Question 355637
You didn't put down limits of integration. 
Here's a link to www.wolframalpha.com that shows the steps to integration.
It's a fairly lengthy procedure. 
Good luck!

http://www.wolframalpha.com/input/?i=integrate+%28+cos%283x+%29%29%2F+%28x%5E2+%2B+1+%29%5E2+