Why imaginary numbers are needed to understand the radius of convergence

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  • Опубліковано 4 лют 2025

КОМЕНТАРІ • 252

  • @zachstar
    @zachstar  4 роки тому +39

    New STEMerch Store: stemerch.com/

    • @masternobody1896
      @masternobody1896 4 роки тому +1

      stupid people: ?
      genius people: { }

    • @uttamkumbhat7991
      @uttamkumbhat7991 4 роки тому +3

      Please make a video on what is mechatronics and its future

    • @mr.knight8967
      @mr.knight8967 4 роки тому

      MATH QUESTION
      Numerical / algebra qué.
      ua-cam.com/video/soN5NmkaXeM/v-deo.html
      One time see

    • @darshan7267
      @darshan7267 3 роки тому

      im confused, for stability sigma shud be negative decaying , but region of convergence says it shud be positive . whats happening?

    • @sleepycritical6950
      @sleepycritical6950 3 роки тому

      I gotta ask, why does it stop any other values outside of the radius like any value not +/-i? For example the Dirichlet series has an abscissca of convergence instead of a radius where it converges for all values past the singularities, that makes sense. Why is the Taylor series however, a radius?

  • @AndrewDotsonvideos
    @AndrewDotsonvideos 4 роки тому +501

    Imaginary numbers? Jeez when are we ever gunna use this stuff!?

    • @phillipgrunkin8050
      @phillipgrunkin8050 4 роки тому +61

      wHaT dO yOu MeAn?¿?¿? iMaGiNaRy NuMbErS aRe InCrEdIbLy UsEfUl FoR tHiNgS LiKe SiGnAl PrOcEsSiNg!¡!¡!
      (Btw love your channel and the math community in general, you guys are so tight-knit)

    • @lilithshopping7904
      @lilithshopping7904 4 роки тому +34

      i and j are your best friends in college....

    • @AndrewDotsonvideos
      @AndrewDotsonvideos 4 роки тому +18

      @@phillipgrunkin8050 :)

    • @robertmorrison1657
      @robertmorrison1657 4 роки тому +6

      @@AndrewDotsonvideos Nice to see you on one of Zachs videos.

    • @thephysicistcuber175
      @thephysicistcuber175 4 роки тому +5

      Imagine not being able to Wick rotate.

  • @xenontesla122
    @xenontesla122 4 роки тому +210

    That also explains why it's called a "radius" of convergence instead of just a region of convergence. Cool!

  • @modestorosado1338
    @modestorosado1338 4 роки тому +122

    When I realized that singularities were the reason behind the radius of convergence of Taylor series, I felt like I had been hit by a train. It blew my mind.
    This is one of the reasons why I find complex analysis so fascinating.

    • @MrAlRats
      @MrAlRats 3 роки тому +1

      I'm dying to learn more! What I really want to know is what property does a function need to have in the neighbourhood of a point (in addition to being infinitely differentiable) to make it possible for its values to be approximated by a Taylor series?

    • @modestorosado1338
      @modestorosado1338 3 роки тому +3

      @@MrAlRats It depends on where you're doing analysis. The nicest set is of course the complex numbers, since there are a lot of conditions that are equivalent to analiticity. For example, if a function is holomorphic at a point, that is enough to ensure the existence of a Taylor expansion (around that point). Obviously this is not true for functions over the reals. As a matter of fact, there aren't any nice characterizations of analytic functions over the reals that I'm aware of.
      You can also look at analytic functions over the quaternions. Unfortunately, analiticity is a very restrictive condition in this case. If I recall correctly, not even linear functions over the quaternions are "quaternion" differentiable. Some are, but not all of them.
      In a sense, the reals are too small to see the whole picture and the quaternions are too big to be well-behaved. The sweet spot is the complex numbers.

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

      Complex analysis is one of the most beautiful areas of mathematics.

  • @hiltonmarquessantana8202
    @hiltonmarquessantana8202 4 роки тому +155

    This problem is beautifully discussed in the book: "Visual Complex Analysis".

    • @triton62674
      @triton62674 4 роки тому +1

      @ ikr, could never be me

    • @jurian0101
      @jurian0101 4 роки тому

      +1

    • @leif1075
      @leif1075 4 роки тому

      @ why too dry or dense and boring?

