PlanetMath (more info)
 Math for the people, by the people. Sponsor PlanetMath
Encyclopedia | Requests | Forums | Docs | Wiki | Random | RSS  
Login
create new user
name:
pass:
forget your password?
Main Menu
Owner confidence rating: High Entry average rating: No information on entry rating
fundamental theorem of calculus for Kurzweil-Henstock integral (Theorem)

Let the $\int$ symbol denote the Kurzweil-Henstock integral. We can then give the most general version of the fundamental theorem of calculus.

Theorem 1   Let $F \colon [a,b] \to {\mathbb{R}}$ and suppose the derivative $F'(x)$ exists for all $x \in [a,b]$ . Then \begin{equation*} \int_a^b F'(x) dx = F(b)-F(a) . \end{equation*}

The reader should note the subtle difference from the standard version. Here we do not assume anything about $F'$ except that it exists. For the standard version we usually assume that $F'$ is continuous, and if we use the Lebesgue integral we must assume that $F'$ is Lebesgue integrable. Part of this theorem is that $F'$ is Kurzweil-Henstock integrable, hence no extra assumptions are necessary.

An example of a function where the standard version has problems is the function

$\displaystyle F(x) := \begin{cases}x^2 \sin \frac{1}{x^2} & \text{ if $x \not= 0$} \\ 0 & \text{ if $x = 0$} . \end{cases}$    

$F$ is differentiable everywhere, but
$\displaystyle F'(x) = \begin{cases}2x \sin \frac{1}{x^2} - \frac{2}{x}\cos \frac{1}{x^2} & \text{ if $x \not= 0$} \\ 0 & \text{ if $x = 0$} . \end{cases}$    

Which is not continuous and in fact unbounded on any interval containing zero.




"fundamental theorem of calculus for Kurzweil-Henstock integral" is owned by jirka.
(view preamble | get metadata)

View style:

See Also: fundamental theorem of calculus

Log in to rate this entry.
(view current ratings)

Cross-references: interval, unbounded, differentiable, function, necessary, theorem, Lebesgue integrable, Lebesgue integral, continuous, difference, derivative, fundamental theorem of calculus, Kurzweil-Henstock integral
There is 1 reference to this entry.

This is version 1 of fundamental theorem of calculus for Kurzweil-Henstock integral, born on 2007-02-23.
Object id is 8964, canonical name is FundamentalTheoremOfCalculusForKurzweilHenstockIntegral.
Accessed 1134 times total.

Classification:
AMS MSC26A42 (Real functions :: Functions of one variable :: Integrals of Riemann, Stieltjes and Lebesgue type)

Pending Errata and Addenda
None.
Discussion
Style: Expand: Order:
forum policy

No messages.

Interact
post | correct | update request | prove | add result | add corollary | add example | add (any)