1. The problem statement, all variables and given/known data Can someone explain to me the logic of this statement: "Since the value of f (x, y) is unchanged when we swap x with y, [tex]\int_0^1 \int_0^x f (x+y)dydx = 1/2 \int_0^1 \int_0^1 f (x+y)dydx.[/tex]" 2. Relevant equations 3. The attempt at a solution [tex]\int_0^1 \int_0^x f (x+y)dydx = \int_0^1 \int_0^y f (y+x)dxdy[/tex] But I do not think that is the same.