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12:05 AM
@Charlie try to enjoy it. its just a mindset.
still no answers
@Charlie let me buy you dinner
 
@mick :/
 
cmon :)
 
@Bananarama Yeah, I do.
Why?
 
goodnight hottie @Charlie
 
@PedroTamaroff It's cool
 
12:12 AM
@mick night
 
@Bananarama Ah, yes.
 
no it's not
 
@Charlie You're not cool.
 
try to be cool is too mainstream
 
charlie is not cool , shes hot :)
bye
 
user116848
12:22 AM
I wonder why I can't get a good girl? I often wonder about it :D
 
@KarlKronenfeld Kaaaaaaaaaaaaaaaaaaaaaaarl.
 
@Pedro Hey what's up?
 
@KarlKronenfeld Algebrain' and combinatorin' hard.
Midterms coming up.
 
Hi @Karl
 
Hey Ted
 
12:39 AM
When does your probability course start Professor @TedShifrin?
And will it be on YouTube?
 
my laps are becoming longer and more disruptive
 
Laps or lapses?
August 18, @skull, and no
 
@TedShifrin :(
 
naps, @Ted
 
12:54 AM
@TedShifrin Ted
Is it more appropriate to write Nöther instead of Noether?
@KarlKronenfeld
@MikeMiller
 
@PedroTamaroff No idea which is more appropriate. In this part of the world it is more common to write Noether.
 
Amazing. @KarlKronenfeld
A user was removed, and I just got 18 rep-points back.
 
1:10 AM
Interesting isn't it @PedroTamaroff? There are times I'll get random, unexplained downvotes from answers months back. Oh well.
 
Heh, indeed it was the guy who was downvoting me. Curious.
@KajHansen Check wether you got some rep back.
 
How can I tell? I don't really keep track of it outside of the hundredths digit.
 
I got a message "+18 user was removed"
 
I guess I was unaffected by said user :P
It seems there have been a few users banned/suspended recently. Is this typical of Math:SE?
 
yes
 
1:20 AM
Strange
 
I got -6, so he liked me more than he hated me.
Only since you joined, @Kaj :)
@Pedro: Even in German I believe it's spelled Noether
 
r9m
@Hippalectryon Well my idea was $$\displaystyle p_{n+1}(x) = \frac{1}{2}p_{n}(x) + (1-\sqrt{x})p_n(x)$$
$$= p_n(x)\cdot\left(1-\sqrt{x} + \frac{1}{2}p_n(x)\right) \le p_n(x)\cdot\left(1-\sqrt{x} + \frac{1}{2}\sqrt{x}\right)$$
$$=p_n(x)\cdot\left(1- \frac{\sqrt{x}}{2}\right) \le p_0(x)\left(1- \frac{\sqrt{x}}{2}\right)^n$$ (by simple induction)
.. now this would have been sufficient for the problem as
$$\displaystyle \sqrt{x}\left(1- \frac{\sqrt{x}}{2}\right)^n \rightrightarrows 0\qquad (x\in[0,1])$$
 
got +2
 
@TedShifrin, the statistician is quick to point out the dangers of correlation $\Rightarrow$ causation. In this case, me joining the site might not be just coincidence. :P
 
@blue Got +18.
So this is a guy who knows us, and hates my in particular.
 
1:25 AM
I would not be so quick to claim the first part lol
 
Way to be paranoid, @Pedro :D
I've downvoted people I don't know at all. One guy earlier today, who applied the divergence theorem to a non-closed surface. He finally admitted he'd misread and deleted.
 
Algebraists talk about fields and rings, but do they ever talk about fields of rings? imgur.com/vsWy1H0
 
Fields of dreams?
 
@KajHansen Google "meadows", be impressed.
 
without knowledge of model theory, I am unable to be impressed
2
 
r9m
@PedroTamaroff What are meadows ? :o
 
@r9m I have no idea,.
$\mathscr S$.
$\mathscr T$.
 
