T+haT=0 x2=(m2+n2)z m tn at vm+nat 卩Tm()=Em cOS +f sin u(x, J,0=2(Em cos Vmi+n'at mn Sin vm+n'at nzA )Sin sIn 带入初始条件 mm tn a ∑ TA nI F sin sIn ∑Emsi 7 Sin nty=a lxul-x(l-y) n,n=  = + + + = , 1 2 2 2 2 ( , , ) ( cos sin )sin sin m n mn mn l n y l m x l m n at F l m n at u x y t E   带入初始条件 sin sin ( )( ) , 1 Axy l x l y l n y l m x E m n  mn = − −  =   sin sin 0 , 1 2 2 = +   m n= mn l n y l m x F l m n a   Fnm = 0 l m n at F l m n at Tmn t Emn mn 2 2 2 2 ( ) cos sin + + + = '' 0 2 2 T + a T = 2 2 2 2 2 ( ) l m n   + =