\[ \left \{x'(t)=a x(t)-y(t),y'(t)=a y(t)+x(t)\right \} \] ✓ Mathematica : cpu = 0.00616993 (sec), leaf count = 43
\[\left \{\left \{x(t)\to e^{a t} \left (c_1 \cos (t)-c_2 \sin (t)\right ),y(t)\to e^{a t} \left (c_1 \sin (t)+c_2 \cos (t)\right )\right \}\right \}\]
✓ Maple : cpu = 0.041 (sec), leaf count = 37
\[ \left \{ \left \{ x \left ( t \right ) ={{\rm e}^{at}} \left ( {\it \_C1}\,\sin \left ( t \right ) +{\it \_C2}\,\cos \left ( t \right ) \right ) ,y \left ( t \right ) ={{\rm e}^{at}} \left ( \sin \left ( t \right ) {\it \_C2}-\cos \left ( t \right ) {\it \_C1} \right ) \right \} \right \} \]