 
2 hours later…
4:03 AM
Let $F(x,a)=\int^x_o \frac{t^p}{(t^2+a^2)^q}dt$, when $a>0, p, q \in \mathbb{Z}^{+}$, prove $F(x,a)=a^{a+1-2q}F(x/a,1)$
Im sure there is some substitution I am missing
 
r9m
@VibhavPant substitute $u = t/a$ ..
 
tries
 
4:22 AM
@r9m oh. forgot to say thanks!
 
r9m
@VibhavPant no problem :-)
 
 
2 hours later…
6:24 AM
When someone can supply me with that polynomial trick, let me know :D .
 
6:39 AM
?
 
Create any polynomial with positive integer coeffecients.
Step 1) Ask for P(1)
Step 2) Ask for P(x), where x > P (1)
Step 3) Convert P(x) to base x.
Apparently you can get the coefficients. This way
 
6:55 AM
Oh I got it :)
 
 
2 hours later…
8:27 AM
"Computer cracks Erdős puzzle" wins grand prize for most-misleading headline of all time, unseating reigning champion "Is the Universe a Simulation?", and paving the way for a new class of painfully misguided coffee shop conversations.
 
8:38 AM
Greetings
@robjohn are you there?
 
Hi @Chris'ssis
I want to do a test to see how long you can hold your breath!
Use this Chronometer to check out!
@Chris'ssis @robjohn
 
@MrWho Hi. Why would I do that?
 
@Chris'ssis Just to know, check out your health.
@Chris'ssis We want to see how long mathematicians can overcome drowning :)
 
@MrWho I don't think the health can be checked out like that. Moreover, this is a risky thing for those with heathy problems. :-)
 
@Chris'ssis Man ! it's not that hard, if you're gonna die just unhold your breath.
Imagine you're under water :D
@Chris'ssis Don't cheat :-D
 
8:42 AM
30 seconds for me
But Im sure I can do more
 
@VibhavPant Report what you think you can.If you have time.
@Chris'ssis Come on :-D you beat integrals.What if you've been thrown in the water? don't you want to survive? you wanna give up? :-D
 
@MrWho If the chronometer is right ,I held my breath for 1 minute 5 seconds
 
@robjohn Summon you to the breath-taking competition !
 
Talking of integrals
 
@VibhavPant Good.mine is 1:10
 
8:45 AM
heh
:)
 
@VibhavPant But it should be 2:00 or 1:45
 
I had this integral to prove: $\int^{\pi/2}_0 \cos^m(x) \sin^m(x) dx = 2^{-m}\int^{pi/2}_0cos^m(x) dx$
 
@VibhavPant Seems like fourier series .
 
I fiddled with the left hand side to get $1/{2^m} \int^{\pi/2}_0 [2\sin(x)\cos(x)]^m dx=1/{2^m}\int^{\pi/2}_0sin^m(2x)dx$
$=2^{-m} \int^{\pi/2}_0 [2\sin(x)\cos(x)]^m dx=1/{2^m}\int^{\pi/2}_0sin^m(2x)dx$
oops
 
@VibhavPant Use Euler formula.
 
8:49 AM
MrWho: The one for complex exponentials?
(I cant get to prove $2^{-m}\int^{\pi/2}_0sin^m(2x)dx=2^{-m}\int^{\pi/2}_0\cos^{m}(x)dx$
)
 
@VibhavPant For this you need to prove anything. It's evident.
How about the simple fact that $$\int_0^{\pi/2} \sin^m(x) \ dx= \int_0^{\pi/2} \cos^m(x) \ dx$$ combined with the formula $\displaystyle \sin(2x)=2\sin(x)\cos(x)$?
 
@MrWho Im sure Eulers Formula will work, but I dont want to get a bad habit of pulling out complex exponential when anything remotely trig appears. (I already try to use L'Hospital rule everywhere)
@Chris'ssis That identity is geometrically intuitive, though I cant get to prove it
 
@VibhavPant I see, complex exponential can make mathematicians less inventive.
 
@MrWho it makes stuff REALLy easy though
 
@VibhavPant I've run out of ink, jot it down then!
 
8:54 AM
@Chris'ssis I already had arrived at $\int^{\pi/2}_0\sin^m(2x)dx$ by using the double angle formula
 
@VibhavPant I got disconnected as usual!
 
@Sawarnik Indian Internet :D
 
:D
Again, the question doesn't mention continuity!
 
@Sawarnik which question?
 
