Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
Σ [n = 1, +∞] (1 - (cos(1/n) + arctg(1/n)/(2*n)))^2
Σ [n = 1, +∞] (1 - (cos(1/n) + arctg(1/n)/(2*n)))^2
Natural Language
Math Input
Extended Keyboard
