Real Analysis 28 | Epsilon-Delta Definition

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  • Опубліковано 16 жов 2024

КОМЕНТАРІ • 41

  • @lesetjamojapelo9825
    @lesetjamojapelo9825 3 роки тому +24

    This guy might just single handedly carry me through real analysis

  • @stat5web
    @stat5web 3 роки тому +22

    this guy is great! highest quality, math content. Keep up the amazing job!

  • @samehnour9262
    @samehnour9262 Рік тому +6

    Please do not stop with these series, you helped me through LA and now in Analysis.. you are single handedly leading me toward my cs degree .. Thank you

    • @brightsideofmaths
      @brightsideofmaths  Рік тому +2

      I will never stop producing math videos :)

    • @tibetatakan
      @tibetatakan 2 місяці тому

      @fermisurface2616 Most of the universities in Europe. They don't have calculus here.

  • @philologusopin47us57
    @philologusopin47us57 Рік тому

    Ive looked through 10 videos now and yours is the first that properly visualizes what delta and epsilon mean. Thx man

  • @sharonnuri
    @sharonnuri 2 роки тому +6

    Could not visualize when I read this theorem in my textbook. Thanks a lot for the clear explanation

  • @123-f9o7h
    @123-f9o7h 11 місяців тому +1

    finding you has made my homework grade go from D to A- no joke, thank you king

  • @sanelprtenjaca9147
    @sanelprtenjaca9147 2 роки тому +2

    We used this not as a theorem, but rather as a definition of continuous function. Interesting.

  • @minamishi
    @minamishi 4 місяці тому

    So this is my informal paraphrase of the delta epsilon definition: "if the limit L exists at x = A, no matter how small epsilon is, there will exist a set of x values, which satisfies the condition |x - A| ≤ delta (where delta is a value we have to find but we know it exists) so that |f(x) - L| ≤ epsilon"....is that correct or close to correct?

  • @dhananjaytudu6864
    @dhananjaytudu6864 Рік тому

    Really great! Very interesting proof and short proof, wonderful 😍

  • @shibshankardey5934
    @shibshankardey5934 2 роки тому +1

    Could you plz upload a video on the uniform and absolute continuity and their difference along with continuity? I am struggling to see any video on them. It will be helpful to many I believe

  • @JojiThomas7431
    @JojiThomas7431 3 роки тому +1

    Useful video. Keep it up.

  • @jhonnattanleonardovelasque9378
    @jhonnattanleonardovelasque9378 3 роки тому +1

    Hey guys! Greetings froms Colombia. I'm fan of your channel. I love all videos. Thanks a lot for this invaluable knowledge. I'll know what tools do you use to write and record the videos?

    • @brightsideofmaths
      @brightsideofmaths  3 роки тому +1

      Thank you very much! I use the nice free program Xournal :)

  • @jronirons5666
    @jronirons5666 4 місяці тому

    Why exclude x_0 with regards to the sequence ? Isn’t x_0 required to be in the domain of said function.

    • @brightsideofmaths
      @brightsideofmaths  4 місяці тому

      Maybe you can specify what you are referring to.

    • @jronirons5666
      @jronirons5666 3 місяці тому

      Sorry, my question is why it is the sequence be an element of I \{x_0} instead of just I? Why exclude the point x_0? I thought we want it x_0 to be in the domain of f.

    • @brightsideofmaths
      @brightsideofmaths  3 місяці тому

      @@jronirons5666 What is the timestamp of the question?
      Usually the point x_0 is not the interesting one but what happens around it.

    • @jronirons5666
      @jronirons5666 3 місяці тому

      5:36

    • @brightsideofmaths
      @brightsideofmaths  3 місяці тому

      @@jronirons5666 How should x=x_0 satisfy the inequality with "greater or equal than epsilon" in the line above?

  • @demaskoh6921
    @demaskoh6921 10 місяців тому

    Referring to the last example in Video 27: is there continuity for irrational numbers by using the epsilon-delta definition? I read in Sutherland (2009) that a function as such would be discontinuous at Q but continuous at R\Q. 🤔

    • @brightsideofmaths
      @brightsideofmaths  10 місяців тому

      We have a continuity for all real numbers. So I don't understand your question completely.

    • @demaskoh6921
      @demaskoh6921 10 місяців тому

      I was referring to your last example in Video 27, in which you said the function (=0 if irrational, =1 if rational) is discontinuous everywhere. @@brightsideofmaths

    • @brightsideofmaths
      @brightsideofmaths  10 місяців тому

      Yes, it's discontinuous on rational numbers and on irrational numbers.@@demaskoh6921

    • @demaskoh6921
      @demaskoh6921 10 місяців тому

      Thanks! But if you have the book Sutherland (2009), could you look at Exercise 4.16? It seems to suggest f is continuous on irrational, but discontinuous on rational. So I'm confused.@@brightsideofmaths

    • @brightsideofmaths
      @brightsideofmaths  10 місяців тому

      As a function from R to R, the function cannot be continuous at irrational numbers but discontinuous at rational numbers.@@demaskoh6921

  • @lwuquh6732
    @lwuquh6732 Місяць тому

    Why do you pick delta to be 1/n. That is not exhaustive of real > 0?

    • @brightsideofmaths
      @brightsideofmaths  Місяць тому

      But for the proof it is sufficient :)

    • @lwuquh6732
      @lwuquh6732 Місяць тому

      @@brightsideofmathswow thanks for the quick reply. So does that mean you can pick any decreasing convergent sequence with limit 0 for delta? Such as 2^-n?

    • @brightsideofmaths
      @brightsideofmaths  Місяць тому

      @@lwuquh6732 For every epsilon how have to find a delta. If 2^{-n} works, then you can use it :)

  • @desperatewanderer742
    @desperatewanderer742 11 місяців тому

    why can't my math teacher be this good

  • @snipergod5216
    @snipergod5216 Рік тому

    has anyone ever told you, you sound an awful lot like PewDiePie?

    • @brightsideofmaths
      @brightsideofmaths  Рік тому +1

      No, no one ever told me that :D

    • @snipergod5216
      @snipergod5216 Рік тому +1

      @@brightsideofmaths ahh well let me be the first one haha. You sound like him in his early days. Are you swedish by any chance? Also, thank you so much for these videos. Really helping me out in my math for econ course :D

  • @MoreDenseThanRationals
    @MoreDenseThanRationals 3 роки тому

    6/10 good video