lim\mathop {\lim }\limits_{x \to 0}\frac{\sin x}{x+\tan x}
\mathop {\lim }\limits_{x \to \frac{\pi }{4}}\frac{1-\tan x}{\sin x-\cos x}
\mathop {\lim }\limits_{x \to 2}\arctan (\frac{x^{2}-4}{6x^{2}-12x})
\mathop {\lim }\limits_{x \to \frac{\pi }{4}}x\cos x^{2}
\mathop {\lim }\limits_{x \to 2}(x^{3}-3x+1)^{-3}