The complex relationship between regular and hyperbolic trig functions

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  • Опубліковано 23 гру 2024

КОМЕНТАРІ • 193

  • @msolec2000
    @msolec2000 6 років тому +212

    9:27 isn't it? or isin(it)? ;)

  • @barthennin6088
    @barthennin6088 3 роки тому +6

    WoW! I haven't been this blown away since when I was shown Euler's identity!

  • @andresxj1
    @andresxj1 6 років тому +7

    I've been a Brilliant member for a year and a half now, and it all began with your special offer.
    I'm delighted with the app! I've learnt a lot and I've enjoyed it so much! So thank you for introducing me to Brilliant and thank Brilliant for sponsoring you!

    • @blackpenredpen
      @blackpenredpen  6 років тому

      Thank you Andy! Glad to hear that you like it!!!

  • @fernandogaray1681
    @fernandogaray1681 6 років тому +63

    I love this kind of videos. I love all the proof videos! Thanks!

  • @nomadr1349
    @nomadr1349 3 роки тому +3

    this is by far the best take on hyperbolic functions I found on youtube so far. And I looked far and wide too!

  • @plaustrarius
    @plaustrarius 6 років тому +8

    looking at the series expansions for exp(x) cosh(x) and sinh(x) is what really drove this point home for me.

  • @idolgin776
    @idolgin776 Рік тому +2

    I've been fascinated by these patterns for a while, and yours is an excellent explanation. Thanks!

  • @retired5548
    @retired5548 6 років тому +32

    complex relationship
    well played, good sir, well played

  • @angeldude101
    @angeldude101 3 роки тому +17

    I actually discovered this when I noticed that cosh and sinh had a structure similar to the inner and outer products of geometric algebra, which are defined as the symetric and antisymetric components of the full product. But the inner and outer products are usually defined with sin and cos... along with i. This is what led me to realize the relation between them and the real and imaginary / even and odd parts of the exponential. The only reason one relation is x^2 + y^2 = 1 and the other is x^2 - y^2 = 1 is because the imaginary factor of y flips the sign when squared.
    It felt so awesome to find that on my own. Now I kind of want to make a visualization of the complex exponential's even and odd parts to try and get the hyperbolic and spherical trig functions to appear on different axes of the same graph.

  • @kennethx7801
    @kennethx7801 3 роки тому +4

    An easy way to remember this is that,
    e^(ix)=cosx+isinx on one hand, on the other, e^ix=cosh(ix)+sinh(ix). Match the even part of one side with the even part of the other side, and do the same with the odd part. You get that cosh(ix)=cosx and sinh(ix)=isinx. Now evaluate these functions at x=it and you get the rest ;)

  • @axelreispereiravaz1699
    @axelreispereiravaz1699 6 років тому +1

    I always asked myself why the hyperbolic trigs functions and the complex trigs functions looked so similar. Even my teacher didn't showed this relation. Now i have my answer ! Thanks BPRP !

  • @theomegaspec7923
    @theomegaspec7923 Рік тому

    Very interesting. I was wondering about the relation between the hyperbolic trig functions and the complex definitions of the trig functions after seeing one of your videos, and you explained these concepts so clearly.

  • @ramkrishnapandey7737
    @ramkrishnapandey7737 4 роки тому +1

    You solve mathematics like you are hanging out with Ur friends😜😜
    And Ur excitement after solving is just awesome. Just because of teacher like u I'm happy of being a mathematic student. Thank you🙏

  • @kostantinos2297
    @kostantinos2297 6 років тому +58

    Is there a geometrical representation of tanh(t), coth(t) etc, just like cosh(t) and sinh(t) are the x and y values of the points of the hyperbola?

    • @cuzeverynameistaken1283
      @cuzeverynameistaken1283 6 років тому +11

      Putting this comment just so if someone else finds it. Right now its late where Im from so I'll try and see if there is one in the morning

    • @filyb
      @filyb 5 років тому +1

      @@cuzeverynameistaken1283 did you find one?

