Complex Analysis: Integral of 1/(x^n+1) feat. pizza contour

Today, we revisit an old classic on the channel, the integral from 0 to infinity of 1/(x^n+1) where n is any real number greater than 1.

Пікірлер: 55

  • @qncubed3
    @qncubed32 жыл бұрын

    Note: Typo at 3:55 should be an element symbol instead of equality ... silly me

  • @user-wu8yq1rb9t
    @user-wu8yq1rb9t2 жыл бұрын

    Without any doubt: You're *The King Of Complex analysis* on KZread. Please continue this playlist. Thank you 💖

  • @birdbeakbeardneck3617

    @birdbeakbeardneck3617

    4 ай бұрын

    math505 is cool too

  • @jackfitzgerald7231
    @jackfitzgerald72312 жыл бұрын

    He sorta looks like Jacob Collier...

  • @mohamedkhoulali7267
    @mohamedkhoulali72672 жыл бұрын

    this channel is so f underrated ! .. the best on complex analysis thank you

  • @azzteke

    @azzteke

    2 жыл бұрын

    underrated by whom please?

  • @davidblauyoutube
    @davidblauyoutube Жыл бұрын

    When I first did this integral and got the right answer, I knew finally that I really understood complex analysis.

  • @darcash1738

    @darcash1738

    5 ай бұрын

    I know nothing about it but I became interested in it rn when I saw him use it on an integral that I thought could only cleanly be done w/Feynman’s technique. Would you say if I were to fully learn all concepts used in this video(and ofc be able to replicate em in other problems), i would have learned the essence of complex analysis? Also, what would you describe the point of complex analysis now that you’ve become well-versed in it 😅 based on how it sounds, is it like a deep dive into the utility of the complex plane for solving problems?

  • @user-wu8yq1rb9t
    @user-wu8yq1rb9t2 жыл бұрын

    *Happy first contour integral with chalk board* Yeah, I watched a whiteboard version of it before, but with some difficulty. But this one is great, in all aspects. And ... Please when you are busy, at least make short videos. Thank you so much dear *QN³* ❤️

  • @Decrupt
    @Decrupt2 жыл бұрын

    Blackboard videos are noice.

  • @azzteke
    @azzteke2 жыл бұрын

    Excellent!

  • @ianmoog123
    @ianmoog1232 жыл бұрын

    wow this is great!

  • @seegeeaye
    @seegeeaye Жыл бұрын

    great job!

  • @bleaks218
    @bleaks2182 ай бұрын

    An interesting, alternative form for the final answer: I = (1/n) * Γ(1/n) * Γ(1-1/n) I = Γ(1+1/n) * Γ(1-1/n) I = B(1+1/n, 1-1/n)

  • @itisajem8645
    @itisajem8645Ай бұрын

    Interesting the result looks like the reflection formula for the gamma function but with 1/n

  • @weselise2489
    @weselise248923 күн бұрын

    you saved me thank you

  • @richardfeynman4523
    @richardfeynman4523 Жыл бұрын

    A question: residue method can only be used to calculate definite or improper integrals but not for indefinite in order to obtain only the primitive?

  • @Nolord_
    @Nolord_ Жыл бұрын

    That's pretty nice. Would it be possible to generalize this result for R=1?

  • @laurimynttinen6009
    @laurimynttinen60092 жыл бұрын

    Can you make a video explaining contour integrals?

  • @ryanblais6208
    @ryanblais62082 жыл бұрын

    Thanks for this great video and explanation. Just a question, at 7:16, should there be two or three poles in the lower right quadrant (positive Real, negative Imaginary)?

  • @qncubed3

    @qncubed3

    2 жыл бұрын

    It doesn't matter since this is only a rough sketch of where the poles could be. Depending on the value of n, the number and position of the poles will be entirely changed. The only pole that we are concerned about is the first one.

  • @ryanblais6208

    @ryanblais6208

    2 жыл бұрын

    @@qncubed3 ah ok, thank you!

  • @javiergilvidal1558

    @javiergilvidal1558

    Жыл бұрын

    @@qncubed3 It is not at all obvious, though nonetheless true, that the integral value remains the same if the pizza slice includes the first two nth-roots of (-1), or the first three, .... or in fact all of them, in which case you have the whole pizza minus a slice with no roots in its interior. Proving that the integral does not depend on how many residues you trap inside your region of integration would be a great exercise. I did it for the first two, and the result is far from obvious until the very end, when a magical simplification comes to save you in the nick of time! Will try to find the general answer tomorrow.

  • @rayandy2460
    @rayandy24607 ай бұрын

    Greattttttt video! However, can n be non-integer?

