If $0 < x < \frac{\pi}{2}$,then

$\lim _{x \rightarrow 0} \frac{1-\cos (1-\cos x)}{\sin ^4 x} = $

The value of $\mathop {\lim }\limits_{x \to 0} \left( \frac{e^x - 1}{x} \right)$ is

If $\lim _{x \rightarrow 2} \frac{1+\sqrt{1+4 \log _2 x}}{2+\left(2 x+\sin ^2 x+2 \cos x\right)(2 x-4)}=m$,then $m(m-1)=$

If $\lim _{n \rightarrow \infty} x_n$ exists and is finite,$x_1=2$,$x_{n+1}=\frac{a+b x_n}{b+c x_n}$ for all $n \in N$,and $c > b > a > 0$,then $\lim _{n \rightarrow \infty} x_n =$

If $\lim _{n \rightarrow \infty} x^n \log _e x=0$,then $\log _x 12=$