(a)
Given, $\frac{dy}{y + 1} = \frac{{- cos}x}{2 + \sin x}\ dx$
$\Rightarrow$ $\int_{}^{}\frac{dy}{y + 1} = - \frac{\int_{}^{}{\cos x}}{2 + \sin x}dx$
$\Rightarrow$ $\log{(y + 1)} = - \log{(2 + \sin x)} + \log c$
When $x = 0,\ y = 1$
$\Rightarrow$ $c = 4$
$\therefore$ $y + 1 = \frac{4}{2 + \sin x}$
At $x = \frac{\pi}{2}$, $y + 1 = \frac{4}{2 + 1}$
$\Rightarrow$ $y = \frac{1}{3}$