\[ y''(x)+\tan (x) y'(x)-y(x) \cos ^2(x)=0 \] ✓ Mathematica : cpu = 0.0233371 (sec), leaf count = 21
\[\{\{y(x)\to c_1 \cosh (\sin (x))+i c_2 \sinh (\sin (x))\}\}\] ✓ Maple : cpu = 0.051 (sec), leaf count = 17
\[y \relax (x ) = c_{1} {\mathrm e}^{\sin \relax (x )}+c_{2} {\mathrm e}^{-\sin \relax (x )}\]