# Integration with i.

1. Apr 7, 2014

### cragar

i was trying to integrate $\frac{1}{(t^2+1)^2}$
By factoring it into $\frac{1}{(t+i)^2(t-i)^2}$ and then doing partial fractions.
then integrating each term using a u substitution. Ok but then how do I get the real part out of this solution. I know the arctan(t) can be extracted out of stuff of this form.

2. Apr 8, 2014

### lurflurf

use
$$\arctan(x)=\tfrac{1}{2}\imath \, (\log(1-\imath\, x)-\log(1+\imath\, x))$$