(b)
$\lim_{x \rightarrow 0}\left\{ \frac{1 + \tan x}{1 + \sin x} \right\}^{cosec\ x}$
$= \lim_{x \rightarrow 0}\frac{\left\lbrack \left( 1 + \frac{\sin x}{\cos x} \right)^{\frac{\cos x}{\sin x}} \right\rbrack^{1/\cos x}}{\left( 1 + \sin x \right)^{1/\sin x}}$
$= \frac{e^{\lim_{x \rightarrow 0}\ \frac{1}{\cos x}}}{e}$
$= \frac{e}{e} = 1$