Integrate by parts to see that the term by term differentiation of the Fourier series for f is the series for f', use induction and Riemann Lebesgue for the k-th derivative series.
Hello,
Does anybody please know how to solve this problem
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i added the definition of f hat
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thank you so much
i was able to do this the proof for k =2 which is the following :
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here is my work :
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how do i proceed ? without using "Riemann Lebesgue" because we have not taken it :S