Imagine some kid searching for alphabet 'i' and gets this.
The kid will think there are a lot more letter to learn ... reading is hard bruh
Math in the 20th century: Galileo and Newton are wrong.
Math in 2021: .._.. prank your friend 5:10
*GOLDEN EQUATION*
Sir Steve Chow please read this comment for a golden equation.
Your videos are very amazing. I have derived a very beautiful equation in which there are all amazing things like Phi,π,e,i and even Fibonacci series(All five in one equation). I request you to please make a video on it. The beautiful golden equation is difficult to type here but still I will try to type. It is as follow:
ϕ(ϕ^(e^(πi)-n)+((-1)^n)(n+1)th term of Fibonacci series) = +((-1)^n)(n+2)th term of Fibonacci series where n is a non-negative integer.
You can check it on calculator it will work. If you want proof of it then reply my comment and I will give my number and I can easily explain it's proof on a call as it will be difficult to explain it in comment.
Thank you for reading this comment. I hope you will make a video on it.
@@mathevengers1131 dude comment that on the video I don't think he'll be able to notice this in a reply, so I think you should post thus as a comment, not a reply
@@mathevengers1131 hey that's pretty neat
Using the Fibonacci series' approximation to phi as a connection, and then making one of the -1 into e^i*pi so that they could be all connected together
For those interested, a pastebin link of the results up to 100: pastebin [dot] com/Z3WGwf2T
Some further reading:
www [dot] goldennumber [dot] net/powers-of-phi/
www [dot] maths [dot] surrey [dot] ac [dot] uk/hosted-sites/R.Knott/Fibonacci/propsOfPhi.html#section1.5
(TH-cam is unfriendly to links, oh well)
5:15 cos^2 z -1 is always negative and we have sqrt negative which involves z. So "i" is still on both sides, just in disguise.
cos^2(z) can be greater than 1 for certain complex z, so cos^2(z)-1 is not always negative.
@@antoniomora4537 Yeah but there's also a cos(z) term on the outside AND a 1/z term on the outsider-outside, so theres bound to be something complex in there.
For z = 2nπ cos(z)^2 = 1, so the whole term equals 0, did I do something wrong?
5:46 the 3rd way
Wouldn't it be possible to generalize the answer like this, i.imgur.com/A7Xc2YZ.jpg ?
Apologies for the handwriting and the inconsistencies in how I write the number "2" in advance :,,)
I actually have a 4th way
e^(i兀/2)=i
e^x=lim n →♾[(1+x/n)^n]
So i=lim n →♾[(1+i兀/2n)^n]
I bet Euler did this kind of tinkering with math for 12 hours every day. 😂
What is i for u?
For me, i=x+(x^2+1)∈ℝ[x]/(x^2+1), or given another ring C with ring isomorphism φ : ℝ[x]/(x^2+1) → C,
i=φ(x+(x^2+1)).
Or equivalently, given any ring C with ring epimorphism η : ℝ[x] → C such that ker η = (x^2+1),
i=η(x).
(here (x^2+1) is the two-sided ideal generated by x^2+1)
For "second" form, you can simplify cos²Z-1 = -sin²Z, which of course brings out another √-1.
This actually doesn't make any sense. Also in the 2nd answer you would almost always have a negative under the sqrt. Or a zero (in the case that z = pi*n). This means you still have an 'i' on both sides. What a nice property of 'i' -- no matter what you do, it won't go :)
😆 Yea I am aware of that and that’s why i said it’s math for fun and i mean it in the beginning. I actually just wanted to do the 3rd one but it would have been too short for a regular video.
@@blackpenredpen Perhaps you've said it was "maths for fun" but fun in maths doesn't mean "calculus for fun with circular reasonnings twice in a row..."
So ok if you want to do random maths but I would rather say "calculus for fun" and précise why this is random maths.
Because I'm not so sure that every viewer understood that was totally random
I would like to precise that writing i=sqrt(-1) can make confusion and you should precise that sqrt(-1) = *+ or -* i
So I know it's possible to write i=sqrt(-1) but you should say that is just to make understand i or that if you really want to use this notation rather i it will bring you to error if you don't think about that sqrt(zz') =/= sqrtz * sqrtz'
That is not thé only non sens.
