#serious-discussion
1 messages · Page 479 of 1
for foreign words, sometimes
als it inherits caps from the noun Möhre
Notfallmöhre
Möhre
nouns are capitalized
beginning of sentences 
headings start in caps as well
also in english?
i think so, yes
i am sure
ah thank you. Is it worth to learn tikz
I have some html5 canvas experience, should be easy to learn it I guess. tikz-graphs fit so nicely to the text.
definitely worth it, another option would be to use e.g. inkscape but I find tikz gives a finer control over the picture layout and how it relates to the whole document
plus there's fun stuff you can do with for loops
nice nice, gonna learn
Szene 1: Die Möhre betritt den Raum. In einem Sessel wartend der Sellerie. Ungeahnt derer, vor dem Fenster schemenhaft für die Zuschauer zu erkennen: die Gurke.
Scene 1: The....for the....the
in front of

Sellerie is celery
Oh
thats sad i tried to use vegetable names that are different in english
Sessel?
Ah
Sessel is armchair 

i don't understand the sentence structure of the celery sentence
i would've used erwartet
oder wartend + sein; wartend, ...
idk
no verb = scary
hmm

i dont enough linguistics to explain
but its the same in english
maybe its a stylistic device
i would buy that, sure
this is common in scene descriptions for theatre
for poetic effect
(which this was supposed to sound like)
that's the impression i got
big words from someone that just failed a safety instruction, but yeah
i bet more people failed
cant you just retake?
imagine failing and not being able to blame it on the german language
yeah it can be retaken as many times as you want
and indeed, native speakers failed it lol
i took it twice and got 39 both times 
then i gave up
watched a fucking 51 minute video and then spent 2 hrs going through the 10 questions
no, they want you to send the certificate with a digital signature
and you can only get the certificate if you pass
What kind of test is this?
amokläufe 
Don't you already know German?
brandfall, sure, but also how to deal with dangerous substances and what to do if there's an accident
ah ok, you deal with dangerous things
brief shoutout to different kinds of fire extinguishers, how to use ladders and defibrillators, etc
i don't
i deal with a laptop
Very dangerous
but other people in the institute do
Edd can explode solving those big matrices
my security briefing was "sign here"
at my first job in industry we skipped the security stuff
and there was an accident
one of my coworkers lost a hand
i could brute force it, too. unlimited tries, and there are 10 questions only. multiple choice, you can select as many as you want from 4 options
and our boss got in big, big, big trouble
because he couldnt prove there was a security briefing
That sounds awful
it is
so something like $\left(\sum_{n=1}^4 \binom{4}{n}\right)^{10}$ options
Edd
yeah i think they're being more careful since a mofo forgot to put on safety glasses during a laser welding thing
thats finite, which concludes the proof
ye, once something happens they make everything way more strict

i do sigproc stuff, but the applications are very industry-oriented
we coop with some institutes that do stuff like inspect railroad tracks, weld stuff, use radar to detect buried mines, and other fun (c.f. super dangerous) stuff
pinpointing your location
wait what do you work in?
sigproc
what's that?
lmao
I love how operator calculus always looks like bad math, but works out

You cant tell me that all of this notation is good, or that all of it is needed
Is there a channel for analysis
There are 2
Go to #get-advanced-access
And then go to #real-complex-analysis or #advanced-analysis depending on what you need
Shieeeeeeeeeeeeet
did they find it?
Wtf new analysis channels?
I thought I liked power series
now seeing this stuff for ODEs makes me head go 
looks like a lot of work for such an ugly solution
wait till you see frobenius
tbh these are outdated methods
people in like the 18th or 19th century cared about solving ODE by power series
nowadays you just approximate a solution by runge-kutta or smth
why is y'' - y = 0 the classic example

