how calculus teacher answers friend’s question

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  • Опубликовано: 25 янв 2025

Комментарии • 616

  • @blackpenredpen
    @blackpenredpen  Год назад +50

    Try this one next: ruclips.net/video/Wb30497-7Hg/видео.html

  • @blackpenredpen
    @blackpenredpen  3 года назад +1901

    The answer is 4 hrs/day.

    • @ChadTanker
      @ChadTanker 3 года назад +119

      well if somebody got a negative number or something thats bigger than 24 its wrong XD
      effectivly limiting the window to 0 - 24

    • @SsinaSlx
      @SsinaSlx 3 года назад +14

      Hi professor glad to see you , I'm from Iran , I love math but I'm a student now, I want to use your fabulous and amazing teaching from 0 to up! regretfully I'm not as well as American people in translating during your teaching, could you please guide me about this issue , how can I use the best teaching for learning and understand with all of my cells !!! In more simple language❤❤🔥🔥Thanks

    • @Roescoe
      @Roescoe 3 года назад +63

      No it's 4(cos2(x)+sin2(x))

    • @graceyu87
      @graceyu87 3 года назад +14

      OMG >.

    • @vaxer.7749
      @vaxer.7749 3 года назад

      @@SsinaSlx چطوری

  • @sujatasharma8560
    @sujatasharma8560 3 года назад +2844

    Just remember the rule:
    Longer the expression, easier it is to solve.

    • @rexthegamergembox
      @rexthegamergembox 3 года назад +266

      i disagree

    • @amroosha
      @amroosha 3 года назад +162

      I agree

    • @amroosha
      @amroosha 3 года назад +138

      It is because usually short term expressions get expanded then factorized while long term expressions only get factorized only because it isn't logical to be expanded even further.

    • @rexthegamergembox
      @rexthegamergembox 3 года назад +34

      @@amroosha try some of the IMO questions, they are huge and they require huge knowledge too

    • @Anik_Sine
      @Anik_Sine 3 года назад +59

      @@rexthegamergembox Most of the time when people create large problems, they usually just combine many small questions so that the time taken to solve it is approximately equal to the time taken to solve an average difficult problem. In cases ,like you mentioned, in though exams like IMO they do combine difficult questions.

  • @rishitpant
    @rishitpant 3 года назад +766

    I want my calculus teacher to ask this on test

  • @MalleusRegum
    @MalleusRegum 3 года назад +797

    OK, let me solve it for you, guys. His estimate is probably an integer. And since the integer is a square, the possible solutions are 1, 4 or 9. 1 is too little, 9 is too much. The answer should be "4 hours".

  • @mayurchaudhari850
    @mayurchaudhari850 3 года назад +199

    One of the many reasons I love calculus is because you could frame something like that 0:00 in a portrait and it could be worth millions just because it looks beautiful.

  • @ANTONIOMARTINEZ-zz4sp
    @ANTONIOMARTINEZ-zz4sp 3 года назад +191

    Thanks so much for your commitment with teaching. People like you make the world a better place.

  • @noodlesandsteak
    @noodlesandsteak 3 года назад +719

    the fact that I’m getting closer and closer to actually solving things like this by myself is scary

    • @blackpenredpen
      @blackpenredpen  3 года назад +147

      lol why

    • @cxllmegeo3557
      @cxllmegeo3557 3 года назад +45

      I’m in 10th and decided to just look at this and I’d I’m already discouraged. But I hope I can solve stuff like this in the future

    • @marshian__mallow2624
      @marshian__mallow2624 3 года назад +93

      @@cxllmegeo3557 don’t be discouraged by hard looking maths. Hard looking maths isn’t what you should worry about. It’s the “easy” questions that get you

    • @levi2732
      @levi2732 3 года назад +15

      @@cxllmegeo3557 im economist but i do maths for fun and i can solve this easly , it's nothing compare to inferential statistics, but one day you will understand thos things and the logique of MATH just be patient

    • @cxllmegeo3557
      @cxllmegeo3557 3 года назад +2

      @@levi2732 I appreciate the encouragement. Can u explain what inferential statistics is cuz I just looked it up and I still don’t get it 😅

  • @andrewmetasov
    @andrewmetasov 3 года назад +181

    Ratio of how scary this one looks to how easy it is solved is just amazing
    Exactly opposite to sin(x)^cos(x)=2

