Mathematics - 2013-02-07 (page 1 of 4)

12:03 AM

See this You can take points $a_k$ arbitrarily.

Sorry. I mis-spoke before. The total contributions is the sum of the contributions to the integral. I should not have used the residue word.

Bartek

But the integrand has to be analytic in $U\setminus\{a_1\,\ldots,a_k\}$! And this doesn't seem to be the case here.

Orange Harvester

That I did not check. Let me see.

Bartek

Here, $U$ is the unit disk. The function can't be analytic if we leave the poles in the disk!

(If we leave even one)

So $a_k$ aren't really arbitrary.

They have to include at least all of the poles. And including more doesn't make any sense, because the non-poles indeed don't contribute anything.

(As their residues are $0$)

It seems to me that the whole method is bad in the answer. Unless we know the zeroes of $f$, we can't calculate the residues of $f'/f$. Unless we can somehow show that some of the zeroes of $f$ are the same as the zeros of $f'$ so that they cancel out in the ratio. Then perhaps we can do something...

But the answer doesn't mention anything like it.

Jay

12:19 AM

@Jason I get messages that it seems you mean to be directed at some one else. Perhaps you need to use more letters.

user19161

@Jay LOL I see, the system is weird.

Khromonkey

proof a+b=ab has only one natural solution?

why is it so clear?

Bartek

No, it's not, sorry.

user19161

@Khromonkey Sorry what is meant by natural solution.

Khromonkey

one where a,b are both natural numbers

Jonas Teuwen

12:26 AM

Four seasons in one day.

Khromonkey

Nevermind I see it

Orange Harvester

@Jay They are directed to me. My actual name is Jayesh.

Bartek

@Khromonkey if a,b are solutions then a divides b and b divides a, so a=b. Now it's easy.

Jonas Teuwen

@OrangeHarvester Where has Jayesh gone to!

Khromonkey

dont take creatine ever it kicks your ass

Orange Harvester

12:29 AM

@JonasTeuwen 30 days restriction!!!

Bartek

I'm sorry to be needy, but I'm really freaking out. I have an exam tomorrow. I would be very grateful if someone could comment on that thing...

Jonas Teuwen

@OrangeHarvester OK!

Orange Harvester

@Bartek Okay. I am learning complex analysis too. So, not very good at it as of now, let me see it in detail.

Bartek

Thanks!

user19161

16k, time to retire...

user19161

12:35 AM

Haha, Mariano has posted 4 solutions to the same problem, fascinating! +4.

Orange Harvester

@JasonBourne Where? Where?

user19161

1

Q: Showing two polynomial rings over $\mathbb{C}$ aren't isomorphic

Im trying to show that the ring of polynomials in one variable over the complex numbers is not isomorphic to the ring over C with two variables modulo $<x^2-y^3>$. Ive shown previously that if the relationship $p^2=q^3$ holds for some p and q in one variable, there exists r such that $p=r^...

user19161

Is someone going to start a post on quadratic reciprocity and post 200 solutions?

Argon

@JasonBourne You can retire to bed this morning

user19161

@Argon Haha, then I can see you in my dreams!

Argon

12:38 AM

@JasonBourne OH NOES! :D

Bartek

@Jason Do you know what Argon looks like?

user19161

@Bartek No. He might show me in future.

Bartek

@Jason then you might be in for nightmare!

user19161

@Bartek Do you know what he looks like?

Argon

Bartek

12:40 AM

@Jason Now I do. Well, that's not so bad. I wouldn't mind that in my dream.

Argon

Hehehe

Bartek

Though I've dreamt better. :)

user19161

Guys I am going to change my username in 20 hours. Watch out for it. It will be ...

Argon

@JasonBourne ...the pressure builds...!

math101

Hey @JasonBourne

Argon

12:45 AM

(Not another Argon joke, by the way)

Jonas Teuwen

Good nights bros.

Argon

Good night

Bartek

@OrangeHarvester I've commented on that answer. Maybe the answerer will reply.

user19161

@math101 Hey.

user19161

@JonasTeuwen Good night bro!

Orange Harvester

12:59 AM

@Bartek Lets hope. (I am solving a different problem set.)

