I hope these help! Understanding the Formal Definition of Limits

In summary, the conversation is about finding delta using the definition of limits, given epsilon = 0.25. The final answer should be delta = 1 and there are additional resources provided to help understand the concept better.
  • #1
gefops
1
0
Could you help me with the problem?

Find delta using the definition of limits, given epsilon = 0,25

lim 1 / (2-x) = -1/3
x->5

Answer should be delta = 1
How can I get it?

Thanks.
 
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  • #2
Apply the definition of limits to

lim 1 / (2-x) = -1/3
x->5
 
  • #3
Note that there is not just one correct answer. If some delta works, then any smaller one (>0) also works.
 
  • #4
You musn't have understood the book or whatever you used to learn about the formal definition of the limit.

I can't go crazily deep into it but I'm sure my links will help you understand the idea behind it.

http://www.5min.com/Video/The-Formal-Definition-of-a-Limit-169078903

This link will give you an idea of the general idea.

http://www.youtube.com/watch?v=-ejyeII0i5c&feature=youtube_gdata

This video (and the one following it in the playlist) give some examples on applying it.

http://docs.google.com/viewer?a=v&q=cache:_OYvmsulbDIJ:www.ocf.berkeley.edu/~yosenl/math/epsilon-delta.pdf+epsilon-delta+limit+example&hl=en&sig=AHIEtbQijZifL9dG46lTjmQMCpKpcrrY1g

This pdf is also very useful.

Personally, most of the places I've seen this version of the limit discussed have always left me in the dark, shameful authors, this idea is so simple & intuitive idk why they can't explain it properly.
 
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FAQ: I hope these help! Understanding the Formal Definition of Limits

What is the meaning of "delta" and "epsilon" in this context?

In mathematics, "delta" (represented by the Greek letter δ) typically refers to a small change or difference in a variable. "Epsilon" (represented by the Greek letter ε) represents a small positive number. In the context of finding delta given epsilon, these terms are used to calculate the maximum allowable change in the input variable to ensure that the output variable stays within a certain range.

Why do we need to find delta given epsilon?

Finding delta given epsilon is an important concept in calculus and analysis. It allows us to determine the maximum allowable change in a variable to ensure that the resulting output stays within a specific range. This is particularly useful when dealing with limits, continuity, and differentiability of functions.

How do you calculate delta given epsilon?

To calculate delta given epsilon, you need to use the definition of a limit. This involves finding the difference between the output value (f(x)) and the desired output value (L), and setting it equal to epsilon. Then, you can manipulate the equation to solve for delta. The resulting value of delta will be the maximum allowable change in the input variable.

Can you provide an example of finding delta given epsilon?

Sure, let's say we have the function f(x) = 2x + 1 and we want to find the value of delta that will ensure that the output stays within 0.5 of the limit L = 5. Using the definition of a limit, we can set the difference between f(x) and L equal to epsilon (0.5) and solve for delta. The resulting equation would be:
|2x + 1 - 5| < 0.5
Solving for x, we get:
-0.5 < 2x - 4 < 0.5
3.5 < 2x < 4.5
1.75 < x < 2.25
This means that the maximum allowable change in x (delta) is 0.25.

Are there any limitations or assumptions when finding delta given epsilon?

Yes, there are certain limitations and assumptions when finding delta given epsilon. Firstly, this concept only applies to functions that have a limit. It also assumes that the function is continuous at the given point. Additionally, the value of delta obtained using this method may not be the most accurate or optimal value, as it only ensures that the output stays within the desired range, but it does not necessarily minimize the change in the input variable.

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