کدام گزینه درست است؟
1 )
$\underset{x\to \frac{-1}{3}}{\mathop{\lim }}\,\frac{\left[ x \right]}{\left| 3x+1 \right|}=+\infty $
$\underset{x\to \frac{\pi }{2}}{\mathop{\lim }}\,\frac{1}{1-\sin x}=+\infty $
3 )
$\underset{x\to \frac{{{\pi }^{+}}}{2}}{\mathop{\lim }}\,\tan x=+\infty $
4 )
$\underset{x\to -1}{\mathop{\lim }}\,\frac{{{x}^{2}}-1}{\left| x-1 \right|}=+\infty $