    • @longsteinpufferbatch4949
      @longsteinpufferbatch4949 3 года назад +8

      How can it be equal to 2? Hmmm shouldn't the maximum value be (1/√2)^(√2/2)
      Or does this have something to do with complex numbers now. I'm sure it does

    • @itsnotyourownbusiness827
      @itsnotyourownbusiness827 3 года назад +4

      @@longsteinpufferbatch4949 it does

    • @raifegeozay687
      @raifegeozay687 2 года назад +12

      this has real sol because of this:
      (number less than 1)^(negative)>1

    • @dadoo6912
      @dadoo6912 2 месяца назад

      ​@@longsteinpufferbatch4949 it has a solution (infinitely many actually) in real numbers. if sine is positive and cosine is negative you can get 2 with real input

  • @jonnyy1238
    @jonnyy1238 3 года назад +79

    thank you so much for your time and effort you put into these videos! as a calc I student i enjoy them a lot.

  • @sylvainstephant2843
    @sylvainstephant2843 3 года назад +600

    Seeing this integral gave me an idea. Is there some kind of recursive integrals where the integration bounds depends on the integral part itself?

    • @nickbloons6535
      @nickbloons6535 3 года назад +10

      As far as I know it's undefined but I'm not totally sure

    • @sylvainstephant2843
      @sylvainstephant2843 3 года назад +41

      @@nickbloons6535 Why would it be undefined? I actually had several things in mind but for the most simple we can look at an equation like I = Integral from 0 to I of f(x) dx. We are looking actually for some fixed point that is compatible with the integral. For example the integral of 2xdx between 0 and 1 is 1 which satisfies the previous equation.

    • @nickbloons6535
      @nickbloons6535 3 года назад +5

      Right but then ur just solving for a variable "l" if im reading ur equation right. That's different than having a function of "l". So when I said undefined I was thinking that unbounded would be undefined but you have a good example of a case where it isn't undefined. This kind of reminds me of the Mandelbrot set but with the equation involving integration. I remember putting something similar to this into demos and getting an error msg, but I don't rly understand

    • @blackpenredpen
      @blackpenredpen  3 года назад +219

      That’s a great question. I will think about it. (I haven’t read your reply Bc I wanted to think about it first).

    • @chitlitlah
      @chitlitlah 3 года назад +5

      Some would certainly be solvable. In the example you gave, if f(x) is just x, you would end up with I = 1/2 x^2 from 0 to I, or I = 1/2 I^2. Just off the top of my head, 2 works there. If you're asking if this ever shows up in physics or engineering, I doubt it but I'd love to see an example if I'm wrong.

  • @superrrishabh9982
    @superrrishabh9982 Год назад +3

    Keep up your hard work
    It's very nice to see someone post videos about calculus, Euler's number etc.
    Not many people take this much time to post such videos
    Thanks for sharing all the knowledge

  • @jonhroldan9582
    @jonhroldan9582 3 года назад +14

    I really like your channel, specially your latest content about series. I'm taking calculus this semester and the current lessons are about infinite series. Your videos helped me to survive my course. You deserve millions of subscribers!

  • @drumjunky1608
    @drumjunky1608 3 года назад +20

    I honestly felt proud of myself being able to figure this out and then you solved it in a fraction of the work I needed to solve it. back to feeling dumb again :(

  • @alberteinstein3612
    @alberteinstein3612 3 года назад +24

    I could do everything except the series ones, those have always been my Achilles Heel of Calculus

    • @cyn8600
      @cyn8600 3 года назад +1

      Cmon you can't be saying that with your profile pic

    • @alberteinstein3612
      @alberteinstein3612 3 года назад +10

      @@cyn8600 it’s been a good 70 years since I’ve studied mathematics, I’m a little rusty

  • @rrrr3666
    @rrrr3666 Год назад +2

    Girlfriend : How do you love me?
    BPRP : Integral of....

  • @HenkVanLeeuwen-i2o
    @HenkVanLeeuwen-i2o Год назад +1

    He is amazing.

