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