1. The problem statement, all variables and given/known data http://img355.imageshack.us/img355/713/84094873bg9.png [Broken] 2. Relevant equations http://img156.imageshack.us/img156/8741/39064854eb6.png [Broken] 3. The attempt at a solution I know that C[a,b] is dense in L2[a,b] thus the equation holds also for f,g in L2. I'm stuck at the last step towards the J*. Can someone give me a hint?