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.
4cos^-1 (x) - 2 * pi = 2 * cos^-1 (x)
4cos^-1 (x) - 2 * pi = 2 * cos^-1 (x)
Natural Language
Math Input
Extended Keyboard
