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Stirling's Approximation: A STUNNING Result For Factorials (ft Imperial College)
Thanks to Imperial for hosting me! Hope everyone enjoyed! I love this approximation since it becomes more and more familiar with each step and leaves such a satisfying final result - please comment with any questions or suggestions for new topics, and as always, subscribe to stay updated.
~ Thanks for watching!
Comment solutions to the challenge down below.
@blackpenredpen … as always I've left you a challenge at the end of this video as well as the last few - if you see this give it a go!
Thanks so much for all the recent support - hitting 1k subscribers has been amazing and so please keep sharing and interacting so I can make even more content!
Thanks again for all the recent support and please keep sharing and interacting!!
#maths #mathematics #integrals #Imperial #MIT #Cambridge #approximation #problemsolving #stirling #approximation #taylor #maclaurin #gaussian #gauss #normaldistribution #statistics #whoknew #fascinating #functions #euler #funproblems #proofs #functions #physics #sums #series #limits #whiteboard #math505 #blackpenredpen #integral #trig #trigonometry
Переглядів: 11 986

Відео

The Power Of Recursion: An UNSOLVABLE Integral
Переглядів 7 тис.14 днів тому
Hope everyone enjoyed! I thought this integral was particularly unique and love how theres so many approaches - please comment all of yours down below!! Please comment with any questions or suggestions for new topics, and as always, subscribe to stay updated. ~ Thanks for watching!Still looking for your answer to my last two video challenges @blackpenredpen ... Thanks again for all the recent s...
IMPOSSIBLE Trig Integral (Solved With Zeta Function)
Переглядів 81321 день тому
Hope everyone enjoyed! I thought this had such nice solution development especially how it changed from trig to sumation so fast. Comment with answers to the challenge and questions or suggestions for new topics, and as always, subscribe to stay updated!! ~ Thanks for watching all. Thanks again to everyone for all the recent support, I didn't expect any of this so I'm extremely grateful! @black...
CRAZY Floor Function Integral (Turns Into A DOUBLE Sum)!
Переглядів 2,3 тис.Місяць тому
Hope everyone enjoyed! Loved the way this simplified so definitely had to share. Comment with your answers to the surprise problem at the end and subscribe for more content like this! ~ Thanks for watching all. @blackpenredpen I challenge you to solve the problem I gave at the end of the video... #maths #mathematics #integrals #summation #floorfunction #euler #funproblems #proofs #functions #ph...
FASCINATING MIT Integral Solved With Recursion And Sums
Переглядів 5 тис.Місяць тому
I hope everyone has found this interesting! I loved how much thinking outside of the box this integral took and so wanted to share it!!! Please comment with any questions or suggestions for new topics, and as always, subscribe to stay updated. ~ Thanks for watching all. Thanks again to everyone for all the recent support, and @maths_505 for reposting another of my videos - he inspired me to sta...
BAFFLING British Olympiad Proof By Induction
Переглядів 3 тис.Місяць тому
I hope this has been interesting! Haven't done any proof based videos for a while but if you enjoy olympiad related content please let me know. Comment with any questions or other suggestions for new topics and subscribe to stay updated. ~ Thanks for watching all! Another huge thanks to @maths_505 for inspiring me from the start and reposting about my channel - he is the GOAT! #maths #mathemati...
Crazy Trig Integral With Feynman's Trick!
Переглядів 2,9 тис.Місяць тому
Huge thank you to @maths_505 who is the GOAT and created this problem. I wanted to share the way that I had solved it but his is equally good (and probably more advanced...). Please comment with any questions or suggestions for new topics. Subscribe to stay updated. ~ Thanks for watching all. #maths #mathematics #integrals #zetafunction #euler #funproblems #proofs #functions #physics #sums #ser...
BEAUTIFUL Floor Function Integral (With Zeta Function)
Переглядів 14 тис.Місяць тому
I hope this has been interesting! This is one of my fav integrals in a while so wanted to share. Please comment with any questions or suggestions for new topics. Subscribe to stay updated. ~ Thanks for watching all. ​⁠@maths_505 Thanks for taking a look at my solution to this too! #maths #mathematics #integrals #zetafunction #euler #funproblems #proofs #functions #physics #sums #series #limits ...
A Beautiful Result In Probability: Subfactorials
Переглядів 2504 місяці тому
I hope this has been useful! Please comment with any questions or suggestions for new topics. Subscribe to stay updated. ~ Thanks for watching all. #maths #mathematics #probability #combinatorics #statistics #stats #funproblems #proofs #functions #physics #sums #series #limits #whiteboard
Proof of Euler's Reflection Formula - Weierstrass Form of Gamma Function!
Переглядів 2354 місяці тому
I hope this has been useful! Please comment with any questions or suggestions for new topics. Subscribe to stay updated. This is a part 2! To understand why Gamma(z) can be written like this see my previous video. ~ Thanks for watching all. #maths #mathematics #proofs #functions #integrals #gamma #gammafunction #physics #sums #series #product #limits #whiteboard
The Weierstrass Form of the Gamma Function - Derivation!
Переглядів 3914 місяці тому
I hope this has been useful! Please comment with any questions or suggestions for new topics. Subscribe to stay updated. ~ Thanks for watching all. #maths #mathematics #problemsolving #proofs #functions #integrals #gamma #gammafunction #physics #sums #series #product #limits #whiteboard

