The Subfactorial is Hilarious

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  • เผยแพร่เมื่อ 25 ม.ค. 2025

ความคิดเห็น • 663

  • @WrathofMath
    @WrathofMath  2 หลายเดือนก่อน +73

    Well, that was fun!
    Join Wrath of Math to get exclusive videos, lecture notes, and more:
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    More math chats: th-cam.com/play/PLztBpqftvzxXQDmPmSOwXSU9vOHgty1RO.html

    • @kilgorezer
      @kilgorezer 2 หลายเดือนก่อน

      i agree, that was fun

    • @donspencer7224
      @donspencer7224 หลายเดือนก่อน

      That was very interesting

    • @none432141
      @none432141 หลายเดือนก่อน

      😢😢😢àaaaaaaaaaaaàaaaaaaaaa😢aàaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaà😢😢😢aà😢😢😢a😢😢​@@kilgorezer

    • @Gmackematix
      @Gmackematix หลายเดือนก่อน

      You say subfactorial. I say the Secret Santa function.

    • @JackeDao
      @JackeDao หลายเดือนก่อน

      Frick this easyer formula ⬇️
      !n=(n-1)^n-2

  • @disnecessaurorex4908
    @disnecessaurorex4908 2 หลายเดือนก่อน +1661

    I feel like "It's 1/e, isn't it?" is the "he is right behind me, isn't he?" of maths

    • @RickofUniverseC-137
      @RickofUniverseC-137 2 หลายเดือนก่อน +28

      Great analogy!

    • @CliffSedge-nu5fv
      @CliffSedge-nu5fv 2 หลายเดือนก่อน +86

      Euler is always there. Sometimes he's downstairs.

    • @blasphemer_amon
      @blasphemer_amon 2 หลายเดือนก่อน +3

      Was not expecting to see a 2021 Abu Dhabi reference here 💀

    • @Asiago9
      @Asiago9 2 หลายเดือนก่อน +13

      It's always an expression to do with pi, e, or ln of something it feels like in these higher level math videos

    • @apokalypthoapokalypsys9573
      @apokalypthoapokalypsys9573 2 หลายเดือนก่อน +9

      ​@@blasphemer_amonit's not a reference to "2021 Abu Dhabi", it is a reference to the thousands of badly written movie scripts with tiresome clichés

  • @enderslice8378
    @enderslice8378 2 หลายเดือนก่อน +2229

    IT'S ALWAYS e LEAVE ME ALONE EULER

    • @patrickwienhoft7987
      @patrickwienhoft7987 2 หลายเดือนก่อน +748

      I love that even in your furious use of caps lock you still have the respect for mathematics to properly write e as lower case

    • @enderslice8378
      @enderslice8378 2 หลายเดือนก่อน +577

      My rage doesn't make me disregard how symbols work. I have standards.

    • @pagjimaagjinen9733
      @pagjimaagjinen9733 2 หลายเดือนก่อน +204

      This smaller case e makes it seem like you say e calmly, and shout the rest

    • @kingnoob3503
      @kingnoob3503 2 หลายเดือนก่อน +51

      Euler will chase you for your life

    • @interconnected.
      @interconnected. 2 หลายเดือนก่อน +28

      I love this reply lmao 🤣

  • @deepdrag8131
    @deepdrag8131 2 หลายเดือนก่อน +815

    “A dark room with several men who aren’t wearing any hats.”
    Oh! The nightmares I’ve had about that!!

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +60

      😂😂

    • @McDonalds-Empty-Cup
      @McDonalds-Empty-Cup 2 หลายเดือนก่อน +44

      Nightmares? I had fantasizes about that

    • @-danR
      @-danR 2 หลายเดือนก่อน +11

      That's Inception level 1
      The deeper nightmare is none of them getting their hats back.
      This is a branch of Applied Mathematics I never knew I needed.

    • @CliffSedge-nu5fv
      @CliffSedge-nu5fv 2 หลายเดือนก่อน +12

      Oh, _hats_ not wearing hats, right. That's what they aren't wearing.

    • @davidwright8432
      @davidwright8432 2 หลายเดือนก่อน +3

      It might not be the lack of hats in such a situation that's hazardous, but the lack of clothing well south of the hat region. Or if not hazardous, perhaps adventurous.
      e ...xactly!

