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