Epsilon delta Definition and 79 Threads

  1. M

    Uncertainty in measurements and epsilon delta definition of a limit

    does the epsilon delta definition of the limit connect to the uncertainty in measurements like this? like if we measure a quantity time with value a with error of + or - delta then my formula will give me v with value L +or - epsilon or is it unrelated?
  2. N

    Epsilon delta surroundings question

    i need to prove that for every delta i call d=delta e=epsilon 1/|x+1|>e we can choosr any e we want so they took e=1/4 but because the innqualitty needs to work for every delta they took x=min{2,(1+d)/2} for d>2 it takes x= 1+d /2 for d<2 takes x=2 uppon what logic they found this...
  3. L

    Can the Levi-Civita Kronecker Delta relation be proven using a matrix approach?

    This isn't a HW question just something I am curious about. I was looking on wikipedia and found a way to prive the Levi-Citiva Kronecker Delta relation that I hadn't seen before. The site claims \epsilon_{ijk}\epsilon_{lmn} = \det \begin{bmatrix} \delta_{il} \delta_{im} \delta_{in}\\...
  4. T

    A question about the epsilon delta definition of a limit

    Hi, I have a question about the epsilon / delta definition of limits, for example the limit of x as it approaches c for f(c) = L. As I understand it, epsilon is basically the number of units on either side of L on the y-axis that makes a range between L + epsilon and L – epsilon with L being...
  5. E

    How is the epsilon delta proof an actual proof?

    I am a first year freshman at UC Berkeley, in Math 1A. We learned the delta-epsilon proof for proving the limit of functions. I won't go through a whole proof or anything, but the general idea is you have a delta that is less than |x-a| (and greater than zero) and an epsilon less than |f(x)-L|...
  6. S

    Epsilon Delta Proofs, finding bounds

    Homework Statement Prove that lim x->3 of (x^{2}+x-5=7Homework Equations 0<x-c<\delta and |f(x)-L|<\epsilonThe Attempt at a Solution The preliminary analysis. The first equation in the relevant equations becomes 0<x-3<\delta And the second equation becomes |(x^{2}+x-5)-7|<\epsilon...
  7. M

    Understanding Epsilon Delta Definitions for Limits: Functions that Satisfy Them

    Homework Statement Im trying to figure out what the difference is between the following two epsilon delta statements and the kinds of functions they satisfy: For all real numbers x and for all delta>0, there exists epsilon>0 such that |x|<delta implies |f(x)|<epsilon vs. there exists...
  8. A

    Epsilon delta definition of limit

    Can someone please explain Epsilon delta definition of limit in detail?
  9. J

    Limit of 2x^2 as x Approaches 3: Using Epsilon-Delta Definition"

    Homework Statement evaluate lim2x^2 as x approaches 3 using formal definition (epsilon and delta) of limit Homework Equations The Attempt at a Solution
  10. Ƒ

    Epsilon-Delta Limits: Finding the Optimal Delta for a Given Epsilon Value

    Given: limit of (sin x)/x as x --> 0 and that ε = .01 Problem: Find the greatest c such that δ between zero and c is good. Give an approximation to three decimal places. Equations: 0 < |x - a| < δ 0 < |f(x) - L| < εAttempt: 0 < |x - 0| < δ 0 < | sin(x)/x - 1| < ε 0 < | sin(x)/x - 1| < .01 0...
  11. Ƒ

    What is the Optimal Delta for a Given Epsilon and Limit?

    Given the limit of \frac{x^2+2x}{x^2-3x} as x approaches 0 equals \frac{-2}{3} and that ε = .01, find the greatest c such that every δ between zero and c is good. Give an exact answer. 0 < |x-0| < δ 0 < |\frac{x^2+2x}{|x^2-3x} + \frac{2}{3|}| < ε |\frac{x(x+2)}{|x(x-3)} +...
  12. Z

    How to Use Epsilon-Delta Definition of Limits to Prove Inequality?

    Homework Statement Let f: \Re \rightarrow \Re and g: \Re \rightarrow \Re be functions such that lim_{x \rightarrow 1} f(x)=\alpha and lim_{x \rightarrow 1} g(x)=\beta for some \alpha, \beta \in \Re with \alpha < \beta . Use the \epsilon-\delta definition of a limit to prove...
  13. H

    Help Doing an Epsilon Delta Proof

    Homework Statement given a function defined by f(x,y) {= |xy|^a /(x^2+y^2-xy), if (x,y) cannot be (0,0) and = 0, if (x,y) = (0,0) Find all values of the real number a such that f is continuous everywhere e= epsilon d= delta In order to prove this, I know I need to do an...
  14. Z

    Proving the limit (epsilon delta) #3

    Homework Statement Prove the following states directly using the formal e, d definition \lim_{x\rightarrow 8} \sqrt{x + 1} = 3 Homework Equations The Attempt at a Solution If 0 < |x-8| < d Then 0 < sqrt((x+1) - 3) < e Let e be given 3 < sqrt(x+1) < e + 3 9 < x + 1 <...
  15. J

    Epsilon delta to prove continuity

    I have an example bit I can't quite follow it...? Use epsilon -delta definition of continuity to prove f(x) = 3x^2 - x is continuous at x=2 Ep > 0 and delta > 0 in terms of Ep f(x) -f(2) = 3x^2 - x -(3*2^2 -2) f(x) - f(2) = 3x^2 -x - 10 f(x) - f(2) = (3x + 5)(x - 2) So far so...
  16. P

