Uniform Continuity: Proof of Limit Existence

In summary, the statement asks to show that if f:(0,1)→ℝ is uniformly continuous, then limx→0+f(x) exists. This can be proven by showing that for any ε>0, there exists an interval (0,δ) where f(x) is within ε of f(δ) as long as x is within that interval. This is possible because uniform continuity implies that the derivative is bounded, preventing the function from "veering off" to infinity. By considering the image of a sequence that converges to 0, the question can easily be solved.
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Newtime
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Homework Statement


Assume [tex]f:(0,1) \rightarrow \mathbb{R} [/tex] is uniformly continuous. Show that [tex]\lim_{x \to 0^+}f(x)[/tex] exists.

Homework Equations


Basic theorems from analysis.

The Attempt at a Solution


The statement is intuitive but I'm having trouble formalizing the idea. Uniform Continuity means the derivative is bounded. So the function can't veer off to infinity or do something like sin(1/x). But of course, this is flimy reasoning at best. Any ideas are appreciated.
 
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Claim: Uniform continuity implies the following. For any [itex]\epsilon > 0[/itex], there's an interval [itex]I(\delta) = (0, \delta)[/itex] such that [itex]f(x)[/itex] is within [itex]\epsilon[/itex] of [itex]f(\delta)[/itex] as long as [itex]x \in I(\delta)[/itex].
 
  • #3
jbunniii said:
Claim: Uniform continuity implies the following. For any [itex]\epsilon > 0[/itex], there's an interval [itex]I(\delta) = (0, \delta)[/itex] such that [itex]f(x)[/itex] is within [itex]\epsilon[/itex] of [itex]f(\delta)[/itex] as long as [itex]x \in I(\delta)[/itex].

Thanks for the help. Fortunately, I just solved the question. It's easy once you consider the image of a sequence that converges to 0.
 

FAQ: Uniform Continuity: Proof of Limit Existence

What is uniform continuity?

Uniform continuity is a property of a function where the rate of change of the function remains consistent over the entire domain. It means that no matter how close the input values are, the output values will also be close. This is in contrast to pointwise continuity, where the rate of change can vary at different points in the domain.

How is uniform continuity different from pointwise continuity?

Uniform continuity differs from pointwise continuity in that it considers the behavior of a function over the entire domain, rather than at individual points. A function can be pointwise continuous at every point in its domain, but not uniformly continuous. Uniform continuity requires that the rate of change of the function is consistent over the entire domain, while pointwise continuity only requires it to be consistent at each individual point.

What is the importance of proving the existence of a limit using uniform continuity?

Proving the existence of a limit using uniform continuity is important because it guarantees that the function is well-behaved over its entire domain. This means that the function will not have any sudden jumps or discontinuities, and its behavior will be predictable. It also allows us to use certain limit theorems and techniques that are only applicable to uniformly continuous functions.

What are the key steps in proving the existence of a limit using uniform continuity?

The key steps in proving the existence of a limit using uniform continuity are: 1) showing that the function is uniformly continuous over its entire domain, 2) choosing a specific value for the limit and showing that it satisfies the definition of a limit, and 3) using the definition of uniform continuity to show that the chosen limit is the only possible limit for the function.

Can a function be uniformly continuous but not have a limit?

Yes, it is possible for a function to be uniformly continuous but not have a limit. This can occur when the function is oscillating infinitely between two values, or when it has a vertical asymptote. In these cases, the function is still well-behaved and consistent over its entire domain, but it does not approach a single value as the input values get closer and closer together.

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