Yes, I treated "2(x - pi/8)" as X, and I think you just missed adding a right parenthesis upon converting from cos to sin. Thank you for your quick response and for solving the 2 problems I posted. One more clarification I'd like to ask for -- how did you get cos x = sin (x+pi/2)? My book does not have it. It has cos(pi/2 - theta) = sin theta

Jun 4th, 2015

Here is the clarification I asked for: how did you get cos x = sin (x+pi/2)? My book does not have it. It has cos(pi/2 - theta) = sin theta