Mathematics - 2012-03-02 (page 2 of 4)

@anon We'll not define the density at that point. I mean we don't care about that point and at $1$. Changing the density at few places does not affect the distribution function, right?

Asaf Karagila

Wise Willow?

Matt N.

Wim Wenders.

anon

Changing the density at few places does not affect the distribution function, right? and yet you wonder why your integration isn't coming out to the full 1 ... :P

Asaf Karagila

Annnnd I'm tired again.

Kannappan Sampath

@AsafKaragila You must be as you typed in those n's several time!

t.b.

12:08 PM

@AsafKaragila chase some diagrams... That'll annoy you so much as to wake you up...

anon

the density has half a dirac delta impulse at y=1/2 such that it contributes 1/2 to the full integral entirely at the point y=1/2, so you can't ignore that point

Asaf Karagila

:|

Matt N.

Look at all the sun. I can't wait for the hay fever and the mosquitoes. Summer is the best time of the year!

Kannappan Sampath

Let me first think. Distribution function is discontinuous at $x=\dfrac{1}{2}$. How?

It cannot be the case!

Gigili

I thought it was winter.

Matt N.

12:10 PM

I wish.

Asaf Karagila

My sarcasm alarm just went off. Who tripped it?!

anon

@Kanna: Because $P(Y\ge y)$ is 0 for $y<1/2$, but $P(Y=1/2)=1/2$

Matt N.

@AsafKaragila : )

@tb http://chat.stackexchange.com/transcript/message/3606206#3606206
So you are a... mathemagician?

anon

Yo peeps, what do you all think of the idea of arrows pointing to/from arrows in diagrams? Scroll up to see my example.

t.b.

@MattN I am aspiring to be one, yes. I still have to work on my mathematical knowledge, my book reviews and my orthography in order to get there.

anon

12:12 PM

Oh, now that I think of it, it's probably a bad idea. The diagram is supposed to be categorical, but it references things inside objects (the dual vector spaces). Nevermind all.

Matt N.

Now someone's tripped my sarcasm alarm. : D

t.b.

@anon Yes, that's my main complaint about it. Also, it doesn't really depict $f^t$ but only its action on one specific element of $W^\ast$.

anon

Well, we describe functions like $x\mapsto x^2$ a lot and it doesn't count as depicting $f$ at only "one specific element" $x$...

Matt N.

@Ilya -> shout at

anon

I suppose we could adopt a policy where labelled arrows are specific morphisms, while unlabelled arrows represent Hom(A,B)'s in generality..

that could get confusing though

t.b.

12:21 PM

I don't want to name all my arrows!

anon

heh heh

maybe we could draw a circle through the arrow to represent Hom .... strokes peach fuzz on chin

Kannappan Sampath

@anon Yes, noted this point. Because of this pmf is an animal I don't know how to tame!

anon

pdf?

Kannappan Sampath

probability mass function, I meant.

(or density, as I called it!)

anon

mass function is for discrete variables. we're looking at continuous, so we call it density

Kannappan Sampath

12:28 PM

Yes! Even I call it density. But some how I got that lingo! Sorry about that confusion!

For the first case, I think we will say there is no expectation, no?

(Expectation does not exist as density does not exist!)

anon

given X<0.5, we have Y=0.5 identically, so of course the expectation is just 1/2

Kannappan Sampath

Should I undelete the answer?

anon

As I see the answer now (a) the density is incorrect and (b) you don't say how to use the density to get the answer. There's also a new comment so that this question is pretty much finished, IMO.

Kannappan Sampath

New comment?

anon

by Dilip, with two upvotes

Kannappan Sampath

12:42 PM

Yes!!!!!!!!!! I knew this thing!!! I did not get this idea!

Asaf Karagila

@tb I always thought men give names to their arrow.

Ilya

@Matt: hi, thanks

Matt N.

Np : )

N3buchadnezzar

If I have a triangle with three equal sides what is it called?

in R3

anon

equilateral?

