COOL Dirichlet Integral 😎

COOL Dirichlet Integral. I calculate the integral of sin(x)/x from 0 to infinity using Feynman's technique and a cool and unexpected geometric series that involves differentiation and integration. Lots of multiples of pi involved. Related to the Fresnel integral. This method doesn't use any complex analysis and is suitable for any calculus student or anyone who loves math. Big thanks to Ian Fowler for recommending this technique, he's the person who inspired me to do the anti-Pythagorean theorem video.
Anti-Pythagorean Theorem: • the anti Pythagorean t...
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Пікірлер: 73

  • @ianfowler9340
    @ianfowler9340 Жыл бұрын

    Again, many thanks for the shout out. I think I speak for everyone here when I say you have a fantastic channel. The graph is what started me thinking of trying to find the nth term formula. First I tried multiples of pi and then it hit me that cosine of multiples of 2pi are much nicer to deal with. No - 1. And the +/- area pairs seemed oddly symmetrical. I did notice what looked like a Laplace Transform but only the next day - good spotting Mokou. The infinite geometric series with 0

  • @joaomartins7361
    @joaomartins7361 Жыл бұрын

    This is not one of the Fresnel integrals. It is the Dirichlet integral.

  • @ianfowler9340

    @ianfowler9340

    Жыл бұрын

    That is true. Honest mistake.

  • @mokouf3
    @mokouf3 Жыл бұрын

    Feynman's technique, or Laplace transform of sinc function. A textbook example, now done with slightly different way, cool.

  • @karan440
    @karan440 Жыл бұрын

    He just confirmed all the stereotypes about math guys 😂 But still he's cool

  • @schizoframia4874
    @schizoframia4874 Жыл бұрын

    This has to be my favorite way to integrate sinx/x with the bounds

  • @joeremus9039
    @joeremus9039 Жыл бұрын

    So beautiful. Thanks for your proof. It really shows the elegance and beauty of analysis.

  • @chengkaigoh5101
    @chengkaigoh5101 Жыл бұрын

    This is just so cool.math works out in so many ways

  • @cycklist
    @cycklist Жыл бұрын

    Thank you for all your wonderful videos this year Dr Peyam!

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Thank you!!

  • @michaelbaum6796
    @michaelbaum6796 Жыл бұрын

    Very cool solution. Thanks a lot👍

  • @etiennebasset7493
    @etiennebasset7493 Жыл бұрын

    Très élégant, merci

  • @user-fy5tn7sy3t
    @user-fy5tn7sy3t Жыл бұрын

    Thank u doctor , we learn from you . Exactly it's a new way and should teach in Integration section

  • @manla8397
    @manla8397 Жыл бұрын

    Merry Christmas Dr peyam. You are always great.

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Thank you so much, you too!

  • @AlfonsoNeilJimenezCasallas
    @AlfonsoNeilJimenezCasallas Жыл бұрын

    Merry Christmas and happy new year, Dr. Peyam, you inspire us!

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Thank you so much, you too :)

  • @jessstuart7495
    @jessstuart7495 Жыл бұрын

    Laplace Transforms are wonderful.

  • @roberttelarket4934
    @roberttelarket4934 Жыл бұрын

    It's a hot integral!

  • @RSLT
    @RSLT Жыл бұрын

    Very Cool

  • @marcelob.5300
    @marcelob.5300 Жыл бұрын

    Good!

  • @dr.rahulgupta7573
    @dr.rahulgupta7573 Жыл бұрын

    Thank you , lower limit of Im (t) . Excellent presentation 👌

  • @castagnos509
    @castagnos509 Жыл бұрын

    0:32 impressive french !

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Merci!!!

