hello.
could you help me with this question?
i dont know how to begin..
thank you.
1. What is the Fourier series of $\displaystyle f'$?
2. If $\displaystyle \int_{-\pi}^{\pi} |f'(x)|^2 dx = \int_{-\pi}^{\pi} |f(x)|^2 dx$ what does that tell you about the coeficients of the Fourier series of $\displaystyle f'$ and $\displaystyle f$?
3. What does $\displaystyle f \in E(-\pi, \pi)$ tell you about the Fourier series of $\displaystyle f$?
RonL