« first day (2440 days earlier)      last day (2595 days later) » 

3:00 PM
it is $c(b^2 + a^2) = 3a$
 
Are you guys busy?
 
Hello
 
(c)a^2 - (3)a + (cb^2) = 0
 
Hi
 
Δ_a = 9 - 4c^2b^2 = m^2
m^2 + 4c^2b^2 = 9
obviously m = 3 and b=c=0
wait
 
3:02 PM
I'd read a midsummers night dream by hamlet @ItiShree
 
Anyone here who can help with a probability exercise?
 
@AlessandroCodenotti just ask
 
Is it good for concept building?
@Dod
@Dodsy
 
@ItiShree no unfortunately not :)
 
@BAYMAX does it have any non-trivial solution?
 
3:05 PM
I had a dream about systems of equations last night
 
Hello everyone!
 
I want something which would strong my base in quadratic equations, I know most of the general things but haven't really read any international authors books so I am asking for some advice on there .
 
oh, b=0 or c=0 @BAYMAX
 
@DHMO This is the first time I've seen you in, like, forever
 
@Daminark ya, i already forgot what language each person here speaks
 
3:06 PM
Actually it is a part of a problem in abstract algebra
yes@DHMO
c cant be 0
 
Gutenmorgen
 
@BAYMAX
(c)a^2 - (3)a + (cb^2) = 0
Δ_a = 9 - 4c^2b^2 = m^2
m^2 + 4c^2b^2 = 9
obviously m = 3 and (b=0 or c=0)
@Dodsy guten Tag
 
No its the morning
 
@BAYMAX if c cant be 0 then m=3 and b=0
@Dodsy i can't use guten Tag to respond to guten Morgen?
 
Oh hhahahahaha
 
3:07 PM
Do anyone know where I can get help/ suggestion on the topic?
 
It is quadratic in a and when we write the solution for a , in the denominator comes c
 
ich dachte, dass "guten Tag" fur die ganze Tag ist
 
Ich bin unhoflich
 
@BAYMAX you're right
 
wait @ItiShree
 
3:08 PM
Yes? @BAYMAX
 
@Iti Just invoke solvability of $S_2$ and you're done!
 
I may be some help but wait a bit!
@ItiShree
 
@DHMO Wo bist du in Germany?
 
@BAYMAX so a^2c = 3a
 
Ok @Baymax
 
3:09 PM
@Dodsy ich bin Deutscher nicht
 
Oh I see
 
@BAYMAX and the question becomes trivial
 
I have a random variable $X$ which has a standard normal distribution and another variable $Y$ defined as $Y=\begin{cases} X\quad \text{ if }-1\le X\le 1\\ -X \quad \text{ if }|X|>1\end{cases}$. I'm asked to show that $Y$ is also a standard normal and then to discuss $X+Y$
 
a(ac-3) = 0
a = 0 or ac - 3 = 0
a = 0 or ac = 3
(a,c) = (0,x) or (1,3) or (3,1) or (-1,-3) or (-3,-1)?
 
so ac = 3 implying a=1 c = 3 , a =3 ,c =1
yes
negatives too
 
3:11 PM
I did the first part, but for the second I get a weird distribution, while a sum of Gaussians should be Gaussian again
 
how is Y also a standard normal?
 
You are right dhmo tag is for the day, I thought you were correcting me
 
I was just kidding, but really I mean, it seems like the main important thing to keep in mind are same canonical factorizations, like $n^2x^2 - m^2y^2 = (nx+my)(nx-my)$ and all that stuff, plus quadratic formula. Like, that's about all I ever use in quadratics @Iti
 
That is why I said 'I am rude'
 
@Dodsy lol
 
3:13 PM
@Daminark
I know but I am preparing for an entrance test and they ask some really weird question on it which require more knowledge and then I thought that I need to brush my skills on these two particular topics.
 
Well, do they just ask you to solve a bunch of them or does being able to solve them not suffice?
Hey @Mike!
 
How's it going?
 
ok you heard of Cengage publications @ItiShree
 
@DHMO if you calculate $\Bbb P(Y\le t)$ you get that is equal to $\Bbb P(X\le t)$ so they have the same CDF
 
3:23 PM
I see you are in senior secondary perhaps!
 
