Introduction to Hyperbolic Trig Functions

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  • Опубліковано 4 лют 2025

КОМЕНТАРІ • 401

  • @DeeEm2K
    @DeeEm2K 6 років тому +401

    I *always wanted* to know what hyperbolic functions were but was too lazy to actually research it. Thanks man, for researching it and teaching to me

    • @armacham
      @armacham 3 роки тому +18

      I didn't want to know, but now I know.

  • @DeeEm2K
    @DeeEm2K 6 років тому +519

    *Cosh, the friend of Josh*
    *Sinh, the brother of Grinch*

    • @AAAAAA-gj2di
      @AAAAAA-gj2di 5 років тому +19

      Dark Mage, the son of Johnny Cage

    • @abdurrahmanlabib916
      @abdurrahmanlabib916 5 років тому +1

      Actually its shine

    • @Test-ri2kr
      @Test-ri2kr 5 років тому +7

      Quick Mafffs Several ways it can be pronounced. I say shine myself. But yah. *Shine, brother of mine*
      How was that one?

    • @Vinny_3041
      @Vinny_3041 4 роки тому +1

      Tanh, the friend of Sam

    • @drenzine
      @drenzine 4 роки тому

      @@abdurrahmanlabib916 SHINE OF X=so shiny i cant see anything

  • @tanelkagan
    @tanelkagan 3 роки тому +160

    Just as an observation, when checking to see if cosh² - sinh² =1, as an alternative to expanding out the brackets in full you can use the difference of two squares identity:
    a² - b² = (a + b)(a - b).
    Here,
    a = (e^t + e^-t)/2; and
    b = (e^t - e^-t)/2.
    Distributing out the 1/2 you can think of these as:-
    a = (e^t)/2 + (e^-t)/2
    b = (e^t)/2 - (e^-t)/2
    So, (a + b)(a - b) reduces quickly to
    (2(e^t)/2) (2(e^-t)/2)
    or simply
    (e^t)(e^-t)
    which is of course e^0, or 1.
    You can decide for yourself which method you prefer!

    • @ChristAliveForevermore
      @ChristAliveForevermore 2 роки тому

      You assumed that e^t identity is true. What if you want to derive based solely on the analytical trig intuition and not the logarithmic intuition?

    • @surpiers
      @surpiers 2 роки тому

      @@ChristAliveForevermore it works either way though, and it’s beautiful seeing it in action

    • @Abdalrhman_Kilesee
      @Abdalrhman_Kilesee Рік тому

      You know how to write a understandable mathematical comment pretty much 🤩

  • @ruhanikhazain7564
    @ruhanikhazain7564 Рік тому +1

    Thanks!

  • @dxk2007
    @dxk2007 3 роки тому +24

    This is the 1 topic I didn't bother learning in high school... and it turns out Relativity is all based on it. Thank you.

    • @lambda2693
      @lambda2693 2 роки тому +1

      only rapidity is based on hyperbolic trig. otherwise your lorentz transforms and fourvectors require only rudimentary algebra s a mathematical prerequisite

  • @digitig
    @digitig 5 років тому +425

    I've been using hyperbolic trig functions for forty years plus, and never knew why they were called "hyperbolic".

    • @pranavsingla5902
      @pranavsingla5902 5 років тому +34

      That is your shortcoming not something to be proud of really

    • @setupchess6288
      @setupchess6288 4 роки тому +254

      @@pranavsingla5902 what is wrong with you? How is he proud of it in any way shape or form

    • @ripudamansingh2
      @ripudamansingh2 4 роки тому +185

      @@pranavsingla5902 such arrogance, damn

    • @yetii09
      @yetii09 4 роки тому +93

      @@pranavsingla5902 he never said he is proud of it...keep your vulgar comment to yourself

    • @btsandtxtloverstraykidzfan3486
      @btsandtxtloverstraykidzfan3486 4 роки тому +64

      @@pranavsingla5902 Wow ever heard of something called " being humble " ?

  • @david-yt4oo
    @david-yt4oo 6 років тому +18

    the whole "the input is twice as big as the area" really blew my mind away. the whole thing was great!

  • @phosphor6472
    @phosphor6472 6 років тому +409

    3:39
    I'm still waiting for the Drake& Cosh series

  • @DavideCanton
    @DavideCanton 5 років тому +30

    A small suggestion: the check is way faster if you decompose (x²-y²) as (x+y)(x-y).
    That way you get e^t * e^(-t) = 1.

