1. The problem statement, all variables and given/known data see attachment. 2. Relevant equations 3. The attempt at a solution ok so the equation is in the attachment. My question is how did ∫2e....etc. in the first line get solved and get the answer in the second line. I tried integration by parts and set 2e^-2/t as the u and sin(3t)dt as dv and then did the uv-∫vdu, but then i get a ecos(3t) form for the ∫vdu and if i kept doing integration by parts i get never ending esin/cos. Anybody can help me or tell me how to solve this much appreciated.