@AlessandroCodenotti well i'm out of this
 
I have a question about how to use a computer to make mathematical calculations. Is that on-topic?
 
@ItiShree after googling,and as per your requirement there is an answer in Quora - quora.com/Which-book-is-best-for-quadratic-equation-for-IIT
well there are many inbuilt calculators and for more scientific treatment you can use softwares like mathematica,Matlab,geogebra,Sage etc@ahorn
 
@BAYMAX Yes, after majoring in maths last year, my pencil and Wolfram Alpha are not helping me.
 
try sage for free!
 
3:33 PM
Okay
 
for plotting , I saw many MSE friends using Desmos !
In Z[i], 3 is irreducible but 2 and 5 are not?
any1
I tried writing 3 = (a + ib)(c + id)
but ?
 
That's correct
 
In number theory, a Gaussian integer is a complex number whose real and imaginary parts are both integers. The Gaussian integers, with ordinary addition and multiplication of complex numbers, form an integral domain, usually written as Z[i]. This integral domain is a particular case of a commutative ring of quadratic integers. It does not have a total ordering that respects arithmetic. == Formal definition == Formally, the Gaussian integers are the set Z [ i ] = { a + b i ...
A Gaussian integer a + bi is a Gaussian prime if and only if either:

one of a, b is zero and the other is a prime number of the form 4n + 3 (with n a nonnegative integer) or its negative −(4n + 3), or
both are nonzero and a2 + b2 is a prime number (which will not be of the form 4n + 3).
 
@BAYMAX it's probably easier to show that 3 is prime
 
@AlessandroCodenotti but 2 and 5 are primes also
 
3:46 PM
Not in $\Bbb Z[i]$
 
Hey guys, there's this kind of odd topic I'm reading about, can anyone help me on this?
 
Depend on what the topic is :P
 
Analytic and algebraic topology of locally Euclidean metrization of infinitely differentiable Riemannian manifold
 
I know someone who can help you, and Nikolai Ivanovich Lobachevsky is his name
 
yes @AlessandroCodenotti 3 =3.1 and 3 divides 3 or 1 , so 3 is prime implying irreducible ?
 
3:47 PM
See you, just remembered of an important appointment
 
I'll talk to my friend in Minsk, I guess
 
@BAYMAX you need to show that this holds for all products
 
@Balarka I appreciate that you know this song
 
Do you know that $\Bbb Z[i]$ is a UFD?
 
@Daminark Tom Lehrer is my favorite
 
3:48 PM
yes
have to ponder but!
 
@Daminark Doing alright. Yourself?
 
Ok, in a UFD you have prime iff irreducible
 
Nice, I only so far have seen the elements song (which I memorized in 7th grade science for extra credit) and this one
@Mike I'm doing pretty well, thanks!
 
ok
so how do we show 3 is prime in $Z[i]$
 
@AlessandroCodenotti then it's just circular
 
3:50 PM
ok @AlessandroCodenotti bye.
 
there was a good quanta article on UFDs a couple weeks ago
 
@MikeMiller 3 is prime in $Z[i]$ ?
3
Q: Prove 3 is prime in the ring $\Bbb{Z[i]}$.

Meitar AbarbanelI am not sure what is the right phrase for primes in some ring. The definition I was gave is that in a ring $A$, $p\in A$ is prime if $\forall x,y \in A$ such that $p\mid xy$, $p\mid x$ or $p\mid y$. I don't know how to start.(I arrived at odd expressions but too long ones) and it is complex fo...

 
I don't care to do homework.
 
@BAYMAX i was joking to avoid answering @dami
 
gasps
2
 
3:55 PM
ha :)
 
Whose friend in Omsk has friend in Tomsk, with friend in Akmolinsk!
 
Oh @Alessandro have you ever heard of the theorem which says that every Borel game is determined?
@Akiva YES
 
The latter of which is apparently Astana now?
 
what is that BTW?
 
Whose friend in Alexandrov, has friend in Petropavlosk, whose friend is now working somehow on the problem in Dnepopetrov
spelling's all messed up
 
3:57 PM
@BAYMAX Tom Lehrer song
"Lobachevsky"
 
nice@AkivaWeinberger
 
I came across this song because someone showed me this subreddit called Youtube Haiku, in which I found a video called "the dankest jump"
Showed it to a friend, and then he sent me the song
 
Pleasurize!
 
