If $y(x)$ satisfies the differential equation

$(\sin x) \dfrac{\mathrm{d}y }{\mathrm{d} x} + y \cos x = 1,$

subject to the condition $y(\pi/2) = \pi/2,$ then $y(\pi/6)$ is

1. $0$
2. $\frac{\pi}{6}$
3. $\frac{\pi}{3}$
4. $\frac{\pi}{2}$