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.
plot: cos(x+y) = cos x + cos y, -4pi <= x <= 4pi, -4pi <= y <= 4pi
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random
