Homework Statement
Let U \subset \Re^{2} be open, and f,g: U \rightarrow \Re are continuous, and \int^{b}_{a} ( \int^{d}_{c} f(x,y) dy ) dx = \int^{b}_{a} ( \int^{d}_{c} g(x,y) dy ) dx for every rectangle [a,b] x [c,d] in U. Show that f = g.
Homework Equations
The Attempt at a...