Bartek

@OrangeHarvester OK, thank you for trying. I think I'll go then to try and do something else for the exam. It's not looking good at all.

Orange Harvester

@Bartek Sorry I could not help. Best luck.

Bartek

Good night.

amWhy

1:16 AM

@JasonBourne You around, soon-to-change-his-user-name-to-??, ?

User.1

Can I post a message here ? Is this chat live, or is it delayed with occasional visitors ?

Alex J Best

It is live

Orange Harvester

@math101 Hello.

math101

Hey @OrangeHarvester

user19161

@amWhy Haven't confirmed.

Orange Harvester

1:26 AM

@math101 Wassup?

math101

Are you familiar with investing

Orange Harvester

Yes.

Financial right?

amWhy

@JasonBourne At least keep your gravatar so we can spot you! (you can email those who are on your "chosen" list, as well!)

math101

Yes

Orange Harvester

Yes. I am familiar with that.

math101

1:27 AM

If you had to invest in what area would you invest?

Orange Harvester

@amWhy Hello!

user19161

@amWhy Well, those people should know how to spot me by now.

Orange Harvester

@math101 Depends on the country!

amWhy

@OrangeHarvester Hey, wassup?

math101

Ok well in North America

not India

Orange Harvester

1:27 AM

@amWhy I'm good.

user19161

Everyone's good, except me. I'm bad. QED.

Orange Harvester

@math101 Not much familiar with North American finances right now.

amWhy

@JasonBourne Am I among the "those people..."?

Orange Harvester

@JasonBourne But you were happy yesterday!

@amWhy That is a question for you to answer, miss. Can you spot him? ;-)

math101

@JasonBourne I am bad too

user19161

1:28 AM

@amWhy Well, those who have been on the site long enough and have talk to me enough should know 9000 ways.

Orange Harvester

@math101 Ohh.

amWhy

I found good use of the word "apropos" today, just a few minutes ago!

math101

@JasonBourne what is your attachment to the number 9000?

user19161

@math101 Oh, hmm... I hope you feel better soon, I don't know what's wrong there.

amWhy

@JasonBourne I am not well.

user19161

1:30 AM

@math101 It is a saying that became popular on the internet. Actually, one is supposed to say "OVER 9000".

Orange Harvester

@amWhy Anything specific?

user19161

It seems that there are more and more secrets in this chat. The plot thickens...

User.1

Okay, the three areas of math that interest me are: Trigonometry, Boolean Algebra, and a little bit of geometry; although I'm not very good at geometry

Orange Harvester

@User.1 Are you in high school?

User.1

Does stack exchange have sites for any of those

amWhy

1:32 AM

@OrangeHarvester No, nothing really specific; it's become my "default" state of being...one which I'd like to change. Not such a good day for me on math.se today...seemed slow, or maybe it's me...

Orange Harvester

@User.1 MSE is the umbrella place.

user19161

@User.1 Yes, this site.

user19161

@amWhy You don't need to cap every day.

Orange Harvester

@amWhy Ohh. :-( Does not sound good. I hope you get better too.

User.1

@Orange, no. WHen I was in high school, bellbottoms and platform shoes had us looking like idiots and sounding like horses clopping around in the hallways

user19161

1:33 AM

I am happy as long as my answer gets at least one vote after a day.

user19161

If not, I delete it.

user19161

So you can see that all my posts are currently at positive votes.

user19161

If one gives the asker a correct answer and he doesn't even give a vote for it, that's really sad.

Orange Harvester

@User.1 Ahh, cool. Well. math.stackexchange.com is the site where you can ask big questions. You can also ask questions in chats here. Rule of thumb is longer questions should be asked on the main site and short ones can be asked here.

amWhy

@JasonBourne No, I know that...I don't always mean good day at math.se = high rep. I just read more into "things" than is healthy...

User.1

1:35 AM

I would like to try "higher" math again, but they teach it so wrongly. You need a much stronger basis in trigonometry to really get calculus into your brain; but at the collegiate level, trigonometry is almost disdained. At best, I think I got 5 weeks of it in a crash cram course mixed with algebra, called "pre-calc" or something. Disappointed to this day

user19161

@amWhy Well, I think there is nothing to read at all. It's just a site.