  • @Frownlandia
    @Frownlandia 2 หลายเดือนก่อน +457

    I have a feeling the men without hats are happy to be partying in a dark room. After all, they can dance if they want to, and they can leave their friends behind.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +96

      True, but one has to worry about the hats going wherever they want to, a place the men may never find

    • @davegrimes3385
      @davegrimes3385 2 หลายเดือนก่อน +45

      And, if they don't dance, well they're no friends of mine

    • @madacsg
      @madacsg 2 หลายเดือนก่อน +1

      It will be definitely a SAFETY DANCE! 😉🤗😄 th-cam.com/video/1p_BvaHsgGg/w-d-xo.html

    • @spectria.limina
      @spectria.limina 2 หลายเดือนก่อน +21

      I'm glad these men are so safety-conscious while dancing.

    • @bruhmoment1998
      @bruhmoment1998 14 วันที่ผ่านมา

      Sadly, however, they cannot go where they want to

  • @Hyreia
    @Hyreia 2 หลายเดือนก่อน +142

    "A derangement" is such a hilarious term for something in math. I love it.

    • @travcollier
      @travcollier หลายเดือนก่อน +2

      I would bet whoever came up with subfactorials was just goofing around.

  • @Ryanisthere
    @Ryanisthere 2 หลายเดือนก่อน +226

    0:38 this is getting very spicy
    several men without hats

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +58

      Spicy indeed, in a world of hatless men, where do we find God?

    • @the_siili
      @the_siili 2 หลายเดือนก่อน

      ​@@WrathofMaththe God is a man without a hat

    • @tweer64
      @tweer64 2 หลายเดือนก่อน +14

      Did they leave their friends behind?

    • @Akio-fy7ep
      @Akio-fy7ep 2 หลายเดือนก่อน +11

      @@tweer64 If their friends don't dance, well they're ... no friends of mine.

    • @HFIAPY
      @HFIAPY หลายเดือนก่อน +1

      *"There's no party like a Diddy party"* 😏

  • @ReinOfCats
    @ReinOfCats 2 หลายเดือนก่อน +75

    I'm a game developer, and a strikingly similar scenario - and result - came up awhile back when doing a deep dive on some item drop rate adjustments.
    Imagine you have a monster that drops an item when defeated at a rate of 1 in 100 times and then you defeat 100 of that monster. What's the chance you've gotten at least 1 of that item?
    Due to the "at least 1", this is easier to count the inverted result of "how many times did you fail to get the item" and repeat 100 times. So: (1-1/100)^100.
    And then invert that result: 1 - (1-1/100)^100. Giving a result of approximately ~63.4% chance of getting at least once.
    Generalizing this as n instead of 100, and then letting an n approach infinity, we get the result: Lim n->inf [1 - (1 - 1/n)^n] = 1 - (1 / e)

    • @Dexaan
      @Dexaan 2 หลายเดือนก่อน +10

      I remember mentally calculating critical chance for multiple critical chances way back in the Warcraft 3 days and my rough math always seemed to end up near either 33% or 66%

    • @Alphabetatralala
      @Alphabetatralala 2 หลายเดือนก่อน +1

      Geometric distribution is a bitch.

  • @der.Schtefan
    @der.Schtefan 2 หลายเดือนก่อน +282

    A dark room with many men in it... Sounds like a Berlin nightclub.

    • @empathogen75
      @empathogen75 2 หลายเดือนก่อน +17

      And then e showed up.

    • @nicholasiverson9784
      @nicholasiverson9784 2 หลายเดือนก่อน +5

      @@empathogen75 only if it was one of Those clubs, with hatless men.

    • @coyets
      @coyets 2 หลายเดือนก่อน +5

      It does indeed sound like a Berlin nightclub, but the calculation was not gender specific, and it could therefore also be applied to any dark room where people remove their hats on entering.

    • @matthiasschulz3569
      @matthiasschulz3569 2 หลายเดือนก่อน +2

      I feel like there's a Flight of the Conchords song about this kind of situation ...

    • @8bits59
      @8bits59 2 หลายเดือนก่อน

      ​@@coyetsyes, obviously. Did you miss the joke?

  • @KookyPiranha
    @KookyPiranha 2 หลายเดือนก่อน +125

    this is literally how i process every combinatorics problem hoping all the terms cancel out when they dont

    • @meatyman4803
      @meatyman4803 2 หลายเดือนก่อน +4

      Finding this guy in a math video is a fever dream

  • @carly09et
    @carly09et 2 หลายเดือนก่อน +253

    This is Weird : I was just doing some economic modelling and this result popped out. This explains the entropy of a market, as it estimates states.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +45

      That sounds very interesting, will have to research

    • @joshuaiosevich3727
      @joshuaiosevich3727 2 หลายเดือนก่อน +17

      You might find it useful that derrangements can be represented by an integral: int_{0}^{/infty} (e^(-x))(x-1)^ndx

    • @carly09et
      @carly09et 2 หลายเดือนก่อน +13

      @@joshuaiosevich3727 That's true. But I was finding the ratio by construction - ie a fractal result. This explained why the result converged on this.

