Domain and Range of the Infinite Power Tower Function

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  • Опубліковано 26 чер 2024
  • This is the part 3 of the Infinite Power Tower!
    start: 0:00
    Idea/example of a fixed point: 2:45
    endscreen: 9:20
    The graphs of x^x, x^x^x, x^x^x^x, ... / 1
    *The Satisfyingly Strange Journey to the Infinite Power Tower*
    Part1: Solving x^x^3=2 vs. x^x^3=3 • they don’t teach these...
    Part2: Solving x^x^...=2 vs. x^x^...=3 • Infinite Power Tower E...
    Part3: Domain and Range of y=x^x^... • Domain and Range of th...
    Part4: Why (cbrt(3))^(cbrt(3))^... converges to 2.4 and NOT 3? • Why it doesn't converg...
    Reference:
    1. mathworld.wolfram.com/PowerTo...
    2. arxiv.org/pdf/1908.05559
    If you enjoy my videos, then you can click here to subscribe ua-cam.com/users/blackpenredpe...
    Shop math t-shirts: teespring.com/stores/blackpen...
    Support Math: / blackpenredpen
    Follow Math: / blackpenredpen
    blackpenredpen,
    math for fun

КОМЕНТАРІ • 288

  • @EpicMathTime
    @EpicMathTime 3 роки тому +25

    The range being from e raised to its additive inverse, to e raised to its multiplicative inverse, is really aesthetic.

  • @johnswingle7648
    @johnswingle7648 2 роки тому +7

    I love how honest you were about not knowing the = sign part! That's great. You still had something to teach me and I appreciate it when people don't try to cover up parts they don't know. First video I've seen of yours and I just subscribed!

  • @dinohall2595
    @dinohall2595 2 роки тому +3

    That blue pen is crying about not being in the channel name. It did so much work for no recognition. We salute you, blue pen.

  • @a.a7mdoo368
    @a.a7mdoo368 3 роки тому +1

    I really wish that i could give you a hug seriously your the most amazing and kind teacher ive ever seen ....... im about to cry cause you really helped me a lot ....

  • @nilss0nDav
    @nilss0nDav 3 роки тому +106

    A question still remains, why did you not already factored pen in blackpenredpen ? sorry dont judge me ... love ya

    • @Arthur-qe8xc
      @Arthur-qe8xc 3 роки тому +9

      blackpen + redpen = pen(black + red)

    • @tonaxysam
      @tonaxysam 3 роки тому +37

      Tecnically, everything in blackpenredpen is multiplying, so it would be
      pen²blackred

    • @EpicMathTime
      @EpicMathTime 3 роки тому +6

      @@tonaxysam You are assuming abelian though

    • @donutman4020
      @donutman4020 3 роки тому +8

      Black * pen * red * pen = pen^2 * maroon

    • @mahatmaniggandhi2898
      @mahatmaniggandhi2898 3 роки тому

      @@donutman4020 lol

  • @krrishmaheshwari4860
    @krrishmaheshwari4860 3 роки тому +1

    2 of my fav channel
    1st one mind your decision and 2 one black pen red pen
    🔥🔥

  • @helo3827
    @helo3827 3 роки тому

    You are my favorite youtuber I never miss your videos

  • @azhakabad4229
    @azhakabad4229 3 роки тому +1

    Another mind boggling video!

  • @stefanocarini8117
    @stefanocarini8117 4 роки тому +58

    You really are an amazing teacher! Thank you

    • @blackpenredpen
      @blackpenredpen  4 роки тому +30

      Thanks! And you found my secret video!

    • @siddharthsoni2101
      @siddharthsoni2101 3 роки тому +3

      How the comment 2 months ago...even though video was uploaded 7 hrs ago

    • @puneetmishra4726
      @puneetmishra4726 3 роки тому

      @@siddharthsoni2101 patreon, may be.

    • @pbj4184
      @pbj4184 3 роки тому +1

      How did you find the video?

    • @siddharthsoni2101
      @siddharthsoni2101 3 роки тому +1

      @@puneetmishra4726 what's the meaning of patreon?

  • @sampson4844
    @sampson4844 3 роки тому

    I am not sure but I remember 3b1b asked a question about this as a homework in his lockdown math series, so this video answered the question,great!!

  • @trapkat8213
    @trapkat8213 6 місяців тому

    Very good presentation!

  • @gobbleguk
    @gobbleguk 3 роки тому +2

    Nice chain chomp

  • @DANGJOS
    @DANGJOS 3 роки тому +2

    Can't wait to try this out on my calculator! Thanks for the Interesting video.

