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How to Construct Infinite Sets
What are the natural numbers? The integers? The rationals? The reals? While we may have an intuitive understanding of these numbers and sets, it is not so easy to actually construct these sets formally. To do so, we must use some axioms of set theory, and using only these assumptions, formally describe what these infinite sets should look like. We will develop various tools in set theory, like ordered pairs, relations, ordering, and equivalence classes, to begin with only zero, and from nothing, build all of the real numbers.
0:00 Introduction
1:46 Set Theory and Basic Notions
8:13 Axiom of Infinity and the Naturals
13:09 The Integers
23:19 The Rationals
26:00 The Reals
36:38 Conclusion
Additional Resources:
Wikipedia article on the Construction of the naturals: en.wikipedia.org/w/index.php?title=Natural_number#Set-theoretic_definition
Wikipedia article on the Construction of the Reals: en.wikipedia.org/wiki/Construction_of_the_real_numbers
Wikipedia article on ZFC: en.wikipedia.org/wiki/Zermelo-Fraenkel_set_theory
Axiom of Choice video: ua-cam.com/video/szfsGJ_PGQ0/v-deo.html
Cardinality of the Continuum video: ua-cam.com/video/iaUwNuaSLUk/v-deo.html
Music:
c418.bandcamp.com/album/dief
Imaginary Interlude by C418
c418.bandcamp.com/album/circle
minimal by C418
love by C418
patriciataxxon.bandcamp.com/album/crocus
Crocus 2 by Patricia Taxxon
Far the Days Come by Letter Box
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Animations were made by Manim, an open-source python-based animation program by 3Blue1Brown.
github.com/3b1b/manim
This video was submitted to 3Blue1Brown's SoMEπ (Summer of Math Exposition Community Edition).
some.3b1b.co/
Переглядів: 5 326

Відео

The Axiom of Choice
Переглядів 100 тис.7 місяців тому
Mathematics is based on a foundation of axioms, or assumptions. One of the most important and widely-used set of axioms is called Zermelo-Fraenkel set theory with the Axiom of Choice, or ZFC. These axioms define what a set is, which are fundamental objects in mathematics. And the Axiom of Choice is arguably one of the most important and interesting axioms of ZFC. But what does it really say? An...
Genius Mathematicians Lost Too Soon
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Some mathematicians changed the field of mathematics at a young age, only to die too early. Let us look at the lives of some of these young, brilliant minds who left too soon. Evariste Galois was a French mathematician who laid the foundations of abstract algebra and Galois theory, proving the quintic's insolubility. Srinivasa Ramanujan was an Indian mathematician who, upon his genius being dis...
But what is a Vector Space?
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Vectors are fundamental tools in mathematics and sciences. Yet different fields like mathematics, physics, and engineering seem to define vectors differently. It is mathematics, unsurprisingly, that formally defines a vector. We will go through this process of formalization, using the foundational tools of abstract algebra to define and construct a vector space. Additional Resources: Wikipedia ...
Why Logarithms Appear in This Integral
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Before the days of Calculus, one Pierre de Fermat wanted to find the area under the function f(x)=x^n. This problem we now call "integration" was then called "quadrature" or "squaring". Fermat was able to square every function f(x)=x^n for any rational n except for one case: n=-1 (that is, the hyperbola). It turns out that this unique nature of the hyperbola was tied to logarithms and Euler's n...
How to Find the Biggest Primes
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How do people find big primes? These primes have millions of digits, and may take years of collective effort and computing power to be found. Unsurprisingly, mathematicians have figured out various ways to more efficiently and accurately find these big primes. In the process, the unique and interesting properties of various primes have also been found. Great Internet Mersenne Prime Search: www....
Cardinality of the Continuum
Переглядів 58 тис.2 роки тому
What is infinity? Can there be different sizes of infinity? Surprisingly, the answer is yes. In fact, there are many different ways to make bigger infinite sets. In this video, a few different sets of infinities will be explored, including their surprising differences and even more surprising similarities. 0:00 - Euclid's Proof of Infinite Primes 1:55 - Bigger Infinities? 2:27 - Set Theory and ...
The Cardinality of an Interval
Переглядів 3,2 тис.2 роки тому
Cantor's Diagonal Argument proves that there are an uncountable number of real numbers. But what about any interval of real numbers? Are those sets uncountable as well, no matter how small the interval?
Can the power of two irrationals be rational?
Переглядів 4,5 тис.2 роки тому
Are there two irrational numbers, let’s say x and y, such that x to the y is rational? The answer to this question brings us through a fascinating journey about transcendental numbers and the Gelfond-Schneider theorem. Additional Resources: Where I found this theorem: math.stackexchange.com/questions/728223/simple-beautiful-math-proof/728276 Music: www.purple-planet.com Animations were made by ...
Why do trig functions appear in Euler's formula?
Переглядів 145 тис.3 роки тому
Why do trig functions appear in Euler’s formula? This was the question I had when I first saw Euler’s formula. This connection between trigonometry and exponents seems so unexpected, especially along with complex numbers. To answer this question, we must journey into the intricate and beautiful mathematical relationship between trig functions, e, and complex numbers. We will look at two differe...