N3buchadnezzar

12:47 PM

in R3?

Kannappan Sampath

In R3??

Asaf Karagila

In a condom? Use Durex instead.

N3buchadnezzar

it is defined by (0,0,3) (3,0,0) and (0,3,0)

anon

doesn't matter what dimension it's in.

Matt N.

: )

N3buchadnezzar

12:49 PM

I would define it as a cube with sidelengths 3 that is sliced along its diagonal

anon

a cube? are you sure you're talking about the figure formed by the line segments joining those three points?

N3buchadnezzar

@anon ***** I am kind of tired

(0,0,3) (3,0,0) and (0,3,0) and (3,3,0)

Asaf Karagila

So it's a pyramid.

N3buchadnezzar

chuckles

Asaf Karagila

You're talking about a tetrahedron, I think.

anon

12:51 PM

that's not a cube, but it is a very slanted pyramid

N3buchadnezzar

@AsafKaragila If I built a Pyramid like that, the Pharaoh would behead me and feed me to the cats!

anon

the base of the pyramid is the triangle defined by the first three points you gave and the top is (3,3,0)

N3buchadnezzar

@anon Yeah, but you could look at it as the area you obtain after slicing a cube with sides 3 along its diagonal.

Asaf Karagila

@N3buchadnezzar You're a Babylonian king. Pharaoh would have had you beheaded anyway. You could try and build a ziggurat instead.

anon

a cube with three sides, you really don't know what you're talking about do you? :P

N3buchadnezzar

12:54 PM

@anon Interpret what I think not what I say!

anon

let me phrase it this way. we start with four points, as you've given. are you creating a solid region out of these four points?

N3buchadnezzar

@anon yes =)

Skullpatrol

@N3buchadnezzar Say what you mean and vice versa.

anon

If so, it's a figure with four vertices that is a tetrahedron (go check a Wikipedia picture), which is most certainly not a cube.

Well, if you say what you mean, then by the symmetric property...

Asaf Karagila

We need two executioners.

N3buchadnezzar

12:58 PM

@anon I am not saying it is a cube, I am saying you can look at it like a cube sliced along its diagonal

And we are looking at the bottom part

anon

even that is not true.

N3buchadnezzar

=(

anon

your figure is a subset of the away-from-the-origin half of the cube after slicing through the diagonal, though

also, I have no idea how that picture is representative

N3buchadnezzar

I think tetrahedra is a shorter name for it though =)

Asaf Karagila

It was sunny, but now it's raining. Now it stopped.

Kannappan Sampath

1:05 PM

@MattN I grabbed a AM, literally grabbed it from the library for Comm. Alg.

Matt N.

@KannappanSampath Aces : )

Kannappan Sampath

It was like fight for the copy, I won the fight thanks to the that kind lady who rescued AM from a research Scholar for me!

anon

"rescued from a research scholar" lol

Kannappan Sampath

Yes!

@anon Rescued AM from...

Skullpatrol

Once on of them research scholars gets their hands on it we'll never get to see it, yee haww!

t.b.

1:11 PM

Hey guys, I gotta go soon. The weather is simply too nice to hang around in front of my computer... Catch you all next week.

Matt N.

@tb See you next week.

Skullpatrol

@tb Later alligator.

Kannappan Sampath

@tb Next week?

anon

that's why I have a laptop

Matt N.

@KannappanSampath He'll be away til next week : (

Asaf Karagila

1:13 PM

@tb Go put on your gold chains, Mr. T.

t.b.

@anon me too, but I don't like working in the sun with my laptop :)

Matt N.

@AsafKaragila Wha..? lol

t.b.

@MattN well, next week it's gonna be winter again, so...

Kannappan Sampath

@MattN Precisely that makes me sad too.

robjohn

Hey guys :-)

t.b.

1:13 PM

Hi, robjohn

Asaf Karagila

robjohn

@tb for another few weeks at least.

