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