@Daminark vaguely
Ok, @BAYMAX I changed my mind, let's show that $3$ is irreducible
Suppose it's not, then $3=ab$
 
yola
 
4:01 PM
So $|3|=|a||b|$
 
yes
 
That is $9=|a||b|$
 
ok
 
Hi
 
hola@MeowMix
 
4:03 PM
Hi
 
hola@Fawad
 
So assuming this factorization contains no units we have $|a|=|b|=3$
 
@BAYMAX hola
 
@Alessandro We briefly mentioned it last class, since we were talking about game topologies (in our homework I think we're gonna get that the binary game is homeomorphic to the Cantor set)
 
Which is the same as saying that $3$ is the sum of $2$ squares, which can't be since squares are congruent to 0 or 1 mod 4
@Daminark ah, sounds interesting, which course is this?
 
4:04 PM
Analysis
 
How do I find x in this equation: wolframalpha.com/input/… ?
 
3 is the sum of 2 squares?
 
Our professor is doing things in what I expect is somewhat non-typical, but which I enjoy
 
If $a=b+ci$ then $|a|=b^2+c^2=3$
 
ohk
 
4:05 PM
@Daminark yeah, that seems like a strange choice of topics, but I like it
 
@ahorn it's a quadratic equation
 
This was more of a side track while we were talking about Banach-Mazur, which I imagine we're going to use next to do stuff about typical functions
Next week we'll do Lebesgue integration
 
@DHMO ok I'll look at it, but why won't WA just give me the answer?
 
Did you do some measure theory already?
 
It should be noted that, in reality, Lobachevsky was a fine mathematician and not a plagiarist at all
 
4:08 PM
@ahorn no idea
 
Hi @Akiva
 
How did your paper go?
 
I probably know the first half hour of a measure theory lecture
Song kinda did starting talking about sigma algebras and additive functions in order to state (without proof) Lebesgue differentiation, which he used to do change of variables
 
@MeowMix Not yet finished
Have you read Death of a Salesman?
(Or seen, since it's a play)
 
4:10 PM
I haven't
What's it about?
 
about the death of a salesman
 
Also @Meow have you seen Lobachevsky?
 
@Daminark So you'll have some measure theory before Lebesgue integration I guess?
 
@Balarka I shouldn't have been as amused as I was by your comment
 
It works even better with a serious, grim face
 
4:13 PM
And @Alessandro I actually meant to say Lebesgue measure
:P
 
which I unfortunately can't produce on this chatscreen for obvious reasons
 
He does die at the end. Spoiler alert.
 
Spoiler Alert: Everybody here dies sooner or later
 
Lol that reminds me of this one scene in asdfmovie where someone's holding a gun to someone else's head like "You're gonna die"
Response: "We're all gonna die"
 
@Daminark ah, I see
 
4:14 PM
Hey, it says "Hey, it says gullible on the ceiling" on the ceiling
 
I think measure theory is interesting, but the proofs are headache inducing
 
"Hey, there's something on your face!" [punch] "IT WAS PAIN!"
 
there is a movie based on him?
 
On who?
 
*On whomst'd've'ff
 
4:16 PM
Sir Lobachevsky
 
Doubt it
 
Have you guys heard of Yksvehcabol Ris?
 
the only modern play I have read is Waiting for Godot, and it amuses me a lot in answering questions like "what's it about?" with "it's a story where nothing happens".
 
@Alessandro Well, gonna get ready for that. Last year's group didn't spend much time on it though
 
4:17 PM
and can I ask for IPA or some equivalent
 
Neither have I
 
Did some stuff on outer measures, Caratheodory extension, Radon measures, Lebesgue measure, and then gets to integration
It does do a bit on these things called Vitali and Besicovitch coverings, along with density, which I've heard falls under the realm of a subject called "Geometric Measure Theory"
 
2 = (1 +i)(1 - i) so not irreducible in Z[i]@AlessandroCodenotti ?
5 = (2 + i)(2 - i), so not irreducible in Z[i]
 
Hm, I see, we took a long detour in measure theory and defined what it means to integrate with respect to a generic measure and then got to the special cases of the Lebesgue and Hausdorff measures
@BAYMAX correct
 
4:20 PM
It's tricky to say, the trajectory of the quarter is definitely not your standard Folland-based analysis class
 
Ah by the way @Baymax do you see that my proof for $3$ actually works for every prime of the form $4n+3$?
 