КОМЕНТАРІ

  • @nickmcstuffins1836
    @nickmcstuffins1836 17 годин тому

    fantastic video

    • @OscgrMaths
      @OscgrMaths 13 годин тому

      @@nickmcstuffins1836 Thank you! Really glad you enjoyed.

  • @akshatsharma8151
    @akshatsharma8151 20 годин тому

    I am happy we have people like you on the internet.

    • @OscgrMaths
      @OscgrMaths 13 годин тому

      @@akshatsharma8151 Thank you so much!

  • @maths_505
    @maths_505 22 години тому

    Very cool as always

    • @OscgrMaths
      @OscgrMaths 22 години тому

      @@maths_505 Thank you!!!

  • @dumitrudraghia5289
    @dumitrudraghia5289 День тому

    Ai un defect la limbă? Sau ești un robot ruginit?

  • @alphalunamare
    @alphalunamare День тому

    I think that this has been most entertaining, refreshing and an original aproach. That was fun :-)

    • @OscgrMaths
      @OscgrMaths День тому

      @@alphalunamare Thank you so much!! Really appreciate it.

  • @lol-ho2kj
    @lol-ho2kj День тому

    Intergration the inversely operating of function and the constant can go to small continuously so there are a loop.decimal

  • @Silver-bq6td
    @Silver-bq6td 2 дні тому

    When n goes to infini it’s not an approximation and it’s equal it’s called an « equivalent » with this symbol ~

    • @OscgrMaths
      @OscgrMaths 2 дні тому

      @@Silver-bq6td Oh good to know thanks!

  • @RogerDou
    @RogerDou 2 дні тому

    Brilliant!Just wonder, are you a high school student?

  • @jaysn1683
    @jaysn1683 2 дні тому

    How many tries did it take to fit all this in the time limit? Mad respect!

    • @OscgrMaths
      @OscgrMaths 2 дні тому

      @@jaysn1683 Thank you!! It was very hard...

  • @Kàrtik21140
    @Kàrtik21140 2 дні тому

    Where are you from bro

  • @Kàrtik21140
    @Kàrtik21140 2 дні тому

    Great 👍

    • @OscgrMaths
      @OscgrMaths 2 дні тому

      @@Kàrtik21140 Thank you!

  • @user-cw1ow1cv2f
    @user-cw1ow1cv2f 2 дні тому

    Really cool content! I love watching you. If you can, can add subtitles as your talking really fast lol. Can’t wait to learn integrals and differentiation at the end of the year!!

