## Deiving Convolution

We define convolution of f,g to be $\int_0^t f(r)*g(t-r)\,dt$. Find the derivative of convolution.

By using Leibintz Rule I get [conv(f,g)]'=conv(f,g')+f(t)g(0) while on most books i see that i can just derive one of the functions. Why is that?