(11-04-2017 11:08 AM)Arno K Wrote: So there it is, the parametrization totally reflects the considered surface, there is no need to integrate f(x,y)=x^2+y^2, using f=1 provides 1/6*(√5*5*π-π), that is correct. So my program does what it shall, as I like to have some help on the calc I think I will leave it as is, that is input in a list so that the help can be printed.

Arno

That's right: the parametrisation, including range of integration, determines the surface while f describes the function that you want to integrate. A priori the two are totally unrelated. The same is true for the flux integral (where n is part of the surface definition and it will automatically come out of the parametrisation).