because you get sine cosine out which is satisfying ig
and matches the other methods we have
geometric calculus is cool af
like $\prod_a^b f(x)^{dx}$ is the geometric integral
gmod
when I learned about this I think I came
STOP BEING HORNY FOR MATH
LOL
What’s the intuition for a staircase with n stairs from (0,0) to (1,1) not having a limiting length equal to sqrt(2)?
i mean have you tried working out the length manually in the case n = 1, 2, 3
I mean obviously the length is gonna 2 for all n but why does it differ from the expected limit if you look at “the limit” geometrically?
ok, i see
imo calling it the "limit" geometrically is up for debate as jagged things and smooth things have big differences between them, i mean you know the old question "How long is the coastline of britain"
it depends on the scale at which you measure it! do you post a marker every mile, every ten miles, etc
or if you looked at a picture of the stock market graph from today and asked "what's the total cumulative change in the value of the stock, counting all ups and downs, all highs and lows"
if you looked at the change every five minutes and added them all up you'd get a different answer than if you looked at the change every hour
the "limit" you're talking about of the staircases is IMO an infinitely jagged thing and we shouldn't expect it to resemble a smooth thing
Ah that makes sense. Though if you decided to define the limit in some fashion similar to being contained in an arbitrarily small rectangle around the straight line, would the difference then be that the staircase has some “measure” (in a loose sense) that’s different than the straight line?
Maths is my crush, i will do what i want.
Darling Mathematics,will you marry me?
hmm ok i have come up with an answer
You could make the zig zags go more steeply and then the length would be even longer
You could make the length infinite
my idea is that the length of a curve c is like
Sorry triangle inequality
$\int_x T(x,f(x), f'(x)) dx$
diligentClerk
where $T$ is a function of both $x, y and dy/dx$
diligentClerk
so we should only expect length to be well behaved with regards to the limit of a sequence of functions $f_n\to f$ if $f_n\to f$ not just "pointwise" but also in terms of the derivative we also have $f'_n(x)\to f'(x)$
diligentClerk
I think for complex analytic functions you get this automatically but not in our example
I’m having a bit of a hard time understanding why the length of a curve is some int{T(x,f,f’)}
I guess I get it, but I have a hard time seeing why x and f’ also need to be arguments for T. Isn’t just f sufficient
https://tutorial.math.lamar.edu/classes/calcii/arclength.aspx this is what i'm talking about, i just abbreviated some stuff
In this section we’ll determine the length of a curve over a given interval.
as we go from $x$ to $x+\Delta x$, if we assume that the curve is locally linear then the length is roughly given by the pythagorean theorem, i.e. $\sqrt{(\Delta x)^2 + (\Delta y)^2}$
diligentClerk
Gotcha gotcha
and i'm using the approximation $\Delta y \approx \Delta x \times (dy/dx)$
diligentClerk
so it simplifies to this $\int \sqrt{ 1 + (f'(x))^2} dx$
diligentClerk
which is what i mean we should only expect length to behave well wrt limits of functions if we also have $f'_n \to f'$ because $f'$ is what actually appears in the definition of length
diligentClerk
That makes sense, does this seem like something that might have an already-existing formalization?
uhhh i don't really know enough analysis to answer that but it I think that we should have the precise theorem that if $f_n \to f$ (where $f_n, f$ are continuous and differentiable) on the interval $[a,b]$ and so does $f'_n\to f$ on the same interval, then the lengths of the $f_n$ should converge to the length of $f$
diligentClerk
I feel like that implication is in the opposite direction than what would answer my question, but I guess it’s satisfying to the extent that for the staircase, the antecedent doesn’t hold so I shouldn’t expect the consequent to hold
Sorry if that was worded confusingly
nah i get what you mean
it's not a direct explanation, it's more just showing that the obvious theorem you would write down doesn't imply that this is true
Seems this question has already been asked on stack exchange: https://math.stackexchange.com/questions/1810336/does-there-exist-a-if-and-only-if-condition-so-that-arc-length-of-a-convergent-s
Not much new there outside of what you’ve explained here
mm nice
the only dog person in this discord, this is shocking stuff
why do we care about phase portraits and trajectories and whatnot
to understand what happens when the equation can't be solved
at first you just do them for linear equations
but later you do them for nonlinear equations (in particular, you often look at their linearizations around equilibrium points)
and the phase portraits can tell you a lot about solutions without you knowing how to actually solve for them
how are you supposed to obtain the trajectories without having the solutions?
(e.g. the poincare bendixson theorem is a big theorem in this regard)
i mean you can't get analytical descriptions of them but you can understand what they do topologically by looking at the vector field that the system of ODEs gives
"topologically" isn't really a technical term here
i guess the better word is "qualitatively"
so, for example, maybe you don't know what solutions are, but using the phase portrait you see that all the solutions are converging to some stable equilibrium
like a sink
so important things to consider would be the limiting behavior of solutions, holes/regions where they blow up, etc?
yep
and sure, just looking at a picture isn't a proof
but the picture can tell you what to do to get a proof
And solutions x(t), y(t) only differ up to constant right?
This is what I have
no that's not true usually
well
no
or
at time t_0, you give an initial condition
the initial condition is just the point where you start
the ODEs tell you how to move from that point
ok that's what I meant, mb. the only difference between different trajectories is different ICs
oh
they could do totally different stuff
imagine math papers using comic sans
Isn’t that not necessarily true for non-convex sets or am I misremembering
(the important thing is, if you pick 2 points, then either the trajectories they are on are disjoint, or they are the same trajectory - as long as time goes forward and backward)
this is just cause if the two trajectories ever collided
then from then on, the derivatives along both are the same
and by the fundamental theorem of calculus, if two functions have the same derivative and are the same at a point, they are the same function.
idk what you mean by this
I'm confused, aren't we multiplying constants most of the time anyways? Why is"don't need to be translations of one another" something important to mention? Aren't they usually not translations of each other?
Like if you have this system over that kidney-bean shaped set, multiple functions can satisfy this system and have the same value c_1 but different values c_2
(Feel free to ignore this if it’s obtrusive to the convo)
i just meant when you said they differed by a constant, to me that means if i take one curve (as a function of vectors in R^2) and another curve and subtract them i get a constant
and that's not always true
(if it were true, one curve would be a translation of the other)
but that's not what you meant so it's fine
i mean i don't consider f here as one solution
i get what you mean but
like to me a solution is only valid on a connected interval
Oh wait
hm
I'm testing it with x = e^t, y = e^(-t) and different constants and they are translations of each other

