1. The problem statement, all variables and given/known data 2. Relevant equations None. Well, dx=du/cosx 3. The attempt at a solution I've substituted it in, got new values for the limits but I have u^-1 on the bottom and so can't integrate it from my current knowledge. Basically I'm stuck with: Integration of u^(-1) du with limits of 1 and 2. Any help appreciated. Apologies for not being able to work the Latex system.