Orange Harvester

@amWhy I understand.

amWhy

@JasonBourne Yes, when the asker has the rep to upvote!

User.1

Real life has gotten in the way. Garsh, why did girls have to come into things during adolescence ? I could have studied math so much better if they never existed

user19161

@User.1 Disappointed in what exactly?

User.1

1:37 AM

@Jason

ooops

Orange Harvester

@User.1 Well, its never too late to start.

user19161

@User.1 Really? I study math better with girlfriends, but I never had one in my entire life.

11

amWhy

And I've never been comfortable with the idea of - or context in which there is - "competition"...

user19161

@amWhy Oh well, take this site a little seriously, but not too seriously.

amWhy

@User.1 Be careful who you wish never existed: some of US might take offense! ;-)

user19161

1:38 AM

One of these days, I am gonna delete this account as well.

User.1

@Jason they zoom you through "pre-calc" like that's really going to get you ready for Calculus. Pig Snot ! Through a trombone !!! Trigonometry exercises the brain and gets is ready for Calculus. That's why I'm so disappointed

Orange Harvester

@amWhy :-) I am glad (very happy) that girls exist! Especially on this site! :-)

3

user19161

@User.1 You know what? I still don't get what you dislike. Could you explain in simple words? =)

amWhy

@OrangeHarvester That's two of your posts I just starred!

Orange Harvester

@amWhy :-D

User.1

1:40 AM

@JasonBourne Better trig means better Calc. that's why I'm disappointed. I would like one college course in algebra, one in trig, then 4 in calculus, then we can take on the high level stuff.

Orange Harvester

@User.1 Could it be because at collegiate level, it was meant to be a review course, and not a full course?

amWhy

@JasonBourne Don't delete, just take a vacation from the site for ...don't undo what you've done...I took a long breather, came back, and was glad I hadn't deleted my account.

User.1

@JasonBourne, But NO !!! Zoom the basics and cram the math. That's the college way

Plus, colleges are so into semesters now; quarters are gone

Orange Harvester

@amWhy That is what I advised him.

user19161

@User.1 Oh well, this is what I think. The trig and algebra is too trivial, you are meant to do all that in high school.

User.1

1:41 AM

I swear, they would do better with quintiles if you ask me

user19161

@amWhy When I deleted my account on tex and eng, they let the users there keep their rep it seems. If I delete this one as well, I don't know what they will do.

amWhy

@User.1 Actually, you don't really learn algebra and/or trig until you need it and use it in calculus...

User.1

Well, anyway, that's just the past, and that's just my gripe, and so enough of the whine

@amWhy I never had more fun in college than those 5 weeks with trig

user19161

@user Really you are supposed to get all that stuff right already in school. Some even start calculus in school.

anorton

@JasonBourne Don't delete your account... you may want it back some day. What purpose does deleting it serve?

peoplepower

1:43 AM

If they taught all of the prereqs immediately before a category theory course, they would never get to natural transformation.

user19161

Also @user the calculus courses are going to repeat similar things over and over again till you get bored.

User.1

@JasonBourne yes, correct, you are supposed to. SUPPOSED TO

Okay, whine out

over and out

user19161

You see, sometimes in life, if you go wrong somewhere, it's hard to get back to the right path.

Orange Harvester

@peoplepower I agree.

user19161

But with much effort it is possible to get somewhere in the end.

user19161

1:44 AM

So get your trig right first and then enter college. QED.

user19161

It's really impt to choose the right college for one's undergrad.

amWhy

@User.1 It really is never too late to start...just jump in, make connections, and keep working...persistence, patience, practice = progress

2

user19161

I was not aware of the great difference between universities back then.

User.1

So, where would a good place be for someone who is old and whose brain cells have atrophied totally, to review algebra, so as to re-study trig the way it should have been done (i.e., the "supposed to" that never happened for me) something like, oh, 10 minutes a day for a few weeks, until I can handsomely handle most 2nd year high school (college 101 level, maybe) algebra word problems and linear problems ?

amWhy

I like alliteration, if no one noticed by now.

user19161

1:46 AM

@User.1 Check out Paul's Online notes. tutorial.math.lamar.edu

user19161

Just to help you get started.