  • @orion3043
    @orion3043 3 роки тому

    Cool beard! I love your chnnel, youre amazing

  • @landsgevaer
    @landsgevaer 3 роки тому +2

    About what happens at the equalities: the upper limit does not generally belong to the domain (or at least it depends on your starting value), but the lower one does.
    Motivation:
    We can look at how the function y_n+1 = x ^ y_n behaves to justify that. We look at how a small perturbation eps around the solution behaves (with eps arbitrarily small):
    - First, for the upper limit where x = e^(1/e) and y = e. You may check that if y_n = e, then y_n+1 = (e^(1/e)) ^ e = e^1 = e as well, so it is indeed a fixed point, consistent with the video. Let's now look at a perturbed value y_n = e+eps. Then y_n+1 = (e^(1/e))^(e+eps) = (e^(1/e))^e * (e^(1/e))^eps = e * e^(eps/e) = e * (1 + eps/e + 1/2*(eps/e)^2 + ...) = e + eps + 1/2*eps^2/e + ... . So we see that a perturbed y_n by an amount eps is mapped onto a perturbed y_n+1 by an amount eps+1/2*eps^2/e (plus higher-order terms that are negligible for sufficiently small eps). That extra quadratic term in eps is strictly positive. Therefore, negative perturbations eps become less perturbed, but positive perturbations become more perturbed. Therefore the solution is stable from one side but unstable from the other. This is called semi-stable, but that *is not* generally speaking a stable fixed point. (Although it does converge for the case where it is specified that y_1 = x, like in the video, since that approaches from below, albeit slowly.)
    - Next, for the lower limit where x = e^(-e) and y = 1/e. You may check that if y_n = 1/e, then y_n+1 = (e^(-e)) ^ (1/e) = e^(-1) = 1/e as well, so it is again a fixed point, as derived in the video. For the perturbed value y_n = 1/e+eps however, y_n+1 = (e^(-e))^(1/e+eps) = (e^(-e))^(1/e) * (e^(-e))^eps = 1/e * e^(-eps*e) = 1/e * (1 - eps*e + 1/2*(eps*e)^2 + ...) = 1/e - eps + 1/2*eps^2*e + ... . So we see that a perturbed y_n by an amount eps is mapped onto a perturbed y_n+1 by an amount -eps+1/2*eps^2*e (plus higher-order terms). At first sight, this seems similar to the previous case. However, interestingly, the sign of the perturbation flips, from eps towards -eps. So also the perturbations flip back and forth between the stable and unstable side and become alternately smaller and larger in magnitude! To resolve the total effect of that, we look at an additional term of the power series to find that y_n = 1/e+eps is mapped onto y_n+1 = 1/e - eps + 1/2*eps^2*e - 1/6*eps^3/e^2 + ... , and repeating the same idea for another iteration this is mapped onto y_n+2 = (e^(-e))^(1/e - eps + 1/2*eps^2*e - 1/6*eps^3*e^2 + ...) = (e^(-e))^(1/e) * (e^(-e))^(-eps) * (e^(-e))^(1/2*eps^2*e) * (e^(-e))^(-1/6*eps^3*e^2) * ... . Keeping only up to third-order terms in eps, this amounts to 1/e * (e^(eps*e)) * (e^(-1/2*eps^2*e^2)) * (e^(1/6*eps^3*e^3)) = 1/e * (1+eps*e+1/2*eps^2*e^2+1/6*eps^3*e^3) * (1-1/2*eps^2*e^2) * (1+1/6*eps^3*e^3) = 1/e + eps - 1/6*eps^3*e^2. Note that the quadratic terms cancel, but when including third-order terms a positive perturbation is mapped onto a slightly smaller perturbation, and a negative one to a slightly bigger one (since the third-order term -1/6*eps^3*e^2 always has the opposite sign compared to eps). So on both sides the perturbation tends towards zero now. Therefore, this *is* a stable fixed point.
    Together, the lower limit of the domain converges, but the upper limit only "semi-converges" (which is therefore not generally convergent, and depends on the starting value for y_1). The domain includes the lower limit but not necessarily the upper.
    #QED
    Just to be sure, I checked this with some numeric computations, and it seems to work out as derived.
    Might be a nice followup video in itself?
    With apologies for the cumbersome plain text notation... ;-)

    • @VaradMahashabde
      @VaradMahashabde 3 роки тому

      Man this is too thorough...

    • @angelmendez-rivera351
      @angelmendez-rivera351 3 роки тому

      It holds at the upper bound too, though.

    • @landsgevaer
      @landsgevaer 3 роки тому

      @@angelmendez-rivera351 Not if you start the iteration y_n+1 = x ^ y_n from a value y_0 > e. So the upper boundaries convergence depends on your starting point. Try it. That is called semi-convergent.

    • @angelmendez-rivera351
      @angelmendez-rivera351 3 роки тому

      Dave Langers I don't think that matters at all. Mathematically speaking, we still say it converges at the upper bound, and this is precisely what you will find everywhere in the literature in the subject

  • @sushamakokate7752
    @sushamakokate7752 3 роки тому +1

    By looking at thumbnail I was like..I know this😀..after watching full video I realised I knew only 40% of this..Thank You!🙏🏻👍🏻

  • @Ironmonk036
    @Ironmonk036 3 роки тому +1

    Love the Mario Chomper Mic!