    • @joea-497kviews2
      @joea-497kviews2 4 роки тому +3

      @@filyb he’s still working on it

    • @filyb
      @filyb 4 роки тому

      @@joea-497kviews2 lmao

    • @paulniziolek9200
      @paulniziolek9200 3 роки тому +1

      @@joea-497kviews2 eta perhaps?

  • @rafaellisboa8493
    @rafaellisboa8493 6 років тому +1

    It's like you can read my mind comrade! second time I was studying some maths and you made a vid exactly about what I was studying, great vid!

  • @Riiisuu
    @Riiisuu 6 років тому +53

    Give this problem a try and when you’re ready, continue the video.
    Did *You* figure it out?

  • @ffggddss
    @ffggddss 6 років тому +2

    Before 1 min: There's a 3rd way to interpret the angle - the arc length subtended on a unit circle, whose equation you've written: x² + y² = 1.
    This may or may not work for the unit rectangular hyperbola; I'm checking into that. It does have the right behavior near 0, and it does go to ∞, but those are no guarantee...
    Fred

  • @6root91
    @6root91 3 роки тому

    I was searching for these formulae (didn't need the proofs, but they were cool too) for about an hour until I found it here and was able to answer my question.

  • @borg972
    @borg972 6 років тому +3

    Great one, thanks!
    If you could do more parameterization videos it would be great since finding them is always so confusing.. also integrations along a curve with parameterization

  • @koltonjones866
    @koltonjones866 6 років тому +2

    Your videos should be required viewing for most math classes. Do you do anything for dicrette algebra?

  • @_DD_15
    @_DD_15 6 років тому +5

    Omg.. The biggest problem of my life.. Finally solved 😱😱😱😱😱impressed

    • @blackpenredpen
      @blackpenredpen  6 років тому +1

      DD
      Yup!!!! : )

    • @_DD_15
      @_DD_15 6 років тому +2

      @@blackpenredpen I have plenty of calculus books and have never seen that one around, weird :)

  • @RichardCorongiu
    @RichardCorongiu 7 місяців тому

    Throw in a bit of an explanation of Eulers formula in terms of the Taylor series of e^x polynomial... love your passion...😊

  • @IrateUngulate
    @IrateUngulate 6 років тому +1

    I just discovered your channel. Your videos are brilliant! Good thing they're your sponsor :D

  • @aidan8858
    @aidan8858 6 років тому +27

    cos(it) + cosh(t) = cosh(it)

  • @leeluu998
    @leeluu998 5 років тому

    I hope you're gonna be a math teacher because yours videos are so clear and precises

  • @irrelevantgaymer6195
    @irrelevantgaymer6195 5 років тому +12

    What I think is cool is if you were to somehow create a 4D graph and declare your x, y, z, and t axis, and call the z axis the imaginary input and call the t axis the imaginary output, the function x^2+y^2=1 on the t axis looks like x^2-y^2=1 and vice versa. So I kind of think of the hyperbolic function as a complex version of the circle function and vice versa

  • @hemanthkotagiri8865
    @hemanthkotagiri8865 6 років тому +1

    Your videos are pretty amazing man. Keep going. 👌

  • @holyshit922
    @holyshit922 6 років тому

    Rational paramerization of hyperbola is based on observation
    (1-t^2)^2+(2t)^2=(1+t^2)^2
    (2t)^2=(1+t^2)^2-(1-t^2)^2
    1=\left(\frac{1+t^2}{2t}
    ight)^{2} -\left(\frac{1-t^2}{2t}
    ight)^{2}

  • @spelunkerd
    @spelunkerd 6 років тому

    I'm headed back to your channel to find the link to "even" and "odd" parts of e^t, described at 15:18. Not sure where to look....

    • @spelunkerd
      @spelunkerd 6 років тому

      Ah, found it here. ua-cam.com/video/oLZoGEcJ2YE/v-deo.html

    • @blackpenredpen
      @blackpenredpen  6 років тому

      It's here: ua-cam.com/video/oLZoGEcJ2YE/v-deo.html

  • @rockapedra1130
    @rockapedra1130 2 роки тому

    Excellent video! This is super interesting! Thanks for making these videos!