КОМЕНТАРІ

  • @IsaacChristopher-z8w
    @IsaacChristopher-z8w 4 дні тому

    Thank you for this video! I understand the AoC much better after watching it. It's fascinating to see how thoroughly set theory is connected with other branches of mathematics. The visuals and audio were fantastic, and you explained things at exactly the right level for me (2nd year undergrad). I feel like I've just watched a very strong lecture at my university. Subscribed :)

  • @birdy_
    @birdy_ 4 дні тому

    4:22 Bernays

  • @eunchanhyung6947
    @eunchanhyung6947 5 днів тому

    talk tuah

  • @eunchanhyung6947
    @eunchanhyung6947 5 днів тому

    poopy fart head

  • @wakeupthewublins69
    @wakeupthewublins69 6 днів тому

    i spent a day trying to prove this with the taylor series, still my most enjoyable day in terms of math

  • @neutralzone7775
    @neutralzone7775 8 днів тому

    Amazing video, Physics major and we use this all the time, now I have a much more intuitive understanding of the Euler's formula

  • @Zack-mp6ys
    @Zack-mp6ys 10 днів тому

    I am familiar with Dedekind Cut a few years back. But this is the first time I learned the rationale behind the rationals.

  • @Zack-mp6ys
    @Zack-mp6ys 10 днів тому

    A whole series of videos of ZFC like this will surely go viral.

  • @AA-100
    @AA-100 17 днів тому

    2^136279841-1, new largest known prime, discovered Oct 12 2024

  • @tommyrjensen
    @tommyrjensen 26 днів тому

    In a university study you would expect a more precise language. You would hear Euclid's proof explained as "there are infinitely many primes", as in, not just finitely many primes. Rather than "there is an infinite number of primes", easily misunderstood as if to say there is a certain number of primes, and that number is infinite. This only becomes meaningful once you also realize that there is a set the elements of which are exactly the primes, and this set has a certain cardinality, and that cardinality is infinite.

  • @c3pheiplay
    @c3pheiplay 27 днів тому

    Thanks! This really helped

  • @RandomLyricsGuy-y5r
    @RandomLyricsGuy-y5r 29 днів тому

    im gonna try and find the biggest perfect number i can fathom Day 1: 137438691328

  • @Locus616
    @Locus616 29 днів тому

    I started gasping and lighting screaming when i saw the end of the taylor series proof. Im bewildered

    • @pelasgeuspelasgeus4634
      @pelasgeuspelasgeus4634 19 днів тому

      That proof is wrong. Taylor series are valid for real integers, not marvel universe numbers like i*x.

    • @Locus616
      @Locus616 19 днів тому

      @pelasgeuspelasgeus4634 *bigger gasp*

    • @pelasgeuspelasgeus4634
      @pelasgeuspelasgeus4634 19 днів тому

      @@Locus616 meaning?

  • @Locus616
    @Locus616 29 днів тому

    I love this

  • @jacobg1219
    @jacobg1219 Місяць тому

    Great video, it's so hard to find maths content that isnt either not related to what you want to find or just incredibly complicated.

  • @pelasgeuspelasgeus4634
    @pelasgeuspelasgeus4634 Місяць тому

    This video is pointless since euler formula is simply wrong. Left side is exp function which ranges from 1 to infinity. Right side is the sum of 2 trig functions each ranging from -1 to 1. So, how can these sides ever be equal? Stop parotting, start thinking.

  • @fahriz9163
    @fahriz9163 Місяць тому

    what's your book there?

  • @Shrutithenerd
    @Shrutithenerd Місяць тому

    You deserve more subscribers, amazing explanation loved it.

