So I've drawn our path "C" and we're traversing it in the positive counterclockwise direction and then I've taken a few sample points for F at any point in the x-y plane that associates a 2-dimensional vector maybe at that point the 2-dimensional vector looks like that, maybe at that point the 2-dimensional vector looks like that and then n is of course the unit normal vector at any point on our curve the outward pointing unit vector at any point on our curve