  • @alejrandom6592
    @alejrandom6592 7 місяців тому

    Easy way:
    exp(it)=cos(t)+i*sin(t)
    But also
    exp(it)=cosh(it)+sinh(it)
    Pairing up the odd part with odd part, and even with even we get:
    cosh(it) = cos(t)
    sinh(it) = i*sin(t)

  • @ian-ht1nf
    @ian-ht1nf 6 років тому +15

    9: 26 "isin(it)"?

  • @m_riatik
    @m_riatik 6 років тому

    please continue this series!

  • @carlosraventosprieto2065
    @carlosraventosprieto2065 Рік тому

    Wow!! Thank you for the video!

  • @nishasharma-gk5bo
    @nishasharma-gk5bo 3 роки тому +1

    Look at this cute face he is blushing while playing with Maths 😍 ,maths must be his love.

  • @zralok
    @zralok 6 років тому +77

    Did you saw the joke isn't it?
    So the similarity of "i sin(it)" to isn't it.

  • @tunneloflight
    @tunneloflight 2 роки тому

    Plot them! The hyperbolic sin and cos “jump” off the tops and bottoms of the sin and cos at right angles in the y-i plane. Likewise, when sinh and cosh are real, sin and cos are at right angles in the y-i plane. Etc…. It is beautiful. Next extend to tan and tanh, sec and sech …. Then extend to Bessel and J functions!

  • @Anonymous-rr5cx
    @Anonymous-rr5cx 5 років тому +1

    Sir at 6:50 u said imaginary looking
    Theta = it
    So t is also imaginary so that they can be real
    Sin theta = real function
    Sin h x= imaginary function
    ??????
    Sir please please clear this doubt
    Thank you

  • @thalesbastos3915
    @thalesbastos3915 6 років тому +1

    Thank you sooooo much!!!

  • @Lucky10279
    @Lucky10279 2 роки тому

    0:57 Shouldn't the area = t? The area 0f a unit circle is A = 2π and the area of a sector of a circle is A*(corresponding angle of sector/2π), assuming the angle is in radians. Hence, the area in the diagram should be 2π•t/2π = t.

    • @ma7-s8j
      @ma7-s8j 2 роки тому +1

      Area of circle with r = 1: pi * r ^ 2 = pi. Not 2pi.

  • @tm89681
    @tm89681 2 роки тому

    Nice lecture👍

  • @thomasolson7447
    @thomasolson7447 Рік тому

    I noticed that to. But I went the arctan route.
    cos(i*arctan(3/4))-i*sin(i*arctan(3/4))=1.9031323020709
    cos(arctan(i*(3/4)))+sin(arctan(i*(3/4))) =sqrt(7)(4/7+3/7i) for tan= i*3/4
    Works just fine this way. You can do geometry with it.
    It's just pythagorous' theorem with an 'i' in it.
    [x/sqrt(x^2+y^2), y/sqrt(x^2+y^2)]

  • @gwalla
    @gwalla Рік тому

    Are there other conic section analogues of the trigonometric functions? Parabolic sine? Elliptical cosine?

  • @luuksemmekrot4509
    @luuksemmekrot4509 17 днів тому

    Cool again! Love your content!

  • @rishinandha_vanchi
    @rishinandha_vanchi 5 років тому

    ellipse eqn in complex extended x-plane-y-axis will be a hyperbola in the Im-x-side. This so parametric forms cos and cosh are complex and real counterparts

  • @h4c_18
    @h4c_18 6 років тому

    What about x=sec(t) and y=tan(t) for 0

  • @edgardojaviercanu4740
    @edgardojaviercanu4740 3 роки тому

    Beautiful!

  • @debaprasadparui4757
    @debaprasadparui4757 5 років тому

    Sir you are awesome....!!!!