How to justify that cosz + isinz is an exponential function without knowing i^2=-1?
I don't see so at the beginning It's already circular reasonnig.
He just copying solution problems from Qora or Stack Exchange websites. or Mathematica
@@ujueije5762 It's possible, I'm french I don't know how do you do maths in the us but I think he should do an erratum For "fun" for sure.
He can say : OK that was fun but, now, where are the circulars reasonnings ? Or something like that. That's my point of view.
3blue1brown’s lockdown series was I think a great introduction to i- one of the ways of thinking of i that stuck with me is a 90 degree rotation in the complex plane
I found 2blue1brown's video really difficult to wrap your head around compared to what I've learned from blackpenredpen
the funniest thing about it is that it is a cricular reasoning. ;)
in order to explain yourself what i is you need a complex plane, but in order to talk about complex plane you need i...
@@michalbotor he built the complex plane first then explained what multiplication by i does.
Besides, one way that you can define complex numbers is as matrices that act on R^2. The field of complex numbers is isomorphic to a certain type of matrices if you want to be fancy.
The fact that you could have simply written
e^iz=cosz+i(1-cos²z)½
=cosz+(cos²z-1)½
i=1/z ln(cosz+(cos²z-1)½)
Without actually solving the quadratic is pretty amazing!
For that derivation could you not just start with Euler's identity, take the log of both sides, rearrange to isolate i and then use the Pythagorean identity to rewrite sin z?
Nice. I didn’t see that. My approach was similar to how I did my previous videos. 😆
@@blackpenredpen The statement with ln(cos x + i sin x) is Cotes' formula, he came VERY close to Euler's form but didn't make the necessary connection to polar coordinates.
So in fact, actually we can derive i with any real numbers rather than 3. Tho we have to take care of the positive and negative signs.
Okay I just noticed that you could just take the euler's formula change isin(z) to √(-1)*√(1-cos²z) which is √(cos²z-1) and its a tremendous shortcut
I came here to say the same. I noticed the difference of 1 - cos squared z is just -sin squared z, and it brings you right back to where you started.
These are all basically 1=1 equations, of course, so they can be arbitrarily simplified or complicated.
Haha I came here to say the same, it rlly annoyed me that he didn't simplify the expression until I realised it brought u right back where u started
@@danielbenton5817 saaame bro, just can't let it through without even an attempt of simplification alright
@@runonwards9290 so how do you know i^2=-1? It's the definition for i, you can't act as it's not here, its just a formula that equals i for any input z
With the first formula, cos^2 (z) will always be less than or equal to one. When it's less than 1, we have a a square root of a negative number (aka i on both sides again). When it's equal to one, you get 1/z * ln(0), which also doesn't work since ln(0) is undefined 😭
"Z can be on the bottom, he likes to be on the bottom anyway... Well I don't know - I have not talked to him for a while." LMAO 😂
I dont know why I watch your videos, but I love them all.
I typically only ever define i squared, but I don't wish to be negative about your video. Thumbs up.
You explains everything
It was like I am having a Big Mac .
I thought this was going to be about explaining why we should say i^2=-1 instead of using the square root in the definition. Square roots are not nice because (-i)^2 is also -1.
Not only that, but j^2 = -1 and k^2 = -1 which is how you get quaternions (ok, you also need ijk = -1).
Haha this is great, I wish there was more room for this sense of playfulness and adventure in the high schools. I feel like we could turn more people onto mathematics.
your content is so underrated
I prefer this:
“i” is the second dimension of numbers.
No i is in the second dimension of numbers, however it is not the whole thing.
The element x in the quotient ring R[x]/(x²+1).
hey.
5:35 kiddin us?
cos2(z) < 1 => cos2(z)-1 so sqrt(cos2(z)-1) already contains i itself.
Sqrt(-1) love your videos
As a physics man, I hate the W function. Non-analytical functions disturb me at a deep level.
I'm so glad I saw this!!!, 😄
How do you check to ensure the calculations for i are correct?
