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.
solve 50 cos(X)^2 +20cos(X) -21
solve 50 cos(X)^2 +20cos(X) -21
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