  • @Rocky-me5cw
    @Rocky-me5cw 6 років тому +642

    "that's pretty much it."

  • @pierreabbat6157
    @pierreabbat6157 6 років тому +44

    If the deck of the bridge is horizontal, the cables are parabolas. If the deck follows the curve of the cables, the cables are weighted catenaries. If you suspend a string at both ends with nothing hanging from the string, it is a catenary, which is the graph of cosh.

    • @Apollorion
      @Apollorion 6 років тому +2

      If you say all of the cables on the suspension bridge have no mass but the bridge-deck does have, with a homogeneous density and is also -horizontal- straight, then you can easily derive that the curve of the main carrying cables is indeed approximated by a parabola.

    • @twwc960
      @twwc960 6 років тому +4

      You are exactly right. It is a very common mistake to assume the curved cables in a suspension bridge are catenaries (hyperbolic cosine curves). In fact, they are not and to a very good approximation they are indeed parabolas. This is true since the road is fairly nearly horizontal and the weight of the road being suspended is generally much greater than the weight of the cables.

    • @realcygnus
      @realcygnus 6 років тому

      This is quite interesting. Somehow I never covered this topic adequately. Is there a function that interpolates between the two(catenaries & parabolas) ? l suppose based on the weight ratios &/or the suspended platforms straightness(to horizontal). I'd guess it must assume an infinite # of vertical hangers?

    • @twwc960
      @twwc960 6 років тому +3

      realcygnus Google "suspension bridge catenary" and there are links to a few papers which do that. The Wikipedia page on "catenary" has a brief discussion under "Suspension bridge curve" with links to a couple of papers.

    • @realcygnus
      @realcygnus 6 років тому +1

      thanks

  • @d1v1212
    @d1v1212 4 місяці тому +1

    老哥讲挺好啊,终于搞懂了

  • @alberteinstein3612
    @alberteinstein3612 3 роки тому +4

    Thanks for sharing this video with me!! These make a lot more sense to me now 😁

  • @ayoubsbai6339
    @ayoubsbai6339 5 років тому +4

    One of the best maths channels on UA-cam :)

  • @ashutoshojha4244
    @ashutoshojha4244 4 роки тому +1

    Thanks so much man you just saved me for my viva tomorrow

  • @urluberlu2757
    @urluberlu2757 4 роки тому +5

    Wow, i'm just climbing to the next level in mathematics, and re-discover it's beauty and real, and complex pleasure with it, thanks of you ;-)

  • @guliyevshahriyar
    @guliyevshahriyar Рік тому

    how you switch the pens is unnoticable👏👏👏
    genius person!

  • @quahntasy
    @quahntasy 6 років тому +8

    Love you for listening to us!

    • @blackpenredpen
      @blackpenredpen  6 років тому +2

      Quahntasy - Animating Universe
      : )

    • @Apollorion
      @Apollorion 6 років тому

      Each good teacher needs to do that.

  • @ImSomebady
    @ImSomebady 6 років тому +1

    Currently just finished calc 3 and starting "advanced calculus and applications" and didn't know where the trig and hyperbolic functions relation came from. Thank you so much!

    • @DatBoi_TheGudBIAS
      @DatBoi_TheGudBIAS Рік тому

      Everybody gangsta till matmaticians invent sech, csch and coth

  • @pablojulianjimenezcano4362
    @pablojulianjimenezcano4362 6 років тому +10

    I always wondered a lot of things about hyperbolic trigonometry and I think your videos will help me a lot!!!^-^

  • @RetroGamingClashOfClans
    @RetroGamingClashOfClans 4 роки тому +5

    7:32 - the legendary marker switching skills omg

  • @pigman6954
    @pigman6954 2 роки тому +1

    this explains everything i was looking for. thanks so much! i'll have to show this one to my math teacher :)

  • @kaistrandskov
    @kaistrandskov 2 роки тому +11

    I absolutely love any connection between pi and e (not to mention i and phi).

