Georgios I tried to find the help page related to ?dsolve/numeric/DAE but unfortunately I couldn't find that. Which version of Maple you are using? I am working with Maple 9. thanks Sayed

Thanks indeed alec That solution which you uploaded was about the integration which in sinh(1/2*Pi*x) had been substituted by cosh(1/2*Pi*x) (at least I saw just that solution!!!). So could you please give me the details? Sayed