\[ \left \{x'(t)=x(t) \cos (t),y'(t)=x(t) e^{-\sin (t)}\right \} \] ✓ Mathematica : cpu = 0.0202381 (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 = 0.171 (sec), leaf count = 18
\[\{x \relax (t ) = c_{2} {\mathrm e}^{\sin \relax (t )}, y \relax (t ) = t c_{2}+c_{1}\}\]