  • @VaradMahashabde
    @VaradMahashabde 3 роки тому +32

    4:22 The equality is missing because think of g(x) = f(x) - x. f(x) is the recurrence function.
    If g(x_0) = 0 and dg/dx > 0, in physics it would be an unstable equilibrium as if you got away from x_0, the repeated application of the recursion will take you further from x_0, hence it is not a convergent value.
    If dg/dx < 0, in physics it would be an stable equilibrium because if you got away from x_0, the repeated application of the recursion will take you towards from x_0, hence it is a convergent value.
    But if dg/dx is Zero, it is only converging from one side, but diverging from the other
    Edit : 3b1b's video explaining ne it much better, obviously
    ua-cam.com/video/CfW845LNObM/v-deo.html

    • @rajibsarmah6744
      @rajibsarmah6744 3 роки тому

      Click here for video ua-cam.com/video/chgnCwcd8oA/v-deo.html

    • @rajibsarmah6744
      @rajibsarmah6744 3 роки тому

      Click here for video ua-cam.com/video/hbj6APyN3Ro/v-deo.html

    • @valeriobertoncello1809
      @valeriobertoncello1809 3 роки тому +2

      But the recurrence function is defined at d(g)/dx = 0 . Do we really have to require that the convergence be the same from left and right?

    • @VaradMahashabde
      @VaradMahashabde 3 роки тому +1

      @@valeriobertoncello1809 it's only trying to give an analogy, I have edited in the post a video which explains it properly

    • @valeriobertoncello1809
      @valeriobertoncello1809 3 роки тому

      @@VaradMahashabde What's the timestamp?

  • @EKbnc
    @EKbnc 3 роки тому

    I really do appreciate the fact that you are willing to say that you don't know how to get the the equalities
    So many people just pretend they know, and in my opinion that's just bad teaching

  • @jayantasarker197
    @jayantasarker197 3 роки тому +34

    Steve sir(blackpenredpen) pls reply to this
    Thank u sir for such tricky questions
    I am in 8th standard
    U made my interest in calculus
    I learnt calculus because of u
    I am from india
    Keep challenging us with such questions
    My name is prittish

  • @TheLarsChannel
    @TheLarsChannel 3 роки тому

    You are an amazing inspiration. How about doing some multivariate analysis?

  • @valeriobertoncello1809
    @valeriobertoncello1809 3 роки тому +9

    I think that in this video ua-cam.com/video/elQVZLLiod4/v-deo.html 3b1b does a really nice job explaining a nice (visual) solution to the puzzle (especially around 19:55). If you watch it, you immidiately understand why the equalities hold, and not only the inequalities. His approach is based on cobweb diagrams: the infinite power tower converges whenever the cobweb diagram between the functions y=a^x and y=x, starting from the input value x, converges to an intersection point of the two functions. The upper bound of this interval of convergence is found when and where y=a^x is tangent to y=x, i.e. there's only one point of intersection between the two functions in which both have slope 1.

  • @peterdecupis8296
    @peterdecupis8296 2 роки тому

    the application of the fixed point theorem is clear for the case z>1; in this case, for zz>e^(-e), and for the bipolar oscillation for z

  • @AdityaChaudhary-oo7pr
    @AdityaChaudhary-oo7pr 3 роки тому

    Amazing

  • @carlosrosales1712
    @carlosrosales1712 3 роки тому +14

    There is a very interesting research paper called “exponential reiterated” that answers your questions among others.