I missed that actually , thanks for pointing out!
@TedShifrin returns!
 
Nope. Fake.
 
Fake?
 
Hi @Alessandro, Demonark, DogAteMy, Zach, Baymax.
 
4:23 PM
@Alessandro One of my books, Lang's Real and Functional Analysis, actually does integration of Banach space-valued functions, did you ever see that?
Oh hey @Ted!
How's everything going?
 
@Daminark nope, we'll do more Banach spaces stuff next year
Hi @Ted
 
Hi @Ted
 
Greetings @TedShifrin, missed me ? Or more accurately, missed my questions ? :D
 
Oh, look, it's Mahmoud!
 
4:27 PM
any good collection of measure theory questions? any where?
yeah excercises of Royden are nice!
 
@Alessandro Makes sense, honestly if there's one thing I don't get about this class, it's that they don't just teach measure theory/integration first, it seems like there's a lot you just can't do without it in functional
In abstraction it's not a problem but basically the first half of our functional was toying with $\ell^p$ spaces, and I'm pretty sure we would've had time to do more stuff if we had $L^p$ spaces and stuff like dominated convergence
 
Lp spaces are nice and they lead to Functional analysis!
 
@Ted So, I have another metric question
Actually, nevermind
 
We defined $L^p$ spaces in abstract and then looked mostly at $L^2(-\pi,\pi)$ with the lebesgue measure to get Fourier series
 
Zach, did you ever show that limit we were discussing, that $\lim\limits_{p\to\infty} \|x\|_p = \max\{|x_i|\}$?
 
4:37 PM
What'd you do with Fourier analysis? I've only ever seen Fourier series as a neat trick for physicists and, as @Baymax said, the isoperimetric inequality
 
Hi Nate
 
Hey Zach how's it going?
 
@Ted Sorry, I haven't
 
heya Nate
 
@Dodsy Nothing much, just playing some word games.
How about you?
 
4:39 PM
Hey Ted how are you today?
 
Not much, we just showed that they exist because of this nice basis of $L^2$, that they converge in the $||\cdot||_2$ norm, that they converge pointwise almost everywhere and then a few tricks calculating the exact values of some series with them
 
Taking care of my nephew with my mom :)
 
How old is he?
 
2
He's a handful, that's for sure.
What word games are you playing Zach?
 
4:41 PM
BombParty
 
Never heard of it! I play chess or NHL when I'm not doing homework or sleeping :)
 
Heh, a Canadian into hockey.
 
CHEMISTRY, Nate.
 
Yeah what are the chances!
 
If you'd like, you can join.
 
4:43 PM
@Nate I see you're associated vaguely with chemistry
 
Ted you never told me what you were up to today! I can't leave yet!
 
Nice excuse.
 
It's true. I hate chemistry but am bound to it by academic endeavours. I need to finish by the 21st and I have two more 'units' left to complete. A unit contains roughly 16 hours of work and can be completed in two days.
 
actually there was an article by AMS on Fourier series ,I am unable to get it now but you can search,@Daminark , it was a nice collection!
 
Tomorrow is my birthday!
 
4:45 PM
@Dodsy Oh, the big 18? 19?
 
I should be allowed to slack red
The big 23 zach
But I decided I'm going back a year this year.
 
Demonark: I strongly recommend the book on Fourier Analysis by Körner. Fabulous.
 
OH
 
So I'll be 21
 
I'm sure @Ted would like to go back to 21
 
4:46 PM
then the book must be fabulous!
 
Hmm, probably not, Zach.
 
Hahahaha
 
Alright, I'll check it out for sure!
 
I'll be 27 when I've finished my undergrad!
I'll be an old man!
 
Yup, three feet in the grave.
 
4:47 PM
:)
 
room chills
 
And one in my mouth already
A foot that is......
 