User.1

@JasonBourne just clicked

amWhy

@User.1 Khan Academy: 10 minute videos...work up until you can cover a couple of videos at a sitting...the site covers everything from basic arithmetic -- algebra -- trig -- geometry -- calculus -- and a bit more too. I think its khanacademy.org

User.1

@amWhy link ?

Freebie ? Online ? I sit, I watch, I learn ?

Orange Harvester

@User.1 I am not sure if you are joking, but 10 minutes a day might be too less to reach a critical understanding (where you can be sure you can carry the concept to next day). You might need to spend 1-2 hours at the minimum.

user19161

1:49 AM

Also, don't trust anyone in your math studies.

user19161

Professors can give you wrong proofs and wrong theorems.

Orange Harvester

@User.1 Yes.

amWhy

@User.1 Free, online, sit and watch, and WORK, and learn...:-)

user19161

Famous universities can give you shit courses.

user19161

Read as much as you can and think as much as you can.

Orange Harvester

1:49 AM

@User.1 For trig

amWhy

@JasonBourne and write as much as you can.

User.1

The more famous the university, the more papers they publish, the less you will ever learn in your real classes; i.e., the 4 year degree

What is the link for Khan Academy

Orange Harvester

@User.1 Not necessary. Its not true.

user19161

@User.1 Not really, there are too many factors involved.

Orange Harvester

Khan Academic

User.1

1:50 AM

That 10 minute video idea sounds like a real winner

Oh, about the 10 minutes, I like to watch them once, then twice, then the third time with stops and replays

user19161

And come here to chat if you need help. I don't know much, but I can tell you that 1+1=2.

amWhy

@User.1 That is true, at four-year colleges (even at 2year community colleges) the PhD's do the teaching...and love to teach...and focus on teaching, not on research.

User.1

@OrangeHarvester I got it. That place is free ?

Orange Harvester

@User.1 Yes. Just click on the links and explore.

amWhy

@User.1 Free and clear...and now even funded in part by Bill Gates! No commercial advertising...

User.1

1:53 AM

@amWhy and User.1 have very similar observations. I do believe that the next time I need to really learn something for my job, I'm going to say screw it for any BigName U, and take my courses at the local city junior college; for EXACTLY THAT REASON !!!

Bill Gates threw his money after that ?

Wow

Why did a number just appear below my User ID ?

Orange Harvester

That is your toal reputation points on SE.

user19161

I have an observation that you may not agree with.

Orange Harvester

@amWhy I must say its hard to understand Bill Gates. On one hand, he buys off political honchos in other countries to sell his windows software, and on the other hand he sponsors Khan Academy and stuff. He sponsored the Polio vaccination program, but the activist group say, he came in very late and is only stealing credit for stuff other people have done.

user19161

The best researchers also teach well. Those who don't teach well might be good researchers but not the very best.

User.1

If any observation is different from mine in any way, no matter how minor, the other person is obviously wrong

user19161

1:55 AM

Same thing goes for universities.

Orange Harvester

@User.1 You must be Linus. :P

User.1

I am so mature

smirk @OrangeHarvester

@Jason, Yes, BigName U,,,, BigShot Ph.D., does not teach his classes. His teaching assistants do it for him

user19161

@User.1 No, read my above lines carefully.

User.1

whatever

user19161

I mean to say that the very best researchers also teach well, but the good but not so good ones don't teach well.

User.1

1:57 AM

Yall have helped me with a couple of good ideas

skullpatrol

The best person to teach you is yourself.

amWhy

@OrangeHarvester I agree...his motives at times smell fishy...I also read a bit about the dispute with the other founder of Microsoft...seems Gates' ambition has cost him some personal ties...and muddied the waters. From my perspective, we need to remember we are each a human being before anything else, and remember that, and act with that in mind.

User.1

so now I have a couple of places to go and see if I can fire up the withered brain cells again

Orange Harvester

@JasonBourne Teaching is a two way art. Resonance frequency and analogy.

User.1

Okay, so I'll see what a week or two with Palu's site and Khan Academy do for me. Or is a couple of weeks enough for me to know ? Do I need to try six months ?

BenjaLim

2:00 AM

@Sanchez Are you around? I posted a question last night on an isomorphism involved in calculating the coordinate ring of $V \times W$

User.1

Palu ---> Paul

user19161

Well, it's your pace.