    • @815TypeSirius
      @815TypeSirius 2 หลายเดือนก่อน +1

      ​@@joshuaiosevich3727 linear algeba ruins everything

    • @joshuaiosevich3727
      @joshuaiosevich3727 2 หลายเดือนก่อน +1

      @@815TypeSirius I'm afraid I'm too dense to get what you're saying.

  • @asmithgames5926
    @asmithgames5926 2 หลายเดือนก่อน +63

    1/e also shows up in another famous math problem, which I'll poorly paraphrase: When dating, what % of the total pool should you check out before committing to one? The answer is 37% of the pool, 1/e.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +31

      With how big dating pools are now due to modern transportation and dating apps, I still have a significant amount of work to do 🤣

    • @robo3007
      @robo3007 2 หลายเดือนก่อน +6

      It also marks the point where the graph y = x^x stops decreasing and starts to increase

  • @whamer100
    @whamer100 2 หลายเดือนก่อน +794

    as a programmer, seeing "!n" just makes me think "logical not n" which evaluates as either 0 or 1 depending if its non-zero lmao

    • @cosmnik472
      @cosmnik472 2 หลายเดือนก่อน +35

      bitwise not also works

    • @dapcuber7225
      @dapcuber7225 2 หลายเดือนก่อน +19

      I'd be more inclined to think bitwise not as I usually write logical not as ¬ but yeah this would be confusing 😭

    • @kuwi1061
      @kuwi1061 2 หลายเดือนก่อน +26

      ​@@cosmnik472 For that ~ is used like this ~n

    • @litfill54
      @litfill54 2 หลายเดือนก่อน +5

      or strict n in haskell

    • @JdeBP
      @JdeBP 2 หลายเดือนก่อน +5

      Those who have programmed in some home computer BASICs will be thinking "pling n".

  • @James2210
    @James2210 2 หลายเดือนก่อน +192

    Brings a whole new meaning to "Statements dreamed up by the utterly Deranged"
    (from the "stop doing math" meme)

    • @trenixjetix
      @trenixjetix หลายเดือนก่อน +1

      I love the goku voiced version

  • @Kapomafioso
    @Kapomafioso 2 หลายเดือนก่อน +16

    11:00 just a note: I think here either the sum should be marked with i < j (not i =/= j), or, if written in this way, there should be 1/2 in front of it. You don't want to repeat elements: A1 intersection A2 and then A2 intersection A1. But the result is correct, the non-repeating sum over i < j is equal to n choose 2.

    • @scottmiller2591
      @scottmiller2591 2 หลายเดือนก่อน

      Came here to say this. The n choose 2 fixes this, since it ignores permutations of the choosing, which is why even though the left hand side is wrong, the right hand side is correct. This also means the higher order indices in the summation later on for the inclusion exclusion formula need to be written as i < j < k ... for all free indices from the set, or put another way 1 =< i < j < k ... =< n.

  • @Frahamen
    @Frahamen 2 หลายเดือนก่อน +62

    that's quite a deranged equation.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +8

      You could say that

  • @furrball
    @furrball 2 หลายเดือนก่อน +85

    I wasn't wearing socks and my toes blew up.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +22

      Sorry 😞

    • @VioletRM
      @VioletRM 2 หลายเดือนก่อน +13

      a small price for science

    • @furrball
      @furrball 2 หลายเดือนก่อน +6

      @@WrathofMath np, that solved having to trim toenails.

    • @Thk10188965
      @Thk10188965 2 หลายเดือนก่อน +2

      Unfortunate

    • @Dexuz
      @Dexuz 2 หลายเดือนก่อน +5

      Your fault for having toes

  • @incription
    @incription 2 หลายเดือนก่อน +30

    In my head I thought "its definitely something like e, or 1/e", and imagine my surprise when I saw the result! Although, not much of a surprise, whenever probability is involved, e will show up.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +11

      Yeah, for the mathematically initiated, it may be far less surprising. but it’s so amusing to take a silly word problem like that regarding hats, and the answer is 1/e 😂

  • @luinérion
    @luinérion 2 หลายเดือนก่อน +26

    5:38 "it will blow your socks off"
    What a relief that it won't blow my _hat_ off 😌

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +9

      The hats are long gone at this point 😂

  • @briancooke4259
    @briancooke4259 2 หลายเดือนก่อน +44

    Your pace and depth are perfect. I would not attempt those formulas on my own, but you made perfect sense if them. Thank you so very much!