  • @brendanlawlor2214
    @brendanlawlor2214 Жыл бұрын

    gracias por este ingenioso regalo de Navidad feliz año nuevo para ti y tus espectadores otro gran amigo 🎁🌲

  • @twoatomsonly7245
    @twoatomsonly7245 Жыл бұрын

    Echt coole Methode merry christmas and a happy new year

  • @pzorba7512
    @pzorba7512 Жыл бұрын

    Excellent votre français. Bonnes fêtes et bonne année 2023.

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Merci beaucoup!! A vous aussi 😁

  • @clementcoine1581
    @clementcoine1581 Жыл бұрын

    Nice video and nice way to compute this integral ! You need the continuity of the function I at t=0 at the end to justify that the integral of I' between 0 and infinity is "I(infinity) - I(0)".

  • @SimsHacks

    @SimsHacks

    Жыл бұрын

    the bigger sin is not verifying the conditions to use the Feynman's trick though 😆

  • @emanuellandeholm5657
    @emanuellandeholm5657 Жыл бұрын

    Happy holidays doctor!

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Thank you so much!! You too :)

  • @holyshit922
    @holyshit922 Жыл бұрын

    Is Fresnel Integral Int(sin(x^2),x) This is sine integral and only thing which we can do to calculate indefinite integral is integrate power series term by term

  • @mephist43
    @mephist43 Жыл бұрын

    Sir, thanks for the amazing video. Could you please also teach me the French you mentioned about simplicity and complexity?

  • @General12th
    @General12th Жыл бұрын

    Hi Dr. Peyam! What a Christmas miracle!

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Hahaha awwww!!!

  • @kmlhll2656
    @kmlhll2656 Жыл бұрын

    Wow and Wow...Wow n times

  • @anushkakar1923
    @anushkakar1923 Жыл бұрын

    Sir can u please tell how to solve the integration [(t-1)^3/2 ]/t dt ? Also please mention the method used for the same

  • @Noam_.Menashe
    @Noam_.Menashe Жыл бұрын

    This isn't the fresnal integral. This is dirichlet's integral.

  • @ianmi4i727
    @ianmi4i727 Жыл бұрын

    The thumbnail's integral lacks the integration limits, so it looks like a mathematical fairytale (a formula for the indefinite integral)!!! XD

  • @LeBretonDu18
    @LeBretonDu18 Жыл бұрын

    et en bon français Doc ! Happy Holidays from France.

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Merci beaucoup :)

  • @Kdd160
    @Kdd160 Жыл бұрын

    Integral from me to me +2pi 👏

  • @milkymilsy
    @milkymilsy Жыл бұрын

    i was watching til the feymann part then i thought "wait isn't this just taking the laplace transform of the integrand then plug in s=0?" and then you divided it into smaller integrals

  • @ianfowler9340

    @ianfowler9340

    Жыл бұрын

    It took me til the next day to see that. Good spotting.

  • @barryzeeberg3672
    @barryzeeberg3672 Жыл бұрын

    2:43 integral of two Peyam . . .

  • @prasanthkumar1770
    @prasanthkumar1770 Жыл бұрын

    Hi doctor, your videos are awesome. Can you please let me know the source book from which you’ve studied the explanation of the video “Life changing quadratic formula” video?

  • @drpeyam

    @drpeyam

    Жыл бұрын

    No book, I learned it from po shen loh himself

  • @prasanthkumar1770

    @prasanthkumar1770

    Жыл бұрын

    @@drpeyam great 👍🏼 thank you for the prompt response.

  • @advaykumar9726
    @advaykumar9726 Жыл бұрын

    Feynman crying in a corner

  • @user-zg8ny5tp4g
    @user-zg8ny5tp4g3 ай бұрын

    Where did (e) come firstly 😢?

  • @marcelocampos665
    @marcelocampos665 Жыл бұрын

    Pourquoi faire compliqué si on peut faire encore plus compliqué? Great !