@AsafKaragila you pitying someone?

Kannappan Sampath

@robjohn Hi Robjohn!

Skullpatrol

@robjohn Hi, Rob

Asaf Karagila

@robjohn No, but Mr. T. might be.

Matt N.

1:15 PM

@tb But weather forecasts are not always right.

t.b.

@robjohn run awaaaaay

Asaf Karagila

Did you guys check for groundhogs?

:3658141 Groundhog Day.

Matt N.

@tb Why don't you open the window and sit in the sun there instead? : )

t.b.

@MattN that's about as worthwhile as watching people eat good food...

robjohn

@AsafKaragila There are several groundhog ceremonies around, but the main one in Punxsutawney, PA differed from the one in New York, NY. There seems to be a regional difference, so I don't know what to apply here :-)

t.b.

1:18 PM

Okay, I'm off. Have a nice weekend y'all!

Jonas Teuwen

@tb Bye!

robjohn

@tb typical :-)

Jonas Teuwen

Bloody kopfschmerz. I need more ristretto 8-).

robjohn

@tb have a good day :-)

Asaf Karagila

@robjohn Well, if you ever find yourself becoming Bill Murray... who you gonna call?

Kannappan Sampath

1:18 PM

Anyone using Geogebra here?

Matt N.

@tb Have a nice weekend.

Kannappan Sampath

(Or any form of help for some graphs will be appreciated!)

Matt N.

@KannappanSampath The one that just left does, afaik.

Kannappan Sampath

Huf!

: -(

Skullpatrol

@robjohn Did you see the star on N3buchadnezzar's comment "Interpret what I think not what I say!" 30 minutes ago?

Matt N.

1:23 PM

I think I'm going to sleep : (

robjohn

@KannappanSampath I have GeoGebra, but I don't use it because I am familiar with another program for drawing.

@Skullpatrol I wasn't here 30 minutes ago.

Kannappan Sampath

@robjohn Which one? Can you please tell me?

O Matt went off! Have a nice nap, man!

robjohn

@KannappanSampath It's a Mac program: Intaglio

:3658313 Oh, yeah; I see it.

Kannappan Sampath

For windows, they don't seem to have a version and the Mac version is pay-and-use!

robjohn

@KannappanSampath yes, I usually find that you get what you pay for :-)

Kannappan Sampath

1:27 PM

Have you graphed using GeoGebra?

@robjohn :-)

(I'd like to graph Maximum functions)!

robjohn

@KannappanSampath I am not used to it so I'd have to learn its capabilities before using it.

@KannappanSampath for example?

Kannappan Sampath

@robjohn max(x,1/2) in (0,1) is one among the three.

robjohn

@KannappanSampath For something like that, I would use Mathematica.

Kannappan Sampath

I don't have it. Is it open source?

Jonas Teuwen

Certainly not.

Kannappan Sampath

1:31 PM

@JonasTeuwen Yes, I asked prof. Google now. But, TPB, the public backup system seems to have some genuine backups! :p

Skullpatrol

@robjohn Have you heard of the absent minded math professor who writes "x" on the blackboard, and says "y" when he means "z", but it should have been "t"?

N3buchadnezzar

So, it has come to this

robjohn

@KannappanSampath Personal version is about $250

@Skullpatrol Um, no.

Jonas Teuwen

@robjohn As a student it is cheaper :-).

But we have a campus license.

robjohn

@N3buchadnezzar come to what?

Kannappan Sampath

1:32 PM

@Skullpatrol Yes, I have. From a book of exercises in Probability :-)

N3buchadnezzar

Studying!

robjohn

@JonasTeuwen I can get those prices, but when I purchased, they were about the same.

@N3buchadnezzar my deepest sympathies.

Skullpatrol

@KannappanSampath I think I read it in George Polya's book "How to solve it."

