卷积满足
(1)交换律:f1(t)*f2(t)=f2(t)*f1(t);
(2)结合律:[f1(t)*f2(t)]*f3(t)=f1(t)*[f2(t)*f3(t)];
(3)分配律:f1(t)*[f2(t)+f3(t)]=f1(t)*f2(t)+f1(t)*f3(t).
下面只证(1)交换律
证明 令u=t-τ,则