  • @ioangauss
    @ioangauss 3 года назад +4

    4:02 just explain that if you change n=u+1 from the normal serie equals to lin(1+x) you fall on the one you have onyour whiteboard :)

  • @lite7769
    @lite7769 2 года назад +4

    You make math sound fun and not like a chore, I love ur videos :)

  • @moinmalik1320
    @moinmalik1320 Год назад +1

    Your videos are always a learning experience.

  • @pierre7770
    @pierre7770 3 года назад +5

    Love maths but love your videos more ! Thank you 🙏

  • @mextitan
    @mextitan 3 года назад +8

    You sir, are a saint, among other youtubers helped understand calc 2,calc 3, and calc 4. I had not taken any college courses in 10 years, and with your help I was able to pass with two A's and a B. So thank you for your time!

  • @oliguilo
    @oliguilo 3 года назад +4

    Thank you for your time ! I wish I had a teacher like you during my studies 😊

  • @mcgrewgs
    @mcgrewgs 3 года назад +8

    1:44 "If you want to make any calculus equation look harder, replace all the 1s with sin^2(x)+cos^2(x)" 🤣🤣
    I'd also suggest replacing all the π with sqrt( 6*sum_{n=1}^{\infty}(n^{-2}) ) for extra fun 😊
    Merry Christmas to you, too!

    • @Z7youtube
      @Z7youtube 2 года назад +1

      i liked yours a lot even tho i didn't know it

  • @abhaykumarsingh7081
    @abhaykumarsingh7081 3 года назад +1

    You're a blessing to all that yearn to learn thank you bprp

  • @Etienne-JEUNEHOMME
    @Etienne-JEUNEHOMME 3 года назад +3

    Thank you ! I love your content and personnality. Have a nice day

  • @saltyconsolegamer9383
    @saltyconsolegamer9383 3 года назад +5

    nicest math you tuber and youtuber at that, always coming in clutch with some cool videos to make my day

    • @gilgameshur-nammu366
      @gilgameshur-nammu366 3 года назад

      Blackpenredpen seems like the coolest professor ever. I would be honored to have a coffee with this guy and talk math

  • @goku-mx5ew
    @goku-mx5ew 3 года назад +6

    I was able to solve limit and the derivative quickly but can't solve both the series love the question and explanation sir

  • @gilgameshur-nammu366
    @gilgameshur-nammu366 3 года назад +16

    I wanted to say that I really appreciate you for being so welcoming and friendly and showing us that math can be fun -- and not so scary after all! Some professors are condescending, but you can tell that blackpenredpen is a wonderful professor that loves his jobs, and loves teaching! Cheers!

  • @Sanwichgamingtr
    @Sanwichgamingtr 3 года назад

    You are a precious teacher. I'm watching you from Turkey and it helps me a lot. Thank you sir.

  • @dylanmcgowan8999
    @dylanmcgowan8999 3 года назад +4

    or instead of squaring it you could put it to the power the ininite tetration of sqrt(2)

  • @UROOZFATIMA190
    @UROOZFATIMA190 Год назад +1

    Wow great content and your subscription is here i am a mathematics ❤and physics lover and your videos are so amusingly AWESOME so marvelous work keep it up.🎉

  • @eduardoponciano8007
    @eduardoponciano8007 3 года назад +24

    Excelente, professor.

  • @spider-uh5ws
    @spider-uh5ws 3 года назад +1

    Have a nice christmas Mr Blackpenredpen

  • @rohitranjan4416
    @rohitranjan4416 2 года назад +1

    You are awesome man!

  • @sunny_25
    @sunny_25 Год назад

    very creative way of bringing a problem to your subscribers

  • @taopinairlinesmathindustry9144
    @taopinairlinesmathindustry9144 3 года назад +3

    I dedicate at least 30mins per math video a day when making them

  • @theprimegames9479
    @theprimegames9479 Год назад

    Best thing is that I didn't even really started to study calculus but I understood most of this video

  • @Anik_Sine
    @Anik_Sine 3 года назад +5

    The basic tendeny of human: not matter how easy or hard a question is, if it is long it seems difficult

  • @nataodutton4344
    @nataodutton4344 3 года назад +2

    love your videos bro this video is so wholesome :)

  • @babai08_
    @babai08_ 3 года назад +2

    Love your videos bprp.

  • @RB79RB
    @RB79RB 3 года назад +2

    Merry xmas and a happy new year to you too! Thx for all the great videos.