  • @calebkan7350
    @calebkan73502 жыл бұрын

    all u need is the beta function then put into gamma form and use euler's reflection formula

  • @user-wu8yq1rb9t
    @user-wu8yq1rb9t2 жыл бұрын

    Finalllllly ......

  • @Thor-yk4cr
    @Thor-yk4cr2 жыл бұрын

    After a such long time....... :D

  • @achenejegodwin6638
    @achenejegodwin6638 Жыл бұрын

    Thank you for that wonderful piece of delivery, pls, can you help when n=5 , I.e f(x) = 1/ x^5 + 1

  • @Pommes736
    @Pommes7362 жыл бұрын

    Is there a way to compute the indefinite integral of this with complex analysis or do you have to have bounds?

  • @qncubed3

    @qncubed3

    2 жыл бұрын

    I'm not sure if contour integration can be used to evaluate indefinite integrals. However, here's a related post I found :) math.stackexchange.com/questions/1999869/evaluate-int-frac11xndx-for-n-in-mathbb-r

  • @Pommes736

    @Pommes736

    2 жыл бұрын

    @@qncubed3 I'm not interested in this school integral per se. I wanna know if it's possible in general for any function without any bounds.

  • @davidraveh5966

    @davidraveh5966

    Жыл бұрын

    @@Pommes736 If you want to gain intuition for things like this, use software to numerically solve your integrals for different bounds; this will inform you of the answer immediately, although to prove that they are equivalent may be difficult.

  • @Pommes736

    @Pommes736

    Жыл бұрын

    @@davidraveh5966 Oh you didn't understand my question. I can solve these integrals without problem, my question was if I can use THIS METHOD for INDEFINITE integrals.

  • @TheHellBoy05
    @TheHellBoy058 ай бұрын

    A much simpler aproach, about how i solved it. Substitute x=t^1/n This makes dx=t^((1/n)-1)dt The given function resolves to the form of beta function. Which later simplifies into eulers reflection formula

  • @lambda2693
    @lambda2693 Жыл бұрын

    There’s actually a better method divide the denominator and numerator with x^n and then apply partial fraction and then resolve the contour

  • @the_nuwarrior
    @the_nuwarrior2 жыл бұрын

    Good

  • @holyshit922
    @holyshit9228 ай бұрын

    I would probably calculate it with Beta function then change it to Gamma function , finally i would finish it with reflection formula for Gamma

  • @bonelesspizza6311
    @bonelesspizza63112 ай бұрын

    But why are you allowed to choose a contour that's only around a single pole? Why not choose a contour that encloses 2 poles? How diff would the answer be?

  • @qncubed3

    @qncubed3

    2 ай бұрын

    It is possible, but then you would have to calculate two residues

  • @user-wu8yq1rb9t
    @user-wu8yq1rb9t2 жыл бұрын

    We are waiting ..... 🧐 It's me, looking at screen, for your notification 🧐

  • @qncubed3

    @qncubed3

    2 жыл бұрын

    Videos coming back by the end of this week :)

  • @ayman1515
    @ayman15157 ай бұрын

    What if we replaced n by 5, how will the integfation be, and what will the answer be?? Do i just replace n by 5 in all the steps of the solution and in the final answer or what??

  • @harisserdarevic4913

    @harisserdarevic4913

    6 ай бұрын

    uh yeah thats what it means to solve something for a general variable n. it holds for any n>1 so you don't have to redo any work

  • @ayman1515

    @ayman1515

    6 ай бұрын

    ​@@harisserdarevic4913 try it for n=5 using this method and try it using decompoaition and if you reached same answer then it is correct. I think for odd power, it has another way of solving

  • @ianmoog123
    @ianmoog1232 жыл бұрын

    lovely accent as well!

  • @qncubed3

    @qncubed3

    2 жыл бұрын

    cheers, from straya mate

  • @ianmoog123

    @ianmoog123

    2 жыл бұрын

    lovely country

  • @ianmoog123

    @ianmoog123

    2 жыл бұрын

    I thought you were english or something by the way you dressed lol

  • @juniorcyans2988
    @juniorcyans29886 ай бұрын

    I wish you were my classmate!

  • @dbf72829
    @dbf72829 Жыл бұрын

    Bad boy you don't clean up your own mess 😤

  • @niom9446
    @niom94462 ай бұрын

    this video looks like asian flammable maths

  • @qncubed3

    @qncubed3

    2 ай бұрын

    :O

  • @hajsaifi3842
    @hajsaifi38423 ай бұрын

    Bêta fonction mène à la même résultat

  • @Hadeeqah
    @Hadeeqah2 жыл бұрын

    Blackboard videos

  • @johndwolynetz6495
    @johndwolynetz6495 Жыл бұрын

    P I Z Z A