\[
\boxed{
{\frac {\rm d}{{\rm d}x}}y \left( x \right) =1/2\,{\frac {-\sin \left( 2\,y \left( x \right)  \right) +x\cos \left( 2\,y \left( x \right)  \right) +\cos \left( 2\,y \left( x \right)  \right) {x}^{3}+\cos \left( 2\,y \left( x \right)  \right) {x}^{4}+x+{x}^{3}+{x}^{4}}{x}}=0}
\]