0 L xC r=L-x, sin 2 L,U(P)=KU(O)∑en kO)∑4]=((0)“m。他么 K)eh2e=0()∑e d  L1 L2 Ln L4 n x z x   =  =  N n n ikr e d f U P KU n n 1 0 [ ] 1 (0) ~ ( ) ~ n r rn = Ln − xn sin    = − − = N n a a n i k L x e dx f KU n n 1 / 2 / 2 ( sin ) 0 [ ] 1 (0) ~    = − − = N n a a n ikL ikx e e dx f KU n n 1 / 2 / 2 sin 0 1 (0) ~   = − − = N n ikL a a ikx n e dx e f KU 1 / 2 / 2 sin 0 ] 1 (0) ~ [  = = N n ikLn U e 1 ( ) ~  0 n