:(x01x+(x0 由式<6我们选择 sin ot (x,1)==,-x+0=, sin ot 则<7>-<9》变为: vut vrr=oxsin at /l v(0,)=v(l,t)=0 x0)=0,(x0)=-x0/ 又令 x1)=y(x,1)+y(x,1)令：u(x,t) = v(x,t) + w(x,t) 由式<6>我们选择： t l x x l t w x t w w 0 sin sin ( , ) = + = 则<7>-<9>变为： ï î ï í ì = = - = = - = v x v x x l v t v l t v a v x t l t tt xx ( ,0) 0 , ( ,0) / (0, ) ( , ) 0 sin / 2 2 w w w v(x,t) v (x,t) v (x,t) I II = + 又令：