  • @Connorses
    @Connorses 2 หลายเดือนก่อน +20

    i was scared for just a second when you started drawing that hat rack

    • @-danR
      @-danR 2 หลายเดือนก่อน +1

      I was wondering how he would manage to hang the hats on it.

  • @dukenukem9770
    @dukenukem9770 2 หลายเดือนก่อน +51

    I’m excited to integrate a “deranged“ math lesson into my sons home-study curriculum!

    • @lollol-tt3fx
      @lollol-tt3fx 2 หลายเดือนก่อน +13

      poor son😂

    • @isavenewspapers8890
      @isavenewspapers8890 2 หลายเดือนก่อน +7

      Oh cool. I love taking an integral of the subfactorial function.

    • @TamWam_
      @TamWam_ 2 หลายเดือนก่อน

      i'm excited to show this to my math teacher

  • @truebino
    @truebino 2 หลายเดือนก่อน +11

    The night theme of Hateno village made this an emotional hat story for me...

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +1

      Takes me back to sophomore year of college

  • @blacklistnr1
    @blacklistnr1 2 หลายเดือนก่อน +14

    I appreciate the gentle transition to combinatorics via hats and Zeus's wrath :))

  • @mondaypunday
    @mondaypunday หลายเดือนก่อน +1

    Well paced, engaging, and playful. Euler would be proud.

  • @HFIAPY
    @HFIAPY หลายเดือนก่อน +2

    0:42 "there's no party like a Diddy party" 💀

  • @jonathanallan5007
    @jonathanallan5007 2 หลายเดือนก่อน +11

    I think that if we asked 10000 people the question (for some arbitrary number of hats, like 20) to give a percentage from 0-100 that no-one gets their hat back there would be quite a peak at 37%.
    Yeah, there would likely be one at 73% too.

    • @bitonic589
      @bitonic589 2 หลายเดือนก่อน

      Omfg it's really everywhere

    • @Kapomafioso
      @Kapomafioso 2 หลายเดือนก่อน

      Why would there be a peak at 73% as well?

    • @jonathanallan5007
      @jonathanallan5007 2 หลายเดือนก่อน

      @@Kapomafioso Second most popular "random" number from 0 to 100.

  • @KylerRaineP.Nangit74
    @KylerRaineP.Nangit74 2 หลายเดือนก่อน +29

    6:39 WHAT YOU'RE LETTING AI?!?!?!

    • @JuniperHatesTwitterlikeHandles
      @JuniperHatesTwitterlikeHandles 2 หลายเดือนก่อน +2

      AI's taking everyone's jobs, not even the set of all permutations where i is fixed is safe....

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +9

      gotta do what you gotta do

  • @IRLtwigstan
    @IRLtwigstan 2 หลายเดือนก่อน +5

    I remember finishing our subfactorials a year ago and I loved them so much. I made a scratch project to plug a number in to give the sub factorial of the number.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +1

      Super fun!

    • @IRLtwigstan
      @IRLtwigstan 2 หลายเดือนก่อน

      @ Hell yeah!

  • @yan-amar
    @yan-amar 2 หลายเดือนก่อน +18

    What I love about mathematicians is that they'll mention Greek gods like it's 1200 BC.

    • @thedoublek4816
      @thedoublek4816 2 หลายเดือนก่อน +2

      When the Wrath of Zeus meets the Wrath of Math.
      "Our fight will be legendary!"

  • @askod420
    @askod420 หลายเดือนก่อน +36

    1:04 say that again

  • @AusTxMale
    @AusTxMale 2 หลายเดือนก่อน +4

    That was well worth the wait. Thanks for such a fun explanation.

  • @uelssom
    @uelssom หลายเดือนก่อน +2

    If you gather enough men without hats, they can do the Safety Dance

  • @ValeBridges
    @ValeBridges หลายเดือนก่อน +3

    2:25 that sounds deranged

  • @user-pw5do6tu7i
    @user-pw5do6tu7i 10 วันที่ผ่านมา

    First of all, amazing video. You taught so much notation, and incorporated in a great way. Having e show up and everything was also very very cool. Seemingly connecting unrelated things. Tremendous work

  • @geoffstrickler
    @geoffstrickler 2 หลายเดือนก่อน +2

    Great explanation, you show how it’s calculated, how it’s relevant, and the end result is actually simple to calculate.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน

      Thank you!