    •  4 роки тому

      @@leif1075 i don't get the subject of your sentence: If the subject is "reading" then "i don't have an interior monologue, so it sucks for me", if the subject is me then "Yes"

    • @giladzxc17
      @giladzxc17 4 роки тому

      This book is great. Im actually studying it right now

  • @RC32Smiths01
    @RC32Smiths01 4 роки тому +45

    The ways in which imaginary numbers work in the real world never ceases to amaze. I think they will be pivotal to many more of life's advancements.

  • @tomasstana5423
    @tomasstana5423 4 роки тому +23

    Its nice that now we know ROC is connected to singularities in complex plane, but we still dont know why .... other than that, great video :)

    • @zachstar
      @zachstar  4 роки тому +11

      Yeah this doesn't actually dive into the 'why' but that's because it is much more difficult to explain that, you have to dive further into complex analysis which is way beyond a video like this.

  • @shashwattrivedi501
    @shashwattrivedi501 4 роки тому +4

    One of the few channels whose content I watch regularly. Good job!

  • @shivangi296
    @shivangi296 4 роки тому +3

    Beautiful! Thanks for the Mandelbrot mention. Guess your wallpaper with “imaginary” friends did a good job!

  • @KillianDefaoite
    @KillianDefaoite 4 роки тому +2

    I'm taking a complex analysis course soon and I had never considered this. Thanks for the great video.

  • @suyashverma15
    @suyashverma15 4 роки тому +39

    This was a total mind-blower, really! Would you like to make a video on fractals and its non integral dimensions also?

    • @mrmoinn
      @mrmoinn 4 роки тому +3

      check out the video on it by 3Blue1Brown

    • @suyashverma15
      @suyashverma15 4 роки тому +6

      @@mrmoinn Yes bro I have seen it and it was awesome too, but I am suggesting it to him too, because I think he can elaborate it on more of the practical side, with all its abstractness that Maths has to offer.

  • @clerklysquid6575
    @clerklysquid6575 4 роки тому +64

    Last time I was this early, pi hadn’t been calculated yet

    • @henryginn7490
      @henryginn7490 4 роки тому +6

      technically it still hasn't, and won't ever be calculated in full

    • @henryginn7490
      @henryginn7490 4 роки тому +7

      Demir Sezer I thought so, but the urge to point out a slight error overruled

    • @-cookiezila-461
      @-cookiezila-461 4 роки тому +1

      Henry Ginn I don't think its an error, its purposely technically true

    • @henryginn7490
      @henryginn7490 4 роки тому +1

      -COOKIEZILA - correct, I phrased it badly

    • @KRYMauL
      @KRYMauL 4 роки тому +2

      Henry Ginn technically at 10^-34 you already calculated pi for all real world applications seeing as Physics breaks down at that point and we don’t know if what happens after that.

  • @anonymousdude7982
    @anonymousdude7982 4 роки тому +53

    Me sitting here in my sophomore year of high school pretending like I understand this.

    • @yimoawanardo
      @yimoawanardo 4 роки тому +5

      You probably do 😃
      I could swear age doesn't matter here. A minimum age would probably be 5 or 6, by the time you get the hang of talking basically lol
      Otherwise 40 or 12, you can understand even the "hardest" maths.
      My personal opinion though.

    • @anonymousdude7982
      @anonymousdude7982 4 роки тому +3

      Yimo Awanardo That may just make me an idiot, but thank you. 🙂

    • @mariogamesrock
      @mariogamesrock 4 роки тому +6

      @@anonymousdude7982 dont worry, your not an idiot, I have no idea what kind of crack that dude is smoking. Until you have a fundamental understanding of basic calculus, which requires advanced algebra and trig, you (rightfully) should have no idea what a taylor series is. Just wait and your time will come

    • @smrtfasizmu6161
      @smrtfasizmu6161 4 роки тому

      Well, you probably already know imaginary numbers, you will soon learn what derivative is and then you will learn Taylor series. Taylor series are just polynomials that approximate functions. They can approximate functions as close as you want them to (by having more and more terms in the polynomial), as long as the function that you want to approximate is analytical. The way you set up the polynomial is that you make sure that derivatives for some input of that polynomial match the derivatives for that same input of the function that you want to approximate. For instance, you set up the first derivative at x = 0 of your polynomial to be equal to the first derivative at x = 0 of the function that you want to approximate. Then add another term in the polynomial such that the second derivative at x = 0 is the same as second derivative at x=0 for the approximated function. And so on. I don't know what math curriculum is where you live, but it is possible that you will learn about derivatives next year. Then you can go back to this video, read this comment again and understand what this video is about.

