\[ \left \{x'(t)=a x(t)-y(t),y'(t)=a y(t)+x(t)\right \} \] ✓ Mathematica : cpu = 0.0047282 (sec), leaf count = 51
\[\left \{\left \{x(t)\to c_1 e^{a t} \cos (t)-c_2 e^{a t} \sin (t),y(t)\to c_2 e^{a t} \cos (t)+c_1 e^{a t} \sin (t)\right \}\right \}\] ✓ Maple : cpu = 0.054 (sec), leaf count = 37
\[\{\{x \left (t \right ) = \left (c_{1} \sin \left (t \right )+c_{2} \cos \left (t \right )\right ) {\mathrm e}^{a t}, y \left (t \right ) = \left (-c_{1} \cos \left (t \right )+c_{2} \sin \left (t \right )\right ) {\mathrm e}^{a t}\}\}\]