fourier series

Quote:

Originally Posted by garden cat

hello.
could you help me with this question?
i dont know how to begin..
thank you.
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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 $f$ ?

RonL