    • @OscgrMaths
      @OscgrMaths 2 дні тому

      @@user-cw1ow1cv2f Okay thank you!

  • @MohdAbuolwan
    @MohdAbuolwan 2 дні тому

    Discovered yet another UA-cam treasure!

    • @OscgrMaths
      @OscgrMaths 2 дні тому

      @@MohdAbuolwan Thank you!

    • @MohdAbuolwan
      @MohdAbuolwan 2 дні тому

      @@OscgrMaths I only recommend that you take it slowly on the viewer because not all people math geniuses like yourself😅

    • @OscgrMaths
      @OscgrMaths 2 дні тому

      @@MohdAbuolwan Sorry!! I'll keep that in mind next time. Thanks again for the comment.

  • @petelok9969
    @petelok9969 2 дні тому

    Very nice

  • @Aman-b5k
    @Aman-b5k 3 дні тому

    Bro i suggest you to upload videos solving jee advanced, it's basically a entrance exam written by 16-18 years old students here in india❤

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      @@Aman-b5k Okay thank you! 🇮🇳

  • @blew319
    @blew319 3 дні тому

    Now show that 1001! + 2 is equidistant from at least two primes. :) Nice proof.

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      @@blew319 I'll give it a shot! Thanks!

  • @Charky32
    @Charky32 3 дні тому

    coudlnt u do Integration by parts, with u = 1/(x^2 + 1)^n and v' = 1?

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      You could try it! I'm not sure how it would work because the derivative of 1/(1+x^2)^n is messy but let me know if you get somewhere!

  • @paulpinecone2464
    @paulpinecone2464 3 дні тому

    They don't teach you this technique for good reason. This derivation is highly exothermic and releases hard beta particles when the terms are separated. Advanced integrations should only be performed in controlled environments with appropriate radical dampers. This sort of irresponsible how-to is a reason why the internet has acquired such a reputation for postings of questionable accuracy.

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      @@paulpinecone2464 😂😂😂 Great response!

  • @user-ww6qh9lx8x
    @user-ww6qh9lx8x 3 дні тому

    very nice

  • @booshkoosh7994
    @booshkoosh7994 3 дні тому

    Superb!

  • @juliaantunes8924
    @juliaantunes8924 3 дні тому

    Great video! Greetings from Brazil🇧🇷

  • @booshkoosh7994
    @booshkoosh7994 3 дні тому

    This is really cool. Thanks! I'm happy to find another great math source on the internet! This sort of passion for maths isn't too common, really. Are you, by chance, an AoPS student?

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      Hey, no I've never come across this before as it seems to be mostly a big thing in the US - but it looks really interesting! Definitely love the idea of having a focus on problem solving.

    • @booshkoosh7994
      @booshkoosh7994 3 дні тому

      @@OscgrMaths Right! Thanks for the videos. Most all AoPS students are math competition participants. Although AoPS advertises for a younger crowd, the biggest community is around the Olympiad training. You have to score in the top 1 percent (literally), on two tests (you have to pass the first test in order to take the second), before you can take a year-round maths training to make it onto the American Olympiad team. There are only 5 people on each team, and there's only 1 team per country. There are over 100 countries that participate, yearly! It really gets intense as test results near, or when the end of a class nears. Usually AoPS classes are 6 or 7 months long, and there isn't a single test for the whole of the 6 months! You usually get a proof that you need to write each week, and then 7 or so problems that you need to solve each week (they only count the total amount of problems solved over the 6 months, and it doesn't matter what your weekly score is). There are usually no instructions for how to solve these problems, but instead there is a book of similar problems with loads of proofs and solutions. It takes nearly 2 or 3 hours to solve a single problem (1 hour if it's a really good day). As one student of mathematics to another, seriously ignore small-fry stuff that most people are comfortable with (non of your videos are like that, but people will probably ask for stuff like that in the future). It's special to do something special, and not something watered-down or just okay. I appreciate your willingness to stick it out. Problem solving is most intuition and persistence, and that is something special which most people aren't very comfortable with. Your video topics are excellent! It takes some imagination to do proper math (most proofs -- if not all -- are based on intuition, and then the justification of it); so don't get bogged-down if people say otherwise. I really appreciate the fact that you are keeping the footage and representation basic, and not cluttering it with complex lighting or video edits. Thanks again!👍😄