let me try other functions
when I subtract them I just get 0
oh
idiot
ok nvm I am not getting constantw
yeah I'm so confused
how are solutions supposed to be different besides with constants like this
any ode's gonna have a unique fundamental set of solutions right?
everyone is mac at me
so the only way we can get different trajectories is with different linear combinations of the fundamental set
but i just blocked my friend bc i made fun of her career path
what am I misunderstanding?
eh
Because it's like my first real encounter with the whole approach of turning one thing into another thing and then studying the properties of that new thing
Like even in my other advanced math classes, I'm still studying the properties of a thing in "its own language" so to speak
Idk. Like I'm getting it, but it feels harder than anything else I've done.
Can we get a “how to get help” mentions over time graph, possibly normalized to number of users?
It really feels like we’re saying it extremely often
^
And a ban count tbh holy crap
theres no easy way to get those numbers without running a bot
if you want it to be measured over time that is
mniip could probably easily add it to bot, but im not sure what that'd help with.
What are the most common reasons for a ban
if you just want a total ban count, we have 3147 banned users
this is different from the total number of bans though
since bans from about 2 years ago have all been thrown out
(when we shifted over to the ticket system, we undid a lot of old bans)
just trolling i guess
got 2 users banned due to rude behaviour
if youve only sent 8 messages on the server, all in #chill , and 3 of them are racist or transphobic, we typically wont give a second chance
we're a little more lenient (read: mutes with strong warnings instead of bans) if the user has contributed to the server in another way
since perhaps they just said whatever message out of ignorance
but thats less common
I wonder what the ratio is of the different types of bigotry for banned users
in my anecdotal experience, transphobia is the most common
That's what I've noticed too but I'm obviously biased to notice it more
also a lot of people in help channels calling others idiots/r*rds/autistic or whatever
which i guess you could classify as bigotry
thats gotten less common recently though
like, even before the new help channels, it was on the decline
which is nice
He was 13 anyway and annoying
Like the people asking for or giving help
both
Wait anyway I teach a recitation at 9:00 tomorrow but I’m not tired bc I took a nap should I just stay up and study all night lmao
youll feel tired eventually.
Honestly this server is impressively well moderated
no it isnt
Ok there are some annoying emote spammers that should be banned or at least muted
if it were well moderated how am i not banned
Spamming
and whatnot
But besides that
Idk I just feel like "public discord math server" are not the words that make me think "good community"
no it isnt
we could have been like, the physics server
what are they like, sir john
How’s that server doing btw
A lot of racism and stuff in the upper ranks from what i understand
Smh I'm trying to suck up to Namington here so I get Honorable
why do you care if you get honorable or not
ya know
Don't interfere
I kinda want to join a large public server
And just die
No like a larger more mainstream and toxic one
probably joining a gamin community will do that
WHAT IF I WAS WRONG AND NO ONE CARED TO MENTION
WHAT IF IT WAS TRUE AND ALL WE THOUGHT WAS RIGHT WAS WRONG
is this from a song?
I've already seen old discussions of this so I know the majority of you will disagree and claim that mutate is weak. Lots of gas lighting trolls up in here. I pretty much just play Arena but I win the majority of my games. The only thing I consistently lose to is mutate decks or one of several super combo decks where suddenly I'm hit for 50+ damage in 1 turn. Mutate literally beats anything that doesn't play faster or isn't more or less an antimutate deck. So then your only options are mutate deck or antimutate deck. I can't even think of another set of cards that comes close to buffing like mutate does.For anyone who disagrees, please tell me how YOU would beat a mutate deck without saying "cancel deck" that's not playing. That's nobody playing.
p.s. Whatever you assume of my deck construction it doesn't change the fact that mutate is the only deck type that I struggle against. In Arena I'll quit discard/ mill matches cus I just don't want to deal with it.
TLDR Most deck types are useless trash against Mutate decks.
Ok what is the best copypasta
negate revel in riches
Manchester Orchestra's official music video for 'Simple Math'. Click to listen to Manchester Orchestra on Spotify: http://smarturl.it/MancOSpotify?IQid=MancOrchSM
As featured on Simple Math. Click to buy the track or album via
iTunes: http://smarturl.it/SimpleMath?IQid=MancOrchSM
Google Play: http://smarturl.it/SimpleMathGplay?IQid=MancOrchSM
A...
Before this gets deleted by reddit admins this asshole took it completely out of context
its an incredible pasta since its 100% genuine
namington is poorly moderated
and he actually thought itd make him look better
The best pasta are always the ones originally written unironically

