$\displaystyle \cos (x)y' + \sin (x)y = 2\cos (x)\sin (x) - 1

$

$\displaystyle y(\frac{\pi }

{4}) = 3\sqrt 2 ,0 \leqslant x \leqslant \frac{\pi }

{4}

$

I've tried to get y' and y by itself and got this mess:

$\displaystyle \int {\frac{{dy}}

{y}} = \int {\frac{{2{{\cos }^3}(x)\sin (x) - 1 - \sin (x)dx}}

{{\cos (x)}}}

$