③解方程:由变分原理 HudT E ddt ∴.E ∫(c%+c.)(y%+c,r可去掉,实函数v=v CaVa+cvb(cava+bvb)dt a v. Hyadr +cacvaHvdt +ccyAyadr+.Hvdr avar+2 ca b atsdr+于Jvdr③解方程：由变分原理   =       d H d E * * ˆ   + + + +  =           c c c c d c c H c c d E a a b b a a b b a a b b a a b b ( )( ) ( ) ˆ ( )  *可去掉，实函数 ＝  *        + + + + + =                    c d c c d c d c H d c c H d c c H d c H d a a a b a b b b a a a a b a b a b b a b b b 2 2 2 2 2 2 2 ˆ ˆ ˆ ˆ