\[ \left \{x'(t)=x(t) \cos (t),y'(t)=x(t) e^{-\sin (t)}\right \} \] ✓ Mathematica : cpu = 0.117741 (sec), leaf count = 41
\[\left \{\left \{x(t)\to c_1 e^{\sin (t)},y(t)\to c_1 \text {Integrate}\left [e^{\sin (K[1])-\sin (K[1])},\{K[1],1,t\},\text {Assumptions}\to \text {True}\right ]+c_2\right \}\right \}\]
✓ Maple : cpu = 0.138 (sec), leaf count = 18
\[ \left \{ \left \{ x \left ( t \right ) ={\it \_C2}\,{{\rm e}^{\sin \left ( t \right ) }},y \left ( t \right ) ={\it \_C2}\,t+{\it \_C1} \right \} \right \} \]