    • @yavuz1779
      @yavuz1779 3 роки тому

      Fake it till you make it

  • @Lion1063
    @Lion1063 4 роки тому +1

    We literally just went over Taylor/Maclaurin series in calc and I was so confused about the radius of convergence, this video was awesome, thanks

  • @felixroux
    @felixroux 4 роки тому +59

    This guy's pfp is a pentagram and he has 666K subs at the moment.

  • @VENOM-ol6pv
    @VENOM-ol6pv 4 роки тому +2

    Complex numbers are awesome!
    Thanks zachstar!☺

  • @brboLikus
    @brboLikus 4 роки тому +23

    Now it makes sense for it to be called the __radius__ of convergence. Because in 2D, it's kind of a misnomer.

    • @angeldude101
      @angeldude101 2 роки тому +2

      1D disks/balls exist and they have a radius and a surface. In fact, the intersection of a circle and a plane is exactly a 0-sphere, which is an object in 1D with a center and a radius, but only actually contains 2 points.

  • @mscir
    @mscir 4 роки тому

    Thanks for this, I was an electronics tech, had to learn complex math but never understood how that played into things, only that it worked. Anything you do on complex numbers would be greatly appreciated.

  • @jamesbra4410
    @jamesbra4410 4 роки тому

    Exception video! By far my favorite channel on UA-cam. Keep up the good work. Perhaps you've readied your audience for Cauchy's Residue Theorem lol!

  • @technoguyx
    @technoguyx 4 роки тому +1

    Very interesting. Never thought to ask myself if there's a deeper reason than the ratio test and even though I did take complex analysis last semester I never made the link. Love these visualizations

  • @Saptarshi.Sarkar
    @Saptarshi.Sarkar 4 роки тому +5

    After 3 years of college Physics, I finally truly understand what radius of convergence means. Thanks.

  • @depressedguy9467
    @depressedguy9467 3 роки тому

    I was 14 i knew about Fourier series but u was the guy to give me the intutive information about it

  • @sandro7
    @sandro7 4 роки тому +3

    This was literally one of my biggest math questions for like a year or two, and I always figured it had to do with just something about the functions moving above and below the function without converging in it (like sinx doesn’t converge to 0), idk y I never thought of smth like this. The idea makes sense bc the derivatives won’t work out if it’s not analytic but I’m curious as to why the function can’t still be defined by the polynomial in other directions where the function is analytic (so the converging area isn’t just a circle).

  • @jonathangrey6354
    @jonathangrey6354 4 роки тому +5

    Even when not including complex numbers, I always assumed the RADIUS part meant all complex numbers within that radius of the center

  • @harrypotter5460
    @harrypotter5460 4 роки тому +4

    Follow-up question for those with a curious mind: Is what Zach did for 1/(1+ x^2) always possible? More formally, is it always possible to extend a real analytic function (one with a Taylor series at every point) to a complex meromorphic function (one with a Taylor series at every point expect on a set of isolated poles) such that the radius of convergence of the Taylor series at a point is the distance from that point to the nearest complex pole? If so, is such an extension unique?

  • @daviddeane4250
    @daviddeane4250 4 роки тому +1

    please make a video on mechatronics engineering and interdisciplinary fields

  • @sarahrogers-pastio7709
    @sarahrogers-pastio7709 3 роки тому

    This is so cool! It's so wonderful finding things that make me fall even more in love with math gah

  • @hk8487
    @hk8487 4 роки тому +4

    best channel for engineers: Zack Star
    and for Mathematicians: 3B 1B

  • @royelhajj2612
    @royelhajj2612 4 роки тому +1

    Beast like always Zach !!!

  • @PhilipSmolen
    @PhilipSmolen 4 роки тому +1

    I love watching stuff I learned years ago, but explained with modern graphics!