  • @dbmalesani
    @dbmalesani 3 роки тому +2

    My attempt to show that the infinite exponentiation tower converges for x = exp(1/e). It is based on showing that the sequence is monotonically increasing and bounded, hence it converges. This argument does not work for x = exp(-e), because the sequence is not monotonic. I tend to be verbose (maybe tedious!) so this comment is quite long!
    Let define recursively the tetration sequence as: y(1) = x, y(n) = x^[y(n-1)] for n > 1. Note that it's a parametric family of sequences, and we limit to the case 1 ≤ x ≤ e^(1/e).
    1a) Let's first show that the sequence y(n) is monotonically increasing, that is y(n+1) ≥ y(n). For the base case (n = 1) we need to prove that y(2) ≥ y(1), which reduces to x^x ≥ x, or x^x - x ≥ 0. This is a calculus exercise, and one can relatively easily show that a) x^x - x = 0 for x = 1 (by direct substitution) and that b) the derivative of x^x - x is given by x^x·[ln(x)+1] - 1 ≥ ln(x) + 1 - 1 ≥ 0 for x ≥ 1 (since x^x ≥ 1 and ln(x) ≥ 0 for x ≥ 1). This implies that x^x - x is non-negative for x ≥ 1, that is x^x ≥ x, which proves the induction base case. One can also double-check graphically using any plotting tool.
    1b) Moving on to the general induction step, let's assume that y(n) ≥ y(n-1), and prove that y(n+1) ≥ y(n). We have y(n+1) = x^y(n) ≥ x^y(n-1) = y(n), which is what we want. I have used the induction hypothesis and the fact that the function x^t is monotonically increasing (as a function of t) for a fixed x ≥ 1.
    2) Let's now prove that y(n) is bounded; remember that 1 ≤ x ≤ e^(1/e) ≈ 1.445. First, y(n) is obviously always positive, that is bounded from below. We now show, again by induction, that y(n) ≤ e. The base case is trivial, as y(1) = x ≤ e^(1/e) < e. For the general induction step, let's assume that y(n) ≤ e, and prove that y(n+1) ≤ e. We have y(n+1) = x^y(n) ≤ x^e ≤ [e^(1/e)]^e = e^(e/e) = e. This last inequality sheds some light on why the upper bound of the x convergence range is e^(1/e): it is the largest value of x such that x^e ≤ e.
    Points 1) and 2) show that y(n) is a bounded, monotonically increasing sequence. Since ℝ is a complete metric space, y(n) converges to a limit L, which concludes the proof. Furthermore, if L = lim y(n) for n → +∞ , by taking the limits for n → +∞ of both sides of the recursive definition of y(n), we have L = lim[y(n)] = lim[x^y(n-1)] = x^lim[y(n-1)] = x^L, which shows that L is the solution to the equation L = x^L. Consistently, this equation has solutions only if x ≤ e^(1/e).
    PS: step 1a) would become simpler by defining y(0) = 1 (carrying exponentiation "0 times" yields 1) and y(n) = x^[y(n)] for n > 0. This still recovers y(1) = x as it should be. But the base induction step becomes y(1) ≥ y(0), that is x ≥ 1, which is trivially true. The general induction step does not change because it still holds y(n) = x^[y(n-1)] for n ≥ 1. In point 2), the base induction step is similarly trivial: y(0) = 1 < e^(1/e) < e.

  • @giandomenicopanettieri5748
    @giandomenicopanettieri5748 3 роки тому

    wooo very good

  • @Jesin00
    @Jesin00 2 роки тому

    Is this function analytic in this range? If so, can we use analytic continuation to extend it further?

  • @chessematics
    @chessematics 3 роки тому +3

    Want daily doses like michael penn

  • @thememer9031
    @thememer9031 3 роки тому

    blackredpen Did you know you don't need the chain rule to calculate d/dx(log(9x)? You can just rewrite it as a sum as d/dx(log(9)+ log(x) because of the log property log(ab) = log(a)+ log(b). Log(9) becomes 0 because its a constant but log(x)
    becomes 1/ln(10)x. Other than that case and a couple of other cases, I recommend using the chain rule but that is also an optimized strategy.

  • @helo3827
    @helo3827 3 роки тому

    You are my favorite youtuber

  • @LShadow77
    @LShadow77 3 роки тому

    Can I suggest the idea for your some future video? This idea was came to my mind at old school years. It is to find the function f(x,t) satisfied following conditions:
    f(1,t) = cos(t);
    f(2,t) = cos(cos(t));
    f(3,t) = cos(cos(cos(t)));
    and so on..
    an x of course is the real number in common case, not an integer!
    So, what about this ffffunction?:)

  • @ganitagya-suryanshkhatri6231
    @ganitagya-suryanshkhatri6231 3 роки тому

    I have one question, why don't you use a simple microphone which you don't need to carry in your hand? Doesn't this become a bit uncomfortable? Btw, awesome video as always!

  • @bobahpooman4045
    @bobahpooman4045 3 роки тому

    thanks man

  • @Informative229
    @Informative229 3 роки тому

    I am from India. Your videos are excellent

  • @petergregory7199
    @petergregory7199 3 роки тому

    I like watching your videos because I can’t keep up. Does that make sense?

  • @federicopagano6590
    @federicopagano6590 3 роки тому +2

    Maybe it's better to think backwards if f (x) is defined over [a,b] it's derivative it's defined over (a,b) it loses ending points

  • @horndude77
    @horndude77 3 роки тому

    We should get you a bigger white board. Great stuff.

  • @krrishmaheshwari4860
    @krrishmaheshwari4860 3 роки тому

    Hi sir how can we suggest you or ask you intresting question's?
    Please tell

  • @user-yg97f5hfvh
    @user-yg97f5hfvh 3 роки тому +56

    Why there are comments 2 months ago even the video is 5 hours ago

    • @utsahsharma5335
      @utsahsharma5335 3 роки тому +16

      Yes right...why is that ?
      EDIT : now I know, he replied to one of the comments saying that this video was unlisted and he has published it now...👍

    • @joeljose182
      @joeljose182 3 роки тому +4

      @@utsahsharma5335 exactly

    • @Vicente75480
      @Vicente75480 3 роки тому +7

      The video was unlisted and somebody found the link

    • @steve2817
      @steve2817 3 роки тому +2

      이름이나아무 와 bprp 보는 한국인이 있었다니 굉장히 반갑네요 엌ㅋㅋㅋㅋ

    • @user-yg97f5hfvh
      @user-yg97f5hfvh 3 роки тому +2

      @@steve2817 저도 굉장히 반갑습니다 엌ㅋㅋ bprp 나무위키에 있는거 보셨어요? 그거 제가한거임 엌ㅋㅋ

  • @NannanAV
    @NannanAV 4 роки тому

    @blackpenredpen Can you explain how the convergence of fixed point rule was derived?

