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.
cos(3x)=0.9 where 0 < x < 180deg
cos(3x)=0.9 where 0 < x < 180deg
Natural Language
Math Input
Extended Keyboard
