1. The problem statement, all variables and given/known data Hi there, I was reading a book discussing on the topic of compact Green's function in 2D. However,I have been stuck for a while on some mathematical manipulations depicted below. 2. Relevant equations 3. The attempt at a solution In 2nd box,I guess the author was trying to pull out the differentiation sign and make use of the fact that the delta function is an even function.However,the delta function in the first box is differentiating with respect to the single term within the bracket rather than t?