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Huy
3:00 PM
@nablablah: What about it do you find poor?
 
@RandomVariable hehe, yeah, thanks! I was amazed to see that so many upvoted and didn't notice that. Indeed, that was pretty deceiving. Finally all looked so nice that no one spent time checking that. :-)
 
The general pedagogical methods of most of the professors I've had, the unwillingness of professors to help students, the excruciating limitations in courses that are offered (some classes the only offer one semester per every 2-3 years, and most of the classes offered that semester all happen at the same so you can't take more than one)
 
@nablablah I had a very bad experience too in my uni.
 
Huy
@nablablah: Things like these theoretically could occur in Europe as well. Some classes overlapping is very natural, I think.
 
The imbalance between higher-tier schools and low-tier schools here seem much more significant than schools around Europe
 
Huy
3:02 PM
@nablablah: How much is your annual tuition fee, btw?
 
Some classes overlapping is fine, but ALL of the classes?
@Huy It's free for me because I am homeless with no income
But in general it's a fortune
 
Huy
How much would it normally be?
Like 15k a year?
 
lol
No
Maybe double that on average
 
Huy
lol
:D
 
For good schools, closer to 50k
 
Huy
3:03 PM
Awesome.
Do you know how much I pay? :<
 
@Khallil I don't see any problem with that
 
@nablablah You mean school fees a year?
 
The tuition per year, yea
Not including other fees
 
@nablablah OMG, that is bad...
 
Huy
@WillHunting: Did you not know that? :o
 
3:05 PM
@Huy No. But I won't be paying that.
 
Huy
@WillHunting: Are you a fortune teller?
 
lol Huy can finally rest feeling like he's proven how shitty america i... oh damnit!
 
The only good thing is if you're like in the top 1% of students, you can get into schools like Harvard and MIT and they will pay for everything
 
@Huy Those are undergrad fees. I won't be doing undergrad there.
 
Huy
@MickLH: I don't need to prove it, it's a fact.
@WillHunting: I see.
 
3:06 PM
Oh, you see, huh? ;)
 
@Chris'ssis That typo :/
 
I would like to do grad school in Europe but I doubt any schools will give me funding
 
Huy
@nablablah: A friend at my uni will be going to MIT soon too and they pay for everything! \o/
 
@TheGame ?
 
Yea, it sucks for dumber people like me
 
3:06 PM
hehe I hope you know I'm in good spirits, @Huy, I just like playing with egos
 
@Chris'ssis The starred message
 
@nablablah I think the grad schools in US are pretty good.
 
worshsip
 
@Chris'ssis I am sure that my estimate is accurate to 8 places, but I haven't gotten much further towards a better asymptotic estimate.
 
@WillHunting They are, but I most likely can't get into them
 
3:07 PM
@TheGame ahhhhhh :-)
 
Huy
@MickLH: Don't worry, my ego is very healthy. :)
 
@nablablah But you scored A's last term!
 
My friend who was ranked #3 in the math program at UChicago (which is a top school) couldn't get into any of his choice schools
 
@Chris'ssis Also, what were you saying about me being offline ?
 
Huy
@nablablah: That is unfortunate. :(
 
3:08 PM
@nablablah Nobody says you have to go to Harvard.
 
@WillHunting If you want to specialize in a particular field, you'll pick particular schools
 
@TheGame When you're not here you're always logged out, right? :-)
 
Or change your field to something you don't like and go to a different school
 
Yep
 
@nablablah There are many good schools, you don't need to go to the top few.
 
3:09 PM
Well, sometimes I am on for some minutes after I leave @Chris'ssis
 
@TheGame I was wondering if you have a second account :D
 
There aren't many school choices for the topic I want to do
 
@Chris'ssis I do but I never use it
I only used my two alts once
 
Huy
@nablablah: Topic being?
 
@nablablah You can try changing topics too.
 
3:09 PM
Topos theory
 
They should be IntegralPicnic and Ramanewbie @Chris'ssis
 
@TheGame I see I see :D
 
@nablablah Oof.
Higher categories are pain in the neck
 
@nablablah I have no idea what that is.
 
Never studied.
 
3:10 PM
Most people I know are either in Europe or at the top top schools
So I'll probably have to specialize in something else but I haven't found anything interesting yet
 
Huy
@nablablah: Come to the ETH! :3
 
@WillHunting A category-theoretic version of topology, and that's all I know =P
 
@nablablah I'm in europe in a top school :D
@nablablah But I was born in Europe lol
 
I will most likely do fourier analysis or riemannian geometry.
 
