# Integration closed contours [duplicate]

$$\int_{-\infty}^{\infty} \frac{x \sin(x)}{x^2 +4} dx$$ I do not understand how to evaluate integrals by using a closed contour and passing to a limit, can someone show me using this example

• I suggest you look at the old questions. Similar questions have been posted over and over again. – Zaid Alyafeai Mar 17 '17 at 17:02
• It took me less than a minute to find math.stackexchange.com/questions/2172184/… – Zaid Alyafeai Mar 17 '17 at 17:03
• i still don't understand – user424889 Mar 17 '17 at 17:43
• What exactly you don't understand ? Write what you have tried so far. – Zaid Alyafeai Mar 17 '17 at 17:51
• @ZaidAlyafeai good catch! why not officially making this a duplicate? – tired Mar 17 '17 at 18:28