    • @DatBoi_TheGudBIAS
      @DatBoi_TheGudBIAS Рік тому

      What's the relation between i and φ? Idk that one lol

    • @mukkupretski
      @mukkupretski Рік тому

      i*i+sqrt(2)^2=phi-phi+1

    • @DatBoi_TheGudBIAS
      @DatBoi_TheGudBIAS Рік тому

      @@mukkupretski ¦:|
      Bruh, Dat doesn't count, the i turns into -1 and the φ is canceled

  • @canyon_online
    @canyon_online 6 років тому +5

    This is awesome. Never seen cosh and sinh in my life until I was asked to integrate it last week for Calc 2. Could not tell you for the life of me what they meant until now. #YAY

    • @zohar99100
      @zohar99100 5 років тому +2

      "Never seen cosh and sinh in my life until I was asked to integrate it last week for Calc 2."... What?!?
      Be like: "Never seen a girl until I was married"

    • @heavennoes
      @heavennoes 3 роки тому +2

      @@zohar99100 those are very different, maybe he was never taught hyperbolic trig and then suddenly he saw a question maybe by a different teacher who assumed the class knows hyperbolic trig and take the derivative of it

  • @lordofkeebs8424
    @lordofkeebs8424 5 років тому +12

    10/10 like the Doramon theme in background

  • @eric_welch
    @eric_welch 3 роки тому +4

    "It's like your friend Josh, but with a C, so cosh" ....pure gold right there :)

  • @overlordprincekhan
    @overlordprincekhan 5 років тому

    There is a quote "The teachers who complicates the study is the biggest state criminal"
    This 4 minute is enough to understand me the lesson taught by by teacher of a whole month. Thanks for that nice explanation!

  • @summerishere5146
    @summerishere5146 2 роки тому +1

    6:25 BLEW MY MIND!!!!

  • @geoffhuang2438
    @geoffhuang2438 6 років тому +5

    Brilliant.org is awesome. I’m glad I saw the site from your video.

  • @sunandachaudhary9936
    @sunandachaudhary9936 5 років тому

    Brilliant is really very concept-oriented website. Keep the good work up. Thankyou

  • @kingsbarber0008
    @kingsbarber0008 5 років тому

    you are the best in what you are doing Sir

  • @sirface7951
    @sirface7951 3 роки тому

    Yestarday i was really curious what exactly is coshx now two of my favourite youtubers (you one of them) made a video about it!

  • @g.v.3493
    @g.v.3493 4 роки тому

    Best explanation of cosh x and sinh x ever! I’ll be looking for your other hyperbolic function videos.

  • @anirudh7137
    @anirudh7137 5 років тому

    Thanks for the simple explanation

  • @yashikakaushal645
    @yashikakaushal645 Рік тому

    dude u are intelligent and funny too
    and I love ur learning

  • @eta3323
    @eta3323 6 років тому +58

    Woow, I always wanted to learn about hyperbolic trig functions!!! Thank you, sir for making this so much easier

    • @sgiri2012
      @sgiri2012 Рік тому

      Can I please know what is

  • @wduandy
    @wduandy 6 років тому +2

    Amazing, please continue with the series.

  • @lambda2857
    @lambda2857 5 років тому +2

    An explanation of the elliptic functions sn, tn, cn, dn, and so on, from
    a geometric standpoint, would be a very good video to make.

  • @rafaellisboa8493
    @rafaellisboa8493 6 років тому

    I enjoyed this video very much comrade, I never knew what hyperbolic trig functions where and they sound very cool and I have been curious about this for a week, thanks!

  • @billharm6006
    @billharm6006 2 роки тому

    I wish my college math teacher had taught hyperbolics this way. I went from, "memorize the formula" to OH! in about one-quarter of a class period's duration.
    And I do love that Ah Ha! moment.

  • @DRUCVSKAMAU
    @DRUCVSKAMAU 5 років тому +6

    at 2:03 he says automatically,and its the funniest thing I"ve ever heard

  • @giacomocasartelli5503
    @giacomocasartelli5503 6 років тому +158

    Great video, just leaves me a question: why are Hyperbolic functions so important and not the Elliptical ones, for example?

    • @friedkeenan
      @friedkeenan 6 років тому +112

      Well we already have the most simple ellipse: the unit circle

    • @angelmendez-rivera351
      @angelmendez-rivera351 6 років тому +62

      Djdjcjcjcj Jfnfjfidnf Actually, hyperbolas are in a way stretched out circles, where a = 1 & b = i.

