Is series $\sum_{n=1}^{\infty}\frac{\cos(nx)}{n^\alpha}$, for $\alpha>0$, convergent?
Solution 1:
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Is series $\sum_{n=1}^{\infty}\frac{\cos(nx)}{n^\alpha}$, for $\alpha>0$, convergent?
Solution 1:
Your approach is correct, and you didn't do any mistakes. Please accept this (or another) answer, so that this question will be complete.