1. Integration

Hi,
I am still bad in integration, I do not know which way to choose, integration by part or substination.
integration x^2cos(x)
So I shoul do like this
integration x^2cos(x)=x^2 (-sinx)-integration2x (-sinx)

2. Yes do that and then do integration by parts again.

$\displaystyle u=2x, \ du=2dx, \ dv=-sin(x), \ v=cos(x)$

$\displaystyle x^2*cos(x)-\left[2x*cos(x)-\int 2cos(x)dx\right]$