    • @angelmendez-rivera351
      @angelmendez-rivera351 6 років тому +31

      Djdjcjcjcj Jfnfjfidnf In fact, by allowing complex numbers, any equation for any of the conic sections can be written in the form of (x/a)^2 + (x/b)^2 = 1.

    • @tomgraham7168
      @tomgraham7168 6 років тому +8

      Angel Mendez-Rivera multiplying by i is NOT a ‘scale’. It is more of a rotation in an argand diagram.

    • @angelmendez-rivera351
      @angelmendez-rivera351 6 років тому +29

      Tom Graham Yes, technically, but if your scalar field of a vector space with a complex coordinates is the set of complex numbers, then that still counts as scaling.

  • @laurensiusfabianussteven6518
    @laurensiusfabianussteven6518 6 років тому +4

    This is what im waiting for

  • @Chaosdude341
    @Chaosdude341 4 роки тому +4

    Thank you! Missed out on these functions in Pre-Calc and Calc I, so I'm figuring this out in Calc II. Love the analysis!

  • @rubensenouf1813
    @rubensenouf1813 6 років тому

    Still amazing ! Thank you for your work ! You make me love math even more with each video !

  • @lorostotos5647
    @lorostotos5647 6 років тому +1

    the bridge cable is a parabola because the cable is practically weightless comparing to the road it holds underneath.the road is horizontal so the load is linear.

    • @AlecBrady
      @AlecBrady 5 років тому +1

      And because therefore the load on it is proportional to the x-length not the arc length

  • @antoniocampos9721
    @antoniocampos9721 2 роки тому

    Thanks for this, man.

  • @OhlordyOh
    @OhlordyOh 5 років тому

    You're an amazing teacher

  • @mattyjackson3857
    @mattyjackson3857 6 років тому

    This is REALLY well explained

  • @krishnasarmavenkatrao6020
    @krishnasarmavenkatrao6020 4 роки тому +5

    "Enjoyment of learning mathematics" That is what I'm here for.

  • @stephentrouse2069
    @stephentrouse2069 5 років тому +16

    I was taught to pronounce it as “shine” and “than” but that was in the 70s in Australia.

    • @CrystalClearMaths
      @CrystalClearMaths 4 роки тому

      I remember learning the same, Stephen.
      Nice to have someone else confirm what I recall.
      Kind regards from the Shoalhaven.

  • @darkiiboii5855
    @darkiiboii5855 4 роки тому +1

    boi ur awesome ❤️

  • @SirPuFFaRiN
    @SirPuFFaRiN 6 років тому +4

    Twitter ftw! Nicely done can you please make an introduction video with differential equations?

  • @wildmonkiesJR
    @wildmonkiesJR 4 роки тому

    Mind blown🤯

  • @peterhui7023
    @peterhui7023 2 роки тому +1

    8:52 The shape of the cables at both sides of the bridge is incorrect. It should be nearly a straight line since it should provide a force against the tower from pulling inwards and the cables are anchored into the massive RC foundation on both sides.

  • @louf7178
    @louf7178 3 роки тому

    Thankyou. Quality lecture.

  • @blacknoir2404
    @blacknoir2404 6 років тому +1

    This inspired me to invent the parabolic trigonometry functions. I have cosp(t) = (3t)^⅔ and sinp(t) = (3t)^⅓. These aren’t very exciting so far.

  • @RichardCorongiu
    @RichardCorongiu 9 місяців тому

    Nice work well explained ...might add a more detailed explanation of Radian measure ???

  • @surrindernayar
    @surrindernayar 2 роки тому

    Hyperbolic function applies to a freely suspended cable called catenary.
    However, the curve of the suspension bridge cable which is uniformly loaded (road) and negligible cable weight is indeed a parabola. Check it out.
    Lots of people make this mistake.

  • @jagatkumartudu
    @jagatkumartudu Рік тому

    Ohhh my God ! What's that I see here ....I thought it's too complicated but it's really funny .thnxxx bro

  • @Arjun-fy6jy
    @Arjun-fy6jy Рік тому

    Great video!
    Can someone please explain why the coordinates on a hyperbola are (cosh t, sinh t) where t is twice the area of the region bounded by x-axis and the line joining the point and origin? Is there like a proof or definition for it?

  • @nonamenoname6921
    @nonamenoname6921 11 місяців тому

    At Uni in the 1990s we were taught to pronounced sinh as 'shine' in Australia.