DesolatorMagic moment
It brings me great joy that in addition to be a raging bigoted asshole, he's also just shit at mtg
mm oo mmm ooo mmmm oooo
yea
now I've become one
the vicious cycle continues
nah that's just being an asshole
is this happening on here or elsewhere?
that should not be happening in here
If you make a typo, that's one thing. But if you don't know how to spell a word and keep getting it wrong, I'm sure the intention is to just tell you so you learn how to spell it.
It's not cocky.
I know what incident you are referring to, and you misspelt it the same way more than once.
No, you think it's cocky for them to call you out for disappearing for 20 minutes while they are waiting in the channel to help. That's not cocky.
she
After she said that, it still took you 25 more minutes to actually reply
So I don't think it matters what she said, you weren't there
Lol
You are way too sensitive, but okay, I'm not interested in arguing with you. Just letting you know that from reading the exchange, I don't think she did anything wrong.
Okay, next time tell her you will wait for someone else to help you rather than continuing to let her help you and then once you get what you need, you come here to complain.
This is so sad
No one is responsible for what other people have said to you in the past. Nothing she said is very egregious, so it really shouldn't have upset you this much.
That's a good analogy.
Please stop pinging me when you reply
This is so silly
I'm done here since I think you are unreasonable
Strike, we all have bad days, but that isn't the way one should cope up.
Getting your spelling corrected is not a valid reason to rant here for 20 minutes
No, the problem is that you think someone correcting you is them being cocky, when it's just them correcting you.
Heard about displacement defense mechanism?
You're frustrated, so since you're frustrated you take it all out on somebody.
On everyone?
Then who?
Please stop ranting here
There's a better way to channelize all your frustration.
this chat belongs in #vent
Hope you could take that into account.
Hmm???
My time to vent: I am in shambles that I was blocked by Read.
That's sad.
dino
Don't laugh at my despair
didnt expect it to escalate like this
Let this one slide.
And i never saw the help channel.
Oh.
I thought "help channel" to be a vent channel or something.
HAHA
Didn't catch you there.
Discord servers who offer to help someone?

I've seen many vent channels. Maybe they do.





nice vaguepost btw
toki mfking doki
fortnoight
Toki is amazing. Toki is cool and trusted and talks and is very active
Why do the discussion channels feel post-apocalyptic? Feels like it’s just a whole lot of wreckage
however, you got no excuse
mniip said yes
i mean, we discourage venting here, so it's best to vent on private server instead
also i'm not man
but ok
yes, why are you still asking?
read their about me 
in shambles
in shambles
in sandals
helpers pretty much don’t even respond to pings lol
i imagine that they all have pings disabled
u don't need to imagine, it's the truth
ppl take the helpers role for the 'color' only
lol
I got blue so I don't need green
this blue is pretty cool though
They set everyone's nickname to a random number
make me grahams number
if a custom bot does it then no
a prime number
oof
wow
next one probably wont be nickname related
why