Gigili

@Skullpatrol: Sorry I missed your message the other day. No, I'm not a native English speaker, obviously.

robjohn

@JonasTeuwen do you periodically have to prove that you are a student to keep the license?

Kannappan Sampath

1:34 PM

@Gigili No nothing is obvious.

Skullpatrol

@Gigili No problem.

Jonas Teuwen

@robjohn I don't know. I just have a campus license :-).

robjohn

@JonasTeuwen That's even cheaper :-)

@JonasTeuwen I got my first copy from a site license that Apple had

Skullpatrol

@Gigili Neither am I.

Gigili

@KannappanSampath : But the fact that I am female is obvious.

robjohn

1:37 PM

@JonasTeuwen I used that very old version until they came out with the personal license.

Asaf Karagila

@Gigili Why would anyone care?

Kannappan Sampath

@Gigili No it is not and yes, I don't care!

anon

Not so much. People can have anything as their avatars and it doesn't mean they're one or the other gender (or trans or w/e).

robjohn

@JonasTeuwen I think I avoided the academic license, fearing I would lose it if I no longer worked at UCLA.

anon

The character in my pic is, in fact, a woman.

Asaf Karagila

1:38 PM

The character in my avatar is not even a human being.

Gigili

I'm not talking about avatar and such silly things, I'd get offended when someone refers to me as "he".

And I was talking to @KannappanSampath, obviously again.

Jonas Teuwen

@robjohn Oh, but you could just buy it yourself then?

Asaf Karagila

@anon Same goes for @JonasTeuwen.

Jonas Teuwen

Thanks.

robjohn

@AsafKaragila Really, I thought it was a pretty good likeness :-D

Gigili

1:39 PM

@AsafKaragila That leads me to a nice conclusion.

Kannappan Sampath

I am not willing to talk anymore about these!

Asaf Karagila

@robjohn Likeness of what?

@Gigili That you're an imaginary thing?

robjohn

@JonasTeuwen Yes, since I am at UCLA.

Skullpatrol

@robjohn Have you read George Polya's book "How to solve it."?

anon

There must be conversation I'm missing.

Oh well.

robjohn

1:40 PM

@Skullpatrol Nope.

@anon what are you missing? :-D

Skullpatrol

@robjohn It's a classic.

Kannappan Sampath

Does anyone want to know that quote, so I can grab that book for you?

Gigili

@AsafKaragila That you're not a human being.

Asaf Karagila

@Gigili Now that's a huge flaw in your logic right there. How would you expect to succeed in mathematics like that?

robjohn

@Gigili Errr...?

anon

1:42 PM

@robjohn: I'm assuming that someone (Kanna?) called Gigili "he" and then Kanna responded to that, so Gigi's "it's obvious" statement is predicated on what she originally said back in that discussion

robjohn

@anon okay, so I am completely out on that one, too.

Kannappan Sampath

@anon Yes I did say 'he' once but I am unaware, right? I am not expected to know everyone's whereabouts! But, I'll flag remark on grounds of racism.

Skullpatrol

@KannappanSampath Don't do it!

Asaf Karagila

That was pretty cool. I saw the flag validations go higher and higher.

anon

@Gigili: To clear things up, were you being rhetorical to parallel your own situation here?

badp

1:46 PM

She can't answer, she's suspended for 30 minutes.

Kannappan Sampath

@Skullpatrol I flagged it. I am pretty serious about these things. I don't expect people to make such remarks.

anon

Because @Kanna is taking it literally - and if it was intended literally then it naturally deserves a flag.

robjohn

@AsafKaragila it drew attention pretty fast.

anon

Thanks for saying, @badp.

Skullpatrol

@KannappanSampath Come on man, racism is apart of life.

anon

1:49 PM

Sure, so is everything that deserves to be changed for the better.

badp

@Skullpatrol It doesn't mean people find it acceptable

Kannappan Sampath

Yes, as you say "apart" from life. It cannot be a part of life. That I am Indian should not bother people. For one, I have never made any remarks like this.