  • @245trichlorophenate
    @245trichlorophenate หลายเดือนก่อน +4

    This is why nobody likes mathematicians. They mix everybodies hats up when noone is looking.

  • @davidbelk46
    @davidbelk46 2 หลายเดือนก่อน +3

    So, if you need to calculate a subfactorial for some reason and you wish to save a lot of time, just divide the factorial by the number e then round to the nearest integer. It works every time.

  • @NestorCustodio
    @NestorCustodio 2 หลายเดือนก่อน +27

    I will never write a "3" or a "2" as legibly as this man did @ 2:30. 😢

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +16

      I was cooking with those

    • @CliffSedge-nu5fv
      @CliffSedge-nu5fv 2 หลายเดือนก่อน

      I did once, and then never again. 😢

    • @terrybull3798
      @terrybull3798 2 หลายเดือนก่อน +2

      However; not equal looked indistinguishable from +/- @11:30 :)

  • @ErikYoungren
    @ErikYoungren 2 หลายเดือนก่อน +3

    5:33 Now I just want to know how likely is it that none of the viewers get both their socks back?

  • @Dagobah359
    @Dagobah359 2 หลายเดือนก่อน +8

    5:34 Missed opportunity to say it would blow our hats off. Booo!

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +3

      I will not be tempted by your cheap puns!

  • @RadicalCaveman
    @RadicalCaveman 2 หลายเดือนก่อน +2

    1/e is so hilarious, I'm amazed there isn't a sitcom about it.

  • @stephenspackman5573
    @stephenspackman5573 2 หลายเดือนก่อน +2

    Fixed points in this sense are cycles of length 1. The obvious generalisation is to permutations with other minimum (and indeed maximum) cycle lengths. These would be practical things to know.

  • @elreturner1227
    @elreturner1227 2 หลายเดือนก่อน +1

    e and pi are the most interesting numbers like “oh you have a weird value for this problem which no field of mathematics even comes close to?” Plug in e or 1/e or e^2 or the eth root of e or e^pi just keep plugging variations of e and pi and it’ll probably work and if it doesn’t even Euler can’t help you

  • @DrMikeE100
    @DrMikeE100 2 หลายเดือนก่อน +1

    Beautiful.... Thanks you! (Dr Mike Ecker, retired PSU math professor)

  • @raphaeld9270
    @raphaeld9270 2 หลายเดือนก่อน +1

    Seems like a useful way to calculate the secret santa arrangements where no-one gets its own gift.
    Thanks for the video, I wasn't sure if it was a joke video at first, but it was pretty interesting.
    You earned a sub :D

  • @MooseEatsBear
    @MooseEatsBear หลายเดือนก่อน

    Man. I thought I was doing really well with understanding this and then I got to the beginning of the explanation at 6:30. You explain things very well but sadly there is a minimum bar of familiarity with the subject required that I just don't have. C'est la vie!

  • @ruin1307
    @ruin1307 2 หลายเดือนก่อน

    Love how this is done sooo much easier with like a for loop and if statement in programming

  • @mab9316
    @mab9316 2 หลายเดือนก่อน

    Beautiful explanation. Thank you.

  • @NexusSpacey
    @NexusSpacey 2 หลายเดือนก่อน +4

    This music is making me think I'm watching a Zullie the Witch video

    • @mjp121
      @mjp121 หลายเดือนก่อน

      I was thinking panenkoek

  • @Jack-O_hedgehog
    @Jack-O_hedgehog 2 หลายเดือนก่อน +2

    This video amazed my mom as I watched this since she never heard of subfactorials before

  • @tomkerruish2982
    @tomkerruish2982 2 หลายเดือนก่อน +22

    Clearly, they were not doing the Safety Dance.
    (Gen X earworm, activate!)

    • @surkh
      @surkh 2 หลายเดือนก่อน +2

      Well, then they're no friends of mine!

    • @lulairenoroub3869
      @lulairenoroub3869 2 หลายเดือนก่อน +1

      But they were men without hats
      And they were dancing
      And they were friends
      The men without hats never claimed they didn't "own" hats. They just didn't have any, currently, as is the case with our dancers

    • @porl42
      @porl42 2 หลายเดือนก่อน +1

      I had exactly the same thing in my head 😂

    • @RandyKing314
      @RandyKing314 2 หลายเดือนก่อน +1

      i was trying to work out a comment like this…well played!

