Finding the Right Delta: Epsilon-Delta Convergence in a Continuous Function

In summary, the conversation is about finding a value of \delta for a given function f:[1,\infty) in order to show continuity. The approach suggested is to use the uniform continuity of the \sqrt{x} function and set \sqrt{x}-\sqrt{y}<\delta/2 and |x-y|<\delta/4 in order to get a maximum value of \delta that will work. The conversation also discusses the idea of finding the least upper bound for \delta, but ultimately concludes that the suggested approach is sufficient.
  • #1
fyziky
4
0
Hello all,
My question is as follows:
f:[1,[tex]\infty[/tex]) is defined by f(x)=[tex]\sqrt{x}[/tex]+2x (1[tex]\leq[/tex]x<[tex]\infty[/tex]) Given [tex]\epsilon[/tex]>0 find [tex]\delta[/tex]>0 such that if |x-y|<[tex]\delta[/tex] then |f(x)-f(y)|<[tex]\epsilon[/tex]

It seems I am being asked to show continuity, and not uniform continuity, so my approach is this, but I am not sure it works:
|f(x)-f(y)|=[tex]\sqrt{x}[/tex]-[tex]\sqrt{y}[/tex] + 2(x-y) after minor manipulation

since [tex]\sqrt{x}[/tex] function is uniformly continuous it is safe to set [tex]\sqrt{x}[/tex]-[tex]\sqrt{y}[/tex]<[tex]\delta[/tex]/2 and defining |x-y|<[tex]\delta[/tex]/4 we get

[tex]\sqrt{x}[/tex]-[tex]\sqrt{y}[/tex] + 2(x-y) [tex]\leq[/tex] [tex]\delta[/tex]/2 + 2[tex]\delta[/tex]/4=[tex]\delta[/tex]
since [tex]\delta[/tex] can equal [tex]\epsilon[/tex] we just need make |x-y|<[tex]\epsilon[/tex]/4

any help would be appreciated, I am not sure i have the right idea here. thank you.
 
Physics news on Phys.org
  • #2
Yes, if you worded the problem correctly, then this will work because all it's asking is to find some [tex] \delta [/tex] that will work. However, just for kicks and giggles, see if you can find the least upper bound for [tex] \delta .[/tex]

EDIT: On second thought, there's really no need to go that extra step. Nothing really insightful to be gained. Forget it. Your answer's just fine.
 

1. What is "Epsilon, delta convergence"?

"Epsilon, delta convergence" is a mathematical concept used to define the limit of a function. It is often used in calculus to determine the behavior of a function as its input approaches a certain value.

2. How does "Epsilon, delta convergence" work?

The concept of "Epsilon, delta convergence" involves using two variables, epsilon (ε) and delta (δ), to determine the proximity of a function's output to a specific value. By choosing a small enough value for epsilon, we can ensure that the function's output will be within a certain distance, delta, from the desired value. This allows us to define the limit of the function as its input approaches the desired value.

3. Why is "Epsilon, delta convergence" important?

"Epsilon, delta convergence" is important because it allows us to rigorously define and determine the behavior of a function as its input approaches a specific value. This concept is essential in calculus and other areas of mathematics, as it helps us understand the behavior of functions and make accurate predictions about their values.

4. What are some real-world applications of "Epsilon, delta convergence"?

"Epsilon, delta convergence" has numerous real-world applications, particularly in physics and engineering. For example, it is used to determine the maximum load a bridge can support before collapsing, or the optimal trajectory for a rocket to reach its target. It is also used in computer graphics to create smooth curves and surfaces in computer-generated images.

5. Are there any limitations to "Epsilon, delta convergence"?

While "Epsilon, delta convergence" is a powerful tool in mathematics, it does have some limitations. It may not work for all types of functions, particularly those that are discontinuous or have sharp corners. Additionally, it can be challenging to determine the exact value of epsilon and delta in some cases, leading to approximations rather than exact solutions.

Similar threads

  • Calculus and Beyond Homework Help
Replies
8
Views
2K
  • Calculus and Beyond Homework Help
Replies
22
Views
337
  • Calculus and Beyond Homework Help
Replies
27
Views
730
  • Calculus and Beyond Homework Help
Replies
5
Views
871
  • Calculus and Beyond Homework Help
Replies
9
Views
2K
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
13
Views
479
  • Calculus and Beyond Homework Help
Replies
9
Views
543
  • Calculus and Beyond Homework Help
Replies
13
Views
2K
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
Back
Top