I was spending more time to find a way to solve this identity. However, I still couldn't figure it out. The identity that I need to prove is: $$\delta (g(x))= \sum_a \frac{ \delta (x-a)}{|g'(a)|}$$ Where $g(a) = 0$ and $g'(a)\neq0$.
I appriciate if someone can help me to solve this. Thanks.