1. The problem statement, all variables and given/known data This is the problem: http://i.imgur.com/AtISqng.jpg its the first series, not the second one with the cos 2. Relevant equations 3. The attempt at a solution so anyways i did this question but i just had one doubt. in every other question like this that i've done, the series summation goes from n=1 or something and goes to infinity. in this question, the summation starts at n=2 and goes to...just n. so can i solve this just as if the summation was going to infinity or do i have to do it differently? Thanks!