  • @chrisstott3508
    @chrisstott3508 2 หลายเดือนก่อน

    A wonderful and beautiful result, thanks.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน

      Thank you for watching!

  • @graydhd8688
    @graydhd8688 2 หลายเดือนก่อน

    Funny, i didn't know subfactorials were a thing but I'm learning about recursion in programming and this is helping me get more perspective on a specific problem I've been stuck on for two days. Essentially i was trying to figure out a formula to assess all permutations of something and worked out the subfactorial without knowing it had a name, i just noticed it was similar to a factorial but adding.

    • @graydhd8688
      @graydhd8688 2 หลายเดือนก่อน

      I didn't get the formula on my own, just that the subfactorial is involved lol

  • @mattadams2292
    @mattadams2292 2 หลายเดือนก่อน

    At about the 18:55 mark, when reindexing to start at i=0 instead of i=2, wouldn't this change the ending index to (n-2) rather than n?
    Once we're considering the limit as n goes to infinity, this change no longer matters, so the 1/e result is unchanged.

  • @danquella330
    @danquella330 2 หลายเดือนก่อน +1

    I kept waiting for the hilarity, and was left with the impression that you math types are easily amused!

  • @gerald56
    @gerald56 2 หลายเดือนก่อน

    Thanks for the presentation! This is a clssical gem of discrete mathematics.

  • @akeem2983
    @akeem2983 11 วันที่ผ่านมา

    Several kids in an alien spaceship can't get their correct hats back

  • @MVRX.
    @MVRX. 2 หลายเดือนก่อน

    Great explanation!

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน

      Thank you!

  • @francocatanzaro96
    @francocatanzaro96 2 หลายเดือนก่อน +1

    4:23 I hear your Easter Egg of putting the Select File Theme from SM64, as Pannenkoek does! Very clever!

  • @George-tk2hj
    @George-tk2hj 2 หลายเดือนก่อน

    This was really fun, and the notation wasn’t too difficult. Thanks!

  • @miezekatze3536
    @miezekatze3536 2 หลายเดือนก่อน +1

    the moment he said "the probability will surprise you" I thought "probably 1/e or sth like that"...

  • @Manisphesto
    @Manisphesto 2 หลายเดือนก่อน +45

    I now wanna question what n!n is, is it n! × n, or n × !n...

    • @callyral
      @callyral 2 หลายเดือนก่อน +24

      parentheses are your friends

    • @matino0820
      @matino0820 2 หลายเดือนก่อน +7

      Id say n × !n bc you put numbers before variables like 2x

    • @mathguy37
      @mathguy37 2 หลายเดือนก่อน +13

      !n!

    • @tobithesergal
      @tobithesergal 2 หลายเดือนก่อน +2

      stuff like this is why im not better at math, that’s very ambiguous

    • @Slxy3rzZZ
      @Slxy3rzZZ 2 หลายเดือนก่อน +3

      well, clearly, the bodmas order wasn't enough 😢😂

  • @fariesz6786
    @fariesz6786 2 หลายเดือนก่อน

    this was satisfying bc when saw the approximation before it felt so random yet underwhelming (like what, you just multiply the factorial by an essentially constant factor?)
    but this explains neatly where it came from

  • @ThePsyko420
    @ThePsyko420 2 หลายเดือนก่อน +1

    I gotta say when i read the title I was expecting the same as factorial except with division instead of multiplication

  • @thetruetri5106
    @thetruetri5106 2 หลายเดือนก่อน +2

    Hmmm Derangements are actually exactly what I need for my experimentations on creating sudokus. Is there also a way to easily figure out what those derangements are instead of just their amount?

    • @buddermybacon
      @buddermybacon 2 หลายเดือนก่อน

      Latin squares

    • @thetruetri5106
      @thetruetri5106 2 หลายเดือนก่อน

      @buddermybacon well latin squares only have n derangements not every possible one though

  • @HelPfeffer
    @HelPfeffer 2 หลายเดือนก่อน

    0:25 yes, it means 1 factorial times n = n

  • @thesmilingbraniac4438
    @thesmilingbraniac4438 2 หลายเดือนก่อน +3

    12:45 writing (-1)^(j-1) feels illegal

  • @nullmeasure6155
    @nullmeasure6155 2 หลายเดือนก่อน

    Hot example, honestly. This is also the most lucid presentation of inclusion-exclusion I have ever seen. Well done.

