def _opbend_angle_low(a, b, c, deriv=<NUM_LIT:0>):
result = _opbend_cos_low(a, b, c, deriv)<EOL>sign = np.sign(np.linalg.det([a, b, c]))<EOL>return _cos_to_angle(result, deriv, sign)<EOL>
Similar to opbend_angle, but with relative vectors