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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _opbend_angle_low(a, b, c, deriv=0):
 """Similar to opbend_angle, but with relative vectors"""

    result = _opbend_cos_low(a, b, c, deriv)
    sign = np.sign(np.linalg.det([a, b, c]))
    return _cos_to_angle(result, deriv, sign)