\[
\boxed{
x{\frac {\rm d}{{\rm d}x}}y \left( x \right) + \left( \sin \left( y \left( x \right)  \right) -3\,{x}^{2}\cos \left( y \left( x \right)  \right)  \right) \cos \left( y \left( x \right)  \right) =0}
\]