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Viewing Version 9 of 'fundamental theorem of calculus'
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Title of object: fundamental theorem of calculus
Canonical Name: FundamentalTheoremOfCalculusClassicalVersion
Type: Theorem

Created on: 2004-03-01 10:55:53
Modified on: 2004-10-26 10:23:30

Creator: paolini
Modifier: paolini
Author: paolini

Classification: msc:26A42

Revision comment (for changes between this and next version):

Changes for correction #13696 ('Barrow's rule').

Preamble:

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Content:

Let $f\colon[a,b]\to \mathbf R$ be a continuous function, let $c\in[a,b]$ be given
and consider the integral function $F$ defined on $[a,b]$ as
\[
F(x)= \int_c^x f(t)\, dt.
\]

Then $F$ is an antiderivative of $f$ that is,
$F$ is differentiable in $[a,b]$ and
\[
F'(x)=f(x)\qquad \forall x\in [a,b].
\]


The previous relation rewritten as
\[
\frac{d}{dx} \int_c^x f(t)\, dt = f(x)
\]
shows that the differentiation operator $\frac{d}{dx}$ is the inverse of the integration operator $\int_c^x$. This formula is sometimes called Newton-Leibniz formula.

On the other hand if $f\colon[a,b]\to \mathbf R$ is a continuous function
and $G\colon[a,b]\to \mathbf R$ is any antiderivative of $f$, i.e.\ $G'(x)=f(x)$ for all $x\in[a,b]$, then
\[
\int_a^b f(t) \, dt = G(b)-G(a).
\]

This shows that up to a constant, the integration operator is the inverse of the derivative operator:
\[
\int_a^x D G = G - G(a).
\]