Need directions to solve this ODE : $\frac{dy}{dx} +\tan{y}=\frac{x}{\cos{y}}$ Actually, it is supposed to be First Order Ordinary Linear DE. I was not able to make it really  linear with all my transformations.
I was given a clue that I need to make substitution $z=\sin{y}$, I think it should lead to linear equation relative to $\sin{y}$. But I stuck at the very begining of substitution, how should I make it for $y$, to dissappear?

$$
y'\cos y + \sin y = x
$$
note that
$$
\dfrac{d}{dx}\sin y = y' \cos y 
$$
use a change of variables.