  • @abdonecbishop
    @abdonecbishop Рік тому

    makes me want to say.....this is wonderful short video.... beautiful work...so ...so ..excellent...but i think you need to add a quick physic conclusion to your video.........this certainly is one of the slickest short video in circulation....why?....because you connects non-Euclidean equilateral triangle's surface area(excess/deficit) change to a Euclidean triangle's total energy change and the triangle's inertial mass change dependent on (a function off) the average of the total number of summed ''-' , '+' and '0' Gaussian curved triangle edges counted ......

  • @davidmorochnick498
    @davidmorochnick498 5 років тому

    QUESTION: With -i out in front of sin(it), [-isin(it)], doesn't the proof fail?

  •  6 років тому +4

    Cool!!!! So one can get the derivative of sinh and cosh using chain+product rule from the equal sin/cos statement, never thought on that :-O I always did that from the definition of sinh/cosh only ("e-stuff").

  • @ugursoydan8187
    @ugursoydan8187 4 роки тому

    thanks

  • @canaDavid1
    @canaDavid1 4 роки тому +1

    Wait... Are the trig functions C -> N? Or can some input a+bi give imaginary output?

    • @justacutepotato2945
      @justacutepotato2945 4 роки тому

      they're C->C. Also, you put C->N, pretty sure you meant C->R or C-> [-1,1].

    • @canaDavid1
      @canaDavid1 4 роки тому +1

      @@justacutepotato2945 yeah, you're right. And I meant C->R.

  • @leoarzeno
    @leoarzeno 4 роки тому

    great video

  • @billazz9176
    @billazz9176 4 роки тому

    RIGHT HERE, RIGHT HERE, RIGHT HERE

  • @artey6671
    @artey6671 6 років тому +2

    You don't even need Euler's formula to show that cos(it) = cosh(t). You can also show that their power series are the same.

    • @koenth2359
      @koenth2359 6 років тому

      Yeah, Tibees just did that Bob Ross style!

    • @artey6671
      @artey6671 6 років тому

      You mean her newest video? I don't see any cosh in there.

    • @koenth2359
      @koenth2359 6 років тому

      @@artey6671 yeah guess you are right. May have misremembered.

  • @drshamajain4149
    @drshamajain4149 4 роки тому

    What we do with the part of the hyperbola on the left side

  • @Thoalfeqargamer
    @Thoalfeqargamer 4 роки тому

    i love you man 💕💕💕💕

  • @TheNerd484
    @TheNerd484 6 років тому +4

    We just went over sinh and cosh in my calc class today. What are the chances? This is a much more complete explination than we got.

  • @RichardCorongiu
    @RichardCorongiu 7 місяців тому

    How's your stock of whiteboard pens ? 😊

  • @helloitsme7553
    @helloitsme7553 6 років тому

    Tbh I've always felt like this is true because I can say integral of 1/1-x^2 dx = integral of 1/1+(ix)^2 and then use u-sub. But at the same time, the integral is tanh(x)

  • @KwongBaby
    @KwongBaby 6 років тому

    What's the usage of sinh and cosh?

  • @mehwishbhatti6207
    @mehwishbhatti6207 2 роки тому

    Can you please make a video relating tan and tanh

  • @bullinmd
    @bullinmd 4 роки тому

    Ever heard of gd(x), the Gudermannian function?

  • @a.a.sunasara9202
    @a.a.sunasara9202 6 років тому +1

    Bruh😍awesome.... Love ot

  • @alaba5085
    @alaba5085 6 років тому

    ¡¡Lo máximo!!

  • @Koisheep
    @Koisheep 6 років тому

    Well to some extent you can also use x(t)=sqrt(1-t) and y(t)=sqrt(t) I mean (?)

  • @siddharthsengar8859
    @siddharthsengar8859 6 років тому +34

    after all i've been through in last year , "Imaginary" is a inappropriate title.

  • @bernardfinucane2061
    @bernardfinucane2061 6 років тому +1

    Very cool

  • @comingshoon2717
    @comingshoon2717 4 роки тому

    Tengo sueño ... pero igual veo estos videos aunque hayan sido contenidos que vi hace muchos años!....

