def angle_between_vectors(a, b):
    """Return the minimum angle between two vectors. The angle returned for
    vectors a and -a is 0.
    """
    angle = (acos(dot(a, b)/(a.magnitude() * b.magnitude())) *
             pi / 180).evalf()
    return min(angle, 180 - angle)
dataset/ETHPy150Open pydy/pydy/examples/Kane1985/Chapter3/Ex6.10.py/angle_between_vectors/swapped operands of `/`