  • @mathteacher2651
    @mathteacher2651 5 років тому

    You're a genius kid!
    Great job!

  • @M4TT4TT4CK
    @M4TT4TT4CK 6 років тому +1

    Math kicks ass

  • @scathiebaby
    @scathiebaby 6 років тому +1

    The Tauist says:
    In 5:35 to 6:25 - the area formulae in the circle get more concise when you use tau := 2pi

    • @dystotera77
      @dystotera77 5 років тому

      Pretty cool but e^(iτ/2)+1=0 isn't really cool

  • @matchedimpedance
    @matchedimpedance 3 роки тому

    The shape of a suspension bridge cable would only be a catenary if the weight of the bridge to be supported was negligible compared to the weight of the cable. But in general that is not the case. Usually the weight of the bridge is more significant than the weight of the cable so in that case the shape of the cable would in fact be more like a parabola.

  • @ElectronicsPeddler
    @ElectronicsPeddler 3 роки тому

    Thank you so very much for posting this; it may not have millions of views but to those who have watched this video, it is immeasurably valuable.

  • @walter9029
    @walter9029 Рік тому

    I wonder, if I will be able to figure out the area t/2 in the hyperbolic case.
    I think of the area of the triangle minus the integral of the squ.root function.

  • @zack_120
    @zack_120 2 роки тому

    COOL! Area(θ)=θ/2 is interesting.

  • @MushookieMan
    @MushookieMan 3 роки тому

    Assuming the weight of the bridge is negligible compared to the weight of the cable is the most insane thing I've ever seen in a derivation. A bridge cable assumes the shape of a parabola, it's easy to show.

  • @ashishpandey5583
    @ashishpandey5583 4 роки тому

    Thank u sir for solving my great problem...... Awesome 😍

  • @trueriver1950
    @trueriver1950 4 роки тому

    8:50 that's not true.
    A free hanging chain or rope does form a cosh curve.
    However that depends on the rope or chain having constant mass power unit length. In other words it depends on the mass of the straight line of the deck of the bridge being zero (if you are a mathematician) or being negligible (if you are a physicist or engineer).
    Likewise, if we make the opposite approximation and treat the rope or chain as having negligible mass per unit length, compared to the mass of the deck, then the rope does indeed form a parabola (to within the approximation we made when we ignored the mass of the rope or chain).
    If we do the fully accurate version, allowing for an appreciable mass per unit length for both the rope and the deck, then the shape of the rope is somewhere between a cosh and a parabola.

  • @davidawakim5473
    @davidawakim5473 6 років тому +7

    4:28 shouldn't the area be 2t? Because the input is the area divided by 2 and 2t/2 = t. Whereas with the t/2 that he put t/2 * 1/2 = t/4

    • @simonwalthers9951
      @simonwalthers9951 6 років тому +3

      I thought the same thing as well but I’m not sure

    • @kseriousr
      @kseriousr 6 років тому +2

      Nope.
      06:20
      t=2.area
      So, area=t/2

  • @mattmackay76
    @mattmackay76 4 роки тому

    That was a great video... thank you so much!

  • @arjyadeep1818
    @arjyadeep1818 4 роки тому

    Please make a video on how " e"( irrational number) is related with hyperbola

  • @KUYAJRIP
    @KUYAJRIP 2 роки тому

    1MILLION SUBS!

  • @aishiaratrika
    @aishiaratrika 3 роки тому

    Thanks 😍

  • @MrBobbybrown7
    @MrBobbybrown7 4 роки тому

    I gather from watching that e in example is Euler's number and not any variable. Would any variable other than e still work?

  • @Godél-p4e
    @Godél-p4e 4 роки тому

    Great video

  • @ysvsny7
    @ysvsny7 2 роки тому

    Thank you

  • @pagames3d
    @pagames3d 2 роки тому

    Thank you !!!

  • @benhbr
    @benhbr 4 роки тому

    The cables on a suspension bridge carry not only their own weight, but also the road. This load is much heavier and horizontally uniform, so the cables actually ARE parabolas!

    • @erynn9770
      @erynn9770 4 роки тому

      Would the cables on power lines or telephone masts be a better example, since they hang freely?