  • @nicholaslau3194
    @nicholaslau3194 6 років тому +18

    Damn clickbait title! I wish professors can use clickbait to make lectures more interesting

  • @afafsalem739
    @afafsalem739 6 років тому

    Yes it's very cool

  • @shoobadoo123
    @shoobadoo123 3 роки тому

    What about cosh(it)

  • @armchairtin-kicker503
    @armchairtin-kicker503 Рік тому

    Then there is Osborn's Rule, a very useful relationship between trigonometric and hyperbolic functions and identities.

  • @musicandmathematics7897
    @musicandmathematics7897 4 роки тому +1

    We have theta be real and t be real also. So, how can we put theta = it ??

  • @khaled014z
    @khaled014z 6 років тому

    hey bprp, there was an integral video involving cos's and sin's I think and you solved it with a creative way of adding 2 solutions of 2 integrals together and I can't find that video, any ideas? thank you :D

  • @decay2__
    @decay2__ 6 років тому +1

    You probably don't know this but you made a pun at 5:49

  • @nicolasinostrozamoreno4248
    @nicolasinostrozamoreno4248 6 років тому

    Why you don't have spanish subtitles ?? Its so interesting

  • @jimallysonnevado3973
    @jimallysonnevado3973 6 років тому

    Still unsatisfied how can you say that this equation can make the area t/2 and is there a way to come up with this formula using calculus like what you can do with sin and cosine by knowing the derivatives first then using taylor then coming up with a formula like eulers identity

    • @blackpenredpen
      @blackpenredpen  6 років тому

      Jim Allyson Nevado as I said in the video. I will do a proof for that. So stay tuned!

    • @jimallysonnevado3973
      @jimallysonnevado3973 6 років тому

      blackpenredpen waiting for that

    • @jimallysonnevado3973
      @jimallysonnevado3973 6 років тому +1

      blackpenredpen oops i apologize for not listening carefully

  • @snejpu2508
    @snejpu2508 6 років тому

    What do you need hyperbolic functions for in math? Of course, except defining them and solving equations with them?

    • @nicolastroncoso1791
      @nicolastroncoso1791 6 років тому

      to simplify the work or notation of multiple real life problems, instead of putting an enormous amount of digits you simply use hyperbolic functions, same as trigonometry in general

  • @azmath2059
    @azmath2059 6 років тому +1

    great video. but try starting from first principles and proving that for a hyperbola x=cosht and y=sinht and see how long that takes you!!

  • @kbotter3955
    @kbotter3955 6 років тому +1

    What does E equal?

    • @lewisbulled6764
      @lewisbulled6764 6 років тому

      2.71828182... it is transcendental.

    • @markorezic3131
      @markorezic3131 6 років тому

      Approximately 2.7182818
      Its a irrational and transcendental number like pi, its related to the exponential function

    • @andi_tafel
      @andi_tafel 6 років тому +2

      (1+1/n)^n if n goes to infinity

    • @dranxelaa6770
      @dranxelaa6770 6 років тому +7

      e=3=pi *isn't* *it* *?*

    • @omarifady
      @omarifady 6 років тому

      Sum from 0 to infinity of 1/n! 😃

  • @aswinibanerjee6261
    @aswinibanerjee6261 6 років тому

    Why you don't advatise for patrion

  • @geoffstrickler
    @geoffstrickler 3 роки тому

    3^2 - 2^2 = 1 too. 😎

  • @rafaellisboa8493
    @rafaellisboa8493 6 років тому

    Could you make a vid about Lobachevsky space pleaseee? don't make me beg

  • @Stanish4Ever
    @Stanish4Ever 6 років тому

    Can u Integrate xtan(x)? 😛 Help me if u can. I really love ur Videos. I learn a lot from them. Thanks

  • @jinnjinn5567
    @jinnjinn5567 2 роки тому

    sinh(x) = -i sin(ix)
    cosh(x) = cos(ix)
    tanh(x) = -i tan(ix)
    sinh(ix) = i sin(x)
    cosh(ix) = cos(x)
    tanh(ix) = i tan(x)

  • @MuthuKumar-mk1320
    @MuthuKumar-mk1320 6 років тому

    lim x → 0 sin2x^(tan2x) ²

  • @_DD_15
    @_DD_15 6 років тому

    Btw, is this a newly discovered relation?

