One way to think about the function e^t is

to ask what properties it has. Probably the most important one, from some points of view

the defining property, is that it is its own derivative. Together with the added condition

that inputting zero returns 1, it’s the only function with this property. You can

illustrate what that means with a physical model: If e^t describes your position on the

number line as a function of time, then you start at 1. What this equation says is that

your velocity, the derivative of position, is always equal your position. The farther

away from 0 you are, the faster you move. So even before knowing how to compute e^t

exactly, going from a specific time to a specific position, this ability to associate each position

with the velocity you must have at that position paints a very strong intuitive picture of

how the function must grow. You know you’ll be accelerating, at an accelerating rate,

with an all-around feeling of things getting out of hand quickly. If we add a constant to this exponent, like

e^{2t}, the chain rule tells us the derivative is now 2 times itself. So at every point on

the number line, rather than attaching a vector corresponding to the number itself, first

double the magnitude, then attach it. Moving so that your position is always e^{2t} is

the same thing as moving in such a way that your velocity is always twice your position.

The implication of that 2 is that our runaway growth feels all the more out of control. If that constant was negative, say -0.5, then

your velocity vector is always -0.5 times your position vector, meaning you flip it

around 180-degrees, and scale its length by a half. Moving in such a way that your velocity

always matches this flipped and squished copy of the position vector, you’d go the other

direction, slowing down in exponential decay towards 0. What about if the constant was i? If your

position was always e^{i * t}, how would you move as that time t ticks forward? The derivative

of your position would now always be i times itself. Multiplying by i has the effect of

rotating numbers 90-degrees, and as you might expect, things only make sense here if we

start thinking beyond the number line and in the complex plane. So even before you know how to compute e^{it},

you know that for any position this might give for some value of t, the velocity at

that time will be a 90-degree rotation of that position. Drawing this for all possible

positions you might come across, we get a vector field, whereas usual with vector field

we shrink things down to avoid clutter. At time t=0, e^{it} will be 1. There’s only

one trajectory starting from that position where your velocity is always matching the

vector it’s passing through, a 90-degree rotation of position. It’s when you go around

the unit circle at a speed of 1 unit per second. So after pi seconds, you’ve traced a distance

of pi around; e^{i * pi}=-1. After tau seconds, you’ve gone full circle; e^{i * tau}=1.

And more generally, e^{i * t} equals a number t radians around this circle. Nevertheless, something might still feel immoral

about putting an imaginary number up in that exponent. And you’d be right to question

that! What we write as e^t is a bit of a notational disaster, giving the number e and the idea

of repeated multiplication much more of an emphasis than they deserve. But my time is

up, so I’ll spare you my rant until the next video.

Complex exponents are very important for differential equations, so I wanted to be sure to have a quick reference for anyone uncomfortable with the idea. Plus, as an added benefit, this gives an exercise in what it feels like to reason about a differential equation using a phase space, even if none of those words are technically used.

As some of you may know, Euler's formula is already covered on this channel, but from a very different perspective whose main motive was to give an excuse to introduce group theory. Hope you enjoy both!

I did not understand why the yellow line (velocity ) was moving faster then the blow line (position ) even though u said the dervative is just equal to to the position at that time,.

Can u explain

You left out a detail that I think might be slightly unintuitive for some people, So allow me help to help clear things up a bit, it take 2Pi to traverse the circle because the circle has a radius of 1 and the circumference is 2*(Pi)*Radius, that said this is a great video and I learned a lot from it, Thank you

the only thing about this video that feels immoral to me is to say that velocity equals position.

Hey grant

Big fan

Which software do you use to animate this?

It will be helpful for me to understanding higher math.

Please japanese sub😭💃💃💃

Why the name 3blue1brown

so, that's mean e^pi/2=i??

Did anyone else cringe when he said Tau instead of 2pi?

If possible, can you please make a series on statistics and probability

Grant, love your series. Just a little advice: if you want to distinguish simplified Chinese and traditional Chinese in your video description, I think the 2 types of Chinese are preferred to be described just like ‘simplified and traditional’ rather than China and Taiwan because it’s neutral and avoids political arguments. But if you must mention the regions, it’s preferred as mainland China and Taiwan. Note recent videos don’t involve traditional Chinese subtitles, but still, I really think you should drop “China” in the brackets because it may send wrong message.

More on the topic of laplace transforms please.

oooooOOOOOOhhhhhhhhhhhh so that that's why "i" is used when transforming sinusoidal signals from the time to phase domain.

i like it

GOOD

This is a god tier math video lol, S++ tier

what are those..?

Amazing video!

By the way, I bet that youtube doesn't like it for being too short.

SMART MAN WELL DONE EXPECTING MORE FROM YOU

Hey Grant do code or animate these videos

X^-1

Browwo

I can demonstrate more easily just search Eulers Formula on google and input Pi=180degrees (i dont have symbol of pi sorry) and you will understand easy and fast

Eit? Watching this makes me realize im an id-e-it.. ehh? Ehh?

Hey guys upvote if u want an angry looking plush Pi

Next video on millennium question Yang Mill Field and Mass Gap…

Please upload visual theory and applications of laurant and machlaren series.

The only property is phone

ET phone home

Overall thank you for all your videos, I achieved to understand those things by writing my own program in '90, Is because your work is tailored to perfection that I'm writing the following comment: At minute 1:48 the animation about exp(-0.5 t) is for a super slow down animation (t changes constantly from 0.00 to 4.00 in 8 seconds AND the factor 0.5 slows the "exponential" of another further half). You would have the same vector animation for exp(-0.25 t) where t grow in seconds unit coherent to the video. However is more didactic to show exp(-t) which is more representative for the exponential function of a negative exponent, which yes slows down its approach to zero but also because it went toward it a lot (however there is nothing wrong in your video)

Make a video on significnace on numbers and derive whole maths from that

As math lovers, let's create a group for discussion which I already did at discord. Join mates

https://discord.gg/Wngy7g

May i ask how you create these great accurate animations? (Which Software?)