    • @pbj4184
      @pbj4184 3 роки тому

      How did you find this video?

  • @andreivlasenko527
    @andreivlasenko527 3 роки тому +1

    but can you integrate this or find length of the curve

  • @espeed10
    @espeed10 3 роки тому

    Given other requirement we need as viewers, it's quite bizarre that you explained fixpoints to us. interesting video tho

  • @ddiq47
    @ddiq47 3 роки тому

    Cool

  • @blazedinfernape886
    @blazedinfernape886 3 роки тому +1

    Wasn't this video posted earlier?

  • @jaysonbunnell8097
    @jaysonbunnell8097 2 роки тому

    looks like i finally have a new favorite maths equation

  • @lorenzovannini82
    @lorenzovannini82 3 роки тому

    What is the marker's brand?

  • @MOHNAKHAN
    @MOHNAKHAN 3 роки тому +1

    Wow, you are wonderful.
    One question from myside plz.
    One person forgot his 4 Digit ATM pin but he remembers 4 things about his ATM pin...
    1) First Digit is half of Third digit
    2) sum of second and third digit is 8
    3) Fourth digit is multiple of first & second digit
    4) All four digits sum is 12.
    So,
    Generate the formula to build the ATM PIN

    • @kevomtb6882
      @kevomtb6882 3 роки тому +1

      Let abcd be a four digit number, where a,b,c,d are elements of the set of natural numbers + {0} (since no ATM pin is negative or has decimal expansion). Also: first digit is half of the third digit (2a=c); sum of second and third digit is 8 (b+c=8); fourth digit is multiple of first and second digit (d=ab); sum of a,b,c,d is 12 (a+b+c+d=12).
      We already have the value of c in terms of a (2a=c), so we can replace c in the second formula (b+2a=8). Solving for b we get b=8-2a.
      Then, we replace b in the formula for d to get d=a(8-2a). By expanding the expression we get d=-2a^2+8a.
      Next, the sum of all the digits is 12, namely (a)+(8-2a)+(2a)+(-2a^2+8a)=12. By arranging and cancelling terms, we get the quadratic expression -2a^2+9a-4=0
      By solving for the values of a you get that a:{1/2, 4}. Since a is a natural number, the only value for a is 4.
      Finally, we just plug in a for every digit formula. 2a=c -> 8=c; b+c=8 -> b=0; d=ab -> d=0.
      In the end, the ATM pin is 4080

    • @MOHNAKHAN
      @MOHNAKHAN 3 роки тому

      @@kevomtb6882 thanks

  • @zanti4132
    @zanti4132 3 роки тому +1

    So basically this problem involves solving x^y = y for the domain and range where this equation is defined. If you are given y, you can the value for x, that being x = y^(1/y).
    What if you are given x? Can you find the value for y?

    • @blackpenredpen
      @blackpenredpen  3 роки тому

      Yes, you can also use the lambert W function for it.

  • @Tempo_Topos
    @Tempo_Topos 3 роки тому +2

    Is it possible to use analytic continuation or other techniques to extend the infinite power tower function?

  • @sardararas3385
    @sardararas3385 3 роки тому

    Good thank you

  • @chonghow1804
    @chonghow1804 3 роки тому

    I couldn't understand anything but I still clicked the like button, because it's black pen red pen hence it must be good

  • @aashsyed1277
    @aashsyed1277 3 роки тому

    IN ORDER TO get the inequalites, for the domain, just plug a number bigger than the bigger number.

  • @nutritionalyeast7978
    @nutritionalyeast7978 3 роки тому

    that was cooool

  • @anadikumar9832
    @anadikumar9832 3 роки тому

    Good

  • @sunitasharma2536
    @sunitasharma2536 3 роки тому

    You are amazing 💙 sir😍😍😍👍👍❤️❤️

  • @russchadwell
    @russchadwell 3 роки тому

    Mind blown

  • @peterdecupis8296
    @peterdecupis8296 2 роки тому

    If you are oriented to a rigorous theoretical approach to the convergence behaviour, that uses no graphic/computational hints (e.g. coboweb...), a complete work is "Reiterated exponentials" by Knoebel, 1981 (free on web); divergence, convergence and alternate oscillation are rigorously explained using classic real analysis theoretical tools.
    An accurate, deep study of the complete proof presented in this article provides all the necessary background if you are interested in a rigorous approach to further generalization of this problem, (e.g. infinite power tower with variable exponents) as is treated by more recent literature(*)
    (* see e.g.: F.J. Toledo "On the convergence of infinite towers of powers and
    logarithms for general initial data: applications to Lambert W
    function sequences")

  • @chessematics
    @chessematics 3 роки тому +1

    Lagrange resolvent...Please explain that

  • @oferzilberman5049
    @oferzilberman5049 3 роки тому +10

    You can have a limit of
    lim a→∞ (x↑↑a) maybe?

