Branch Cuts and Integrals

Hello again,

I've come across a new topic that involves solving integrals that involve logarithms. The examples in the text are not too clear how this is done. Can anyone help me solve these:

$\displaystyle \int_{0}^{\infty} \frac{logx}{1+x^4} dx$

$\displaystyle \int_{0}^{\infty} \frac{(logx)^2}{1+x^2} dx$

$\displaystyle \int_{0}^{\infty} \frac{\sqrt{x}logx}{1+x^2} dx$

Any help would be really appreciated. I just can't seem to figure out the right steps to go about solving these problems. I learn backward and need to see examples I understand to get the concept. Thanks in advance!