@VibhavPant $f(f(x)=\text{something}$
 
9:00 AM
@Sawarnik yeah, I saw it later
 
@VibhavPant that was a really silly mistake to make!
 
yeah :|
@MrWho eulers forumla doesnt seem to work
I get back to the original lintegral
integral*
 
hi folks
 
hi
@vibhav Would you like some peasy questions?
 
@Sawarnik why not
 
9:14 AM
@VibhavPant Ok, then find a continuous real to real function that gives each value in $\mathbb{R}$ exactly thrice.
 
@Chris'ssis :-D You escaped !
 
hmm
wait
oh
almost
 
I'm pretty insane, I'm gonna start spivak next week!
 
@MrWho :?
 
@Sawarnik My linear algebra is weak, but damn it, I'm gonna start it anyway.
 
9:23 AM
@robjohn Just let me know if you managed to evaluate my integral by using that limit. It would be nice if it worked.
 
@VibhavPant done?
or hints?
 
@Sawarnik hints please
 
@VibhavPant Which text are you studying from?
 
@VibhavPant consider an increasing zig zag :)
 
@MrWho Apostol
 
9:29 AM
@VibhavPant Oo. Grreat.
@VibhavPant Should I reveal the answer?
 
@Sawarnik sure
Im stumped :(
I can figure out the graph though
 
wow
 
:D
Now, can you find a continuous real to real function that gives each value in $\mathbb{R}$ exactly twice? @Vibhav
 
hmm
I can figure out the graph
 
9:36 AM
:O
 
although getting the function is what I am stuck at
 
\frac {i}{m} = \int_{0}^{\pi/2}cos^m(x)dx
 
@VibhavPant Did you consider that such a function might not exist! :P
 
ah
yeah
 
Prove it then.
Its easy.
:D
 
9:39 AM
Well
 
$\frac {i}{m} = \int_{0}^{\pi/2}cos^m(x)dx$
 
Since $f$ takes each value in $\mathbb{R}$ exactly twice
 
@VibhavPant You tackled integral?
 
@MrWho I could do it geometrically
 
@VibhavPant How?
 
9:42 AM
@MrWho Wait a min!
 
@Sawarnik Okay :)
 
@MrWho compare the two graphs of $\sin^m(x)$ and $cos^m(x)$ both have the same area between 0 and pi/2
 
@MrWho What's i btw?
 
@Sawarnik Complex number $\sqrt -1$
 
Oh ok.
I don't know complex integration.
 
9:44 AM
@Sawarnik I just go with the flow of numbers, put it there, and play with it :)
 
@Sawarnik define $x_1$ and $x_2$ such that $f(x_1)=f(x_2)$, so there must be a number $c$ between $x_1$ and $x_2$ for which $f'(c)$ = 0 (or $c$ is the local maxima)
 
@VibhavPant Ok.
 
Since $c$ must occur twice too
 
@VibhavPant Mean value theorem?
Proved by Lagrange.
 
@MrWho Rolles theorem, to be precise
Yeah, so as I was saying
 
9:46 AM
@VibhavPant Yeah, some textbooks don't differentiate.
 
@VibhavPant You don't know if its differentiable.
So no Rolles.
 
@Sawarnik well what about the local maxima?
It certainly has a local maxima
given that the function is continuous
 
@KarlKronenfeld I know.
@VibhavPant Or a minima :) Well ok.
 
@Sawarnik yeah
@Sawarnik then apply IVT to get a contradiction
 
9:49 AM
@VibhavPant Good :)
 
@Sawarnik Does apostol have solution manual?
 
nope
alright, I need to go
(test)
 
 
1 hour later…
11:18 AM
@KajHansen That is the Cayley table. It is the internal grid part of a multiplication (or composition in this case) of the elements of $D_{100}$. It starts with rotations $S_{0}$ to $S_{99}$ and reflections (going anticlockwise through) from $R_{0}$ to $R_{99}$. If I had the reference rows and coloumns you would see that as the elements go along they are assigned a 100th (in this case) of colour spectrum. The resulting colours in the middle are the colours of the composition.
 
$$\int_0^1 \frac{ \operatorname{ EllipticK }(x^2)- \operatorname{ EllipticE }(x^2)}{x^2} \ dx$$
 
@Alizter Thanks :-)
That one is newly created.
 