Skullpatrol

@KannappanSampath But we have to learn to deal with it.

anon

My concern is that she might have been trying to point out to Kanna how he was coming across to her by paralleling sexism with racism, and that she did not communicate it well and Kanna obviously took it literally. I can't say what her intent was.

Skullpatrol

Interpret what I think not what I say!

robjohn

1:51 PM

@KannappanSampath since anyone can claim to be from anywhere and take whatever pseudonym they want here, I assume, for the sake of argument, that what they say is true, but don't assume that that is really true. Nor does it matter.

Asaf Karagila

The reason I dislike the flags here is that people just get the single line, without the context of the message.

5

Jonas Teuwen

Hah, trolled.

Skullpatrol

That should be the job of the moderator: to find the context.

Juan Manuel

@AsafKaragila I read the context. Obviously I cannot get too far back in so little time before someone else flags it, but I think it was a correct flag

robjohn

@JonasTeuwen howso?

Asaf Karagila

1:54 PM

@JuanManuel Oh, I'm not talking about this specific case. I'm talking about the general case.

Jonas Teuwen

Well, he dislikes the flags and it gets flagged, oh well.

badp

@Skullpatrol Chat is an instant communication medium, if something is offensive it should be removed instantly as well. If the message is removed ten minutes after it's been posted does it really matter?

Jonas Teuwen

Oh, not stars 8-).

Juan Manuel

@AsafKaragila oh, ok then

anon

How much moderator action does the math chatroom get compared to the other chatrooms. I'm really curious :P

Juan Manuel

1:55 PM

I agree the flag system should be looked at

Skullpatrol

@badp Good point.

badp

@anon If you have 10k reputation across the network you'll find out the answer is "very little"

Asaf Karagila

He has 15k or so on a single site, isn't that enough?

Kannappan Sampath

So, we are good Chat room, then!

anon

One other question. Does the suspension prevent her from reading the content of the chat in the duration, or did she leave voluntarily?

badp

1:58 PM

A non-troublesome one, perhaps :P

@anon She left voluntarily.

Angrily, perhaps, but voluntarily.

Kannappan Sampath

So, the answer to the previous question about the moderator activity is not to be revealed or something?

anon

No, the answer was "very little"

Kannappan Sampath

Oh, thank you @anon.

anon

I conjecture normal 10k users only get flags from the rooms they're actually in. I never see any from any other rooms.

robjohn

@anon perhaps we should hang out in more rooms :-)

Asaf Karagila

2:02 PM

Nope. I see flags from other rooms all the time.

robjohn

@AsafKaragila even rooms your not in?

anon

Hmmm....

Kannappan Sampath

Probably because you own this room!

Asaf Karagila

@robjohn Indeed.

badp

@anon That's probabaly wrong, but you know that better than I can do.

anon

2:03 PM

Maybe I'm just on other tabs in my browser and the flags go away..

badp

As a moderator I get flags from all rooms.

robjohn

@badp I am not surprised by that, but why does Asaf see them from other rooms?

Asaf Karagila

Because I am so awesome!

2

anon

This is curious.

robjohn

@AsafKaragila and the König! :-)

badp

2:05 PM

@anon Flags do tend to get acted on fast. Perhaps too fast

Skullpatrol

@robjohn You should try to check out "How to solve it" by George Polya if you get a chance, it's a good little math book. I think Polya once taught Von Neumann and said he was the only student he feared.

badp

Often times the flag popup cannot load in time for me to actually see the flag.

robjohn

@Skullpatrol I will see if I can snag a copy.

Kannappan Sampath

@robjohn what does snagging a copy mean? Google has no reasonable meaning I can attach with this context!

anon

snag = grab

Kannappan Sampath

2:08 PM

Thank you!

robjohn

@KannappanSampath get a copy.

Kannappan Sampath

:-)

robjohn

@Skullpatrol Is it this small 1-2 page document?

