1. The problem statement, all variables and given/known data Show that δ(x-x') = d/dx Θ(x-x') 2. Relevant equations ∫ f(x') δ(x-x') dx' = f(x) Θ(x-x') vanishes if x-x' is negative and 1 if x-x' is positive 3. The attempt at a solution I saw a relation of the δ function but I don't know why is it like that. Integral of δ(x-x') from -∞ to x is 1 if x>x' and 0 if x<x' I'm not sure how to start. Any suggestions?