Here is my task:
Calculate directly and using Stokes theorem $\int_C y^2 dx+x \, dy+z \, dz$, if $C$ is intersection line of surfaces $x^2+y^2=x+y$ and $2(x^2+y^2)=z$, orientated in positive direction viewed from point $(0;0;2R)$.
I did it using Stokes theorem, but I don't know how to do it directly. Any idea? Result is $0$.