  • @kendakgifbancuher2047
    @kendakgifbancuher2047 4 роки тому +1

    would like to see, how polynomial series "approach" that 3d plot at the end

  • @matiuspakpahan7612
    @matiuspakpahan7612 4 роки тому +4

    i wish you were my lecturer when i was in college

  • @benjaminbrat3922
    @benjaminbrat3922 4 роки тому +10

    Yes, I remember the dawning of understanding when I realized that the radius of convergence was actually... a radius... of convergence. (But in C)

  • @balconydemon4750
    @balconydemon4750 4 роки тому

    this gave me goosebumps

  • @johnchessant3012
    @johnchessant3012 4 роки тому +1

    Even more fun is how you can use the radius of convergence to find an asymptotic formula for the Maclaurin coefficients. I learned that in the book "generatingfunctionology" by Herbert Wilf.

  • @Arkunter
    @Arkunter 4 роки тому

    Wow that was pretty nice.... I really enjoy these quality shorter videos!

  • @samin3997
    @samin3997 3 роки тому

    This vedio helped me learn series solution of differential equations ❤️

  • @geneeditor9545
    @geneeditor9545 4 роки тому

    Great teaching. It helped me a lot to understand the topic.

  • @rafaelaassuncao9729
    @rafaelaassuncao9729 4 роки тому

    dude that blew my mind

  • @Godél-p4e
    @Godél-p4e 4 роки тому +1

    Great video

  • @johnginos6520
    @johnginos6520 4 роки тому

    Can you do a video on dynamics in social sciences, particularly economics, there has been work done on how gauge theory and differential geometry can be used in modeling economic issues

  • @denelson83
    @denelson83 4 роки тому

    That graph you introduce at 5:33 should have had its colours assigned based on the phase of the output.

  • @Chemi4001
    @Chemi4001 3 роки тому

    this video makes me   W O K E
    thanks, Zach Star

  • @perappelgren948
    @perappelgren948 4 роки тому

    Short video, but very to the point. 👍👍

  • @thephysicistcuber175
    @thephysicistcuber175 4 роки тому +1

    Complex analysis

  • @codewriter3000
    @codewriter3000 4 роки тому

    Make a tier list of every course you took in undergrad and grad school

  • @chrisray1567
    @chrisray1567 4 роки тому +1

    Is there another step past imaginary numbers? Like quaternions? Do they describe 3-D spherical regions of convergence?

  • @MissTexZilla
    @MissTexZilla 4 роки тому

    you can use imaginary numbers to calculate particle masses and fumble around with no boundary theories and apply those to either the general universe or stuff like blackholes.

  • @mindaugasdubosas7602
    @mindaugasdubosas7602 4 роки тому

    Could you create a video for a general engineering major? What they do, jobs they can get etc? :)

  • @jurian0101
    @jurian0101 4 роки тому

    A exceptionally fantastic case of poles ruin series expansion is the Sundman series of the 3-body astrodynamic system. The Sundman series is a CONVERGENT infinite series that solve arbitrary 3-body problem. Wait, what?!
    Per a PBS Spacetime episode, the catch is that in order to obtain that infinite series, a certain intricate manipulation on the complex plane is required - merely avoiding the poles (collisions of the bodies), which lead to an infinite series performing so poorly, converging only if 10^(N million) terms is added up. It is by no means a practical solution. :D
    (cf. Solving the Three Body Problem - PBS Spacetime)

  • @alwaysdisputin9930
    @alwaysdisputin9930 3 роки тому

    6:27 Oh yeah! That's a fine pair of baps right there. Those real number only guys are missing out

  • @Callie_Cosmo
    @Callie_Cosmo 4 роки тому

    As John Malani would say
    “You had me at ‘solved’”

  • @lolthistruebias5057
    @lolthistruebias5057 4 роки тому

    Hey Zach! Can you maybe make a video about nuclear engineering?

  • @DanteKG.
    @DanteKG. 4 роки тому

    Had a mental image of a dangerous place that fictional characters have to go to in order to fix something.
    "The machine is outputting anomalies with no reason!
    -We have to go down into the complex dimension to fix it..
    -Why? What will we do there??
    -Hunt for singularities"

  • @lateefahmadwanilaw8948
    @lateefahmadwanilaw8948 4 роки тому

    Thank u sir

  • @michaeljaf5734
    @michaeljaf5734 4 роки тому

    You should make a video on construction engineering.

  • @michaelupdike-bz6rg
    @michaelupdike-bz6rg 4 роки тому

    Do quaternions ever come up in a similar manner? Or even high dimensional numbers.