    • @tonaxysam
      @tonaxysam 2 роки тому

      infinity
      I mean, if x > 1, (x↑↑a) > x^a, and the limit when a -> ∞ of x^a is ∞, so lim a→∞ (x↑↑a) = ∞ if x > 1. If x

  • @dzakytamir3048
    @dzakytamir3048 3 роки тому

    I really missing the marathon series, Lets do it again plzz

  • @user-mt9ux2di6u
    @user-mt9ux2di6u 3 роки тому +9

    Hello blackpenredpen, I looked at math on the internet (cuz it's fun) and I found a video that showed an amazing way to prove Euler's formula, plz put it in a video
    Let f(X)=e^(-ix)*(cos(X)+i*sin(X))
    We'll take the derivative and after simplification (I won't write it because it will be so annoying to write in a comment) we will get that the derivative is 0 meaning that our original function is a constant c and after plugging into the function X=0 we will get c=1 meaning that:
    e^(-ix)*(cos(X)+i*sin(X))=1
    Meaning that:
    e^ix = cos(X)+i*sin(X)
    And that's it, I think that this is so amazing and I hope you put this in a video (plz)

  • @safinahammed4391
    @safinahammed4391 3 роки тому +1

    You are just amazing 💖❤️, boss of Math

    • @rajibsarmah6744
      @rajibsarmah6744 3 роки тому +1

      Please🙏

    • @rajibsarmah6744
      @rajibsarmah6744 3 роки тому

      Click here for mathematics video ua-cam.com/video/chgnCwcd8oA/v-deo.html

    • @rajibsarmah6744
      @rajibsarmah6744 3 роки тому +1

      Click here for proof of Green's theorem ua-cam.com/video/hbj6APyN3Ro/v-deo.html

  • @hnnagarathna7286
    @hnnagarathna7286 3 роки тому

    Blackpenredpen 😎😎😎 cool

  • @muralik3065
    @muralik3065 3 роки тому

    I have a doubt related to integral of √tanx. For the integration of dx/x²-a², we can also use 1/2a ln|x-a/x+a| instead of hyperbolic tangent right.
    Edit: please clear my doubt. I hv an exam in my skl tomorrow

    • @angelmendez-rivera351
      @angelmendez-rivera351 3 роки тому

      Technically speaking, the usage of ln|(x - a)/(x + a)|/(2a) is correct.

  • @rithikr6380
    @rithikr6380 3 роки тому +2

    5:09 I thought this formula was only applicable if the base were a constant. Can someone explain how he used it for (x^y), even though x is dependent on y?

    • @markstavros7505
      @markstavros7505 4 місяці тому

      You're right. I realized that too when I watched it. I've been working on this function on my own for a while before seeing this video. I had different results

  • @user-yk3ue1jq1v
    @user-yk3ue1jq1v 3 роки тому +1

    超可愛的麥克風

  • @siah2930
    @siah2930 3 роки тому +1

    It's been a while since I've taken calculus, can someone remind me why we know the function converges if the absolute value of the function's derivative is less than one?

    • @landsgevaer
      @landsgevaer 3 роки тому +1

      The magnitude of the deviation from the solution is multiplied by that derivative with each iteration. So if its magnitude is smaller than 1, it means that the deviation decreases and the solution converges (at least when sufficiently near). Similarly, if the derivative is positive, you converge from one side, and if the derivative is negative you hop around from left to right around the solution.

  • @kapoioBCS
    @kapoioBCS 4 роки тому +15

    Very intersting arxiv paper , simple enough for first year university students 👍

    • @pbj4184
      @pbj4184 3 роки тому

      How did you find this video?

    • @NikitaNair
      @NikitaNair 3 роки тому

      @@pbj4184 Time travel??!!!

    • @pbj4184
      @pbj4184 3 роки тому +2

      @@NikitaNair Someone I asked said they found a link to this video in the description of some other video. Watching videos before they're released is really cool!

  • @deepanshupandey6208
    @deepanshupandey6208 3 роки тому

    Bprp what is the factorial of π

  • @venomousmath7661
    @venomousmath7661 Рік тому

    Sorry I'm not understand that how you tell about the fixed point, for x^y =y , you are considering the input as y ,the output is y too, then for the coordinates you just got (x,5) let say y=5 ,but x isn't fixed isn't it ? How come the point fixed ? For one more ,the x should be the input the y would be the output isn't it ? Is the y in the x^y is the input ,while the y on the right hand is output , the whats x suppose to be ?

  • @mahatmaniggandhi2898
    @mahatmaniggandhi2898 3 роки тому

    but y=x/2 has a slope smaller than 1 and it still doesnt converge. shouldnt the slope be zero at infinity for it to converge in infinity?
    but y is not infinity so at the border of our domain our range and our slope will be infinity or rather undefined

  • @abhishekraj8055
    @abhishekraj8055 3 роки тому

    nice pokemon

  • @mokouf3
    @mokouf3 3 роки тому +1

    Can I ask a question?
    I wanted to solve an ODE: y'' + xy' + ky = 0, where k is constant.