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      @@booshkoosh7994 Thank you so much for this comment! Having my videos get bigger has been amazing but it has led to more negative comments too and so your kind words really mean a lot. Glad to know there's people out there who understand what I'm going for. I also completely agree with your view of maths on problem solving and I've found the equivalent program in the UK - the first exam is around October, so I'll definitely go for it then. Thanks!

    • @booshkoosh7994
      @booshkoosh7994 2 дні тому

      @@OscgrMaths Absolutely! Happy to help! Good luck on the exam! 😄

  • @doowi1182
    @doowi1182 3 дні тому

    Great video - you have an amazing way of explaining and keeping the audience engaged. Subscribed!

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      Thanks so much! Very kind of you.

  • @gastivy948
    @gastivy948 3 дні тому

    love the sweater can you share your playlist??

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      Ah another molchat doma fan!! I could try and put together a playlist for you - what other kind of music do you like?

  • @Calcprof
    @Calcprof 3 дні тому

    I like this. The usual way (to approximate ln(n!) by an integral, makes the Sqrt[2 pi n] difficult to get.

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      Thank you so much! The usual way is the weak approximation but introducing the gamma function is what helps provide the sqrt2pin part! Glad you enjoyed.

    • @Calcprof
      @Calcprof 3 дні тому

      @@OscgrMaths I shold have thought of it. This approximation for exponential integrals is a standard in asymptotic analysis

  • @NXT_LVL_DVL
    @NXT_LVL_DVL 3 дні тому

    Now find the first 1000 consecutive non-primes . Anyone can find a 1000 consecutive non-primes. That's a pointless question.

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      These numbers are 1000 consecutive non-primes!! All of them can be factored in a way other than themselves and one so therefore they are non-primes!

    • @NXT_LVL_DVL
      @NXT_LVL_DVL 3 дні тому

      @@OscgrMaths but it would be interesting to see where the first sequence of 1000 consecutive non-primes numbers occur amoung the integers.

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      @@NXT_LVL_DVL Oh that's a really interesting question! Could probably do that by coding a prime sieve in python or excel.

  • @Sammy-qt9it
    @Sammy-qt9it 3 дні тому

    Huxley?

    • @OscgrMaths
      @OscgrMaths 3 дні тому

      I did spend some time in Huxley! Then they put me in Skempton as there was a free room with a whiteboard and it's just down the road.

  • @Aman-b5k
    @Aman-b5k 4 дні тому

    Love you from India bro ❤❤❤

    • @OscgrMaths
      @OscgrMaths 4 дні тому

      @@Aman-b5k Thank you! ❤️

  • @dakcom-mk6mp
    @dakcom-mk6mp 4 дні тому

    Very neat

  • @dakcom-mk6mp
    @dakcom-mk6mp 4 дні тому

    Cool

  • @octs609
    @octs609 4 дні тому

    Nice vid. Also on a side note, do you just own a really big white board or is it at the college in the title? (a rather vague question I hope you'll indulge)

    • @OscgrMaths
      @OscgrMaths 4 дні тому

      It's at the university Imperial College in London! My other videos are on my own smaller whiteboard. Hoping to make more on the bigger ones at the uni since they're easier to lay working out on. Thanks for the comment!

  • @JAzzWoods-ik4vv
    @JAzzWoods-ik4vv 4 дні тому

    Try passing the audio of the video through a low pass filter to te remove high frequency humm

    • @OscgrMaths
      @OscgrMaths 4 дні тому

      @@JAzzWoods-ik4vv Oh that's a really helpful suggestion thanks so much!

