def _eq_10_42(lam_1, lam_2, t_12):
 a = (0.5 * (lam_1 + lam_2))
 b = (0.5 * (lam_1 - lam_2))
 return ((t_12 * np.exp(a)) * _sinch(b))

def _eq_10_42 ( lam_1 , lam_2 , t_12 ) : a = ( 0.5 * ( lam_1 + lam_2 ) ) b = ( 0.5 * ( lam_1 - lam_2 ) ) return ( ( t_12 * np . exp ( a ) ) * _sinch ( b ) )
equation of functions of matrices: theory and computation .