\[ a y'(x)+f(x) \sin (y(x))+y''(x)=0 \] ✗ Mathematica : cpu = 0.0441315 (sec), leaf count = 0
, could not solve
DSolve[f[x]*Sin[y[x]] + a*Derivative[1][y][x] + Derivative[2][y][x] == 0, y[x], x]
✗ Maple : cpu = 0. (sec), leaf count = 0
, could not solve
dsolve(diff(diff(y(x),x),x)+a*diff(y(x),x)+f(x)*sin(y(x))=0,y(x))