Skullpatrol

How to Solve It

How to Solve It (1945) is a small volume by mathematician George Pólya describing methods of problem solving. Four principles How to Solve It suggests the following steps when solving a mathematical problem: # First, you have to understand the problem. # After understanding, then make a plan. # Carry out the plan. # Look back on your work. How could it be better? If this technique fails, Pólya advises: "If you can't solve a problem, then there is an easier problem you can solve: find it." Or: "If you cannot solve the proposed problem, try to solve first some related problem. Could yo...

Kannappan Sampath

Polya is an amazing Mathematician!

anon

2:12 PM

In general, any historical mathematician whose name we remember / is attached to things was an amazing mathematician.

Kannappan Sampath

:-)

Skullpatrol

@anon Have you read this book anon?

Kannappan Sampath

May be it's time for my dinner. I will come back in an hour or so. Thank you people!

anon

I've looked at it, don't really remember anything

Skullpatrol

@KannappanSampath Bye.

@anon I remember the story about the absent minded math professor who writes "x" on the blackboard, and says "y" when he means "z", but it should have been "t."

anon

2:18 PM

indeed

Skullpatrol

George Pólya

George Pólya (December 13, 1887 – September 7, 1985, in Hungarian Pólya György) was a Hungarian mathematician. He was a professor of mathematics from 1914 to 1940 at ETH Zürich and from 1940 to 1953 at Stanford University. He made fundamental contributions to combinatorics, number theory, numerical analysis and probability theory. He is also noted for his work in heuristics and mathematics education. Life and works He was born as Pólya György in Budapest, Austria-Hungary to originally Ashkenazi Jewish parents Anna Deutsch and Jakab Pólya who converted to Roman Catholicism in 188...

robjohn

@Skullpatrol: is this the book you mean?

Skullpatrol

@robjohn Bingo!

robjohn

I have to go take Lilly for a walk. bbl

Skullpatrol

@robjohn Later alligator.

Kannappan Sampath

2:29 PM

Back.

Skullpatrol

@KannappanSampath So soon, that was a quick meal.

Kannappan Sampath

Yes, indeed! I did not like the food today, though I like the meal this day of the week mostly!

@RajeshD Hi!

Does anyone know how to reduce the screen size of the image I upload to the site?

Rajesh D

2:57 PM

hi

Kannappan Sampath

I figured that out finally!

Rajesh D

@kannappan : just a small Question if you don't mind

Kannappan Sampath

@RajeshD Sure you may ask!

Rajesh D

where did you do +2 and how did you happen to choose math

Kannappan Sampath

@RajeshD I did my +2 at Trichy in Tamil Nadu.

(Sorry for late reply. I was writing this answer)

Skullpatrol

3:08 PM

@KannappanSampath Here is the source of the quotation that I was talking about earlier, if you're interested Kannappan: gap-system.org/~history/Quotations/Polya.html

Kannappan Sampath

(I will remove this messages now! So, if read please let me know, @RajeshD)

Rajesh D

and you were not bothered about the iit bandwagon ?

yeah you can

Skullpatrol

"In order to solve this differential equation you look at it till a solution occurs to you."
"This principle is so perfectly general that no particular application of it is possible."
"Geometry is the science of correct reasoning on incorrect figures."
"My method to overcome a difficulty is to go round it."
"What is the difference between method and device? A method is a device which you used twice."

Kannappan Sampath

@Skullpatrol Thank You. I did go to the link. I am also replying to Rajesh. So, couldn't confirm the receipt of link. Thank you once again.

Rajesh D

that happened to me aswell but a long time ago............i was totally ignorant of chemistry...which proved fatal

cool

Kannappan Sampath

3:14 PM

Yes. Chemistry and Physics decide! I am poor in Physics, I admit!

Rajesh D

ok

Kannappan Sampath

I missed group theory sitters on the main site! :-(