def alpha_angle(pivot=None, com=None, axis=None):
"""Calculate and return the rotor alpha angle."""
# The CoM-pivot axis.
com_piv = com - pivot
com_piv /= norm(com_piv)
# The mu_xy vector.
z_axis = array([0, 0, 1], float64)
mu_xy = cross(z_axis, com_piv)
mu_xy /= norm(mu_xy)
# The alpha angle.
return vector_angle(mu_xy, axis, com_piv)
def alpha_angle(pivot=None, com=None, axis=None):
"""Calculate and return the rotor alpha angle."""
# The CoM-pivot axis.
com_piv = com - pivot
com_piv /= norm(com_piv)
# The mu_xy vector.
z_axis = array([0, 0, 1], float64)
mu_xy = cross(z_axis, com_piv)
mu_xy /= norm(mu_xy)
# The alpha angle.
return vector_angle(mu_xy, axis, com_piv)