  • @taylorlorenztransormation3102
    @taylorlorenztransormation3102 3 роки тому

    I love your videos

  • @bee_irl
    @bee_irl 4 роки тому

    Very good video

  • @yourmathtutorvids
    @yourmathtutorvids 4 роки тому +2

    My face when it started moving at 5:45 😳 haha

  • @nakodares5982
    @nakodares5982 4 роки тому

    One thing I don’t quite follow is that the function you showed doesn’t have a real output for every number in the complex plane. For example, x = 1 + i. So in this case, when it comes to that 3D plot of values for numbers in the complex plane, what would you plot as the output (z value)? It seems like your 3D plot was continuous over the complex plane, but then does that mean that the z value on your 3D plot wasn’t actually the value of the function? In which case what was it? I assumed it was because that’s what the y-axis is in 2D on the real number line.
    EDIT: I had a quick think and I assume you are just plotting the magnitude of the complex output. In which case I would guess that asymptotes in the complex plane remain asymptotes when you take the magnitude or something like that, in order to have the idea you presented about the radius of convergence hold up even when plotting the magnitude of the function.

    • @zachstar
      @zachstar  4 роки тому

      Your edit is correct, I was just plotting the magnitude since that's all that was needed to show the singularities. I couldn't done phase with color but the program I was using doesn't seem to allow me to do that (I can only change color based on the z value)

    • @nakodares5982
      @nakodares5982 4 роки тому

      @@zachstar Thanks for the reply and the video!

  • @amineelfardi4311
    @amineelfardi4311 4 роки тому

    Can you please explain PID conlroller

  • @Eyalkamitchi1
    @Eyalkamitchi1 4 роки тому

    Does this mean that the the Taylor series convergence over the imaginary plane? Because only then will the "convergence block" for the polynomial will be met. If so, how does it(Taylor series) do it(converge over the imaginary plane)? Or at least, why does it do that too, beside the real number line.

  • @simmikedia3347
    @simmikedia3347 4 роки тому

    hey...how do you do such animation...these really intresting...wish even i could learn how to do...and your explanation are very clear ...keep going...all the best

    • @zachstar
      @zachstar  4 роки тому

      The software I use is in the description :)

    • @simmikedia3347
      @simmikedia3347 4 роки тому

      @@zachstar Thank you😃😊

  • @charlescowan6121
    @charlescowan6121 Рік тому

    I had a shitty Calc 2 instructor who glossed over many sections. So when I got to upper division physics where series solutions were an expected skill, I really struggled! However when I studied complex analysis, I had a few very profound "Ahha" moments.

  • @SuperS953
    @SuperS953 4 роки тому

    Is going to the complex numbers enough? Could an extension to quaternions or other bigger fields reveal more singularities?

    • @angeldude101
      @angeldude101 2 роки тому

      With regard to arithmetic closure, the complex numbers should be all that's needed as far as I'm aware. That said, there are alternatives that are mainly useful for different geometries, so the quaternions are best for representing rotations in 3D space, while the split-complex numbers are great for working with hyperbolic geometry.

  • @vazmeee
    @vazmeee 4 роки тому

    Hi zach. Could you help us understand the beta binomial distributions anytime exploring all possible ranges of alpha and beta in a intuitive way. I've always had some trouble wrapping my head around when it comes to values

  • @pabloariza2295
    @pabloariza2295 4 роки тому

    woahhh thiis was rly cool

  • @mathmachine4266
    @mathmachine4266 3 роки тому

    (In reference to something he mentions at the end)
    Do removable singularities REALLY effect the radius of convergence? I mean, I have pretty much an unhealthy obsession with math, so, from my personal experience, under most circumstances, if there's a removable singularity, the rules of math will just pretend it isn't even there. So I'd be really interested to see a counter example to that behavior.

  • @pebotin
    @pebotin 4 роки тому

    Very nice video..

  • @halim_Ha
    @halim_Ha 4 роки тому

    Is there any linear algebra in your channel

  • @furkansarihan
    @furkansarihan 4 роки тому

    Thank you...

