\[ \left \{x'(t)=x(t) \cos (t),y'(t)=x(t) e^{-\sin (t)}\right \} \] ✓ Mathematica : cpu = 0.0234421 (sec), leaf count = 39
\[\left \{\left \{x(t)\to c_1 e^{\sin (t)},y(t)\to c_1 \int _1^te^{\sin (K[1])-\sin (K[1])}dK[1]+c_2\right \}\right \}\] ✓ Maple : cpu = 0.207 (sec), leaf count = 18
\[\{\{x \left (t \right ) = c_{2} {\mathrm e}^{\sin \left (t \right )}, y \left (t \right ) = c_{2} t +c_{1}\}\}\]