'Angular velocity from time differentiating the DCM.'

def _w_diff_dcm(self, otherframe):

    from sympy.physics.vector.functions import dynamicsymbols
    dcm2diff = self.dcm(otherframe)
    diffed = dcm2diff.diff(dynamicsymbols._t)
    angvelmat = (diffed * dcm2diff.T)
    w1 = trigsimp(expand(angvelmat[7]), recursive=True)
    w2 = trigsimp(expand(angvelmat[2]), recursive=True)
    w3 = trigsimp(expand(angvelmat[3]), recursive=True)
    return (- Vector([(Matrix([w1, w2, w3]), self)]))
