u'x=1/（x＋y^2＋z^3）u'y=2y/（x＋y^2＋z^3）u'z=3z^2/（x＋y^2＋z^3）du=u'xdx+u'ydy+u'zdz=1/（x＋y^2＋z^3）dx+2y/（x＋y^2＋z^3）dy+3z^2/（x＋y^2＋z^3）dz
