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• (가)$\displaystyle \sum _ {n=1} ^ {\infty} \frac{1} {n \left (\ln \left (n+1 \right) \right) ^2}$
• (나)$\displaystyle \sum _ {n=1} ^ {\infty} \arctan \frac{1} {n}$
• (다)$\displaystyle \sum _ {n=1} ^ {\infty} \frac{\cos \left (n \pi \right)} {\sqrt n}$
• (라)$\displaystyle \sum _ {n=1} ^ {\infty} \frac{1} {n \left (1+ \frac{1} {\sqrt[3]{2^2}} + \frac{1} {\sqrt[3]{3^2}} + \cdots + \frac{1} {\sqrt[3]{n^2}} \right)}$