because itd be the same joke twice?
beaned
@primal crater assigning a role to 70k people
a bot will do it in seconds
as if we've ever planned ahead
I didn't realize I was gonna have to learn so much german for alg. geo
first hilbert's nullstellensatz, now Krull's hauptidealsatz
wtf is this
LOL
How do you even say that, my guy
i mean the first one is just hilberts root theorem translated i guess
the second one idk
my english maths vocab is not sufficient there
i love math but i wouldn’t learn another language for it lol
I think it's "principal ideal theorem"
I swear I remember reading that back in the 70s or 80s or something at yale you had to learn a language commonly used to publish math to get a math major
or maybe it was in their grad school
had to learn russian or french or something
I think that used to be a thing at several places.
My school has a language req
I can't remember if it's just the math dept or not tho
I do not like systems of differential equations
For the sole reason of I do not understand drawings
I like euler method, cus its simple to solve those equations. But I didnt bother yet with the analysis approach
math major moment
lol true
nah what
drawings slap
even though i cant draw for shit
lol
it is pretty cool
quatum phyics in interesting got to learn calculus to understand it tho
i haven’t actually gotten to calculus 3 yet but i’ve looked over it a bit and it looks really cool
im in cal 1 going for engineering
aerospace engineerin going to a college close to get regular classes done
hope i can transfer to georgia tech
satz just means statement (theorem)
hauptsatz means something like, principal theorem or main theorem
haup-on-deez-natz
if only calculus was sufficient for quantum stuff
maybe people would stop overhyping it so much
relevant xkcd:
id swap special relativity and magnets tbh
you can visualize the underlying mechanics behind special relativity quite easy even without an understanding of the mathematics that births it
good luck doing that with magnets
why do magnets need a north and south pole??? why arent there poleless magnets?
I feel old
On the bright side I suppose faygo soda is fairly cheap.
really what
calc is not sufficient for quantum mech lol
nami was saying if only it was, maybe then it wont have been so popular
quantum mech is overrated.
You sussy baka, Nyah
can't even solve classical problems 😐
You sussy baka, Nyah
You sussy baka, Nyah
but i have wanted to do it for over 10 years 

what
bro i didn't even know i was gonna do math until literally maybe 3 years ago max

how do ppl find out about this shit so soon yo
BRUH!
you know you have to go through books.
You sussy baka, Nyah
probably coz my dads a physicist

yeah ik i have to go through books
lol
I think that chart is referring to the way they are typically introduced in a physics curriculum. So the necessary math for magnets is multivar calc, not fuckin lie theory
idk man, multivar doesnt help me understand why they work
it helps me compute shit about them sure
lol
I want to do quantie!!!!!
Really?
math makes me feel very self confident but then I realize I'll die broke and lonely /s
yeah
I'm getting out of here
Bruh
This video gave me blood pressure.
ok
Lmfao
Lol
fuck fb
That is so cool

do you guys know of any good website to practice trigonometry, which has a choice of practicing basic things or advanced. just annoyed of looking at worksheets which don't even have answer keys
Khan academy?
any other too?
I don't know any
Read got rid of the Helper role 
I would tell her that's based, but she blocked me 
brilliant costs some dolla dolla bills, i am broke, but everything else works, khan academy looks fine
and then type in 'trigonometry'
😎

HOLY SHIT! thats a gold mine Right there!
Give my boi azeem321 helper role please'
he deserves it
ask mods for helper role
Helper role is literally punishment
lol i posted it as a joke because those are quite hard problems, but if you think you can do them then glad to be of assistance
i agree with janman
just give the man a role, he Deserves some colorful text in his life.

someone getting helper role is just giving them 500 pings a day
1984 pings
if i can't do them now, ill do them in the future regardless. Slowly climbing the ladder. no one knows math at the start, but they eventually get it.
helper role has rights now though
like what
close question channels
need a hint on help-20 pls
anybody know if this paper is legit? Looks like it proves the remaining unknown Moore graph does not exist, the one with degree 57 and diameter 2. If so the wikipedia page for moore graph needs to be updated, as it's no longer an open problem. https://arxiv.org/abs/2010.13443
Have you checked if this paper has been submitted/accepted for publication anywhere?
this is beautiful
...
you have role pings disabled don’t you @neat lintel
nope
how many pings do you get a day
is there any way to think about $\int \frac{f(x)}{dx}$?
gmod
No clue, but the person has a Math net ru page and it seems pretty extensive.
Yeah, you're dividing a function by a differential form to get section of the tangent bundle, but you can't integrate that kind of thing
alright thanks
anyone mind answering this question for my data project?
How Much Phone Screen Time Do You Have per Day? (In Minutes)
and
How Much Computer Screen Time Do You Have per Day? (In Minutes)

Thanks ShatteredSunlight, yeah it seems like the author is legit
fortnite
This might be heresy, but is there anyway to get a role where the help channels are inaccessible/not visible?
you can also tick the "hide muted channels" in the server settings and hide them.
but you will have to manually hide each channel and can't just hide the category
computer time -> infinity
0.2103495009000539124852931855 minutes (how long it takes me to turn my alarm off in the morning and turn it back on at night, measured using an atomic clock)
3.419 * 10⁵² minutes (measured using observations from a collection of telescopes around the earth's orbit, time dilation effects unaccounted for, accuracy subject to atmospheric effects)
you're welcome
thanks