  • @timofeysobolev7498
    @timofeysobolev7498 4 дні тому

    Great video!) Love your content!)

  • @crehenge2386
    @crehenge2386 4 дні тому

    All I could see was your head...

  • @sandpaper7781
    @sandpaper7781 4 дні тому

    Very nice. Now do integral of sqrt(tanx) 😅

    • @OscgrMaths
      @OscgrMaths 4 дні тому

      I've given this problem a go before... if it's bounded you can use kings rule quite nicely but as an indefinite integral it's very long 😅😅!

  • @that_one_reply8805
    @that_one_reply8805 4 дні тому

    I didn’t study this yet but it seems interesting can you please tell me what it is?

    • @OscgrMaths
      @OscgrMaths 4 дні тому

      @@that_one_reply8805 Sure! Which part is it that you haven't seen before?

  • @eppssilon
    @eppssilon 5 днів тому

    Man I didnt miss this at all, but math is still cool just not school

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@eppssilon School can make maths seem so dull - but it's not always like that! Thanks for the comment!!

  • @divyamgoyal6935
    @divyamgoyal6935 5 днів тому

    Commenting for better reach All the best

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      Thanks so much!! Very kind of you.

  • @Georgeclassified
    @Georgeclassified 5 днів тому

    While working with factorials recently in college I came across Stirling's Approximation and after some digging I found out about an expansion of it that captures almost 100% of the behaviour of x! with x belonging to the interval (-1,infinity).This can also be further extended to represent the factorial function for all real numbers, with staggering , although slightly reduced accuracy using the recursive property of x!(x!=x*(x-1)!).For those who want to plot the formula and graph it, here it is: x!=(2π)^0.5 *e^-(x+1) *(1/(x+1))^0.5*(((x+1)*((1/(810(x+1)⁶))+(x+1)*sinh(1/(x+1)))^0.5)))^(x+1) [-1<x<infinity]

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      Wow that's so interesting!! Thanks for the comment this is great.

    • @Georgeclassified
      @Georgeclassified 5 днів тому

      @@OscgrMaths You are very welcome!!Also your video on stirlings approximation is amazing but I think that's obvious by now! By the way if you are interested in seeing the accuracy of it here is an example π!=7.18808272898 (with gamma function of pi+1). With extended stirliing's approximation π!=7.18808287903. You can see how close the 2 evaluations are.Infact, especially after I found out about this, this became my favourite analetic formula, because I think that it captures the behaviour so well that it can be considered an approximate analetic formula for x! for all real x.I have written a paper about it too!😄

    • @Georgeclassified
      @Georgeclassified 5 днів тому

      ​@@OscgrMaths Yeah I know right!!Also you are very welcome, and by the way your video on the original stirling's approximation is exceptional, and so was your smooth derivation with integration!!!Also, if you are interested in seeing the accuracy of the formula I ll write how it works for π!.Here: π!=7.188082729... (Γ(π+1)) π!=7.18808287903...(Extended stirling's approximation).By the way this is my favourite analetic formula in mathematics, as it is so accurate for all x greater than -1 and x less than that with its extension to all negatives with the recursive property, that I think it can be regarded as an approximate analetic expession for x! for all real x rother than an asymptotic expansion!!!

    • @Georgeclassified
      @Georgeclassified 5 днів тому

      @@OscgrMathsYou are very welcome!!By the way amazing explanation of Stirlings approximation, your derivation was amazing!!!Also this is now my favourite analetic formula because it is so accurate that I like to regard it as an approximate analetic expansion for x! rather than an asymptotic expansion!!

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@Georgeclassified Absolutely, it's quite incredible how accurate it is!

  • @justsomeguy2001
    @justsomeguy2001 5 днів тому

    Wow.

