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Differential EquationsSuperchallengeBoundary Values & Fourier Series

Boundary Values & Fourier Series · Superchallenge problem

Find the Fourier sine series of f(x)=x4−2πx3+π3xf(x) = x^4 - 2\pi x^3 + \pi^3x on [0,π][0, \pi], and use it to evaluate ∑k=0∞(−1)k(2k+1)5=1−135+155−⋯\displaystyle\sum_{k=0}^{\infty}\dfrac{(-1)^k}{(2k+1)^5} = 1 - \dfrac{1}{3^5} + \dfrac{1}{5^5} - \cdots.