It goes as follows. Exercise 4 asks me to find the Fourier representation for:

(sorry I link this from outside this forum, but I couldn't attach the image not today, nor even a few days ago)
I've already done this part and verified with Mathematica my results by plotting. I'll post it downwards.

Then problem five says: Using the previous exercise verify that:

$\displaystyle 1+\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+\frac{ 1}{5^2}+....=\frac{\pi^2}{6}$

$\displaystyle 1+\frac{1}{3^2}+\frac{1}{5^2}+\frac{1}{7^2}+\frac{ 1}{9^2}+....=\frac{\pi^2}{8}$

$\displaystyle 1-\frac{1}{2^2}+\frac{1}{3^2}-\frac{1}{4^2}+\frac{1}{5^2}-....=\frac{\pi^2}{12}$

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