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