11:43 AM
$\frac{\mathrm{d} }{\mathrm{d} x} \int_{u(x)}^{v(x)}f(t,x)dt=u'(x)f(u(x),x)-v'(x)f(v(x),x)+\int_{v(x)}^{u(x)}\frac{\partial }{\partial x}f(t,x)$
What is the proof?
@robjohn @Chris'ssis @DanielFischer @EveryBody !!!
 
The old triple exclam...
 
@KarlKronenfeld Any help would be appreciated !
 
11:59 AM
@MrWho Consider $$F(u,v,x) = \int_u^v f(t,x)\,dt.$$ The partial derivatives of $F$ with respect to $u,v$, and $x$ are easy (or at least easier) to find. The rest is the chain rule. (And you have swapped $u$ and $v$ on one side of your formula.)
 
0
Q: Differentiation of multivariable function proof

MrWhoI'm looking for the differentiation of multivariable function integral $$\frac{\mathrm{d} }{\mathrm{d} x} \int_{u(x)}^{v(x)}f(t,x)dt=u'(x)f(u(x),x)-v'(x)f(v(x),x)+\int_{v(x)}^{u(x)}\frac{\partial }{\partial x}f(t,x)$$ Thank you!

 
12:23 PM
@BalarkaSen Don't let the tractor beam pull!
 
Apparently, my account is still here. (I am not complaining!)
@Alizter What?
 
@BalarkaSen I thought you were trying to get away
 
I was. And successfully for a couple of days I think.
I have enhanced willpower now. Yay!
 
@BalarkaSen I made a cayley table for a couple more groups after you were gone. Including $A_4$
 
I saw you mention that you made for $D_{100}$. can you post it?
 
12:28 PM
 
Nice. I wonder why multiple copies of stuffs appear for large groups.
Is it obvious or am I being silly?
Same happened for $\Bbb Z/360\Bbb Z$, no, @Alizter?
 
@BalarkaSen Did you see $Z_5[i]$?
 
@Alizter No! Post it!
 
$\Bbb Z_5[i]$
$\Bbb Z_{29}[i]$
 
Can you do it for some large number instead of $5$? I am interested in large stuffs.
 
12:32 PM
 
Ah, you already did.
 
$\Bbb Z_{360}$
@BalarkaSen I do not have the limit anymore
just pixel limit, my screen isn't infinite
 
@Alizter yes, precisely. See the "almost" copies there?
that's what made me thinking.
 
See how $\Bbb Z_{29}^2$ is so similar to $\Bbb Z_{29}[i]$
 
Is the above $\Bbb Z_{29} ^2$?
 
12:35 PM
@BalarkaSen Btw if you click on the images you can see it better
@BalarkaSen Yes
You can see the sub cayleys :)
 
@Alizter indeed, the deformation patterns look similar.
 
@Alizter There are only 29 rows
 
@KarlKronenfeld Click on the image
 
I did that
 
Can you see the mini cayley tables inside?
Each square is another coloured version of $Z_{29}$
 
12:38 PM
oh
 
:)
 
how do decide the color scheme?
 
@KarlKronenfeld The elements are ordered (usually lex) and then they each get split equally on the spectrum. The lowers would be redder and the highers would be purplerrer.
 
Have you tried alternative orders? Whenever you order a subgroup and then list it and each of its cosets in the corresponding order, you will get the mini cayley tables.
 
yes
 
12:49 PM
@Alizter Have you tried symmetric groups?
 
I can do other colours but I was lazy and just partioned hue in HSV
@BalarkaSen I will have a go at that actually. Trying to get $A_4$ on its own working was a pain. But I think $S_n$ maybe easier
Here is $A_4$ with a green blue colour scheme so its easy on the eyes
 
Yeah.
 
in no particular order
 
@Karl Do you have any idea what's going on with the large groups?
oh, wait, i see @Alizter already answered that.
so on every part of the graph, there is a little cayley hiding.
 
Yes
 
12:55 PM
wait, no, i still don't get it.
if you have $\Bbb Z_n \times \Bbb Z_n$, then you're putting another cayley inside each squares.
but what happens for $D_{100}$?
 
