omega3 < omega < omega4

def _g_3(self):
        """omega3 < omega < omega4"""
        # return 3 * (1.0 - self._n_3()) / (self._vertices_omegas[3] - self._omega)
        return (3 * self._f(1, 3) * self._f(2, 3) /
                (self._vertices_omegas[3] - self._vertices_omegas[0]))