$\lim_{x\to\infty}\left(\frac{\cos\left(\frac{1}{x}\right)}{\arctan\left(\frac{1}{x}\right)}\right)$

$\frac{4a^3-5a}{2a-1}$

$\frac{\cos x}{1-\sin x}-\frac{\cos x}{1+\sin}=43\tan x$

$\frac{\left(\sin\left(2x\right)\right)}{1-\cos\left(2x\right)}$

$\frac{6x}{x^{2+4}}$

$36^2+24x+4$

$\lim_{x\to0}\frac{2+x^2+\cos\:\left(x\right)}{x^{2n}}$