  • @josephpalad7815
    @josephpalad7815 3 года назад +2

    Happy Holiday, have a blessed Christmas.

  • @Heramb_Pathak5879
    @Heramb_Pathak5879 Год назад

    Finding an answer of a question is at its level, but making such a monstrous "looking" question is at another level.

  • @alexrozenbom3430
    @alexrozenbom3430 3 года назад +1

    Happy new year to you too.

  • @jmtx.
    @jmtx. 3 года назад +1

    Thank you for all your effort! It's always fun to learn something new.

  • @fizixx
    @fizixx 3 года назад +1

    It's true that, if you love what you do, you don't work a day in your life. Your effort is appreciated.

  • @SUPERIDOLLOVER
    @SUPERIDOLLOVER 3 года назад +1

    Best maths teacher I ever had

  • @masterspace5479
    @masterspace5479 3 года назад +2

    Never ask him what time is it

  • @mwiibakuyokwa1354
    @mwiibakuyokwa1354 3 года назад +2

    You have inspired me a lot ,, from Zambia Africa.

  • @global169
    @global169 2 года назад

    Thank you so much for helping me I am forever grateful for you taking the time to help us.

  • @balathevar1828
    @balathevar1828 2 года назад

    I like your creativity. Thank you for helping the young scholars!

  • @leprofeet9989
    @leprofeet9989 3 года назад +1

    Happy new year, math guy!

  • @cauedemelosilva4381
    @cauedemelosilva4381 3 года назад +1

    Best way to answer a simple question. Great work, congrats.

  • @Adam-pj2qh
    @Adam-pj2qh Год назад +1

    Bro you are insane

  • @kalafi0r702
    @kalafi0r702 2 года назад

    Dude, I literally understand nothing, but somehow I really enjoy watching these videos

  • @greghansen38
    @greghansen38 3 года назад

    And we're grateful to you!

  • @gasorpasorpasorpasorpobrow7419
    @gasorpasorpasorpasorpobrow7419 3 года назад +2

    you do realy excellent work and you re a part of what makes me want to become a math teacher!!

  • @goldentwister888
    @goldentwister888 3 года назад

    Definition of a problem being way easier than it looks

  • @fisicaenpastillas8768
    @fisicaenpastillas8768 3 года назад

    I simply can't stop watching your videos, really thankful!

  • @Ou_dembele
    @Ou_dembele 3 года назад +1

    Merry Christmas and happy new year professor

  • @Prashant1239
    @Prashant1239 Год назад +1

    Damn! It is so easy ,it took me 2 min to give solution to this question,but i don't even give my 2 hrs to youtube lol.

  • @xdkiller1385
    @xdkiller1385 Год назад +2

    I'm in the 9th grade and I'm getting very close to solving these on my own! It'll be very exciting for me to do a problem like such on my own, and I hope that's soon!

  • @master4755
    @master4755 3 года назад +3

    1:41 I don't understand why the answer is not 1 because (1+0)^infinity = 1 ?

    • @MrTomas7777
      @MrTomas7777 3 года назад +1

      No. 1^infinity is indeterminate. Put it simply, the 0 from 1+0 isn't exactly 0, it's a number very close to 0, and the infinity is the reciprocal of that number.

  • @mosanasir4465
    @mosanasir4465 3 года назад +5

    Why do I watch his videos as a high schooler and not understanding a thing

  • @Ndiedddd
    @Ndiedddd Год назад

    This was actually way easier than I thought!

  • @petereziagor4604
    @petereziagor4604 3 года назад +1

    Thank you Sir.
    You're the best

  • @ardakara2003
    @ardakara2003 2 года назад

    Your videos are my source of joy❤❤

  • @ZamanAristoOrCleon
    @ZamanAristoOrCleon 3 года назад

    Thank you! Have a happy holidays and happy new year! This man is so cracked he is the GOAT!!!

