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15:00
@robjohn I like this form much more
$$\lim_{n\to\infty} \frac{1}{n^2} \int_0^{\pi/2} \left(\sum_{k=-n}^{n} e^{\large 2k x i}\right)^3 \psi^{(-2)} (x+1) \ dx=\frac{3\pi}{4} \log(2\pi)$$
15:20
wow, when plotting polar functions how come W|A gives me the same limacons when I set the domain for t as [-pi,pi] and [-pi/2,pi/2]?
oh forgot chat has latex
make that $[-\pi,\pi]$ and $[\frac{-\pi}2,\frac{\pi}{2}]$
ha forgot to notice everyone else's avatar is blanked out except mine
I think i'll post this as a question
MJD
MJD
Sometimes it happens that the image of the function in the plane has $f(x+\pi) = -f(x)$, so the images of $f$ on $[0,\pi]$ and on $[\pi, 2\pi]$ overlap.
There was some discussion of this recently in connection with why $r = \sin n\theta$ has $n$ leaves when $n$ is odd, but $2n$ leaves when $n$ is even.
oh I see. Do you know if this is the case with all limacons?
MJD
MJD
I'd have to see the particular function you were plotting.
May be relevant here:
1
Q: Mathematical roses with $4n+2$ petals

WCharginIn polar coordinates $(r, \theta)$, the equation $$r = \sin\left(a \theta\right)$$ gives a rose with $a$ petals if $a$ is odd, or $2a$ petals if $a$ is even. Thus, the number of petals generated for some values of $a$ are a | petals =======+======== 1 | 1 2 | 4 3 | 3 ...

