1. The problem statement, all variables and given/known data [tex]\int[/tex]cos3xdx 2. Relevant equations cos3x = cos2x * cosx 3. The attempt at a solution Let u= cos2x du=(x/2) + (cos2x/4x) v=-sinx dv=cos uv-[tex]\int[/tex]vdu -cos2xsinx - [tex]\int[/tex]-sinx(x/2 + cos2x/4x)dx -cos2xsinx -[tex]\int[/tex]xsinx/2 + (sinxcos2x/4x) -cos2xsinx - (1/2)xsinx +(sinxcos2x/4x) -cos2xsinx -(sinx-xcosx/2) + (sinxcos2x/4x) .... aaaand that's about where I get lost/stuck. i can't figure out how to finish off the problem. i get to the last line on the far right and get confused. any help would be much appreciated.