    • @tupperwallace9048
      @tupperwallace9048 6 років тому +2

      Yes, considering that the history of mathematics goes back millennia. Wikipedia dates them to the 1760s.

  • @mathteacher2651
    @mathteacher2651 5 років тому

    Another great video - kid!

  • @duggydo
    @duggydo 6 років тому

    cos(it)=cosh(t) is interesting. cosh(it)=? is a more interesting question though.

    • @MarioFanGamer659
      @MarioFanGamer659 6 років тому

      cosh(it) = cos(t)
      Like, it's simply inserting i*t into x for cosh(x) and get cos(t) as the result just like as if you have inserted i*t for cos(x) and get cosh(t) as a result.

  • @kingbeauregard
    @kingbeauregard 6 років тому

    Is it possible to actually understand complex numbers, or are they simply an abstract tool in the world of mathematics? Like, I can understand integers as "counting things", real numbers as "measuring things", and sines and cosines as "the vertical and horizontal weights of a diagonal line". But imaginary numbers and complex numbers ... ? I don't see them in the real world anywhere. Maybe I'm not looking hard enough?

    • @camilincamilero
      @camilincamilero 6 років тому

      I think of them as vectors that rotate at a certain frequency, or phasors. They are used all the time in electrical engineerig, in the field of power systems.

    • @kingbeauregard
      @kingbeauregard 6 років тому

      I don't doubt the utility of complex numbers in real-world calculations, but they seem to be a way to arrive at a real-world result rather than a representation of the real-world result: for example, if two electrical signals are out of phase with one another, the result is the superposition of sine curves, with no visible evidence of any imaginary components. So I'm wondering if they appear visibly in the real world anywhere. If someone asked where I can see Fibonacci Numbers I could point to a sunflower. Is there anywhere I could see complex numbers?

    • @Harkmagic
      @Harkmagic 6 років тому

      Complex numbers are as real as the rotation you are doing in your problem. For most engineering and physics applications those rotations are very real. Hell, 3d rotation can't even be mathematically described properly without quaternions, which are basically more complex imaginary numbers.

    • @kingbeauregard
      @kingbeauregard 6 років тому

      Show me an imaginary number. Don't just tell me that they factor into the arithmetic of sine waves; show me an imaginary number in the real world. I'm not sure it can be done, but if it can, I'd like to see it.

    • @Harkmagic
      @Harkmagic 6 років тому

      Showing an imaginary number is no more possible than showing a real number. Numbers are not real physical things that you can point to or reach out and touch, even our real numbers are just abstractions used to represent reality.
      So if I tell you to stand up and turn and face to your left and tell you that is the number 'i' it is just as valid as saying telling you to count the number of fingers on your hand and telling you that it is the number '5'.

  • @rot6015
    @rot6015 6 років тому

    OMG!!!! @&@&&@&@&@; THIS IS SO EXTREME LIKE THE TITLE!!!

  • @quahntasy
    @quahntasy 6 років тому +3

    ALGEBRAIC EXPRESSIONS HATE HIM.

  • @dwarkeshdhamechahiteshdham7336
    @dwarkeshdhamechahiteshdham7336 6 років тому

    Wow

  • @menjolno
    @menjolno 5 років тому +1

    Notice how close they are to co shit.

  • @ny6u
    @ny6u 4 роки тому

    Gorgeous

  • @AmogUwUs
    @AmogUwUs 4 роки тому +1

    *slaps theta* TAG YOU'RE (it)

  • @draztrazh6497
    @draztrazh6497 5 років тому

    The return of black shirt red shirt.