(The answer to the $r=\sin n\theta$ thing is that when $n$ is odd, it also has $2n$ leaves, but the leaves overlap in pairs, so you can only see $n$ of them.)
Okay, I'm plotting limacons... functions in the form r=acost or r=a(b+c cost) where cos is replacable with sin... does the overlap occur for all such functions?
technically though r=acost in not a limacon
MJD
MJD
For $r = a\cos t$ that's exactly what is happening there. Notice that you have $r(t+\pi) = -r(t)$ just as I said a minute ago. For $r = a(b+c\cos t)$ I will have to ponder a little more.
How do I tell W|A to plot theta only between -pi/2 and pi/2?
15:33
for example " polar plot r=3+2cost [-pi/2,pi/2] "
MJD
MJD
That doesn't work for me: screenshot
W|A can behave weirdly with regards to small differences in queries. Write "cos t" as "cost" and it should work
MJD
MJD
I rather suspect that W|A is not doing what you think it is regarding the limit on theta. What if it were ignoring the [-pi/2, pi/2]? Then you would see the same result for both ranges.
In fact, that is exactly what it is doing.
Notice that it says it is plotting cos x, not cos t.
That's what it tells me it is doing: screenshot
it's not... I'll show you a screenshot
MJD
MJD
In your screenshot, it says it is plotting “r = 3 + 2 cos(x)”, but “t = -pi/2 to pi/2”, just as I said.
15:42
oh, I get your point now
that's weird
MJD
MJD
Now look at this screenshot, which tries to get it to plot t over a very small interval from -0.00001 to 0. Obviously it is ignoring that request and plotting the whole thing anyway.
Maybe we'll have to insert the query in mathematica syntax
MJD
MJD
I believe that for the general limaçon you need to go over the entire interval of length 2π.
I just got what I'm looking using an android app for plotting polar functions
the overlap thing does not apply to limacons
MJD
MJD
Right, because the relation $f(x+π) = -f(x)$ does not hold.
15:48
yes
thx for pointing me to the fact W|A was ignoring my domain, otherwise I would've been misled
@Chris'ssis It comes down to $$4\psi^{(-2)}(1)\int_0^\infty\left(\frac{\sin(x)}{x}\right)^3\,\mathrm{d}x$$
@robjohn that seems right.
@robjohn What tools did you use?
@Chris'ssis Riemann Sums :-)
@robjohn Nice ... :-)
@Chris'ssis Numerically it matches, but Mathematica cannot evaluate $\psi^{(-2)}(1)$ in closed form
15:58
@robjohn It can, just write it in another form, that is $\displaystyle \int_0^1 \log(\Gamma(x)) \ dx$
@Chris'ssis But why can it not evaluate it as PolyGamma[-2,1]?
@robjohn Let me check.
@Chris'ssis I've done that integral before.
@robjohn W|A is able to provide with the desired closed form.
@Chris'ssis I was looking at one of your answers and I want to ask you if your geometrical method for evaluating $\int_1^e \ln x\space \mathrm{dx} can be used for limits other than $1$ and $e$ or does it only work for these limits?
oops
$\int_1^e \ln x\space \mathrm{dx}$
@Chris'ssis does ur geometrical method only work for these limits?
16:10
@hb20007 There are some nice examples where the geometrical method works great. If I'm not wrong, there is a nice one given on a Harvard-MIT contest, but I need to find it.
it's a very cool method if it can be applied to other limits
@hb20007 Try to compute $$\int_0^1 \arcsin(x) \ dx$$
it even for functions other than $ln x$? awesome
@hb20007 On MSE main I only answered very easy questions.
brb
okay
16:25
@DanielFischer This is embarassing. I'll report this to the people who wrote the problem.
16:44
@Chris's sis, is it $\frac{\pi -2}{2}$ ? -- also, I can't seem to find the series you posted a week ago (I was going to take another crack at it now that I've brushed up on double series) -- could you repost it (or post another one like it)?
@DavidKirby Yes, this is the answer. I don't know which series you refer at.
@Chris's sis, it was a double series involving Zeta -- that's all I recall at the moment (oh, and I recall it was a real brain blender).
@Chris'ssis is the area between a function and the x-axis within certain limits (x=a, x=b) always equivalent to the area between its inverse and the y axis between y=a, y=b?
@hb20007 well, make a drawing to better understand what happens with the example above.
@DavidKirby let me see ...
@Chris'ssis I did. I got the answer to the second integral you gave me using your geometrical method which works very nicely but I had to assume that the thing I asked you holds true (it always does, right?)
@hb20007 well, you have there $(x=0, x=1)$ and $(y=0, y=\pi/2)$ that means you have different limits. It depends on how you choose the limits. That's why I told you to make a drawing.
Anyone familiar with the identity $(2)$? I am interested in a non-probabilistic argument.
@BalarkaSen I read that as "autism conference." After realizing such a stupid mistake, I can just hope that I, myself, am not suffering from it...
Australian Mathematical Society, silly.
I should go to sleep.
16:59
@ParthKohli Oow, I read the same thing too! :D
@Chris'ssis True. But by drawing a rectangle with height $\pi/2$ and width $1$, I was able to get the area required by minusing the area of the rectangle by the area between the inverse sin curve and the y axis, which I assumed to be the integral of sinx betwen $(x=0, x=1)$
@hb20007 Wait, what are the last limits?
oops mistake
$(x=0,x=\pi/2)$
@hb20007 Good job! :-)
@DanielFischer Here math.stackexchange.com/questions/820651/… is the correct version
17:04
Seriously though, I think Terry Tao is one of the best mathematicians currently living.
@hb20007 so, all gets reduced to computing $$\frac{\pi}{2}-\int_0^{\pi/2} \sin(x) \ dx$$
And, he is one of the very few people who surpass Ramanujan, @Chris'ssis. Such a person with vast knowledge on several branches of mathematics is rarely seen.
@Chris'ssis Yes. Thank you... This is really cool. Can I apply my 'assumption' to other questions or is it by chance that the area between the inverse curve and the y axis is the same as the area between the 'actual' curve and the x axis within the same limits on each respective axis?
@BalarkaSen the set of mathematicians is not totally ordered for any order relation
4
@hb20007 Yes, you can apply it in many questions, but you need to pay attention at the limits.
17:06
@G.T.R Haha, true. But I said one of the best not best.
@Chris'ssis yup, they must be the same... Thx again for taking the time, I sort of asked you the question out of the blue
@hb20007 To better understand things, check this - en.wikipedia.org/wiki/Young%27s_inequality
@BalarkaSen you compared Ramanujan and Tao, but are they comparable in the first place ?
@G.T.R Yes, I think so. That's because of the fact that Ramanujan is the founder of modern algebraic number theory and Tao is the founder of modern combinatorial number theory.
@BalarkaSen Ramanujan is a god that cannot be compared to anyone else. Ramanujan himself is a different world.
17:10
Not a god, nope. No one is a god, @Chris'ssis.
You're being too narrow minded on a specific branch. Modern mathematics has contribution of several mathematicians.
@Chris'ssis so Ramanujan is a maximal element ? Tao may be one too
Ramunajan was more impressive because he was arguably 'ahead of his time'. See the most highly rated answer for this question
55
Q: Mathematicians ahead of their time?

hb20007In every field there's always that person who's just years ahead of their time. For instance, Paul Morphy (born 1837) is said to have retired from chess because he found no one to match his technique that very much resembles modern chess theory. So, who were the Paul Morphys of mathematics?

