> eqn:=cos(x)=-1/cosh(x);

                                           1
                      eqn := cos(x) = - -------
                                        cosh(x)

> for i from 1 to 10 do  fsolve(eqn,x,(i-1)*Pi..i*Pi) od;

                             1.875104069


                             4.694091133


                             7.854757438


                             10.99554073


                             14.13716839


                             17.27875953


                             20.42035225


                             23.56194490


                             26.70353756


                             29.84513021

> plot({cos(x),-1/cosh(x)}, x=0..6);

> 
> 
