The function f(x) is the integrand-the function you’re integrating.Integrals have the basic notation ∫ f(x) dx: In other words, you’re trying to find the area under a curve by integrating along the x-axis. The dx part of an integral tells you which variable to integrate The x in dx tells you to integrate with respect to x. When you see a ∫ and a dx, it means to integrate. Take the derivative of the function f(x) = 3x – 2. You’ll see dx in various forms, including in this notation (d/dx) which means “ take the derivative with respect to x.”įor example, if you see the following formula: The dx notation describes this limiting procedure and it’s what we use to find derivatives. If you’ve studied limits in calculus, you’ll know that the limit is found by getting very close to an x-value.įor example, you might find the limit at x = 1 by looking at what happens when x =. We use it in calculus to analyze continuous functions, making the intervals between the x-values smaller and smaller-so small in fact, that the intervals are very close to zero.įormally, dx is called the differential operator. More specifically, it’s an infinitesimal (really small!) change in two x-values written in Leibniz notation. The term “ dx” means a small change in x. In fact, during the 17th century they were the subject of many political and religious controversies, and in 1632 there was actually a ban on infinitesimals issued by Roman clerics. The study of infinitesimals began early in fact, Archimedes, the Greek mathematician who lived from about 287 BC to 212 BC, gave the first logically rigorous definition of them.
The word “calculus”, in that context, meant accounting or reckoning, and came from the name of a small counting pebble. The study of these infinitely small intervals is intrinsic to Calculus in fact, Calculus has historically been known as ‘infinitesimal calculus’ or “the calculus of infinitesimals’. These are functions whose limits approach zero as the function approaches infinity. The word has also, on occasion, been used to refer to functions which tend to zero. Summing up infinitely many infinitesimals gives us an integral. We call it a differential, and symbolize it as Δx. That instant in time, when graphed on a curve, becomes an infinitely small interval-an infinitesimal. At the core of Calculus is the idea that, to really understand a curve, you have to understand what is happening at every instantaneous moment in time.
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