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน

      Thanks a lot!

  • @SatisfyingWhirlpools
    @SatisfyingWhirlpools 2 หลายเดือนก่อน

    My favorite part about it is that the sequence appears more slightly strange (the terms don’t all end in 000…)

  • @MaxwellClarkeNZX
    @MaxwellClarkeNZX 2 หลายเดือนก่อน

    Seems like there's an easier way to count using a recursive definition:
    let Ai be the set which has *exactly one* fixed point at index i. This means that index i is a fixed point, and the rest is a derangement: !(n-1).
    Likewise for Bij (the set which has exactly two fixed points).
    So the number of derangements is going to have the form !n = n! - ((n choose 1) ⋅ !(n-1) + (n choose 2) ⋅ !(n-2) + ... + (n choose n-1) ⋅ !(n-(n-1)) + 1)
    Then I'm sure we can do some re-arranging.

  • @arnoldvanhofwegen2255
    @arnoldvanhofwegen2255 หลายเดือนก่อน

    A better analogy would be people celebrating Christmas and picking a ballot with the name of a participant from a pot where nobody is supposed to pick the one with their own name.

  • @actuallyasriel
    @actuallyasriel 11 วันที่ผ่านมา

    I started getting the sweats when we started taking a limit. God fucking damnit, Euler!

  • @bud-yo
    @bud-yo หลายเดือนก่อน +1

    Oh wow that changes a lot

  • @David_Lloyd-Jones
    @David_Lloyd-Jones 2 หลายเดือนก่อน +1

    As is obvious from their accurate, lifelike portraits, the men in this diagram are misidentified. They are actually Man 47, Man 312, and Man 14,703.
    1. 2. and 3 all died in the pneumonia epidemic of 1919.

  • @GreigaBeastDS
    @GreigaBeastDS หลายเดือนก่อน

    What happens when we move the exclamation mark to the other side? I imagine it gets quieter instead of louder.

  • @GayAnnabeth
    @GayAnnabeth 2 หลายเดือนก่อน

    oh hey, alternating harmonic series, love to see it

  • @kinexkid
    @kinexkid หลายเดือนก่อน

    I love how at 2:00, the row for the hats was above the row for the men like they were wearing them lol. I hope that was intentional

  • @DontWatchWhileHigh
    @DontWatchWhileHigh 2 หลายเดือนก่อน +2

    Me: There's no way there's an explicit formula for this
    Also me after watching the video: Oh right I did this in combinatorics like 7 years ago

  • @xenomancer1
    @xenomancer1 2 หลายเดือนก่อน

    This entire video is a single unacknowledged safety dance joke.

  • @WhyCatsCantFly
    @WhyCatsCantFly 2 หลายเดือนก่อน

    the file select theme in the background makes this so beautiful

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน

      It's a classic!

  • @thatkindcoder7510
    @thatkindcoder7510 2 หลายเดือนก่อน

    Honestly amazed by how you could confidently go deep into a topic in such an entertaining way. Might be slightly jealous...

  • @VPN14494
    @VPN14494 หลายเดือนก่อน

    Correction at 9:22 it should be |A2|

  • @graxxor
    @graxxor หลายเดือนก่อน

    I can’t get over the fact that bro draws his stick men without any arms.

  • @LordHonkInc
    @LordHonkInc 6 วันที่ผ่านมา

    Well damn, learned something new today. Strange this never came up in my university lectures even though we went through combinatorics pretty thoroughly (that said, I barely passed that course xD)

  • @verdatum
    @verdatum หลายเดือนก่อน

    In case no one else has mentioned it, really weird harmonics in the background music. It cuts through like an alarm signal on small speakers. Good content though!

  • @orsoncart802
    @orsoncart802 2 หลายเดือนก่อน +1

    That reminds me, not of hats but of doggies’ Rsoles:
    The doggies held a meeting,
    They came from near and far,
    Some came by motorcycle,
    Some by motorcar.
    Each doggy passed the entrance,
    Each doggy signed the book,
    Then each unshipped his Rsole
    And hung it on the hook.
    One dog was not invited,
    It sorely raised his ire,
    He ran into the meeting hall
    And loudly bellowed, "Fire."
    It threw them in confusion
    And without a second look,
    Each grabbed another's Rsole,
    From off another hook.
    And that's the reason why, sir, 
When walking down the street, 
And that's the reason why, sir, 
When doggies chance to meet, 
And that's the reason why, sir, 
On land or sea or foam, 
He will sniff another's Rsole 
To see if it's his own.
    In this case e = 1 explains all the sniffing! 😁

