1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution I have the same final answer except without the X/2 + power series(n=1), I just have the same power series except its n=0. Is there any reason why they are pulling out n=0 and changing it to n=1? I did a similar problem which seems I could do the same thing but they left it as n=0.