@Huy You forgot the M
 
3:11 PM
@Huy ETH would be good for me but they probably won't give an international student any funding, especially since I'm nothing exceptional
 
Huy
@nablablah: You COULD consider starting to work if you considered coming here. :D
 
So I'd have to teach and work an extra job while also working on my dissertation? Not sure if I'd want to do that
 
Huy
@nablablah: I'm doing it and I'm by no means gifted.
 
Yea, I'll probably just stick to U.S. schools
 
@robjohn Yeap. I wonder what is the magical way of getting the precise limit there. That limit is so different from what I've seen so far ... I even ask myself if our knowledge allows us to compute it precisely.
 
3:12 PM
@nablablah Good, then I'll see you there, lol.
 
@Chris'ssis My approach is based on getting a better asymptotic approximation for $$\sum_{k=1}^n\frac1{n^2+k^2}$$
 
If I can't get into any schools I want or find a different specialization, I'll probably just quit math and start working
 
@robjohn Your approach is very nice. If no one beats you, my bounty goes to you. :-)
 
@robjohn You are up early, lol.
 
@Chris'ssis What question ?
 
3:15 PM
17
Q: Computing $\lim\limits_{n\to\infty} \Big(\sum\limits_{i = 1}^n \sum\limits_{j = 1}^n \frac1{i^2+j^2}-\frac{\pi}{2} \log(n)\Big)$.

Chris's sisIn the chatroom we discussed about the asymptotic of $\displaystyle \sum_{i = 1}^n \sum_{j = 1}^n \frac1{i^2+j^2}$, and if we think of the inverse tangent integral, it's easy to see that $\displaystyle \sum_{i = 1}^n \sum_{j = 1}^n \frac1{i^2+j^2}\approx \operatorname{Ti}_2(n)\approx \frac{\pi}{2...

 
@Mike Mystical greetings.
 
question eligible for bounty in 29 minutes
 
@Chris'ssis Why offer a bounty when you have an answer already?
 
@TheGame I have a problem for you.
 
@BalarkaSen What is it ?
 
3:18 PM
@WillHunting I need to know the precise limit there. I'm very curious about that, very very curious!
 
@TheGame Compute the center of $\text{GL}_n(\Bbb R)$.
 
@Chris'ssis Will this question be in your book as well?
 
What's the center again ? @BalarkaSen
 
@WillHunting It's far above my head.
 
@TheGame The centre is between the left and the right, lol.
 
3:19 PM
$\{z \in G | az = za \; \forall a \in G\}$ @TheGame
 
@WillHunting -___-
@BalarkaSen So basically I need to list all the invertible commutative matrixes ?
 
The elements which commutes with all elts of $G$, i.e.
@TheGame Mmhmm.
 
@BalarkaSen There aren't a lot :/
dat answer
 
That's not an answer, @TheGame
=P
 
I know :)
 
3:22 PM
And there are precisely $|\Bbb R|$ many of them. That is a lot.
 
$\aleph_1$
 
Yes.
$2^{\aleph_0}$. I don't believe in CH.
 
-___-
@BalarkaSen Hey wait
 
Already am.
 
I got an obvious answer (I think) but you will probably not accept it
 
3:24 PM
Fire away
 
Thanks, @Mick!
 
The center of $M_n(\mathbb{K})$ is $\{\lambda I_n\mid\lambda\in\mathbb{K}\}$ hence the result, as they are all invertible for $\lambda\neq0$
 
My copy of Marsden's Calulus II and III arrived, now waiting for volume I.
 
How, @TheGame?
Prove it.
 
@BalarkaSen How what ?
That's a property of the matrix ring
 
3:26 PM
That the center of $M_n(\Bbb K)$ are the scalar matrices over K.
@TheGame No prove it.
No sneaky answers.
 
-____- ok let me think of a stupid proof :D
 
@TheGame You misspelled think.
 
@WillHunting No I didn't ! (no, no i did not edit that >:0 liar liar)
:D
@BalarkaSen Uh so
 
@TheGame The evidence is in the pencil, lol.
 
@BalarkaSen They obviously have to be diagonal right ?
I don't have to prove that ?!
 
3:27 PM
who knows. i don't do noncommutative rings.
=P
 
@BalarkaSen Do they do you?
 
-__-
I meant, It's obvious for me, I just wanted to make sure you did not want me to prove it too @BalarkaSen
 
@BalarkaSen Very weird that Artin's Algebra only treats commutative rings.
 
