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.
sum k=0 to inf (2cos(1/2(pi/2+2pi/3)))^k
sum k=0 to inf (2cos(1/2(pi/2+2pi/3)))^k
Natural Language
Math Input
Extended Keyboard
