1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Find delta given epsilon

  1. Mar 12, 2010 #1
    Could you help me with the problem?

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

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

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

  2. jcsd
  3. Mar 12, 2010 #2
    Apply the definition of limits to

    lim 1 / (2-x) = -1/3
  4. Mar 13, 2010 #3


    User Avatar
    Science Advisor

    Note that there is not just one correct answer. If some delta works, then any smaller one (>0) also works.
  5. Mar 13, 2010 #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.


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


    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 [Broken]

    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.
    Last edited by a moderator: May 4, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook