I am revisiting some of the double integral problems, but I am having trouble conceptualize the area of the domain to integrate.
Ex: $f(x,y)$ of $(x,y) = 1/2$
where $0 < x < y < 2$
How do I know the area of interests is the upper or lower triangle? This is a very basic question. But as soon as the question changes between $x < y$ or $y < x$, I will get confused about the area I am suppose to integrate from.