@hb20007 That does not make one a god.
Riemann was ahead of his time too.
There is a potato in this room.
Riemann... weird no one mentioned him there
17:15
Hullo @bolbteppa
@Sawarnik Maybe not. his works were mainly based on that of Lagrange, Abel, Kronecker and Ruffini.
Riemann was the superior mathematician.
@DavidKirby In his time, yes.
Galois was perhaps the most 'ahead of his age'
17:16
I had a nightmare again.
@JasperLoy the cake is a lie
Ramanujan's appeal is that of the outsider, which may explain the 'god like' reverence around these parts (ie, the Internet)
@G.T.R I don't see any cake.
Hey Balark, very tired, very very tired, must sleep, just seeing what's up
@JasperLoy you never played Portal, did you ?
17:17
@Chris'ssis Everyone stand on the shoulders of the giant. There is nothing like someone's "own world".
@G.T.R No, so I don't know what you are talking about. However, my answer to a question yesterday had a cake.
@bolbteppa what's your project about? do you mind giving a short intro?
@BalarkaSen Did you read some of Ramanujan's work on series and integrals?
@bolbteppa Is he Balark? I think he was Bakrala.
@Chris'ssis Some of it. It's in Waldschmidt's site.
We could argue Raj did not stand on the shoulders of giants, since he was secluded from mainstream mathematicians when he independently came up with his work
@hb20007 I think I'd disagree.
interesting
Ethan is Ramanujan incarnate, lol.
@JasperLoy and here is the cake youtube.com/watch?v=RVInBsib04M
17:23
@Chris'ssis Are you familiar with any of Ramanujan's geometric work?
@BalarkaSen I read less about that. I was mainly interested in his work on series and integrals. (well, and still interested in his work)
@Chris'ssis Ramanujan rarely did any geometric work, you see. He was mainly an algebraist.
Does that convince you that he is not a god?
@BalarkaSen Well, that "god" you don't need to take it literally, but it's just a way of expression the fact that he was exceptionally awesome in all he did.
She was just using an expression
if u wanna take it literally
even Greek gods specialized
I am a banana god. I eat bananas.
17:28
Great, now everyone says it's an expression if they can't find arguments.
@JasperLoy can you sing this ? youtube.com/watch?v=LH5ay10RTGY
@BalarkaSen Well, but that was the point, really. I don't pray myself at Ramanujan god.
Anyway, talking about which mathematicians are gods is a waste of time. Let's talk about bananas instead, lol.
@G.T.R lol
@G.T.R Could this possibly be "Day-O"?
Banana Boat Song?
@BalarkaSen hmm no, it's way sillier
17:31
I gotta get going. Bye everyone.
I have nightmares almost every time I sleep. Then I will shout and wake up.
17:52
Not many lhf today.
@Chris'ssis Given the expression I gave? Perhaps I need to upgrade my Mathematica
@DanielFischer I'm trying a new approach of posting answers as quickly as possible. This led to a bunch of typos in that answer I posted earlier. I much prefer taking my time. But then the types of questions I can answer are limited.
18:09
Hello there !
@RandomVariable Don't sell yourself for less than you're worth. And find a compromise between being quick and typo-free that you're comfortable with, it's not worth stressing out just because maybe Ron Gordon types faster than you.
@DanielFischer Even Ron has mentioned to me that he now has a hard time writing up answers fast enough. And Ron is a much faster typist than I am.
There should be someway in which we can do the latex typing faster
@Chris'ssis What was that funny problem you had with 2014 everywhere ?
something like an app in our tablet/ipad which can recognize and associate symbols used in latex and auto generate latex code
somebody pls help out with this math.stackexchange.com/questions/820540/…
18:25
It's this one
$$\lim_{n\to\infty} \left(\frac{1}{\displaystyle \binom{2014}{2014}}+\frac{1}{\displaystyle \binom{2014+1}{2014}}+\cdots+\frac{1}{\displaystyle \binom{2014+n}{2014}}\right)$$
@physicsenthusiasist Sometimes it almost seems like people are posting answers before the question has even been asked.
@R
@RandomVariable I don't understand how ppl can post answer without the question been asked
@JasperLoy
@physicsenthusiasist They can't. I was just trying to emphasize how fast answers are sometimes posted.
18:31
@Chris'ssis let $n$ be a positive integer and let $a_1,a_2\dots a_n\in \mathbb R$ with $a_1+a_2\dots a_k\leq k$ for $k=1,2\dots n$ prove $\frac{a_1}{1}+\frac{a_2}{2}\dots\frac{a_n}{n}\leq \frac{1}{1}+\frac{1}{2}\dots \frac{1}{n}$
no
@RandomVariable Well I am not sure of that, there are lots of questions on stackex which are unanswered , may be popular questions get quick answers
why specify all integer values larger then 1 for $k$
there are k different sums @Ethan
oh
18:34
$a_1\le1$ and $a_1+a_2\le 2$ and $a_1+a_2+a_3\le 3$ and ...
didn't catch that
sorry
Helloes.
Peoples of the math.
looks like induction should be used
What are you doing Ethan?
i would try to rearrange a couple of the first ones, and see how they relate to each other
so just chilling
18:36
Nice. Congratulations.
But I meant that math above with @seaturtles
see the banana ^ (no, not the solid blue one)
Oh, you where doing my inequality
I didn't notice
just clarifying it for ethan
INB4 INDUCTION.
no wait
i got this
multiply each sum in the equality $a_1+a_2+\cdots a_k\leq k$ by some constant $c_k$
18:40
Multiply.
You need to pick a grammer book son.
damnet
$\frac{a_1}{1}\leq \frac{1}{1}$
$\frac{a_1}{2}+\frac{a_2}{2}\leq 1$
@PedroTamaroff grammer?
$\frac{a_1}{2}\leq \frac{1}{2}$
@Bananarama Ethan can haz grammer.
$\frac{a_1}{1}+\frac{a_2}{2}\leq \frac{1}{1}+\frac{1}{2}$
18:42
Isn't it grammar?
Yes.
I did it on purposes.
*porpoises
@seaturtles lels
18:46
@Bananarama
$a_1\leq 1$
$\implies a_1+a_2\leq 1+a_2$
@ethan You called me?
@JasperLoy yea im graduating hs in like 4 hours
@Ethan So what news have you got? Where are you going?
I graduated two weeks ago
@JasperLoy here can we talk in irc 4 a sec
18:49
@Hippalectryon what is $a\wedge b$?
@JasperLoy freenode
@Hippalectryon wtf la première question
@Bana gcd
@Ethan Why not just email me?
@G.T.R le a$\times$b ?
18:49
channel
@Ethan What do I type there to get in?
make up a nick name
and for the channel type
#w731q
@Ethan That is the channel?
yes
@Ethan Do I check the box?
18:51
nah
@DanielFischer I incorrectly stated that my internet connection at home is 6 Mbps. It's actually half that. So we're basically in the same boat. I actually prefer watching videos on my phone since the connection is so much faster.
for channel type #w731q and then click connect at the bottom
after you have made up a nick name
@Ethan I am in there.
somebody pls hv a look at this
2
Q: Derivation of the prolongation formula for finding symmetries of diff equations from Olver