OK, leave it if it's obvious. @TheGame
 
@BalarkaSen Well then
 
3:28 PM
@WillHunting Haha, no?
I like his approach
 
@BalarkaSen No?
 
@BalarkaSen Suppose you have a diagonal matrix with non equal coefficients
 
anabelianity is stupid
 
Like $a_{k,k}\neq a_{b_b}$
Then one can find a matrix which does not commute, once again.
QED
 
I didn't even get your proof but I trust it.
 
3:30 PM
eww
0
Q: Coefficients of Lagrange polynomials

The GameLet $n\in\mathbb{N}^*,A=(a_1,\dots,a_n)\in\mathbb{K}[X]^n$ all different numbers and $B=(b_1,...,b_n)in\mathbb{K}[X]^n$ all different numbers. Let $L_{A,B}$ be the polynomial verifying $\forall i\in[|1,n|],L_{A,B}(a_i)=b_i$. We know that this is a Lagrange interpolation polynomial and can be wr...

:/
 
Haha someone even downvoted
 
nooo
Better :)
 
@Khallil I don't claim to have proven it, but I do enjoy hypergeometric manipulations and it all seemed to fall into place
 
question eligible for bounty in 2 minutes
18
Q: Computing $\lim\limits_{n\to\infty} \Big(\sum\limits_{i = 1}^n \sum\limits_{j = 1}^n \frac1{i^2+j^2}-\frac{\pi}{2} \log(n)\Big)$.

Chris's sisIn the chatroom we discussed about the asymptotic of $\displaystyle \sum_{i = 1}^n \sum_{j = 1}^n \frac1{i^2+j^2}$, and if we think of the inverse tangent integral, it's easy to see that $\displaystyle \sum_{i = 1}^n \sum_{j = 1}^n \frac1{i^2+j^2}\approx \operatorname{Ti}_2(n)\approx \frac{\pi}{2...

 
3:47 PM
Very nice question @TheGame but I ask you is the notation $[|1,n|]$ a common notation? I know that it means the set $\{1,\ldots,n\}$.
 
@SamiBenRomdhane I think it is
@SamiBenRomdhane However I am French, and we have many strange notations and names
 
@Chris'ssis I am working on getting a better approximation, Euler-Maclaurin doesn't work as is, but I may be able to adjust it.
 
@robjohn Great! :-)
 
Strange notations and names ? comme quoi? @TheGame
 
3:56 PM
@SamiBenRomdhane There are so many :) Like the Lagrange Identity instead of the Brahmagupta–Fibonacci identity, etc
 
At least it isn't strange for me since I studied in all my life with the french books but now yes in this site we feel that we are strange :-)@TheGame
 
@SamiBenRomdhane Are you french too ?
 
No I'm tunisian and we study the sciences on french language@TheGame
 
Oh I see
 
Who here knows some logic?
 
4:09 PM
I think I do
 
@TheGame: Are you familiar with Boolean Algebra?
 
Kind of.
 
0
A: Verify Demorgan's Law Algebraically

NickBy Complementarity Law, $$P + \overline P = 1 \space\text{ and }\space P \cdot \overline P = 0$$ (Note: I shall only be using $P + \overline P = 1$ as its dual is automatically true) First Law:: DeMorgan's $1^{\text{st}}$ law states $\overline{X+Y} = \overline X \cdot \overline Y$ It is suffi...

Am I right when I did this?
(I asked this question specifically to get a formal proof but I ended up making a rough proof from the complementarity law)
@TheGame: Is my answer right? If it isn't, do you have a better proof?
 
Seems true to me
 
Yay
Sometimes when I right proofs or answers, I have logical holes in them.
My answers are like swiss cheese.
They smell like swiss cheese too.
@TheGame: I'm not convinced I've written the best proof. Do you think I should put a bounty on it or do you think I should settle with my own stinky answer?
 
4:16 PM
Do as you want :) but yours seems fine
 
@TheGame maybe you're interested in getting the bounty I offered ... :-)
 
Uh :/
@Chris'ssis Nah i'm making a problem for you :)
 
@TheGame: why did @GitGud call the properties axioms? I call them laws. What do you call them?
 
@TheGame I prefer you to make some solutions. I'm already pretty busy with some problems. ;)
 
Axioms/laws
 
4:19 PM
@TheGame: Ah. So, this is a gender issue.
lol
@TheGame: Do you have any integration cheats?
Most integration problems look like they need some absurdly clever thinking to crack.
 
