1 / sqrt(2 + 2 (-0.9) cos(w) + ((-0.9)^2 - 1) cos(w)^2) from 0 to pi

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.