Hi. I have a function F as follows: F := 1/16*sin(Pi*cos(h))^2*sin(Pi*sin(h))^2/cos(1/2*Pi*cos(h))^2/cos(1/2*Pi*sin(h))^2; It has a maximum in the interval 0..Pi/2 at Pi/4. If I do: Fder := diff(F, h); solve(Fder, h); > (1/2)*Pi, -(1/2)*Pi, 0, Pi the solution Pi/4 is missing from the set returned by solve, and solve does not even issue a warning about the incomplete solution set. Surely Pi/4 is a solution, as you can find it visually: plot(F, 0..Pi/2); and also numerically: fsolve(Fder, h=Pi/4+0.1); > (1/4)*Pi