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