Once again I am stumped by integration with substitution. I have two problems which are probably a breeze for some of you, but I just seem to be doing this ---> .

1. $\displaystyle \int\frac{4x}{x^2 +3}$ where the substitution is $\displaystyle u = x^2 + 3$

and

2.$\displaystyle \int\cos^3(x)$ where the substitution is $\displaystyle s = \sin(x)$

Thanks for any help