not the atmospheric effects
no don’t ask pls
i will, i am sorry, they left me no other choice, i want my family back ...
anyways
lets see
when we say complex numbers
do we mean the unreal numbers, or real numbers + imaginary ones
Only imaginary numbers
Ig
what we would we call the set that contains real + complex numbers
would it be computable numbers?
complex numbers are in the form a + bi
You'd call it the complex numbers
so you could say real number + imaginary
No, a + bi is a complex number
yea
it has a real ‘part’ and imaginary part
where a is the real component and bi is the imaginary one
Complex = imaginary
oh that make sense
It's complex
yea
yeah its kinda confusing
based on what i understood, complex can be non real, while imaginary has to be non real
yea?
yeah, that checks out
Ah ic i acc didnt know that lol
0 is imaginary probably
Yeah, in a+bi, you say the real part is a and the imaginary part is b
it is also real
Ik just thought complex and imaginary were the same smh
ultimately it doesnt matter though, i have never encountered a reason to consider purely imaginary numbers
Ah gotcha
yea ig it's easy to think that
I know complex numbers have actual applications but I guess imaginary numbers don't?
the imaginary numbers are just another copy of R inside C
They have applications
Qm, qft
is there a name for the set that contains algebric + non algebric numbers
yea it's used as a complex number
or would we just go with complex
every (complex) number is algebraic or not algebraic, so ...
number isnt really a well defined term
then, infinity?
no
Infinity is not a number
what even makes a number?
is it the "value"
because imaginary numbers dont really have that known concept of values
yet they are considered numbers
well
i would define a number to be an element of a skew field
numbers are things you can add, subtract, multiply, divide (with an exception of division by 0)
make sense
also, lets say a graph, with a curve, we made sure that each Y has no more than one X
does that mean that this graph has a function ?
it means that the curve is the graph of some function
(in absence of any other disqualifying information at least)
damn, theres like an infinit possibilities of graphs, didnt expect each of them has an functional expression
oh for real?
lol
didnt know that
so basically, if i see a graph, that doesnt mean it has a formula?
wow
yeah just draw some squiggly line, that squiggly line doesn't have a formula that's exactly equal to it at all points
though you can find formulae that approximate any graph arbitrarily well @real sigil
yeah i guess you can aproximate a formula for every curve you see
you can actually prove that you can for reasonable curves, ie. all the ones you could draw without picking up the pen
it sounds quite weird to me how you can formulate every curve
well, you can approximate any function with a polynomial as well as you want, so that lets you formulate any curve as close as you want
i can't really explain in detail since you don't know calculus
sadly
the main idea is that you can approximate any function with a piecewise linear function
basically a bunch of small connected lines
by making the lines small enough it approaches the function
then you can approximate the piecewise linear function by a polynomial as well as you want, so overall you're approximating any function arbitrarily well by a polynomial
so we transform the curve into tiny lines?
like old people used to do to circles in order to calculate their perimeter
yeah exactly
in that case, is it easy to make a formula for those lines?
well it depends on your definition of "formula", you can get a piecewise function that describes those lines
it would look something like
$$
f(x) = \begin{cases}
m_1x + b_1 &\text{ if } x \in I_1 \
m_2x + b_2 &\text{ if } x \in I_2 \
\vdots \
m_nx + b_n &\text{ if } x \in I_n \
\end{cases}
$$
uli
i've named the intervals $I_1, \dots, I_n$
uli
so we basically cut the function into a lot of tiny bits that are very close to being linear
yeah thats one of the main ideas in calculus
if you zoom in closely something is linear
then if you take lots of those linear guys and add them together you get the function
this cant possibly contain all of the graph, but will sure makes it alot easier to understand
makes sense
you're not capturing the function exactly
rather forming a sequence of approxmations
that can approximate the function arbitrarily well
yeah its sad how this is the best thing we can do
ill try to invent a computer that can make formulas
gimme a good 15 yaers
well
and aloooooot of patience
forget functions
there are real numbers that don't have formulas
in fact "most" of them don't
the argument is really simple
computable numbers 
there's only a countable number of formulas, but uncountably many real numbers
yeah theres like a ton of nonfinite numbers with no formulas to represent them whatsoever
infanct its an infinit amount of numbers
do you know what countable/uncountable means?
i guess?
countable means it has some sort of representation
like sqrt x or cos x or something
countable means you can enumerate them all, the natural numbers are countable since 1,2,3,... enumerates them
uncountable means you can't
the natural numbers, integers and rational numbers are all countable
oh so we are talking about decimal numbers and non decimal
words in a finite alphabet are countable
you can enumerate them by listing first all 1-letter words, then all 2-letter words, etc
every word will be eventually listed
the way I like to think about it is every computer program can be represented as a finite list of zeros and ones, therefor they are countable
and since the real numbers are uncountable there must be real numbers that cannot be calculated by programs
what are examples of something uncountable
it pains me to say that i dont cognize what that is
the real numbers, the set of all infinite binary strings 00010101... (which is equiv to reals in base 2)
is countable and uncountable a state of one single number or a set?
it is a property of a set
in that case, no set is actually countable
right?
because they have equally infinit amount of numbers

