When I'm learning convergence, my teacher just show me about condition to convergence or not. But I haven't meet a function that contain both trigonometric and normal polynomial. When I asked one of my friends, he tell me that using Taylor to developed $\cos x$, but I'm afraid that is not the good solution.
$\int_0^\infty\frac{\cos^2(x)}{x^2+5x+11}dx$
Thanks :)