Hi. Its very simple - in this way the region is the part of plane where x and y (0,1). As we see that U=x/y will be non-zero at (0, infinity) quater. V=x*y will be non-zero at that (0,1) part of the quater. Theh the section will give us such a region x,y in (0,1). Or know it and just need to sketch this?
Regards