well maybe not equally
"uncountable" is in a rather precise sense a "larger" way for a set to be infinite
the set of natural numbers, while infinite, is not very "large"
when were cardinal hierarchies invented? gotta be 1910s
two infinite sets are said to have the same size if you can map one to the other and back again in a 1-1 fashion
the idea of uncountable sets probably comes from 1700s
the infinity provided in the amount of numbers of the natural set
should be smaller than the
infinity provided in the amount of numbers of the rational set considering it has the same numbers + more
am i collecting you this way?
actually maybe 1800s
funny that's actually not true
how come lol
they're actually the same "size"
.
there's as many natural numbers as there are even numbers
and as there are rationals
but less than there are real numbers
but there's as many real numbers as there are complex numbers
this is weird lol
they all make sense once you see the proofs/reasoning
its like we are no using the same constitution in different comparisons
it is a finicky notion
ok i get whats before this, but what changes exactly so that real numbers are said to have more numbers
hard to say "what changes exactly"
cant we still do a 1-1 fashion in between real and natural?
no
too many, that's the problem
we don't have enough natural numbers
so maybe to motivate this a little
there's this thing called the pigeonhole principle
so basically, this theory (rule) indicates that infinity is equal to infinity, but only in some cases
where if you have n+1 pigeons and n holes then two of the pigeons have to get comfy 
if you have a function f : X -> Y, where X and Y are finite sets, with, say, m and n elements respectively
if f is surjective, then necessarily m <= n
if f is injective, then necessarily m >= n
if m <= n, then there exists a surjective f, and if m >= n then there exists an injective f
this is why we use surjections and injections to talk about "sizes" of sets
because these generalize beyond the finite case
albeit you lose some things
e.g. an infinite set can inject into a proper subset of itself
surjective means every y has an x with f(x) = y
but this is why, generally, when we ask, is X a larger set than Y, we are really talking about whether there exist injections/surjections between X and Y
and injective means f maps every x to a unique y
so if we represent X with natural numbers, and Y with real numbers, we would have F (x) = y being an injective function
?
we could come up with an injective function yes
you can form an injection from N -> R because the size of N is less then R
but we wouldn't be able to come up with a surjective one
but you cant form an injection between N and, say Q?
yes you can
you can
this "function" we are using, can it be any type of function?
you represent the rationals in a square then you take the diagonals to get a list [r1,r2,...] of all the rationals
since any rational number is somewhere in the square, say at (x,y) you have the rational number (x/y) then eventually it is in our list
since we made a list you can make a function from a natural number to that element in the list f(n) = r_n
bing bang there's your surjection
so basically, this shows how clear it is that Q contains N
no, see this
"contains" doesn't mean much when it comes to size
it shows we can find a map from N to Q that "hits" every rational number
this is precisely what I meant when I said
[8:48 PM] mniip: e.g. an infinite set can inject into a proper subset of itself
so this is a surjection
sure
do we not have a surjection when it comes to even numbers To whole numbers?
we do
but still he said theres as many natural numbers as there are even numbers
wait my bad i meant natural
you can build a surjection both ways
so they're more-or-equal than eachother
i.e. equal
yeah so if we show N is more or equal to Q (the rationals) then they must be the same "size" since N is in Q so N is also less then or equal
no its not a problem if you show a >= b and b <= a then a = b
"equal" refers to our invented notion of equal size
but we already know that N=/= Q
you're confusing set equality with cardinality equality
N is not Q but their size is the same
since you can map N -> Q and Q -> N in a 1-1 fashion
is there somehow a dependable term that is exactly like sur/in jection but does not include "equal", making it absolutely bigger/smaller than the given value
well if you had >= and != then you get >
(greater equal, and not equal implies greater then)
so what is the function surjection helping us prove here? if it isnt for determining the > or <
its kind of null how we go back to = from >= and <=
do you know what a bijection is?
its basically an invertible function
ie. surjective and injective
like, the amount of X = Y
yeah thats it
for finite sets it makes sense, since {a,b,c} and {1,2,3} can have the mapping f(a) = 1 ... etc
now for infinite sets it gets tricky, but this is the definition of size we're using
listing the integers as [0, -1, 1, -2, 2, ...] gives us a function from N to Z that's bijective
therefor size(N) = size(Z) by our definition
