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