A beautiful infinite series result

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  • Опубліковано 7 січ 2025

КОМЕНТАРІ • 16

  • @xleph2525
    @xleph2525 День тому +16

    The final result can be further simplified using the reflection formula for digamma:
    Final result: 1/x - pi*cot(x*pi)

  • @Gqtor
    @Gqtor 19 годин тому +3

    The answer should instead be (digamma(1+x)-digamma(1-x))/2 as differentiating the power series yields a factor of 2 as noted in 7:35.
    Neat derivation!

  • @CM63_France
    @CM63_France 12 годин тому +1

    Hi,
    "ok, cool" : 0:20 , 1:14 ,
    "terribly sorry about that" : 3:20 , 6:25 , 6:27 , 8:26 .

  • @Mephisto707
    @Mephisto707 День тому +4

    I remember when I first read the wikipedia entries for the zeta, gamma and digamma functions. Those pages showed all sorts of identities correlating those 3 functions, including several series expansions. At the time I was like, how on earth can all of these identities be found? Your channel is answering that question for me and I thank you for that.

  • @MrWael1970
    @MrWael1970 14 годин тому +1

    For the minute 3:32, the (1-(pi^2*x^2)/(pi^2/x^2)) this leads to 1-(x^2*k^2). I notice that the solution shall be modified. Overall, thank you for this innovative problem.

  • @alipourzand6499
    @alipourzand6499 День тому +2

    Best place to discover new functions !

  • @mrityunjaykumar4202
    @mrityunjaykumar4202 День тому +2

    @6:11 it should be 4^k or 2^2k in the denominator since x^2k at x=1/2

  • @balpedro3602
    @balpedro3602 20 годин тому +1

    Nice, but I want to point out that for the natural even values of the zeta function the is a classic formula involving powers of pi and the Bernouilli numbers (this formula generalizes the Euler's solution of Basel's problem, btw). The fomula reads \zeta(2n)=(-1)^n(1/2)(2\pi)^{2n}B_{2n}(1/(2n)!). This along with your calculation provides a generating formula for either even values of the zeta function or, equivalently, even values of the Bernoilli numbers (btw, all odd values of the Bernouilli numbers, with the exception of the first, which is 1/2, are zero).

  • @xleph2525
    @xleph2525 День тому +2

    This approximate train of thought is where the rather famous result:
    sum_{1}^{infinity}{(zeta(2n)-1)/n} = ln(2)
    comes from! Unfortunately I have never seen any series that use zeta(2n+1). Perhaps you have seen some, though?

  • @kappasphere
    @kappasphere День тому +1

    This is crazy, I didn't expect the initial solution to be this easy, not to mention all the identities that came of it

  • @leroyzack265
    @leroyzack265 День тому +9

    Are these Kamal special functions?

    • @anonymous_0416
      @anonymous_0416 21 годину тому +1

      Biology & Chemistry lover spotted 😂

  • @thewarlord8904
    @thewarlord8904 3 години тому

    Well we could have done this by using sinx/x expansion and taking log on both sides but still brilliant

  • @lukesaul2919
    @lukesaul2919 29 хвилин тому

    sum k=1 to 10 🔥

  • @rishabhshah8754
    @rishabhshah8754 День тому

    hii, could you please try this integral, I(α) = \int_0^1 (x^{50}(α-x)^{50}) dx
    i had this in an exam recently, i tried to use feynman 50 times. i made a mistake but i still got the correct answer 😅

  • @giuseppemalaguti435
    @giuseppemalaguti435 День тому

    Utilizzando la definizione di ξ,e scambiando i simboli di Σ,risulta S=-Σln(1-(x/n)^2)..n=1,2,3...a questo punto....boh...