$\displaystyle \lim_{x\to 0}\frac{cosx-cos(3x)}{sin(x^2)}$

I'm having trouble finding things to cancel out to get the right answer.

and also

$\displaystyle si(x)=\int_{0}^{x} \frac{sin(t)dt}{t}$

$\displaystyle \lim_{x\to 0} \frac{si(x)-x}{x^3}$

Same thing