  • @blackpenredpen
    @blackpenredpen  3 года назад +30

    Just more examples similar to the telescoping series 2:45 ruclips.net/video/IokDRtD1TkM/видео.html

  • @lilbanana6159
    @lilbanana6159 Год назад +1

    Friend: Bro whats the emergency number...hurry up
    blackpenredpen: *hands over an entire integral*

  • @the_mashinist2023
    @the_mashinist2023 2 года назад

    Greetings from Greece.You are very practical 😀

  • @ThoseInterestingStories
    @ThoseInterestingStories Год назад

    I am a year 12 student (only like 4 weeks in) and I have never done calculus before however due to unbelievable amount of blackpenred pen content I’ve been watching recently I managed to solve it without ever learning calculus

  • @Luka_D_Snots
    @Luka_D_Snots 3 года назад +2

    This problem is fierce at the outside, weak at the inside, relatable to most of the teenagers on internet

  • @Nutshell_Mathematica
    @Nutshell_Mathematica 2 года назад

    Need more question like this

  • @BharatOp007
    @BharatOp007 Год назад

    You are a great calculus teacher ❤

  • @angshu7589
    @angshu7589 2 года назад +1

    Missed opportunity to use tetration instead of squaring

  • @jayantbandal1709
    @jayantbandal1709 Год назад +1

    Can you answer ( 3125x + 2059)/256= y. ( x and y are integers) find x and y

  • @achalanand2213
    @achalanand2213 3 года назад

    This guy is amazing.

  • @IMAN_IIT_PATNA
    @IMAN_IIT_PATNA 3 года назад +4

    Now, we can conclude that this person always makes our day 😃🙂

  • @Amb3rjack
    @Amb3rjack Год назад +1

    Jus brilliant!!!

  • @carlosomarmartinezcarmona1485
    @carlosomarmartinezcarmona1485 3 года назад +1

    Gracias a todos mis maestros de matematicas por enseñarme tan bien como para entender este tipo de videos

  • @reemakumari7153
    @reemakumari7153 Год назад +1

    Thanks sir ❤❤❤❤

  • @rafaelbelda6140
    @rafaelbelda6140 3 года назад

    you are amazing!!

  • @Sans________________________96
    @Sans________________________96 29 дней назад +1

    While many selected
    integrate, limit, series and differentiate
    AI : need selected one

  • @VijayYadav-x2s2h
    @VijayYadav-x2s2h 3 года назад +3

    A lot of love from India ♥️

  • @78anurag
    @78anurag 3 года назад +1

    This is the final boss of calculus

  • @asdjhasdgayhuioawe
    @asdjhasdgayhuioawe 2 года назад

    Keep up the great work 😃

  • @MythicubeYT
    @MythicubeYT Год назад +3

    I just have to enjoy 9th grade and enjoy math while it’s still (kinda) easy, looking at this just hurts my brain

  • @doublepositivezero8329
    @doublepositivezero8329 3 года назад +1

    This has consumed 100% of my time.

  • @MohitKumar-eu4pz
    @MohitKumar-eu4pz 3 года назад +1

    Love ur video buddy

  • @hassanalihusseini1717
    @hassanalihusseini1717 3 года назад +18

    Thank you, but as a physicist I am missing the units! :-) 4h/day? 4min/week? 4months/Year?
    Very nice video so! :-)

  • @сашарассадин-щ5ъ
    @сашарассадин-щ5ъ 3 года назад +1

    Great video!

  • @cmdhacker_2005
    @cmdhacker_2005 3 года назад

    I have no idea what you just did but it looked cool

  • @luizkemo
    @luizkemo 3 года назад +4

    thanks a lot for all your content, you really taught calculus to me and now i feel so comfortable using it on everywhere i can (lol)
    im so greatful, thank you bprp :)

  • @ovi9999
    @ovi9999 2 года назад +1

    In ROMÂNIA we learn this things since 17 years old. So this exercise is very easy for us.

  • @tonyhaddad1394
    @tonyhaddad1394 3 года назад +2

    Thank u for sharing with us the beauty of math , and merry christmas and happy new year ❤🎊

  • @patrickboner
    @patrickboner 3 года назад +1

    I can't really focus enough to watch all your vids but the ones i do are really good

  • @pablohurtado3505
    @pablohurtado3505 3 года назад

    You are the best bro....

  • @durgeshpawar.3698
    @durgeshpawar.3698 3 года назад +1

    [√(n)-√(n+1)]. Is equal to zero(0), not infinity

    • @benheideveld4617
      @benheideveld4617 2 года назад

      Correct Durgesh, it is a telescoping series where the second term for n cancels with the first term for n+1. However, the to be summed term diverges, so this makes it questionable whether the sum can be said to exist…