V2Φ=0 x=0 n元y n元x ① SIn 1 n元x A Sin :2 0 0 0 1 0 1 0 0 0 sin sin x x a y y n y a n n n n U n x A e a n x U A a    = = =  =  − =  =   =   =  =    =    =   =  =  