Orange Harvester

@User.1 Depends on your background really.

amWhy

Sometimes it seems logic-oriented questions/answers get little respect (or maybe it's a matter of little viewer-ship).

user19161

@amWhy Just relax.

Orange Harvester

2:01 AM

@amWhy Yes. Logicians are a small group I think, as compared to say analysts.

User.1

I have written software for 20+ years, the whole world has been bits and bytes, and once or twice I get to reduce algebra to a digital formula in some registers. I'm in embedded systems at the really low levels; oscilloscopes and pins and stupid manuals written by people who can't write

user19161

@OrangeHarvester Many logic questions here are trivial ones that any freshman should know.

Orange Harvester

@JasonBourne Ahh. May be.

user19161

@User.1 DOesn't take much math to be a programmer.

amWhy

@OrangeHarvester and some of them here are pretty "nit-picky" ....

Orange Harvester

2:03 AM

@User.1 I am an electrical engineer. I worked with device drivers for some time in college. And on embedded systems. I get your pain!!

user19161

At the level of mathematical logic and axiomatic set theory, one has to be picky.

User.1

@Jason will you PLEASE SHUT UP !!!! As soon as people realize that, our paychecks go even with High school grads !

4

user19161

HAHAHA

Orange Harvester

@JasonBourne If you want to design good programs, maths is very necessary!

amWhy

@JasonBourne Yes, that's true...many are...but most students aren't exposed to logic in high school...and some don't take it in college.

Orange Harvester

2:04 AM

Most of the foundations of object oriented programming and functional programming etc are highly mathematical, also math goes a long way to give you a good sense of architecture of a program (especially algebra).

User.1

@OrangeHarvester, you do wires and chips ? Can we do private messaging ? I have a great invention with a low cost and a big market.

but I don't know how to put a chip on a board

amWhy

@JasonBourne Precise, not necessarily picky. And one can be a logician with a heart. One needn't be a computer.

user19161

@User.1 Anyway, I say that because I see many programmers asking very basic questions on this site.

amWhy

@OrangeHarvester And logic is crucial too

Orange Harvester

@amWhy Yes! Logic is assumed!

amWhy

2:05 AM

Not that logic and math aren't related....They are, indeed.

User.1

Most software writers are just plain sloppy in everything they do with their mind; you can see it immediately in their code

Orange Harvester

@User.1 There does not exist a private messaging on this site. I am not comfortable giving out my email.

User.1

plus, Mr. BossMan is forever threatening them to finish faster; "...damn the future, we're going out of business now !!!..." and that sort of thinking

no, please don't

Anyway, keep me in mind if you're ever looking for something to do.

Orange Harvester

Okay!

skullpatrol

If I leave, will you feel more comfortable?

user19161

2:08 AM

@skullpatrol HAHAHA

user19161

Hey @math you returned.

Orange Harvester

@skullpatrol ROTFL. No, I would be even more uncomfortable, with no skullie to defend me, people would not be afraid anymore!!

User.1

This seems like a decent crowd. I hope I can remember how to get back in here

What is the path to a given chatroom

Orange Harvester

It is in your address bar.

user19161

I am going to sleep. I will see some of you in my dreams.

User.1

2:10 AM

Okay, I log in to StackExchange.com, then,,,, help my brain

skullpatrol

L8er

amWhy

@JasonBourne okay

Orange Harvester

@User.1 Bookmark this link

User.1

@Orange got it

thanks

skullpatrol

(removed)

User.1

2:11 AM

Nite-O, thanks to all

uhm

how do I leave ?

Just close the tab ?

yes.

L8er

Nite-O to all

@amWhy I guess that you are in logic.

@User.1 Good night.

amWhy

@OrangeHarvester One area I like...But it's as much a tool for me as it is a domain of study...philosophy of math I like, abstract math, too...

skullpatrol

2:14 AM

Math is the poetry of logical ideas. -Einstein

amWhy

@OrangeHarvester what's you area of focus/interest? Or are you like me...liking it all

@skullpatrol Nicely put!

@skullpatrol I never heard that before! Thanks for the quote...