  • @fireblossom9618
    @fireblossom9618 4 роки тому

    Was the title different before? I swear it was something about a calculus 2 question idk might've been something else

  • @HackersSun
    @HackersSun 4 роки тому +10

    Is THAT what Taylor's series is used for?
    Oooooohh
    This is cool I can see the why

  • @kingofgoldnessr9364
    @kingofgoldnessr9364 4 роки тому

    I have the 3d graphing program he has but have no idea what to input to get that out, any tips?

  • @MozartJunior22
    @MozartJunior22 4 роки тому

    I feel like this would be the best demonstration of complex numbers actually existing and being something you cannot ignore. In all other explanations, complex numbers are only a convenient addition.
    Also, I hate how an 8 minute video is now considered "shorter than usual"... I miss the old UA-cam days where you can get your videos as bite sized knowledge. Nowadays each video is an f-ing documentary.

  • @bernhardriemann3821
    @bernhardriemann3821 4 роки тому +1

    hey man can you please tell the animation software you use for your videos?

    • @zachstar
      @zachstar  4 роки тому

      For this one you can find the software used in the description :)

    • @bernhardriemann3821
      @bernhardriemann3821 4 роки тому +1

      @@zachstar thanks a billion

  • @jackskelotojack
    @jackskelotojack Рік тому

    Is it just me or does this explain the powers in the fifth season in the way they can sess stuff out

  • @ilke3192
    @ilke3192 4 роки тому +16

    I was like "why does this have only 120 views" then I realised I am very early... Wow

    • @ifusubtomepewdiepiewillgiv1569
      @ifusubtomepewdiepiewillgiv1569 4 роки тому

      i agre - i am making this comment to see how many comments are added by the time i reload this

    • @princelumpypackmule1101
      @princelumpypackmule1101 4 роки тому

      Now it's at 120 x 10 views

    • @necaton
      @necaton 4 роки тому +1

      @@princelumpypackmule1101 Now it's at 120^10 views...or at least it should be

  • @sumedh2358
    @sumedh2358 4 роки тому

    i want to learn & understand mathematics like you. how can i learn? please suggest me book or tutorials for mathematics from basic.

  • @varimas
    @varimas 4 роки тому

    Can i ask what program you use to plot in 3D?

  • @jamesjenkins9480
    @jamesjenkins9480 4 роки тому +1

    Have you checked out manim, 3blue1brown's math animation library? I feel like that would be super useful for you.

  • @physicsboi1744
    @physicsboi1744 4 роки тому

    Hey Zach! What software do you use for maths animations?

    • @zachstar
      @zachstar  4 роки тому

      In the description :)

    • @physicsboi1744
      @physicsboi1744 4 роки тому

      @@zachstar oh ty love ur videos :) Still remember when it was used to be MajorPrep

  • @arjunarya2658
    @arjunarya2658 4 роки тому

    5:37 reminds me of the Julia sets, probably has no connection though

  • @iTeerRex
    @iTeerRex 4 роки тому

    If you rotate this 5:35 by 90 degrees you get a much better picture ;-)

  • @44xeon79
    @44xeon79 Рік тому

    Does that mean that a complex function would have a "sphere of convergence"?

  • @erickperez5930
    @erickperez5930 4 роки тому

    Hi guys, I need to plot some complex functions but I don´t know to program. Any software recommendations?

  • @demianpryima1015
    @demianpryima1015 4 роки тому

    how do you find this stuff

  • @ahusky4498
    @ahusky4498 4 роки тому +2

    and this is why complex numbers fueled my passion for mathematics :D

  • @lexs7218
    @lexs7218 Рік тому

    for all calc 2 students who don’t understand why when and how the Taylor series actually converges to the function as to as more and more terms,…. well, well, well,….. i could answer that question but then you wouldn’t suffer like i did staring at wikipedia pages of Cauchy integral formula looking things

  • @shreyassinha6945
    @shreyassinha6945 4 роки тому

    Hey what tool did he use to graph complex nos in 3d? Anyone?

    • @zachstar
      @zachstar  4 роки тому

      In the description!

  • @rednassie1101
    @rednassie1101 4 роки тому

    Does anyone have any tips for a student having to learn calc1, calc2 and calc3 (about half of calc2 and 3) in about 4 weeks? Asking ofcourse for a friend :P

    • @fernandobanda5734
      @fernandobanda5734 4 роки тому +1

      I have a question: why?