The first half are rotations
the second half are relfections
reflections are ordered bu starting at a point and then moving nth segments anticlockwise for the new symmetry line
and rotations are roatating whatever
 
What's with the 4 similar objects?
 
Look at $D_3$ first
 
12:59 PM
Aha.
 
So starting of from left to right we have 0 degrees, 120, 240 and then reflection at 0 degrees, 120, 240
 
Yeah, nevermind.
 
Get it?
 
Yes.
 
:)
 
1:00 PM
There's the problem with thinking of every group as galois groups of some algebraic number field.
=P
Don't forget the poor quaternions, @Alizter
 
@r9m maybe you like it ... $$\int_0^1 \frac{ \operatorname{ EllipticK }(x^2)- \operatorname{ EllipticE }(x^2)}{x^2} \ dx$$
 
@BalarkaSen Actually. I made something else with quarternions yesterday.
 
Oh?
 
OK. And what's that?
 
1:13 PM
Graphical multiplication
You feed my program unit quarts and it produces this pretty diagram :)
 
Ah.
 
the last image is from wikipedia
 
i know.
 
@BalarkaSen Only problem is that I didn't really show order of multiplication
 
you mean i "after" j and i "before" j?
if not, it won't be able to discriminate k and -k
you'll then get $Q_8/\langle -1 \rangle \cong \Bbb Z_2 \times \Bbb Z_2$.
 
1:17 PM
@BalarkaSen Programatically it works. I mean the graphics don't show order. You just have to assume that the result is a good indication of the order
 
I see.
Yeah, the diagram shows that.
 
Ah well back to $S_n$. I need to make some good permutation machinery unlike the quick pile of junk I produced for $A_4$
 
i can't help unless i know how you are programming those stuffs. never did enough graphics coding.
 
@BalarkaSen I am not doing the graphics part. There is one graphics part and that is done. All I have to do is program a group and it produces the cayley diagram by itself.
Like a function that maps groups to cayleys
 
oh. you can't use the group presentation?
 
1:21 PM
presentation?
 
google it.
 
eh not quite like that. What I do is add elements to a set. then I define the operation. Then my well written structure checks it is really a group and then voila a group/
So really what I have to do is program something that maps element n and element m to some element k
 
how do you define operation?
 
in the style of $S_n$
@BalarkaSen It is a function taking two group elements and returning anotehr
 
r9m
@Chris'ssis totally out of my league :| ..
 
1:24 PM
you don't mean you are defining each element and operation out by hand, i suppose? @Alizter?
i mean, one would be mad to do that for $D_{100}$
 
@BalarkaSen No each element in any set is basically an integer. The group operation is a map from these two integers to another. However it acts like they were elements of that group
 
i am talking about the programming here, not the definition itself.
i know the definitions, but i am wondering how are you programming those.
 
@BalarkaSen Could you wait 15 mins? I need to go and eat. When I return I shall explain better.
 
the only way of coding i see is by presentation of a group.
 
:)
 
1:28 PM
@Alizter ping me stuffs, i have to go.
 
Do you say "I wrote a check of 100€" or "I wrote a check for 100€"? I was told the first form is wrong...
 
1:48 PM
does anyone know if a university can expel a student convicted of a crime whilst a student?
2
 
2:19 PM
Mmmm
@Lost1 Stop lurking in the cookie jar
@BalarkaSen yo
$$
f_p(n) = \int_0^{\log p} \exp( \exp(x) + n x) \,\mathrm{d}x = a_{p,n} e + b_{p,n} e^p
$$
Where $p, n \in \mathbb{N}$, and $a$ and $b$ are integers dependent on $p$ and $n$
nice
$$ \Gamma(n) = \int_{-\infty}^\infty e^{-e^x + n x}\,\mathrm{d}x $$
 
@BalarkaSen Right so to program a group $G$ I need it to be isomorphic to $\Bbb Z_{m}^{\circ}$ where $m$ is the order of $G$ and $\circ$ is some operator such that the isomorphic holds. This is how its programmed. The operator is the real defining property of the group. It takes two group elements and gives another. Now programmatic functions can behave differently to normal mathematically constructed ones. The function programmed behaves as if the elements were from $G$ if that makes sense?
 
2:39 PM
Hi, everyone!
 
hello
 

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