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.
cos60 = (a*a+b*b-60*60)/(2ab), cos120 = (a*a+b*b-80*80)/(2ab)
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random