  • @Veroniquekky
    @Veroniquekky 2 วันที่ผ่านมา +1

    0:07 using /dots and not /cdots between multiplication operations makes me so sad 😂😂😂

    • @Veroniquekky
      @Veroniquekky 2 วันที่ผ่านมา +1

      But also having the 5 center dots isn’t the most appealing either 😭

  • @NoriMori1992
    @NoriMori1992 2 หลายเดือนก่อน +3

    Enjoyed the SM64 music 😊

  • @MURDERPILLOW.
    @MURDERPILLOW. 2 หลายเดือนก่อน

    1:32 oh god there was a puzzle like this in proffessor layton, you had to figure out how likely it was that 2 people got their hat but one person didnt. I guessed EVERY number from 1-100% only to realise it was 0%

  • @stickmaker10111
    @stickmaker10111 หลายเดือนก่อน

    Dude your penmanship is so nice

    • @WrathofMath
      @WrathofMath  หลายเดือนก่อน

      Thank you!

  • @SquidLikesTalking
    @SquidLikesTalking 2 หลายเดือนก่อน +2

    What a fantastic video, such an enjoyable watch, the mario 64 music was just the cherry on top

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +2

      Thanks so much! Trying to get the music at the right volume, I think I got it just about right this time.

    • @dottn
      @dottn หลายเดือนก่อน

      I didn't realize there was music until I saw these comments.
      I was listening at a lower volume, and your voice was quite clear, but there was this annoying beeping sound like a reversing truck every now and then.
      Turned out to be the high notes of the music track starting at 3:50, from which only they were audible to me.

  • @suyunbek1399
    @suyunbek1399 2 หลายเดือนก่อน +3

    Hat two? What did you say?

    • @WrathofMath
      @WrathofMath  2 หลายเดือนก่อน +2

      Yeah, hat two, fit on that thang

    • @suyunbek1399
      @suyunbek1399 2 หลายเดือนก่อน

      @WrathofMath get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class get out of my class

    • @apokalypthoapokalypsys9573
      @apokalypthoapokalypsys9573 2 หลายเดือนก่อน +1

      ​@@WrathofMathtfw anti-intellectualism on a maths channel

  • @MitchBurns
    @MitchBurns 2 หลายเดือนก่อน

    e is also closely related to pi. e^pi*i=-1. Also if f(x)=f^4(x), f(x) could equal both e^x, or sin(x). Also, since you mentioned rounding, both pi and e round to 3.

    • @josenobi3022
      @josenobi3022 2 หลายเดือนก่อน +1

      Or you know, cos(x) and basically any sine function of the form a*sin(x+b) or a*cos(x)+b*sin(x)

  • @chad3814
    @chad3814 2 หลายเดือนก่อน

    @1:50 "...not a single man has gotten his hat back. Our question is... how many now have lice?"

  • @denischen8196
    @denischen8196 2 หลายเดือนก่อน

    Is there a math symbol or function for how many permutations of n have m fixed points where 0

    • @cocoabutter5888
      @cocoabutter5888 2 หลายเดือนก่อน

      Something like n-m choose n maybe?

  • @rodrigoqteixeira
    @rodrigoqteixeira 2 หลายเดือนก่อน

    Nice. You can instead of divising by e multiply by the precomputed 1/e or e^-1

  • @ollllj
    @ollllj 2 หลายเดือนก่อน

    do we have a mathertmatical sign for "total electrical resistance of parallel resistors", which is: inverse of all resistances, summed up, and the sum is then inverted again: (resistor1^-1+resistor2^-1...)^-1
    This also occurs (identical function) in "exponential smooth-step function" for "smoothing (more than 2) meta-balls or more complex signed-distance-fields" (commutatively), the simplest one one that is commutative and that allows for independent "sharpness" factors.

    • @julioaurelio
      @julioaurelio 2 หลายเดือนก่อน +1

      That's H(n)/n, where H(n) is the harmonic mean of n numbers.
      This operation also appears when finding the equivalent capacitance of capacitors in series.

  • @Marinealver
    @Marinealver หลายเดือนก่อน

    So, what would the 2.5 dimension look like?

  • @patrickmcginnis7
    @patrickmcginnis7 หลายเดือนก่อน

    I've been looking for thisa for years, But what if you have 70 hats and 6 men and do it d times, and a hat won't repeat on a man, and no permutation will repeat over d?