    • @2appleboy
      @2appleboy 3 роки тому +1

      My gut says to use Laplace or Fourier Transform method

    • @mokouf3
      @mokouf3 3 роки тому +1

      @@2appleboy Thanks. This brings me nearer to the solution. this is the key to solve 2D wave equation.

    • @angelmendez-rivera351
      @angelmendez-rivera351 3 роки тому

      You use infinite series too.

    • @mokouf3
      @mokouf3 3 роки тому

      Actually I did find that I got the wrong 2D wave equation solution. The r part should look like xy'' + y' + kxy = 0 instead. I found that both Laplace/Fourier Transform don't help me get to the solution I saw in WolframAlpha.
      I have to learn more functions before trying.

    • @mokouf3
      @mokouf3 3 роки тому

      Moreover, those solutions are non-elementary...3D wave equation is much easier.

  • @theimmux3034
    @theimmux3034 3 роки тому

    3b1b has a Lockdown math video about this infinite power tower

  • @sciencifier3232
    @sciencifier3232 3 роки тому +10

    Did you bought the wireless mic???😂😂😂

  • @perdomamanimarca4926
    @perdomamanimarca4926 3 роки тому

    Cool..

  • @StevenPhD4
    @StevenPhD4 4 роки тому +2

    Why is it unlisted??

    • @pbj4184
      @pbj4184 3 роки тому

      How do you find unlisted videos?

  • @fuckoff1754
    @fuckoff1754 3 роки тому

    Nice Mic!!!!!

  • @logicalproofs7276
    @logicalproofs7276 3 роки тому +5

    Blackpenredpen this is a challenge for you
    Find the value of x when x⁹⁹=99to the power x
    Note that x is not equal to 99

    • @joonasgreis2781
      @joonasgreis2781 3 роки тому +1

      I would like to see this solved in few different ways. And at least with Lambert W function. There are few solutions on the internet, but I can't wrap my head around them for some reason. Like this one: math.stackexchange.com/questions/1292773/solving-xy-yx-analytically-in-terms-of-the-lambert-w-function. How does −ln(y) equals −y*ln(x)/x in second last step? What am I missing here?

    • @joonasgreis2781
      @joonasgreis2781 3 роки тому

      Found it! here is a good explanantion about the whole solution: ua-cam.com/video/ZVnW6WAM_Co/v-deo.html

    • @angelmendez-rivera351
      @angelmendez-rivera351 3 роки тому

      Are you looking for all complex solutions, or only one real solution? Because if x is not an integer, then 99^x := exp[ln(99)·(x + 2nπi)] for any integer n. If x^99 = exp[ln(99)·(x + 2nπi)], then x = exp[ln(99)/99·(x + 2nπi)], and x = exp[ln(x) + 2mπi] for any integer m. Therefore, ln(x) + 2mπi = ln(99)/99·(x + 2nπi), 99·ln(x) + 198mπi = ln(99)·x + 2·ln(99)·nπi, implying ln(99)·x - 99·ln(x) = [198m - ln(198)·n]·πi.

  • @mightybatillo
    @mightybatillo 3 роки тому

    But why do you have a chain chomp?

  • @hatdog3886
    @hatdog3886 3 роки тому

    Misss you bprp

  • @satyamverma101
    @satyamverma101 3 роки тому +1

    wait didnt you already post this video a few months ago?

    • @blackpenredpen
      @blackpenredpen  3 роки тому +1

      It was unlisted and I just published it now

    • @pbj4184
      @pbj4184 3 роки тому

      @@blackpenredpen How to watch unlisted videos? I've asked others but I thought it would be best if I asked you 😁

  • @mathteacher313
    @mathteacher313 3 роки тому

    AZE..Salam aleykum...Halal olsun əmoğlu😁😊

  • @NageshNagesh-wo1ox
    @NageshNagesh-wo1ox 3 роки тому +1

    Can you name a best book of calculus (differentiation,calculus, area related to calclus ,and more .) Which can make me to zero to best?
    Please any one @ *blackpenredpen*

    • @XanderGouws
      @XanderGouws 3 роки тому +2

      I recommend searching for "Paul's Online Notes". It's a great resource that covers everything from Algebra to Differential equations clearly (and for free).
      Best of luck!

  • @SpeakShibboleth
    @SpeakShibboleth 3 роки тому

    Doesn't it converge for x=0?

  • @twistedsector
    @twistedsector 4 роки тому +16

    Only 420 people found this secret video?

    • @utsahsharma5335
      @utsahsharma5335 3 роки тому +1

      Ahh, he commented in one of the comments that this video was unlisted and he published it now.

    • @pbj4184
      @pbj4184 3 роки тому

      How did you find this video?

