fourier series

• April 8th 2008, 05:30 AM
garden cat
fourier series
hello.
could you help me with this question?
i dont know how to begin..
thank you.
• April 8th 2008, 01:56 PM
CaptainBlack
Quote:

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