\[
\boxed{
 \left( {\frac {{\rm d}^{3}}{{\rm d}{x}^{3}}}y \left( x \right)  \right) \sin \left( x \right) + \left( 2\,\cos \left( x \right) +1 \right) {\frac {{\rm d}^{2}}{{\rm d}{x}^{2}}}y \left( x \right) -\sin \left( x \right) {\frac {\rm d}{{\rm d}x}}y \left( x \right) -\cos \left( x \right) =0}
\]