In the 2nd way, you can sostitute square of cos^2 - 1 with square of ( - sinz )^2 that is equal to i*sinz...and if you don't want i on the right side, I think you have to put the condition: z=2kπ with k of the set of integers, so k=-2, -1, 0, 1, 2, 3...
Yo BlackPen/ You know that Formula Board in the background? Where can I order one of those boards?
Nice background music....
Huge appreciation from India.... 🇮🇳🇮🇳🇮🇳
You could skip the algebra (2nd) by simply ln both sides on any of the +- versions of Euler's formula and then divide by z.
You know I also thought the same in past but at that time I don't know how to squeeze "i" from euler's equation. Now I know thanks ❤️❤️❤️
So when z = 0 then i is undefined?
The equation at the bottom of the second method is basically euler's formula. cos²z-1=-sin²z. Rearranging you get e^{iz}=cosz+isinz
can you make video on the fact that you can make 1 to equal -1?
He is a genius.
Could you do examples of Gram-Schmidt process please?
2:30 if you divide by 2 on both sides, you get something that looks like cosh(x)
whats the Use of this identy for i?
teach me how to be this happy
@@blackpenredpen *GOLDEN EQUATION*
Sir Steve Chow please read this comment for a golden equation.
Your videos are very amazing. I have derived a very beautiful equation in which there are all amazing things like Phi,π,e,i and even Fibonacci series(All five in one equation). I request you to please make a video on it. The beautiful golden equation is difficult to type here but still I will try to type. It is as follow:
ϕ(ϕ^(e^(πi)-n)+((-1)^n)(n+1)th term of Fibonacci series) = +((-1)^n)(n+2)th term of Fibonacci series where n is a non-negative integer.
You can check it on calculator it will work. If you want proof of it then reply my comment and I will give my number and I can easily explain it's proof on a call as it will be difficult to explain it in comment.
Thank you for reading this comment. I hope you will make a video on it.
i is happy :D
woah i was just wondering about this and you uploaded about it @-@
Hey! @blackpenredpen :) Could You Please!! do a video on solving infinitely nested square roots but with increasing powers? And potentially differentiating and integrating them or something?
like X*sqrt(X^2*sqrt(X^3*sqrt(X^4.....
thank you!! :)) Also, I love what you do on this channel, you're amazing :)
Wow!!! I love this
It's only mathematics.New math was, well, actually not too bad, it needed an explanation.Ok, moving on then....
O que é a função W?
For the second approach where he did e^iz =.... MINUS e^i(-z)=..., what gave him the reason to take the difference of the two? Like hw would u no that u start off by doing that?
i is just the co-ordinate (0,1), where co-ordinates are multiplied according to the operation (a, b) * (c, d) = (ac - bd, ad + bc). Thus i*i = (0, 1)*(0, 1) = (-1, 0) = -1 if we decide to write (1,0) = 1.
R^2 is a lot of things, is the complex world, is the vector's world, it's a plane, etc
Isnt there an i on the right anyway as cos^2 is smaller than 1 almost always?
Love those kinda intros
simplify with cos²x-1=-sin²x to cancel the square root ?
In the second definition of “i” what is the value of “z” ?
In method #2 next to last step: you have sqrt(cos^2(z) - 1) which is equal to sqrt(-sin^2(z)) which is equal i*sin z. So this step is just e^iz=cos(z) +i*sin(z) which is Eulers identity where you started! Beautiful circular calculation.
For the second way, what if z=0?
Quite Easily Done!
what am i?
@@shivamchouhan5077 I will give proof when bprp will read it. I am trying to contact him by sending the same comment from last 20 videos on both of his channel but he is not reading my comment. I hope he will read it.
i like this video very entertaining me.👍👍
hyperbolically, if j^2=+1 and e^(jz)=cosh(z)+j⋅sinh(z), then:
what is j?
wait but the third one isn't yielding the desired answer. W(-pi/2) = ipi/2, thus...
(-2/pi)(W(-pi/2)) = (-2/pi)(ipi/2) = -i
You can check on wolfram alpha by entering the original equation, it also gives the answer as -i. What's up with that?
