Ok, I have this calculus question and I've been obsessing over it. I won't be able to contact my teacher until this Friday, and it has been bugging the hell out of me as I go over and over my notes trying to figure this out. So if you think you might be able to help, then please try! My professor mentioned something in class, and I asked him about it, but I realized I ended up asking about something else instead. So I'm stuck trying to figure this out. We just moved into finding the area underneath a graph. We had this problem where we were given something in Riemann sum and we had to determine the region of the graph. I found the answer easily assuming it was using right end points only. So maybe I misunderstood him or didn't catch something. Thanks! What I don't get is how he was able to determine that it was in fact using right end points. I have a picture of the notes I took. I understand that as you increase n to infinite, the sample point x1* becomes a. There is a leap from that step to where he was able to plug in 1 and n, which are the beginning and end points of a right end point function. I don't see how realizing x1* becomes a helps me in determining right end points, in fact, it makes me think it's a left end point because a = x0.