I am having trouble figuring out how an integration works. Consider the function, y = x2 . The antiderivative is x3 / 3 or in other words its x2 (x/3). How come multiplying the original function by (x / n) (where n represents the exponent + 1) will lead to the area under the curve. Put in another way, let's define the above in terms of a graph. Consider the function y = x2 and you want to find the area from 0,1. All you are doing to find the area is x2 (x/3) . You are creating a rectangle in which the dimensions are x2 by (x/3). If the function we were dealing with were x3, the rectangle that would yield the area under the curve would be x3 by ( x / 4) http://img237.imageshack.us/img237/6906/image1sj.png [Broken] How come the above rectangle just happened to be the total area under the curve? How did this work out and why does it work out? In order to try and figure this out, I searched the history of calculus and found this from wiki, but I didn't really understand it: Spoiler In this paper, Newton determined the area under a curve by first calculating a momentary rate of change and then extrapolating the total area. He began by reasoning about an indefinitely small triangle whose area is a function of x and y. He then reasoned that the infinitesimal increase in the abscissa will create a new formula where x = x + o (importantly, o is the letter, not the digit 0). He then recalculated the area with the aid of the binomial theorem, removed all quantities containing the letter o and re-formed an algebraic expression for the area. Significantly, Newton would then “blot out” the quantities containing o because terms “multiplied by it will be nothing in respect to the rest”.