  • @Киноварь
    @Киноварь Місяць тому

    The game.

  • @ketaksingh5465
    @ketaksingh5465 Місяць тому

    amazing man! subscribed

  • @williamnathanael412
    @williamnathanael412 Місяць тому

    22:50 I almost immediately think, why can't the reals be ordered like you do with the integers? Compare the absolutes of two numbers, and give the priority to the positive should their absolutes be equal. Unless of course, you are talking about Dedekind cuts.

    • @MikeRosoftJH
      @MikeRosoftJH 7 днів тому

      Okay, surely you can do that; but that's not a well-ordering relation, because not every set has a minimum. Consider an open interval from 0 to 1; it can be seen that re-ordering negative numbers doesn't change anything. What's the minimum of this set? 1/10? But 1/100 is closer to zero. 1/1000 is even closer. And so on; for any positive number x there is one closer to zero, such as x/2. The infimum of this set is of course 0 (any set bounded from below has one); but that's not a minimum because it's not an element of the open interval. In fact, a well-ordering relation on real numbers can't be constructed in the usual sense; no formula can be proven to define one (in the sense that there exists exactly one set satisfying that formula and that set is a well-ordering of real numbers). The existence of such a well-ordering is a consequence of axiom of choice; without axiom of choice it's consistent that real numbers can't be well-ordered.

  • @aphschl4347
    @aphschl4347 Місяць тому

    Thanks for the video really helpful for my university class.

  • @ZimingWang-cl7nb
    @ZimingWang-cl7nb Місяць тому

    This is a perfect video! I just have one question: why is natural number to the power of natural number the set of all positive integer functions? Can someone please explain it for me😢

  • @HousmanNat-z8r
    @HousmanNat-z8r Місяць тому

    Ratke Spurs

  • @pictureking1958
    @pictureking1958 Місяць тому

    Amazing video but I still have one question. Like how do you classify e^ix as imaginary or real? Like for imaginary i must be multiplied to the number and for real no i at all. But this e^ix has i in the exponent, so I got confused at this part.

    • @pelasgeuspelasgeus4634
      @pelasgeuspelasgeus4634 14 днів тому

      Is that the only thing confusing you? How about the fact that one side (exp function) goes from 1 to inf while the other side (sum of 2 trig functions) is obviously finite? How can they be equal?

  • @rambleitch
    @rambleitch Місяць тому

    14:46 wouldn't the domain be a subset of the power set of X? if x belongs to a particular Xy_1 it cant belong to any other such Xy_2 so the domain would be like disjoint subsets of X?

  • @marcoottina654
    @marcoottina654 Місяць тому

    17:00 The musical choice is fantastic! It truly whisper the idea of "there's some powerful concept here to be grasped, but it's doomed indeed". Genius! Also, the part immediately preceding it has got a VERY inspiring music, which lift the spirit to the idea of "this concept is very powerful, harnessing the power and patience of infinity to gain the ability to be exact"! (17:00 _unless_ ... *there's a hole** ) also, the ending speech and the "almost pun" is ... delightful! I love it!

  • @ddg-norysq1464
    @ddg-norysq1464 Місяць тому

    4:00 technically there has to be none leftover in the codomain, not the image of f

  • @dragonfly.effect
    @dragonfly.effect 2 місяці тому

    The best statement of AC I've come across is: Let S be a set of nonempty sets. Then the Cartesian product of (all) the sets in S is nonempty. Of course this statement implies that such a Cartesian product exists, but otherwise it seems totally obvious, and feels a lot clearer than any description of choice functions or choice sets. 😊

  • @filippocontiberas
    @filippocontiberas 2 місяці тому

    I wonder the cardinality of the complex numbers set (that set is also not ordinable like the real numbers set).

  • @idiomaxiom
    @idiomaxiom 2 місяці тому

    how can an axiom follow from something?

  • @worldnotworld
    @worldnotworld 2 місяці тому

    Very good explanations! You might have spelled out what "two to the power of aleph one" was; that had my audience slightly confused. My only complaint is the music, especially in the middle: dreary and unpleasantly atonal, including a weird "chchcht" noise that with my headphones on gave me the feeling something was being sprayed up the middle of my nose...

  • @litverse663
    @litverse663 2 місяці тому

    How didn't I know about this channel earlier? The world needs to know about the channel.