I might go play some chess.
Or take a nap.
 
you've surely heard that saying before right guys?
Am I saying it wrong
 
I've heard that
 
4:51 PM
oh good I thought it was some weird Canadian saying
 
Tell me aboot it.
 
@TedShifrin so what are you up to today what are your plans are you writing a new book or discovering a new physical law or inventing the cure for cancer?
Low blow Zachary!
 
I think he's busy teaching kids and working on his back pain
 
That sounds about right
 
Have you thought about the hyperbola problem, Nate?
 
4:52 PM
I will!
Want to play a game of chess ?
 
Sure. We can talk about it there
And that will keep me up instead of taking a nap :P
 
Zach, what even is your sleep/nap schedule?
:P
 
On the weekends, like 0:00-11:00
Then perhaps an hour nap in the afternoon
On school days, 23:00-6:30
and a 2 hour nap in the afternoon
During the summer though, like 4:00-14:00 with no naps
 
Military time!
 
During weekends I still manage to be tired as ever. But perhaps that's my eating habits
 
4:58 PM
@Daminark Was that you?
 
Yup
 
I found you suggested as Akiva is our mutual friend :P
 
$(1 + 3\sqrt{-5})$ is irreducible but not prime in $Z[\sqrt{-5}]$ ?
 
5:23 PM
@AlessandroCodenotti
 
Is it possible to show that $\lim_{n\to\infty}(1+1/n)^n=e$ by merely using $\begin{align}e=\sum_{k=0}^\infty\frac{1}{k!} \end{align}$ and the binomial theorem?
 
Perhaps
 
do you know some proof?
i don't want to use the following
$e^x=\lim_{n\to\infty}(1+x/n)^n$, because I haven't learned the definition of $e$ that way
 
there is a trick to $1^{\infty}$ form!
 
So zach there are no solutions for the x and y and when I graph it it does show an infinite number of solutions
So im now trying to prove that?
 
5:36 PM
Huh?
You want to find, with proof, all integer solutions
 
4x^2 - y^2 = 15
But there are an infinite number of integer solutions
 
No there ain't. :P
 
There are an infinite number of y values and x > -10 , < 10 x is not equal to -5 to 5
I guess I'll have to keep thinking about it
:)
 
If you need a hint, don't hesitate to ask.
 
@Sha I've seen a proof at some point in my life which uses $e$ as the unique number $x$ such that $\int_1^x \frac{1}{t}dt$
 
5:49 PM
@Daminark yea I think that's how my book defined it
but I don't have to use that right?
shouldn't it be possible to just take the limit of this binomial expansion?
 
It probably should work, like those define the same thing so clearly there's something
Somehow, though, I think that using log as an intermediate is somewhat nicer than directly playing with binomial series
 
yea well a fellow student tried to explain to me via whatsapp how to do it, and it's impossible to fellow without mathjax :P
oh right
but I'm almost there XD
if I could just take the limit, i'm there
because, by using the binomial theorem, I already have that $(1+1/n)^n$ is the $n$-th partial sum of the taylor expansion of $e$
 
What's preventing you from taking a limit?
 
well it'd be taking this limit:
$\begin{align}\lim_{n\to\infty}\sum_{k=0}^n\begin{pmatrix}n\\k\end{pmatrix}\left(‌​\frac{1}{n}\right)^n\end{align}$
 
You know the partial sums in the Taylor series converge to $e$, then you know that $\lim_{n\to\infty} (1+\frac{1}{n})^n = \lim_{n\to\infty} \sum_{k=0}^n \frac{1}{k!} = e$
 
5:56 PM
hmmm that's also true
 
Also hey @Steamy!
 
so I show that for each $n$, $(1+1/n)^n$ is the partial sum
 
ohi
 
(and hi Steamy!)
and therefore you don't really have to prove anything
 
Yup, and you would already know that the partial sums converge so you're done
 
5:57 PM
Hi @Steamy
 
expect state the fact that the limit of there partial sums evidently is the power series of $e$
haha nice :P thanks!
 
@Daminark $(1+1/n)^n$ is not the same as $\sum_{k=0}^n\frac{1}{k!}$
 
rip
 

« first day (2440 days earlier)      last day (2595 days later) »