If $f\left(x\right)=\frac{\sqrt{1+\sin x}-\sqrt{1-\sin x}}{x}, x\ne 0$ is continuous at $x=0$, then $f\left(0\right)$ is

The value of $f$ at $x=0$, so that the function $f\left(x\right)=\frac{2^x-2^{-x}}{x}, x\ne 0$ is continuous at $x=0$, is

Note: Assume base of logarithm as $e$, everywhere.

If $f\left(x\right)=\left\{\begin{array}{l}\begin{array}{cc}\frac{e^{5x}-e^{2x}}{\sin 3x},& x\ne 0\end{array}\\ \begin{array}{cc}\frac{k}{2},& x=0\end{array}\end{array}\right.$ is continuous at $x=0$, then the value of $k$ is