Hello! I wanted to solve this integral but really didn't understand the method show in the book. Can anyone help me out please. sorry I don't know how to show the integral sign, here it is integral of - to + infinity (Cos(x)/x^2 + 2x +5 )dx here Cos(z) = Re[exp(iz)] I tried to reduce the denominator to a (a+b)^2 thing and then use a method that I didn't understand ( so I copied it from the book). I need to know the stepwise solution if possible. Thank You!