  • @schwaartz
    @schwaartz 2 місяці тому

    Maybe it's just me, but I find the music very distracting. 10/10 for all the rest.

  • @shadow-ht5gk
    @shadow-ht5gk 3 місяці тому

    Fantastic video

  • @-_-_-_-_
    @-_-_-_-_ 3 місяці тому

    Love the video! I do have one small criticism wholly unrelated to the mathematics: the background music is too loud to the point that it gets a bit overwhelming when wearing headphones. Everything else was pretty much perfect.

  • @navigatorspark5215
    @navigatorspark5215 3 місяці тому

    beautifully explained

  • @user-Loki-young0515
    @user-Loki-young0515 3 місяці тому

    0.011111...and 0.1 is actually the same number in binary, its like 0.999...=1, since the difference should be small enough to be 0, hence the same number🙃

  • @JohnJones-tx6rt
    @JohnJones-tx6rt 3 місяці тому

    Basic and unforgiveable mistakes? Set theory defines numerals as numbers, otherwise there are no sets or combinations. A set is a heiroglyph or picture of objects that look like mathematical symbols. The properties of the members within the heiroglyph are not transferred onto the set or heiroglyph. The stand-alone iconic form of a number is, and is called, a numeral. A numeral is void of a mathematical container, application or calculus, and a collection of them must be significant for it to be called a set or collection, for example a set of cutlery is significant because it is a tool. Numbers are not transferable between applications, and are themselves void, and not countable, existing only in their calculus. The introduction of infinity into set talking points is an attempt to place the first non-number into a count, usually placed at "the end" because it has no stop - numbers are created through a stop. The largest number is the last stop in the count, such as 6, or 13. Mathematicians will disagree. Mathematicians do not like philosophers.

    • @shadow-ht5gk
      @shadow-ht5gk 3 місяці тому

      Don’t try to comment about something you have no understanding in, you clearly haven’t taken any serious math courses

  • @crypttonite
    @crypttonite 3 місяці тому

    mileswmathis.com/nash.pdf

  • @crypttonite
    @crypttonite 3 місяці тому

    r u contributing to the advancement of PROPAGANDA? A lil dramatic. How many have been lost to history? TODAY a MATH & SCIENCE genius is CENSORED & completely ignored by the fraud that is mainstream math & science. Miles W Mathis.

  • @subhamchatterjee343
    @subhamchatterjee343 3 місяці тому

    Great job brother ❤

  • @bankeragaming8581
    @bankeragaming8581 3 місяці тому

    A am a mathematican my name its banmien 15 years a am creat new math name math its a black mathematics and very good theory

  • @BruceMaximusLee
    @BruceMaximusLee 3 місяці тому

    This channel will have a bright future

  • @fergalhennessy775
    @fergalhennessy775 3 місяці тому

    Really good animation!

  • @ayaannasar8950
    @ayaannasar8950 3 місяці тому

    Weirdly enough, this doesn’t sound like an axiom at all (even though it is called one). Kinda like Euclid’s 5th postulate.

    • @sabotagedgamerz
      @sabotagedgamerz 3 місяці тому

      I mean this video is phrased quite weird, but roughly the axiom states you can choose an element from any non-empty set, which does sound like a statement basic and assumed enough to be an axiom.

    • @methatis3013
      @methatis3013 3 місяці тому

      You cannot prove it using only ZF axioms, at least when it comes to infinite sets. That's why we state it as an additional axiom, although some argue that we shouldn't

    • @gileadedetogni9054
      @gileadedetogni9054 2 місяці тому

      ​@HappinessReborn some of its implications and equivalences are quite weird, like the banach-tarski paradox or the well ordering principle (that I still don't believe)

    • @shadow-ht5gk
      @shadow-ht5gk 2 місяці тому

      @@gileadedetogni9054you don’t believe the well ordering principle?

    • @gileadedetogni9054
      @gileadedetogni9054 2 місяці тому

      @shadow-ht5gk no man, I'm a well ordering principle atheist

  • @mohamedmouh3949
    @mohamedmouh3949 3 місяці тому

    thank you so much 🤩🤩🤩. much better than class

  • @samylahlou
    @samylahlou 4 місяці тому

    Excellent video !!!! Perfect explanations. Nice !!

  • @zeitgenosse
    @zeitgenosse 4 місяці тому

    11:51 That should be A(m,1) = A(m,0)^+ = m^+