Funny story, or maybe I'm just dumb and don't understand why my professor is being all petulant about this. ∫∫h(x,y)dA If z = h(x,y) and h(x,y) = f(x)g(y) ∫∫f(x)g(y)dxdy = ∫f(x)dx∫g(y)dy I did this on my own while working through some double integral hw. Seems obvious, and the answers were always correct. Used it on the test, got a 0 for each question I did. Was told to prove it for credit, so I did. No credit given. Now the teacher demands I give him a single page from a textbook with this in it before I can earn credit and I'm pissed because it's not in any of our libraries textbooks, yet I've found googledocs from other universities that show it as an example. Sooooo please, please. If any of you out there have a textbook with this example in it, please tell me what it is so I can hunt a copy down and not get a fail where I should have had a 92. I will owe you one cookie for your efforts.