def cross3(u, v):
    """
    Returns 3 tuple that is  the 3 dimentional vector cross product of
    3 vector u crossed onto 3 vector v
    """
    return ((u[1] * v[2] - v[1] * u[2],
             u[2] * v[0] - v[2] * u[0],
             u[0] * v[1] - v[0] * u[1]))