This is a very interesting point that you brought up. Nothing done in the video is wrong. There is a way to solve for i and get (2/pi)(W(-pi/2)). However, it is important to keep in mind that the Lambert W function has multiple branches. To write a specific branch, you write the base as a subscript of W (similar to how you write a base of a logarithm). With no base, the principal base is assumed, which is base 0. In WolframAlpha, you type "productlog(base, value)." (2/pi)(productlog(0, -pi/2)) = i, but (2/pi)(productlog(-1, -pi/2)) is also i. Put this into WolframAlpha.
Wolframalpha evaluates the 3rd solution as -i
What could be the issue?
i see what you did there
Instead of using natural log, you could just transform your exp(iz) in the left side to cos + i*sin, cos would go away, and you will have
I*sin(z) = sqrt(-1)*sin(z), so i=sqrt(-1)
I don't understand why you added the number 1 to the fourth line? thank you !
Aye aye, captain!
Hey there is a mistake in final result domain of cos theta is not satisfied
Friend: What is i?
Me: duh. i is you.
You can get to the second form from Euler’s formula by immediately replacing i*sin(x) with sqrt(-1)*sqrt(1-cos^2(x))
Every electrical engineering student knows.Hey, thank you.Can you do more on complex numbers?
sqrt(cos^2z-1) is just sqrt(-sin^2z), which is just isin(z). So the final answer is just 1/z*ln(cos(z)+/-isin(z)). You could save a lot of trouble and just take the logarithm directly of e^(iz) and dividing by z. Or have I missed something?
tell about hyper factorials as a product of super factorials
For the second answer, if you use the Pythagorean trig identities to simplify √(cos²z-1) you get √(-sin²z) which is just i*sin(z) so you're right back where you started... though the plus or minus is interesting
5:00 so 1 under sqrt is cos² + sin², and after substitution you get back to √-sin² => cos + i*sin
Another way would be expressing constant i as a function of F where F is a multivalued solution of equation x^2 = -1 .
I think that in the second one, i is still present in the right part on the equation; infact in the square root there is -sin^2(z) than can be rewrite as sin(z)•i
How about i=ln(-1)/π ?
i=sin/sn
Right?
I expect a Pokemon to come out of that pokeball and teach us math.
Nice :)
You:
What is *I* ?
My English teacher:
New grammar level here
Please continue this hahaha series 😭😭😭😭
It's cos^z-1
Very funny !
e^iz×e^-iz=1 how is this can anyone explain please?
What Euclidean geometry say about his fifth postulate?
Is it true if i say, i is not sqrt(-1), but i²=-1 ??
I really thought he was gonna say something like
1 + 1 = 2 and 2 = 1 + 1 at the beginning.
i = sqrt -1 and sqrt -1 = i
Can you prove that i is constant?
2021: Who am i?
2051: what is i
@blackpenredpen but "what is square root of two?"
So i can be any z?
But if you use z=2pi in the second formula you have i=0...
I think it's because the coefficient of the quadratic equation is equal to 0, so maybe to be rigorous we should add "for all e^(iz) with z != pi/2+2kpi k integer"
this is not the problem actually, here is a simpler one:
e^2i*pi=1(eulers formula)
take the In both sides
2pi*i=0
which is wrong because neither of factors are equal to 0.
the mistake here (and also the same mistake you did) is amussuming the function e^z is one-to-one (true for real numbers but not for complex numbers)
the thing i mean is if e^a=e^b, you cant say a=b in complex world (but you can in real world) because if b=a+2n*pi*i(n is integer),
e^b
=e^(a+2n*i*pi)
=e^a*e^(2n*i*pi)
=e^a (because e^(2n*i*pi)=1 by eulers formula)
But i=e^i(π/2+2πn) 😅 so we could add infinitely many solutions to the 3rd way isn't it ?
Can u solve for z?
2nd solution?
i can solve but the comment section is too small for it , to fit in .
Cant we pur the 2nd equation equal to square root of negative 1 and solve for z? Just a speculation,any math veteran please correct me
Hospital....where is the hospital???
what if z = 0?