A = arccos((2*x^2 + 3^2 + 9^2 - 6^2) / (2 * sqrt(x^2 + 3^2) * sqrt(x^2 + 9^2)))

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.