1. The problem statement, all variables and given/known data For this forum they use the following integration: 3. The attempt at a solution Where does (u+a) come from? In step 2 why does the side on the left of the plus sign become zero? In step 3, how does A(0+a√π/λ) = a This website likes you to work on problems but I can't work on something for which step 1 is a mystery.