@Chris'ssis is 5.060 the beginning of a known limit ?
Do you any integration cheats ??
@Nick I'm not an integral pro
 
@TheGame: I'm not an integral beginner. I'm on level 0.
 
Level $i$ squared
 
That's a magnitude i cannot dream of.
$$\int \frac{\cos x - \sin x}{1 + \sin2x} \, \text{d}x$$
Is there a direct way of doing it?
 
$[|..|]$ is hipster notation, @TheGame
 
4:27 PM
I messed this up today. Maybe someone can tell me how I can not screw up in future.
@BalarkaSen: Greetings BalSensai
 
@Nick Ahem. Hello.
 
@BalarkaSen: Ahem. Scooby Dooby Doo
 
@Chris'ssis Any thought on $\displaystyle\sum_{k=1}^\infty\dfrac{Li_3(k)Li_5(k)\psi^{(3)}(k)}{Li_2(k)Li_4(k‌​)}$ and its extension $\displaystyle\sum_{k=1}^\infty\psi^{(3)}(k)\prod_{u=1}^m\dfrac{Li_{m+1}(u)}{Li_‌​m (u)}$ ?
 
That's ugly, @TheGame
 
@TheGame I'm not scared at all ... I only laugh at them :-)
 
4:29 PM
@Chris'ssis I know but i'm interested
 
@Chris'ssis: You must scare them by laughing.
 
@TheGame These must be some telescoping sums
 
@Chris'ssis $m\in\mathbb{N}^*$ is fixed
@Chris'ssis Oh I made a typo
$$\displaystyle\sum_{k=1}^\infty\psi^{(3)}(k)\prod_{u=1}^m\dfrac{Li_{2m+1}(u)}{L‌​i_‌​{2m} (u)}$$
Here
Not telescoping anymore
 
@TheGame lol, the first variant was funny :-)))))
 
@TheGame You made a typo again
 
4:32 PM
@Chris'ssis The first one was totally relescoping -__-
@BalarkaSen Where ?
 
Li on the denominator.
 
@BalarkaSen Check the LaTeX source, it's a rendering issue I think
 
Oh right probably
 
@TheGame: It's hilarious. It cost me 6 marks out of an otherwise perfect score.
 
@TheGame in general I find you a funny person, you often make me laugh. :-)
 
4:34 PM
@Chris'ssis Thanks :) Any idea on the sum though ?
 
@Chris'ssis 16 year olds are funny in general.
 
@Nick Want the answer ? :P
 
@TheGame As I told you, at this moment I'm working on something else. I'll try them later on.
 
Ok
 
@TheGame I hope they lead somewhere ... not just some deadends ... :-)
 
4:36 PM
@TheGame: No. Ofcourse not. I just want some floating bananas to swim ashore. (I mean I just want the key to opening the door to the answer)
 
@Nick Here you go
@Nick What is $1+\sin(2x)$ ?
 
@TheGame: $(\sin x + \cos x)^2$
Yup. That does it.
:D
 
elelele
There you go
Finished
 
I hate it when I need to use my brain.
 
:D
@Nick Bananas always help
 
4:44 PM
@TheGame: ... You obviously have never slipped on a banana peel.
 
@Nick Oh, you mean the one I threw before your feet last time ? :D
 
@TheGame: Charlie Chaplin, Is that really you?
(It's so sad that I confuse the names of people with the same moustache)
 
Hehe
 
Hi people, I have a question about random vectors and noise... Could you lend a hand?
 
Ask first :)
 
4:50 PM
So, please don't take it as a spam, but take a look here!
Please put some thought on it because I'm really confused!
Is this for me?
Thanks!
 
@nullgeppetto: It's all I can give you.
 
In my country this gesture is very very insulting!
 
Huy
@Khallil: sup.
 
... This is the internet. You are no longer in your country. Here, it is a peace offering.
 
Fair enough!
 
4:53 PM
afk
 
(Are there any Japanese fellows in this room who would be offended if I upload a picture of raised eyebrows?)
@nullgeppetto: Apologies anyway.
 
@Nick, no worries at all! Just kidding! My problem is much more significant (for me) now!
 
great
afk
Good night :D
 
:) sleep tight!
 
5:08 PM
back
 
Huy
Welcome back, @TheGame.
 
Hey, @Huy. ^_^
 
Huy
What are you up to these days, @Khallil?
 
Oh, I didn't go down the hypergeometric route. I simply integrated by parts and did some integrand rearrangement, @Mick.
I've been playing a lot of the new Naruto Ultimate Ninja Storm game, @Huy.
How about you?
 