    • @rednassie1101
      @rednassie1101 4 роки тому

      @@fernandobanda5734 definitely for a friend and NOT for my university programme with teachers that don't know how technology works and end up saying "Well, it's in the book so go read that"

    • @fernandobanda5734
      @fernandobanda5734 4 роки тому

      @@rednassie1101 It's pretty crazy to learn that many topics that fast, even if they weren't complicated.

    • @fernandobanda5734
      @fernandobanda5734 4 роки тому

      @@rednassie1101 Sorry if I don't have useful tips. Just concentrate and practice, I guess. :/

    • @rednassie1101
      @rednassie1101 4 роки тому

      @@fernandobanda5734 haha, thanks for the heads up. Have a good day

  • @generalbandege1184
    @generalbandege1184 3 роки тому

    My precalc *ss just trying to keep along! XD

  • @Timothyday88
    @Timothyday88 4 роки тому

    I thought I was good at math until I saw this. Thank you

  • @diegomoreno3237
    @diegomoreno3237 4 роки тому

    Awesome

  • @thetntsheep4075
    @thetntsheep4075 4 роки тому +1

    What a coincidence, we were just learning about Maclaurin series at school today.
    How can you "centre" a series around a point other than zero? Is this something to do with Taylor series?

    • @alexanderbasler6259
      @alexanderbasler6259 4 роки тому +1

      Yeah, that's exactly it! Taylor series are simply a generalisation of Maclaurin series. Instead of having the n-th derivative at zero and then x^n as the terms in your sum, you simply take the n-th derivative at the point y where you want to centre the series and then multiply by (x-y)^n instead of just x^n. (The 1/n! stays the same). Interestingly, as this is nothing but a shift of the argument of the function, to prove that Taylor series in this sense exist requires nothing more than to prove that Maclaurin series exist. Hope that was somewhat illuminating!

    • @erynn9770
      @erynn9770 4 роки тому +1

      Essentially you only do a bit of renaming.
      Say you want to do the series at x=1. Then you introduce a z so that z=x-1 and transform your Formula. Now you notice that your x=1 conveniently is at z=0, say to yourself " x, z, what's a name anyway" and calculate for z=0 like you would for x=0. Afterwards you rename again and replace every z by x-1. So e.g. z² becomes (x-1)².
      That's it!

    • @thetntsheep4075
      @thetntsheep4075 4 роки тому

      Pretty elegant explanations, thanks! It makes this video fit together much more nicely.

  • @pierredonias8940
    @pierredonias8940 4 роки тому

    But how do you find the radius of convergence in the first place?

  • @ΑντώνηςΝικολακάκης-ω2γ

    Me studying 1-1 functions, sees this.
    Me. Exe stopped working

  • @dukeofworcestershire7042
    @dukeofworcestershire7042 4 роки тому

    Can someone explain to me how the divisions in fields of maths in the American school system work? (Calculus 1, Calculus 2 etc.)

    • @zachstar
      @zachstar  4 роки тому

      For me calc 1 was limits, derivatives, integrals for the first time (related rates, optimization, volume of revolution, etc).
      Calc 2 was integration techniques (by parts, trig sub, etc), then series/sequences and Taylor/maclaurin series
      Calc 3 is multi variable calculus where you first learn the partial derivative, 3d graphs, double and triple integrals, and a little vector analysis.
      After that you enter into the courses that we all know by name like differential equations, linear algebra, real analysis, and so on.

    • @dukeofworcestershire7042
      @dukeofworcestershire7042 4 роки тому

      @@zachstar I see! Is that stuff covered in high school or is it a university thing?

    • @zachstar
      @zachstar  4 роки тому

      @@dukeofworcestershire7042 There are high school students who complete all three of the calc courses but it's not the majority (my school only offered up to calc 2 actually). Plenty take calc 1 but after that there's a big drop in terms of who goes to calc 2.

    • @dukeofworcestershire7042
      @dukeofworcestershire7042 4 роки тому

      @@zachstar I see. Where I live it's a bit more standardized, all students take the same math courses. I'm what I think is equivalent to a highschool freshman and have been getting into math lately, but because the vast majority of good content is English there is a certain cultural barrier as some stuff doesn't translate well between school systems, thus making it difficult to figure out where to start

  • @theunknown4834
    @theunknown4834 4 роки тому

    Try using geogebra instead of desmos