\[ \tan (x) y'(x)+y''(x)-y(x) \cos ^2(x)=0 \] ✓ Mathematica : cpu = 0.023499 (sec), leaf count = 21
\[\{\{y(x)\to c_1 \cosh (\sin (x))+i c_2 \sinh (\sin (x))\}\}\] ✓ Maple : cpu = 0.038 (sec), leaf count = 17
\[ \left \{ y \left ( x \right ) ={\it \_C1}\,{{\rm e}^{\sin \left ( x \right ) }}+{\it \_C2}\,{{\rm e}^{-\sin \left ( x \right ) }} \right \} \]