    Mutlivariable Epsilon Delta Proofs

    Like many people on this forum, i am seemingly having a lot of trouble grasping the concepts of Epsilon Delta proofs and the logic behind them. I have read the definition and i realize for e>0 there is a d>0 such that... 0<sqrt((x-1)^2 - (y-b)^2) < d then f(x,y) - L <e (excuse my use of...
  17. M

    Understanding Epsilon Delta Proofs

    I understand most of the logic behind the formal definition of a limit, but I don't understand the the logic behind an epsilon delta proof. The parts I'm having trouble with are these: 1. How does proving that, the distance between the function and the limit is less than epsilon whenever the...
  18. R

    Why Does the Epsilon Delta Rule Simplify Expressions in Vector Calculus?

    The epsilon delta rule states \epsilon_{ijk}\epsilon_{pqk}=\delta_{ip}\delta_{jq}-\delta_{iq}\delta_{jp} I am constantly using this but get stuck when it is applied. For example \epsilon_{ijk}\epsilon_{pqk}A_{j}B_{l}C_{m}=(\delta_{ip}\delta_{jq}-\delta_{iq}\delta_{jp})A_{j}B_{l}C_{m}...
  19. P

    Epsilon delta to N & M Definition

    Okay for a simple finite limit: e.g. lim (3x) = 3 x->1 in the end I say: "Therefore for every |x - 3| < delta, there exists an epsilon such that |3x-3| < epsilon" Hence I can make delta really really small and the y bounds of epsilon will constrain the limit. So let's come to...
  20. R

    Solved Epsilon-Delta Proof: Is it Coherent?

    [SOLVED] Epsilon Delta Proof Does this limit proof make total sense? Given : "Show that \lim_{x \rightarrow 2} x^{2} = 4." My attempt at it :0<|x^{2}-4|<\epsilon which can also be written as 0<|(x-2)(x+2)|<\epsilon. 0<|x-2|<\delta where \delta > 0. It appears that \delta = \frac...
  21. K

    What is the Epsilon-Delta Definition of a Limit and How Does It Work?

    I can't get my head around the epsilon-delta definition of a limit. Unfortunately I don't have a teacher to ask (I'm teaching this to myself as a self interest) so this forum is my last resort -- google hasn't been kind to me. From what I've seen, I don't really understand how the definition...
  22. D

    Proof ε-δ: Epsilon Delta Proof of lim x->a of ((3x²-3a²)/(x-a)) = 6a

    I’m going to say from the beginning that I need to hand this problem in. I'm not looking for the answer, I think I already have it, just want a critical eye. I need someone to look over this problem and tell me if it's good. Not just if it's right but if it's perfect. I always get the...
  23. L

    Walkthrough of Epsilon Delta Limits Question

    Could someone please give me a walkthrough of the following question(and answer)?? I really can't understand it... lim x^2 = 9 x->3 if 0<|x-c|<delta then |f(x) - L|< epsilon so... x^2 - 9 = (x+3)(x-3) |x^2 - 9| = |x+3||x-3| Here's the problem.The book states: An...
  24. H

    Proving Lim x = -2, x^2+3x+7 = 5 | Epsilon Delta Proof Help"

    I'm supposed to prove that lim x -> -2, x^2+3x+7 = 5 Here's what I have: |x^2 +3x+7 – 5| < ε |x+2| < δ |x^2+3x+2| -> |(x+2)(x+1)| < ε whenever |x+2| < δ |x+1||x+2| < δ |x+1| |x+1||x+2| < δ|x+1| < ε ε / |x+1| > δ , as x -> -2, |x+1| -> 3, therefore: ε / -1 > δ But...
  25. D

    Epsilon-Delta Proofs: Understanding the Process

    Hi, Why is it, that when ever epsilon-delta proofs are done, once delta is found in terms of epsilon, it is reinputed through again? Is there any point to this really?
  26. G

    Epsilon delta proof, 3-space help

    I am trying to show that a certain function, f(x) has a limit that approaches 1. Does anyone have any sites i can look at for epsilon delta proof for 3-space? I've saw the ones for two space, but they aren't really helping me out in this pickle.. thanks.
  27. D

    Epsilon Delta and The Triangle Inequality

    I must prove \lim_{x\rightarrow 3\\} x^2 = 9 I get this... \mid x+3\mid\mid x-3\mid < \epsilon if 0< \mid x-3 \mid < \delta then it says with the triangle inequality we see that \mid x+3\mid = \mid (x-3)+6\mid \le \mid x-3\mid +6 therefore if 0< \mid x-3 \mid < \delta , then...
  28. H

    Epsilon Delta Proof, need clarification

    Prove that lim_{x \rightarrow c} \ \ \frac{1}{x}=\frac{1}{c} \ ,c\neq0 Proof We must find \delta such that: 1. 0<|x-c|<\delta \ \Rightarrow \ | \ \frac{1}{x}=\frac{1}{c}|<\epsilon Now, 2. | \ \frac{1}{x}=\frac{1}{c}|=| \ \frac{c-x}{xc}|= \frac{1}{|x|} \cdot...
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