作变换:(=t-7 则齐次化问题为: t't'-a W(x∈R2,t>0) W|=0=0,W|=0=f(x,)(x∈R) 由达朗贝尔公式得: W(x,t',t) f(a, r)da 2a Jx-at 即 W(x, t,t)= f(a, rda 2a Jx-a(t-r0.8 1 0.6 0.4 0.2 0 x t 0 0.5 1 1.5 2 −1 −0.5 0 0.5 1 n 11 作变换： 则齐次化问题为： 2 0 0 ( , 0) 0, ( , )( ) t t xx t t t W a W x R t W W f x x R       = =  =      = =  t t  = − 由达朗贝尔公式得： 1 ( , , ) ( , ) 2 x at x at W x t f d a     +  −   =  即： ( ) ( ) 1 ( , , ) ( , ) 2 x a t x a t W x t f d a       + − − − = 