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