param theta: Degrees from vertical, clockwise, in radians
          :return: (x, y)