Hello.

I stopped at this one:

$\displaystyle \lim_{ x \to 0} \dfrac{1-\frac{1}{2}x^2-cos\left( \frac{x}{1-x^2}\right)}{x^4}$

I did not try the L'Hospital's Rule, Am searching for a perfect solution.

Maybe using the infinite series ?

But it seems brutal.

Any help?