  • @zeteya
    @zeteya 5 днів тому

    All that work for the wrong answer

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      -pi^2/6 is the correct answer... You can check it in an integral calculator if you aren't convinced!

    • @Endermanv-ot2if
      @Endermanv-ot2if 2 дні тому

      Prettier to write -Z(2).​@@OscgrMaths

  • @masonholcombe3327
    @masonholcombe3327 5 днів тому

    Question, at the end you replaced the lower bound of the integral with -inf because we're dealing with large values of n but at the start you only used the first 3 terms of the taylor expansion (which would be for approximating small values of n). Is this not contradictory? Great video though, very nice result!

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      Thanks for the comment! If it were a Maclaurin expansion (centred at 0) for a function of n it would be only be valid for small values of n, but since it's a Taylor expansion around the point n for a function of t, whatever value we choose for n (even if it's very large) it just means the approximation will be most accurate roughly around that area. Hope that makes sense! Feel free to ask any more questions you have.

  • @liamturman
    @liamturman 5 днів тому

    Awesome Job! Is there any way to prove that they are asymptotically equivalent or is that a little to advanced?

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@liamturman Thanks so much! You might be interested in this document from the university of connecticut which provides a few different and very interesting proofs for this (one of which involves bernoulli numbers!) kconrad.math.uconn.edu/blurbs/analysis/stirling.pdf

  • @muskyoxes
    @muskyoxes 5 днів тому

    For the longest time i could "derive" every part of the approximation except the 2 pi. The 2 pi makes sense today for the first time

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@muskyoxes Glad it makes sense now!! Thanks for the comment.

  • @JujutsuMath
    @JujutsuMath 5 днів тому

    you got good content keep it up, are you doing a maths uni degree ?

  • @Gameboygenius
    @Gameboygenius 5 днів тому

    New here. Never heard anyone pronounce ln as lun. Its usually either ell-enn or stubbornly calling it log.

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @Gameboygenius I think it might be a British thing? I always said it as ell-enn because I first learnt most of my calculus online from american channels but my teachers and classmates have recently been calling it lun and I've reluctantly converted... Thanks for the great comment!

    • @patrickcorliss8878
      @patrickcorliss8878 4 дні тому

      @@OscgrMaths lun is great. Hope it catches on !!

  • @suzum0978
    @suzum0978 5 днів тому

    Not so rigorous and you seem to be abusing notations (such as taking n into infinity in the bounds while it's still there in the expression) . But it's still convincing for a Physicist ! Good job mate

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @suzum0978 Yeah that part with n in the bounds is a little rough - that's why it's definitely an approximation! But thanks for the comment either way. If you want a slightly more rigorous (but less accessible which is why I didn't include it) derivation, it can actually be done with a contour! By considering 1/n! as a taylor coefficient in the maclaurin series of e^z and then computing it with the cauchy integral formula. You can try and work out the line integral using the saddle point method. The dominant portion near the saddle point is approximated by a real integral and Laplace's method. Actually Laplace's method is useful in evaluating this integral in general so is also worth considering (especially since the saddle point method is kind of a complex extension of laplace's method). Hope this is interesting and thanks for the comment.

    • @suzum0978
      @suzum0978 5 днів тому

      @@OscgrMaths this sounds exciting, I hope you make video about it if you have time in the future!

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@suzum0978 Okay great!

  • @adw1z
    @adw1z 5 днів тому

    If we use higher order terms of f(t), we can keep going and derive the so-called Stirling Series! What was found here is the leading order term of that series

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@adw1z Yes! And each will be more and more accurate. Thanks so much for the comment!

  • @lucahaines4655
    @lucahaines4655 5 днів тому

    Lovely, thank you

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@lucahaines4655 Thanks so much!

  • @dakcom-mk6mp
    @dakcom-mk6mp 5 днів тому

    Nice video

    • @OscgrMaths
      @OscgrMaths 5 днів тому

      @@dakcom-mk6mp Thank you!