a similar thing can be done with Q by taking diagonal slices
isnt every infinite set-contained function bijective?
as either >= or <= will deliver us back to = which bijection
not either, you need both
yeah...
wdym "infinite set-contained function bijective"
ah
1 sec lemme show you the proof that R is uncountable
meaning it is not bijective with N
basically, suppose f : N -> R is bijective
we can represent each real number as an infinite decimal (rationals become 0.400000000000...)
then we flip every digit in the diagonal creating a new number
since we flipped the first digit it is not equal to the first number, since we flipped the second digit it is not equal to the second number...
our new real number cannot be in the set
by construction
therefor f is not bijective and so R is uncountable
https://youtu.be/elvOZm0d4H0 is a good video if my explanation is bad
Sometimes infinity is even bigger than you think... Dr James Grime explains with a little help from Georg Cantor.
More links & stuff in full description below ↓↓↓
Minute Physics video on this topic http://www.youtube.com/watch?v=A-QoutHCu4o (somewhat more fast-paced... but we did film ours BEFORE his was uploaded, so similarities are coincident...
f : n -> R is not bijective, meaning R is absolutely bigger than N
can we prove also that Q is asbolutely bigger than N?
no, card(Q) = card(N) but card(R) > card(N)
since we can find a bijection from N -> Q by taking the diagonals of
given that q=n, then r>q
yes
oh makes sense
so R is the bigger one, whilst the ones below it are equally equal to each other
yeah
damn thats an interesting way to validate it
actually it gets hairy, there might be infinities between N and R
wdym infinities
that was a famous problem in math
like, a set A with card(A) > card(N) but card(A) < card(R)
In mathematics, the continuum hypothesis (abbreviated CH) is a hypothesis about the possible sizes of infinite sets. It states:
There is no set whose cardinality is strictly between that of the integers and the real numbers.
In Zermelo–Fraenkel set theory with the axiom of choice (ZFC), this is equivalent to the following equation in aleph numb...
it turns out it's independent, ie. there might or might not but either way we'll never know since our axioms are not strong enough
or: you can assume its true or its false and it doesn't effect anything
i think the safest choice is to assume bijection
if its not right then its not wrong
no?
i'm not a logician so idk ¯_(ツ)_/¯
yeah i get it
there are also sets larger then R
theres a theorem that the set of all subsets P(A) is always larger then A
so the set of all sets of real numbers is a bigger infinity then R
the set of subsets
like the sum of whats inside R
this looks kind of weird but ok
in fact P(N) = R which kind of makes sense if you consider decimal expansions as lists of natruals
is what
|P(A)| > |A|
this is a strict inequality
youll never have |P(A)| = |A|
in the finite case, it turns out that |P(A)| = 2^|A|
this isnt hard to justify with elementary combinatorics.
i think so, yeah
(though formally speaking, such a justification is probably circular... but meh)
proof by thinking: for each element of A we could include it or not include it in the subset, that's 2 possibilities for each element of A so 2^n possible subsets
i mean i guess you can justify it as long as |P(A)| = 2^|A|
well, that doesn't work in the infinite case
basically another contradicty boi
also why tf does wikipedia use xi for an element of A 
thats pretty random lmao
suppose $f : A \to P(A)$ is surjective, and consider $$B = {a : a \notin f(a)}.$$ there must exist an $a \in A$ with $f(a) = B$ since $f$ is surjective, but this causes a contradiction since $a \in B = f(a)$ contradicting the construction of $B$ which implies $a\notin f(a)$
uli
surjection usually cause thus kind of paradox
thats why we take bijection for infinit sets
bijections are just 2 directional surjections
(assuming the axiom of choice)
(its phrased using injections, but you can just flip the arrows of an injection to get a surjection)
the paradox is what makes f : A -> P(A) impossible to be bijective
yeah its meant to simplify it
I could have assumed f was bijective as well since bijective implies surjective
obviously lol
What are some interesting/cool facts or properties of Lagrange Polynomials?
They were not discovered by Lagrange but instead by Edward Waring
They can be used to give very high order numerical approximations of integrals (see Gaussian Quadrature)
Is it just me or can they be derived by using cramer's rule on a vandermonde matrix system
That sounds very interesting, thanks!
A matrix of matrices
a matrix of matrices of matrices
a matrix of matrices of matrices of matrices
we now just invented “infinite matrix composition” cool name huh?
M[(a(b(c(d(e……….if there were infinite letters in the alphabet)))……)]
how about matrix cat transposed
really tho, can we have a matrix in a matrix?
Yes ! You can look at matrices with coefficients in any ring
And there exists a lot of rings of matrices
Any commutative rings* (I don't know otherwise if it works well)









