# Why are they called differentiate & integrate ?

1. Jun 20, 2011

### physixer

Why are they called "differentiate" & "integrate"?

I was wondering why. When we differentiate, don't we result in an equation that describes the slopes of many other equations ( + C ) ? So, we'd be "integrating" many equations, different from each other by C, into a single description.
Inversely, when we integrate something, we get many solutions ( + C ). Aren't we producing many from one? In other words, "differentiating"?

Just curious. I'm too lazy to google the original reasonings for these terminologies :P

edit: oops, this should be in General or Calculus forums. Sorry for that.

Last edited: Jun 20, 2011
2. Jun 21, 2011

### tiny-tim

hi physixer!

i think the noun "differential" originates from "difference" methods …

eg 1 4 9 16 25 …

the differences are 3 5 7 9 …

(and the second differences are 2 2 2 …)

so when we differentiate, we start with f(x+h) - f(x), which is an infinitesimal difference, which eventually was called a differential​

and the verb "integrate" comes from the (ancient greek) idea that an area or volume can be approximated by adding up all the slices, ie combining all the parts into the whole (and "integral" means "whole")

3. Jun 21, 2011

### arildno

Re: Why are they called "differentiate" & "integrate"?

First off:

Producing the (+C)-solutions are generelly called finding the anti-derivative of a function.

The fundamental theorem of calculus says that we may accurately perform the integration process by finding an anti-derivative, and calculating the difference between the anti-derivative's function values.

The integration process on its own is to add together an infinite number of pieces, i.e, making something "whole"/integrated as tiny-tim said.

4. Jun 21, 2011

### physixer

Re: Why are they called "differentiate" & "integrate"?

Okay, thanks!