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.
2cos(pi/5)1/2 (5 - sqrt(5) - 2 sqrt(5 - 2 sqrt(5)))
2cos(pi/5)1/2 (5 - sqrt(5) - 2 sqrt(5 - 2 sqrt(5)))
Natural Language
Math Input
Extended Keyboard