Huy
@Khallil: My pupils just took their first exam with me and will get it back on Friday. :3
 
5:19 PM
What did the exam test, @Huy?
 
Huy
@Khallil: Factorials, binomial coefficient, binomial theorem and a bit of differentiation. =)
 
How hard was the exam, @Huy?
 
Huy
@rehband: I think it wasn't hard. But I don't think they would agree. ._.
 
@Huy :D
 
Have you got the questions with you, @Huy?
Hey, @rehband. What it do?
 
Huy
5:21 PM
@Khallil: I do, but most of them are in German.
 
Nein! This is unacceptable!
 
@Huy Let's hear them :D
@Khallil Yo Khallil. What it do? What that mean?
Danke
 
test $\LaTeX$
 
Question 2 looks decipherable. Is the task to prove the equality in the question by induction for all natural $n$ that are $\geqslant 2$, @Huy?
 
okay, so I suppose Latex doesn't work here?
 
Huy
5:23 PM
@Khallil: Exactly.
 
It just means what's up, @rehband.
It does, @Fujoyaki. Check out the starboard on the right.
 
@Khallil Nothing much, having some fruit and talking to strangers on the internet
 
I'll give the test a go, @Huy.
^_^
 
Huy
@rehband: So how would you judge it?
@Khallil: It should be really easy for you. :D
 
@Huy Who is this test for?
 
Huy
5:25 PM
@rehband: They will be done with high school in summer 2016.
So it's their second last year.
 
@Huy The test seems fair enough. :) We didn't do that type of stuff in high school though!
 
From Google translate, it looks ez pz lemon squee z!
 
Huy
You didn't treat differentiation? O.o
 
How old are the students you're tutoring, @Huy?
 
Huy
@Khallil: It really should be once you're done with differential calculus.
@Khallil: Teaching? Between 16-18, mostly.
 
5:27 PM
@Huy We did of course, but very unrigorous. Didn't once see the differential quotient in high school
 
Huy
@rehband: Then... how the hell did they motivate the derivative? O.o
 
Differential quotient, @rehband?
 
Huy
@Khallil: $\frac{f(x+h) - f(x)}{h}$.
 
Oh, the limit definition of the derivative.
 
@Huy Pictures and vigorous hand waving :( My high school sucked
 
Huy
5:28 PM
@rehband: I see. :(
@rehband: Wanna see my test from last semester about power functions and stuff like that? I really liked that one. :D
 
@Huy Please!
 
Huy
@rehband: The first few exercises are a bit boring but some were really cool I thought. :3
I really want to make them draw graphs and stuff like that more often because they suck at it so much =_=
 
@Huy Yeah very cool exam indeed
Lots of drawings hehe
 
Huy
@rehband: Yeah, I really find it a pity most pupils who don't care about maths can't draw graphs within a reasonable time without a calculator.
@rehband: On my exam about differentiation, some didn't even manage to draw $f(x) =x^3$ but drew $f(x) = x^2$ instead.
 
@Huy Do your pupils use calculators in class?
 
Huy
5:34 PM
@rehband: They are allowed to during class but I strongly recommend them only to use them to check their results afterwards. I told them at the very beginning it won't be permitted at the exam and I design exercises and exams such that there are no real hard computations to do.
 
Calculators should be forbidden in high school math classes! :P
 
^
 
Huy
@rehband: BTW, do you have any ideas for the following? matheducators.stackexchange.com/questions/4438/…
 
Signs of September + approaching midterms: I'm already out of close votes and downvotes for the day. Third day in a row. [/whine ; maybe I need to set up a dedicated Whining Room]
 
@Huy I dont feel qualified to give you advice since I'm still a total newbie, but I really enjoyed basic things about groups (e.g. symmetric group) and rings when I first learned it
 
5:40 PM
A ring is commutative when it fits on any finger
 
Huy
@rehband: Do you think it would be an appealing topic for pupils that age? :s
 
@Huy Hmm, not sure. Did you have anything else in mind?
 
Huy
@rehband: I'd really like to do some linear algebra but don't think there's enough time to get to topics that are interesting =_=
 
@CareBear Hi, Thursday, lol.
 
@Huy I see. Yea getting all the way to eigenvalues, diagonalisation etc. would take a while in a high school course :P
Have they learned basic logic stuff yet?
 
Huy
5:47 PM
@rehband: I never came across basic logic before university, I doubt they have.
 
I gotta jet! Take care!
 

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