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real analysis Difference between continuity and uniform continuity Mathematics Stack Exchange

To verify continuity, one can look at a single point $x$ and use local information about $x$ (in particular, $x$ itself) and local information about how $f$ behaves near $x$. For example, if you know that $f$ is bounded on a neighborhood of $x$, that is fair game to use in your recovery of $\delta$. Also, any inequality that $x$ or $f(x)$ satisfies on a tiny neighborhood near $x$ is fair game to use as well. A piecewise continuous function doesn’t have to be continuous at finitely many points in a finite interval, so long as you can split the function into subintervals such that each interval is continuous. Why are there more number of elements in the “Integrable functions set” than “Continuous functions set” (here by elements i mean integrable and continuous functions ofcourse) ???. Can anyone plz help me understand this out in as simple words as possible.

What is a continuous extension?

Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. However to verify uniform continuity, you can’t zoom in on any particular point. You can only use global information about the metric space and global information about the function $f$; i.e. a priori pieces of information independent of any particular point in the metric space. For example, any inequality that every point of $X$ satisfies is fair game to use to recover $\delta$. If $f$ is Lipschitz, any Lipschitz constant is fair to use in your recovery of $\delta$. These different points of view determine what kind of information that one can use to determine continuity and uniform continuity.

  • The derivative of a function (if it exists) is just another function.
  • Exactly, the delta of uniform continuity is not changeable, which decides the ball of x, y.
  • These functions almost always occur with the inclusion of floor into the regular set of algebraic functions you are used to in calculus.
  • In the definition of uniform continuity, $\exists \delta $ precedes neither $x$ nor $c$, therefore it can depend on neither of them, but only on $\epsilon$.
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What is the difference between continuous derivative and derivative?

The difference is in the ordering of the quantifiers.

Integrability on the other hand is a very robust property. If you make finitely many changes to a function that was integrable, then the new function is still integrable and has the same integral. That is why it is very easy to construct integrable functions that are not continuous. I know that a bounded continuous function on a closed interval is integrable, well and fine, but there are unbounded continuous functions too with domain R , which we cant say will be integrable or not. The derivative of a function (if it exists) is just another function. For all $\varepsilon$, there exists such a $\delta$ that for all $x$ something something.

  • The difference is in the ordering of the quantifiers.
  • I know i need some kind of visualization which i guess is easy, but i could not make it out on my own, so i turned to u guys.Thanks for any help.
  • As the other answer here says, each interval is continuous.

What’s the difference between continuous and piecewise continuous functions?

In the definition of uniform continuity, $\exists \delta $ precedes neither $x$ nor $c$, therefore it can depend on neither of them, but only on $\epsilon$. A piece-wise continuous function is a bounded function that is allowed to only contain jump discontinuities and fixable discontinuities. These functions almost always occur with the inclusion of floor into the regular set of algebraic functions you are used to in calculus.

Absolutely continuous functions

A continuous function is a function where the limit exists everywhere, and the function at those points is defined to be the same as the limit. Note that in the second definition, the universal quantifier $\forall c$ now also follows the existential quantifier $\exists \delta$. Connect and share knowledge within a single location that is structured and easy to search. At first glance, it may seem like a.e.-differentiability should be a nice enough property to ensure FTC is true, but there are counterexamples (like the Cantor function).

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This statement means there is some person $p$ who owns EVERY car. Thus this person doesn’t depend on the car (since he has all of them, or in other words; given every car, he has it). Others have already answered, but perhaps it would be useful to have at least one of the answers target the elementary calculus level. This property is unrelated to the completeness of the domain or range, but instead only to the linear nature of the operator.

The subtle difference between these two definitions became more clear to me when I read their equivalent sequence definitions. The reason for using “ap calculus” instead of just “calculus” is to ensure that advanced stuff is filtered out. The word “calculus” is often used for some really advanced topics that have little relation to what’s in an elementary calculus course, but “ap calculus” is pretty specific to elementary calculus content.

Relation between differentiable,continuous and integrable functions.

You can think of absolute continuity as a way of shoring up that kind of pathology, i.e. it eliminates so-called singular (in the measure-theory sense) functions. As observed by Siminore, continuity can be expressed at a point and on a set whereas uniform continuity can only be expressed on a set. Reflecting on the definition of continuity on a set, one should observe that continuity on a set is merely defined as the veracity of continuity at several distinct points. In other words, continuity on a set is the “union” of continuity at several distinct points. Reformulated one last time, continuity on a set is the “union” of several local points of view.

A function needs to be continuous in order to be differentiable. However the derivative is just another function that might or might not itself be continuous, ergo differentiable. What is the difference between continuous derivative and derivative?

Bounded is insufficient; but bounded derivative probably works. I wasn’t able to find very much on “continuous extension” throughout the web.How can you turn a point of discontinuity into a point of continuity? How is the function being “extended” into continuity? Then, the definition you provided is exactly saying that Q is absolutely continuous to the ‘default measure’. Since Q is induced continuous delivery maturity model by f, it seems natural to extend the definition to f (I don’t know if such Q and f are 1-1 correspondent, and the def will make even more sense if so). And it is suggesting that absolute continuity of g w.r.t f can be motivated.

I know i need some kind of visualization which i guess is easy, but i could not make it out on my own, so i turned to u guys.Thanks for any help. The conditions of continuity and integrability are very different in flavour. Continuity is something that is extremely sensitive to local and small changes. It’s enough to change the value of a continuous function at just one point and it is no longer continuous.

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