下证卷积满足结合律,即 f1()2(t)]*3(2)=()+[2(1)*3(O) 为此,令 g()=f()*1()=」f(D(=)dz s()=/2()*f()=f2(t-v)/3(v)dv 则[(O)*厂2(O)*厂()=g()*/() =g()/3(t=l)d f1(z)(-)dz/3(t=l)d7 下证卷积满足结合律, 即 [f1 (t)*f2 (t)]*f3 (t)=f1 (t)*[f2 (t)*f3 (t)] 为此, 令   + − + − =  = − =  = − s t f t f t f t v f v v g t f t f t f f t ( ) ( ) ( ) ( ) ( )d ( ) ( ) ( ) ( ) ( )d 2 3 2 3 1 2 1 2    则    + − + − + − −     = − = − = f f u f t u u g u f t u u f t f t f t g t f t ( ) ( )d ( )d ( ) ( )d [ ( )* ( )]* ( ) ( )* ( ) 1 2 3 3 1 2 3 3   