  • @BennettAustin7
    @BennettAustin7 5 років тому

    Geez that cable problem of the Golden Gate Bridge was on my pset for physics. Hardest thing

  • @danthewalsh
    @danthewalsh 2 роки тому

    So you kind of glossed over the result on Brilliant. The shape of the arch on an ideal suspension bridge is, in fact, a parabola, because the cable is not holding its own (negligible) weight, but is holding the weight of the road below it, which can be assumed to provide a uniform force density downward.

  • @biswajitmath21
    @biswajitmath21 4 роки тому

    Great brother

  • @grinreaperoftrolls7528
    @grinreaperoftrolls7528 6 років тому

    it also works for y=1

  • @chrismiller6579
    @chrismiller6579 5 років тому

    Please give us some examples showing how to use the hyperbolic functions. Everyone has had physics problems where we use the trig functions to decompose vectors into their constituent parts along directions that are more convenient. How do we use hyperbolic functions?

    • @DatBoi_TheGudBIAS
      @DatBoi_TheGudBIAS Рік тому

      I would think about the cables on the suspense bridges

  • @jackiekwan
    @jackiekwan 6 років тому

    Finally! Waited for it for so long #YAY

  • @mathfacts5290
    @mathfacts5290 4 роки тому

    Double angle identity
    Tan(2@)=2tan@/1-tan^2@
    Can we verify it for @=45 degree.?

  • @kaleabtesfaye-o8q
    @kaleabtesfaye-o8q 11 місяців тому +1

    where did those e come from, everyone just jumps to the formula, I want to know were those e come from?

  • @WahyuNurudin
    @WahyuNurudin Рік тому

    is t an angle? does it have special angle like in trigonometry like 30 degree, 45 degree, 60 degree, 90 degree?

  • @holyshit922
    @holyshit922 6 років тому

    Try to parametrize both circle and hyperbola with rational functions
    It can be useful in integration
    I try to reduce integrand to rational function if possible

  • @JBaker452
    @JBaker452 6 років тому

    When I was an architecture student I designed a catenary structure ;-)

  • @agrawalnidhu8091
    @agrawalnidhu8091 4 роки тому

    What is the physical significance of hyperbolic trig functions ? Like trig functions are the trig ratios of the different sides of a triangle having the angle defined.
    @blackpenredpen pls reply

  • @ManiFunctor
    @ManiFunctor 6 років тому

    Great video!

  • @SriRam-ec3fd
    @SriRam-ec3fd 4 роки тому

    both are equal to 1 is that mean we can simply equate this two identities

  • @mango417
    @mango417 4 роки тому +21

    "Isn't it?" ……
    My brain: Yes
    Me: No

  • @machobunny1
    @machobunny1 6 років тому +3

    Just wondering, where does the exponential identity for cosh and sinh come from? Does looking at Euler's identity for sin and cos derivation answer that?

    • @astudent9206
      @astudent9206 4 роки тому

      cosh(t) = cos(t). Euler's expression pretty much sums up that. BTW, bprp has made a video on it

    • @Namchha1
      @Namchha1 2 роки тому +1

      @@astudent9206 cosh(t)=cos(it).

    • @YorangeJuice
      @YorangeJuice 2 роки тому

      for cosh:
      suppose you wanted to calculate cos(i). start with the maclaurin series for cosine and plug in i. you will find that cos(i) is equal to the sum from 0 to infinity of 1/(2n)!, which I will call S for brevity. Recall the maclaurin series for e^x, which i will call exp(x). notice S looks similar to exp(1), but there are a bunch of extra 1/[odd factorial] terms in exp(1). we can get rid of these extra terms by adding exp(-1) to exp(1). this will cancel all of the 1/[odd factorial] terms, but we will be left with extra 1/[even factorial] terms. we can divide by 2 to get rid of these extra terms, and after all this, we see that S is equal to (exp(1)+exp(-1))/2, which means cos(i) is equal to (exp(1)+exp(-1))/2. this can be generalized by instead doing cos(ix) to find that it will be equal to (e^x + e^-x)/2 and define this to be cosh(x). we can then find cosh(ix) using this definition of cosh and euler's formula to see cosh(ix)=cos(x)

  • @ben1147
    @ben1147 6 років тому

    Thank you!

  • @amankg7
    @amankg7 3 роки тому

    Does taking (sec t, tan t) as parameters of unit hyperbola lead anywhere? Why prefer cosh, sinh over simple trig functions?