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