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Darboux's theorem (analysis) (Theorem)

Let $ f:[a,b]\to\mathbb{R}$ be a real-valued continuous function on $ [a,b]$, which is differentiable on $ (a,b)$, differentiable from the right at $ a$, and differentiable from the left at $ b$. Then $ f'$ satisfies the intermediate value theorem: for every $ t$ between $ f'_{+}(a)$ and $ f'_{-}(b)$, there is some $ x\in [a,b]$ such that $ f'(x)=t$.

Note that when $ f$ is continuously differentiable ( $ f\in C^1([a,b])$), this is trivially true by the intermediate value theorem. But even when $ f'$ is not continuous, Darboux's theorem places a severe restriction on what it can be.



"Darboux's theorem (analysis)" is owned by mathwizard. [ full author list (2) | owner history (1) ]
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Other names:  intermediate value property of the derivative

Attachments:
proof of Darboux's theorem (Proof) by paolini
converse of Darboux's theorem (analysis) is not true (Example) by Gorkem
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Cross-references: restriction, places, even, continuously differentiable, intermediate value theorem, right, differentiable, continuous function
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This is version 4 of Darboux's theorem (analysis), born on 2002-06-06, modified 2004-02-25.
Object id is 3055, canonical name is DarbouxsTheorem.
Accessed 7485 times total.

Classification:
AMS MSC26A06 (Real functions :: Functions of one variable :: One-variable calculus)

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is the converse true? by Gorkem on 2005-07-30 03:06:28
is the convese of darboux's theorem true? i mean, if f(x) does not have any jump discontinuity, then is it certain that there exists a function F(x) such that F'(x) = f(x) ?
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