  • @shinyeontae
    @shinyeontae 4 роки тому +2

    Your mic is the best

    • @pbj4184
      @pbj4184 3 роки тому

      How did you find this video?

    • @pbj4184
      @pbj4184 3 роки тому

      @@shinyeontae When he published it

    • @pbj4184
      @pbj4184 3 роки тому

      @@shinyeontae Oh I see. That's nice

  • @keepitplainsimple1466
    @keepitplainsimple1466 4 роки тому +2

    Least popular video of BPRP ever after so much time...
    Great Video, no crowds at all😄😄😃😁😁😂

    • @lightyagami6647
      @lightyagami6647 4 роки тому +1

      This video is unlisted
      So you might think that way😅😅😅

    • @pbj4184
      @pbj4184 3 роки тому +1

      How did you find this video?

  • @janjansen4711
    @janjansen4711 3 роки тому

    What about -1 ?

  • @user-ec4fc8mq9z
    @user-ec4fc8mq9z 3 роки тому

    Doesn't d/dy(x^y) equals d/dy(y) which is 1, so the point is not convergent?

    • @angelmendez-rivera351
      @angelmendez-rivera351 3 роки тому

      Иван Павлов No, because y is not a variable, y is an unknown.

  • @jayantanayak4981
    @jayantanayak4981 3 роки тому +1

    0:52 that's what she said🥺😞😭😭😭

  • @siddharthsoni2101
    @siddharthsoni2101 3 роки тому +1

    Given an acute non-isosceles triangle ABC with circumcircle Γ. M is the midpoint of segment BC and N is the midpoint of arc BC of Γ (the one that doesn't contains A). X and Y are points on Γ such that BX || CY || AM. Assume there exists point Z on segment BC such that circumcircle of triangle XYZ is tangent to BC. Let ω be the circumcircle of triangle ZMN. Line AM meets ω for the second time at P. Let K be a point on w such that KN || AM, ωb be a circle that passes through B, X and tangents to BC and be a circle that passes through B, X and tangents to BC and ωc be a circle that passes through C, Y and tangents to BC. Prove that circle with center K and radius KP is tangent to 3 circles ωb, ωc & Γ.
    Can you solve this question plz...

    • @siddharthsoni2101
      @siddharthsoni2101 3 роки тому

      @Leonhard Euler nope its an igo question (iranian geometry olympiad)

  • @silver4905
    @silver4905 3 роки тому

    Since when did he have a blue pen

  • @muradbashirov6435
    @muradbashirov6435 3 роки тому

    Check the 3b1b's "Power tower puzzle" video

  • @adityjha7240
    @adityjha7240 3 роки тому +1

    Hey!
    Can you please make a video about the Zeta function at irrational number Such as 'e' Or pi''
    Please try it
    Hey blackpenredpen please reply👍👍 or any body can

    • @angelmendez-rivera351
      @angelmendez-rivera351 3 роки тому +1

      Do you mean the Riemann Zeta function ζ(s)? If so, there is nothing interesting about the function evaluated at e or π. In fact, there is nothing to be said about the function evaluated at those values, because no closed form for the function at those values exists.

    • @adityjha7240
      @adityjha7240 3 роки тому +1

      A very thank you To you

  • @jibiteshsaha4392
    @jibiteshsaha4392 4 роки тому +1

    Can anyone explain how did the inequality at 4:15 come from
    Any proof??
    I really tried a lot to find it
    Please someone help
    How can we prove the criteria for convergence of fixed point??
    🙏🙏🙏
    It's bugging me for days

    • @Bambani-tr7jw
      @Bambani-tr7jw 4 роки тому

      Description

    • @jibiteshsaha4392
      @jibiteshsaha4392 4 роки тому

      @@Bambani-tr7jw I don't get it brother
      It is just showing the criteria
      "Absolute value of first derivative of function of y should be less than 1"

    • @jibiteshsaha4392
      @jibiteshsaha4392 4 роки тому

      @@Bambani-tr7jw how does this conclusion come from
      I don't get it

    • @hetsmiecht1029
      @hetsmiecht1029 4 роки тому

      @@jibiteshsaha4392 check the description of the video. He put a reference to an article which should explain it.
      Edit: it can be nicely visualised with a 'cobweb' construction (see the second reference in the video description).

    • @jibiteshsaha4392
      @jibiteshsaha4392 4 роки тому

      @@hetsmiecht1029 I looked into it and I didn't get how the fixed point convergence criteria comes
      I just don't want to memorize it and consider it is true
      Or else I would be interested in chemistry
      I tried but didn't get the specific part of reference in which that proof is given

  • @AbdoulBmuxx
    @AbdoulBmuxx 3 роки тому +1

    *You are really my true teacher,I am doing Mathmatics at in India,first year*

  • @LukeThunder
    @LukeThunder 3 роки тому

    ❄️❄️❄️❄️❄️❄️❄️❄️❄️❄️❄️❄️❄️❄️❄️❄️

  • @sansarsah2966
    @sansarsah2966 3 роки тому +1

    Are you japanese or Russian?