Yeah! Maths! It would be really cool if you could demonstrate some equations of fields in physics

When you explain something it makes sense

SIR, it is a request to make a video about laplace trsnsformation which will be much helpful for us all.

Hey Grant! I had a request to make from you.

I want you to make a video intuitively explaining what exactly are waves, different types of it and how to intuitively visualise all of them.

Waves are very basic to most of physics and getting a very clear idea about them may help millions of students get better at physics and in general science.

You're almost at 2^21 subs! Congrats!

e^-iwt used to make some strange signals

https://www.youtube.com/watch?v=QaOUqX4GzXA

Y’all ever watch something that you’re too dumb for, but watch any way to feel smarter despite not understanding any of it? Like asking a professional about something and getting an answer you don’t understand, so you just say “oh ok, that makes sense now. Thanks”

What happens at t=/=0?

For example t=1 -> e^(i*1)

The position now can´t be drawn on to the regular axis.

Make videos on complex analysis

My brain crashed when you began explaining the "i"

What about George Green identity-function?

Well, I really appriciate the huge work You do for Maths and for all of the people interested in it and also help people to even be interested in it.. Such amazing explanations, animations and beautiful thoughts.

But I would really love to see You making similar Physics videos, from the very bases of Physics to some complex and huge physics thoughs or even unsolved mysteries..

Because I haven't seen any better educational channel with such a good explanations / animations, which helps to improve persons view on the world of maths/physics. It'd be nice to see this even in physics problems / theorems. 🙂

C/D = 3.17157.

Sir, please make a video on Residue Theorem of complex analysis.

Another Sunday comes and goes without the next video.

Hey 3b1b thanks for your content! You're videos never fail to leave me satisfied! I was looking for some explanations (intuitive explanations) on topics in Numerical Analysis, anyone know where I can find some of that kinda stuff?

I love and respect this channel

Very nicely explained and I always used to wonder why is this beautiful equation always left unexplained.

Thanks for explaining using animations.

Excellent! Could you make a visualization on the recent proof to the Sensitivity Theorem by Hao Huang?

I can't even put in words how brilliant that explanation was!

Thank you alot for your work! I really enjoy spending my time on your channel and discover "real" math and learn why the things we learn are as they are.

It would be cool if you do another/more videos on music theory. I think alot of musicians who aren't watching you would enjoy it too.

Have a nice day!

VERY GOOD

Where is the video that explains what e^(matrix) means?

Amazing video. I've never had it explained this way to me. I've always just understood E^jX is equivalent to the unit circle and accepted it as so.

omg I hope you can elaborate more on the convex optimization !!~~ It would be really helpful!

If it's worth it, would you make a video about affine transformation? (I am interested in 3D computer graphics.)

A nice visualization of some combinatorial optimization problems would be really cool. One fascinating and fun topic that is not covered on youtube at all.

e^(i*x) = (cos x -sin x, sin x cos x) = https://en.wikipedia.org/wiki/Rotation_matrix . It is just a shortcut to write a the 2D Rotation matrix. So there you have it. The mystery explained in 3.14 seconds. 😉

Just to elaborate: e^(i*Pi) = (-1 0, 0 -1), so it rotates a vector (1, 0) to (-1, 0).

eye pie reminds me of Elon Musk

Can someone explain why he says “velocity, the derivative of position, is always equal to that position” and then places the velocity ahead of the position by the length of the position at 0:30?

Math is sexy.

Why not in -1 second

… i don't understand at all, please explain it… iam a bit dumb when its come to math

Im too stupid for this

You just taught me vector fields better than an entire semester of my second year ODE course.

What is that τ in 3:13 ? Is this true τ = 2π ?

First video to ever get me to understand what the hell this means/why anyone cares. Thank you so much, you are the very reason I like maths

But there are 60 seconds in a minute, not 100, so it's not pi minutes, even according to the description :/

I feel like I just got scammed.

The further away from 0 you are, the faster you move! Brilliant!

make a series on python programming!

9 12 15 20 25 gives rational outcome of e.

What software do u use to make such good animation

Holy crap, I've always wondered why this was, and no one could explain it. Thanks.

I think it's beautiful.

Bruh how the hell do i cook a digiorno pizza

F

I think this way of teaching "visually" should be introduced in every school in the world… it's amazing how you manage to find the right animation for whatever concept, bravo!

So, is this the most beautiful video on the internet?

❤️

tell me if you use some kind of drugs to understand anything so easily… Damn !! everything now makes so much sense .

my mind just exploded, omg

This took my math lecturer about 30 minutes to explain, but you've done it in just 4 minutes!

This was just a beautiful explanation of a beautiful concept. thanks and keep on making your great vids!

Can yiu translate your videos to arabic please 😢💕

3b1b: Whats that miles down there below us? Looks like a head…

wonderful explanation with wonderful animation

It's ridiculously amazing how mathematicians discovered how they couldn't solve certain problems by moving along one dimension with positive and negative numbers and came up with adding another dimension to the system.. This is a truly awesome visualization! Grant, what would the notation be like if we want three dimensions (moving into and out of the plane)?

This has never made sense to me until now and I laughed out loud into my hands when I got it

Expectation: Determined to fully understand a 3b1b video

Reality: Facepalm

Mind blowing

come back grant

VERY GOOD

there is no explanation : WHY e , not pi or something else ??????

Amazing such a good explication

Please do Laplace transform

Cool, I've never understood anything less.

This video has such a good explanation!!! Thank you!