$\lim _\limits{x \rightarrow 0} \frac{\sin x}{\sqrt{x+1}-\sqrt{1-x}}$ is equal to

$\lim _\limits{x \rightarrow \pi / 4} \frac{\sec ^2 x-2}{\tan x-1}$ is

$\lim _\limits{x \rightarrow 1} \frac{(\sqrt{x}-1)(2 x-3)}{2 x^2+x-3}$ is equal to

If $f(x)=\left\{\begin{array}{cc}\frac{\sin [x]}{[x]}, & {[x] \neq 0} \\ 0, & {[x]=0}\end{array}\right.$, where [.] denotes the greatest integer function, then $\lim _\limits{x \rightarrow 0} f(x)$ is equal to

$\lim _\limits{x \rightarrow 0} \frac{|\sin x|}{x}$ is equal to