Question Number 12927 by satish1992.mishra@gmail.com last updated on 07/May/17
$$\Sigma\mathrm{cos}\:\left(\frac{\mathrm{1}}{{n}}\right) \\ $$
Commented by prakash jain last updated on 07/May/17
$${n}\:{from}\:\mathrm{0}\:{to}\:\infty? \\ $$$$\underset{{n}=\mathrm{0}} {\overset{\infty} {\sum}}\mathrm{cos}\:\left(\frac{\mathrm{1}}{{n}}\right)? \\ $$