pencilI am having a problem with the derivation of the prolongation formula from PJ Olver's text :"Applications of Lie groups to differential equations" Page 105,106. Considering a differential equation with independent variable(x) and one dependent variable(u). (x,u) $\subset$ $X \times U$ The fir...

@Hippalectryon oui
18:56
@G.T.R c'est simpa non ? (mon prof est sadique :c )
When will it be my turn to speak French
@nablablah Why don't you ?
I don't have time to learn
@JasperLoy
c c
c c
@Hippalectryon GDC = Grand Diviseur Commun?
@cc = PGCD
c c
c c
19:07
oh fine I thougth it was mistranslated sorry
notations are terrible in general, $\wedge$ can mean AND in logic, or wedge product, or min
19:20
@Ethan did you manage to solve it?
@Bananarama sorry i stopped trying
you should post it on the main site
you where in the right track though
I solved it in a contest a while back
but I wanted to see if @Chris'ssis liked it
since no one in this chat seems to talk about combinatorics I though I'd migrate to popular topics here.
Hi @Banana
@nablablah hilo
what's up?
Nothing much; you?
19:26
watching bleach
Watching it do what
2
it's the name of an anime
@Hippalectryon a "pretty great common divisor" perhaps, not the greatest ('cuz that's hard), but it's pretty great
19:27
probably @seaturtles can tell you it sucks
@nablablah Hey
@JasperLoy
photogenic common divisor
@MikeMiller
the common divisor that looks best when you take a picture of it
c c
c c
19:29
@mixedmath hehe (PG = Plus Grand in French, = greatest)
@cc the gcd of ... ?
@Bananarama Thanks for the question. It's a cute one. Right now I'm working on $$\int_0^{\pi/2} \int_0^{\pi/4} \frac{\sin^2(x y)}{y \sin^2(x)\sin(\pi y) } \ dy \ dx=\log\left(\frac{\displaystyle 2\Gamma\left(1+\frac{\pi}{8}\right)\sqrt{\frac{2}{\pi}\cdot \tan\left(\frac{\pi^2}{8}\right)}}{\displaystyle \Gamma\left(\frac{1}{2}+\frac{\pi}{8}\right)}\right)$$ that I created today. I try a second solution.
c c
c c
nah forget it
@Hippalectryon trying to understand en.wikipedia.org/wiki/…
It's funny how Asaf always removes set-theory from combinatorics posts. He must have done it a lot of times.
@Ethan Find the closed form of $$\int_0^{\infty} \left(\frac{\sin(x)}{x(\cos x+\cosh x)}\right)^2dx$$
brb
19:53
Wait ... (no, it doesn't work since they aren't arranged in a proper way) I didn't read the question well.
oh
what happens to upvotes you get after hitting the cap?
@Bananarama maybe the induction would be good.

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