  • @bertrandviollet8293
    @bertrandviollet8293 Жыл бұрын

    Is there a simpler way to find the answer?pourquoi faire simple quand on peut faire compliqué

  • @Adyioppjh678
    @Adyioppjh678 Жыл бұрын

    Are you Persian? It would be cool if you make a video teaching in “Farsi”

  • @drpeyam

    @drpeyam

    Жыл бұрын

    I already did!

  • @Decrupt
    @Decrupt Жыл бұрын

    Dirichlet integral?

  • @FreeGroup22
    @FreeGroup22 Жыл бұрын

    Ton français a l'air vraiment propre.

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Merci :)

  • @michaelempeigne3519
    @michaelempeigne3519 Жыл бұрын

    comment ca s'ecrit la phrase que tu as dit ?

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Pourquoi faire simple si on peut faire compliqué?

  • @michaelempeigne3519

    @michaelempeigne3519

    Жыл бұрын

    @@drpeyam merci et ​Joyeux noel

  • @manstuckinabox3679
    @manstuckinabox3679 Жыл бұрын

    I'm sorry doctor, you made a mistake, two PiM is an undefined value, there could only be one Dr.PiM ;),

  • @drpeyam

    @drpeyam

    Жыл бұрын

    Awwwww

  • @kumarashutosh9554
    @kumarashutosh9554 Жыл бұрын

    Sir I got a question Can you please help on it The question says " find the locus of the centre of curvature of a given function , eg. f(x)= sinx

  • @drpeyam

    @drpeyam

    Жыл бұрын

    No idea

  • @kumarashutosh9554

    @kumarashutosh9554

    Жыл бұрын

    @@drpeyamwith all respect sir! inspite being a PhD student , you shouldn't give up like that

  • @drpeyam

    @drpeyam

    Жыл бұрын

    I’m not a PhD student

  • @ianfowler9340

    @ianfowler9340

    Жыл бұрын

    That poses an interesting question. So given a general point (a,sin(a)) on the graph y = sin(x) we need to: (1) Find the curvature, k, at the point (a,sin(a)). This is usually done using k = y ' '/[ (y ')^2 + 1]^(3/2). We can talk about where this formula comes from using the definition of curvature and some properties of y ', y ' ' and arc length, but that is a discussion better left for another day. Let's just accept it for now. And we don't need to bother with the absolute value . Either the + or - will do so let's just take the +. It will not change the general description of the locus. (2) The curvature of a circle is constant and = 1/radius. So we construct a circle having radius = 1/k as calculated in (1). This gives a unique circle but with an unspecified center. (3) Now we take that circle and move it so that it it is tangent to y = sin(x) at the point (a,sin(a)). There are actually 2 possible circles with radius 1/k tangent to sin(x) - one on each side of (a,f(a)). That's where the absolute value of k comes in. But as I said, it won't change the general description of the locus of the center. Let's just pick the side of the curve that is concave down. (4) By moving the circle so that it is tangent to (a,sin(a)) we have now fixed the center - called the "center of curvature". Say (h,k). Our job now is to find the values of h and k as a function of a. We will need the fact that f ' (a) is the slope perpendicular to the radius (negative reciprocal stuff) and that (a,f(a)) lies both on the radius and on f(x). Then solve a quadratic system in h and k .Then we let "a" roam freely over the real numbers, replace h and k with x and y and we get parametric equations of the locus of the center. (5) This sounds reasonable, in principle, but the parametric equations you get for h and k are wildly complicated. I tried it and obtained nothing easily recognizable - for me anyway. (6) I'm not trying to trash the idea - I think it's a good one. Maybe I'll try a much simpler function. I'll let you know.

  • @kumarashutosh9554

    @kumarashutosh9554

    Жыл бұрын

    @@ianfowler9340 I have still doubt that if there are two possible circles , then how did you insure that it will not effect the locus of required centre ( the concave down)

  • @a21imanadhikary83
    @a21imanadhikary83 Жыл бұрын

    I am a grade 12 student, but I did not understand it, why 😭😭😭😭🥺🥺🥺