Orange Harvester

@amWhy I like it all, and not just math, :P I like it all from biology to mechanical engineering to economics, but I am good at very few things. Till now, I have proved to be good at analysis and numerical methods (mainly because of my engineering background.)

skullpatrol

@amWhy np :)

amWhy

@OrangeHarvester I hear you...I majored in math, philosophy, psychology, AND comp sci, talk about a mix!

Orange Harvester

@amWhy :D I am actually not sure. Though I am interested in other things a lot, its a little difficult for me to do those other things persistently, and find myself yearning to do mathematics instead. I don't know if that is called liking or passing interest.

@amWhy Wow! Nice!

skullpatrol

2:19 AM

@OrangeHarvester Yearning to do something is more than a passing interest, no?

amWhy

@OrangeHarvester I tend to procrastinate pursuing many of my interests by turning to math; I don't know if that's telling me anything!

Orange Harvester

@skullpatrol I was talking about other things. If you like A and B, but you rather want to spend your time doing B, do you really like A?

skullpatrol

A and B can be related.

Eric

Evening everyone

skullpatrol

hi

amWhy

2:22 AM

Alas...back to math.se...sigh!

Orange Harvester

@amWhy Bye!

skullpatrol

L8er

have fun

Orange Harvester

@amWhy I tend to combine views of Hardy and Feynman. Ferynman says we as human differentiate between the the various fields, for the universes it is all a glass of wine.

And as Hardy says, some people can do only somethings well, that is their thing.

amWhy

I'll keep the window open...just taking a break from chat...thanks all!

Orange Harvester

:-)

skullpatrol

2:25 AM

:-)

amWhy

@OrangeHarvester My problem is that I've always done pretty much everything well! It may not seem like a problem...but when one must choose...I have problems!

Orange Harvester

@amWhy I understand. Been there!

skullpatrol

They say that is your calling.

Orange Harvester

Yes.

skullpatrol

Your life's calling.

Orange Harvester

2:28 AM

Right now, its my mom calling. So see you guys later. :P

skullpatrol

lol

L8er

skullpatrol

3:08 AM

Hi

@Khromonkey

Khromonkey

Holy dynamite!

thanks

sup?

skullpatrol

Chillin'... you?

Khromonkey

Im listening to some Schubert

do you know Schubert?

skullpatrol

Some.

Khromonkey

the 8th symphony is my favorite

do you guys know someplace in the web to learn combinatorics?

skullpatrol

3:15 AM

Wikipedia? but the best place to start, in my opinion, is the library.

Khromonkey

Oh, sorry, i didn't mention I live in Mexico.

skullpatrol

Try the nearest University/College library.

Khromonkey

I have a copy of van Lints book

skullpatrol

Use whatever you can get your hands on and get started.

Khromonkey

Ok

I actually own a ton of books

skullpatrol

3:20 AM

Then you have a ton of work.

Khromonkey

the only problem is I am $$\mathbb extremely lazy$$

that doesn't look cool. How can I make it look cool?

skullpatrol

$\Huge\text{Extremely lazzzzzzzzy}$

Khromonkey

that's what I meant

skullpatrol

;-)

Khromonkey

Does category theory have many requirements?

All the cool stuff I want to read allways say something is bound by a tower

skullpatrol

3:30 AM

Have you looked here?

Khromonkey

yes, I read the portion on category theory in Serge Langs algebra

but I didn't really develop any intuition

Alex J Best

Not sure exactly what you want, but these notes look pretty good, I haven't had the chance to get very far in though.

mimuw.edu.pl/~jarekw/pdf/Algebra0TextboookAluffi.pdf

anon

I like CRing.pdf a bit

Khromonkey

the no cry parenting guide?

anon

your google savvy is low..

Khromonkey

3:33 AM

I use bing

anon

`Showing results for crying.pdf`
`Search instead for cring.pdf`

Khromonkey

-said no one ever-

Alex J Best

@Khromonkey That explains it then

Khromonkey

everyone knows yahoo is the best by far

I love the word savvy

its like you're sophisticated but hip at the same time

when you say it

Thanks guys, i'm going to take a look. See you later,take care and don't exceed the 0.20% alcohol level

skullpatrol

L8er

well-known? by who??

anon

3:44 AM

45...?

robjohn

@Bartek The zeros and poles of $f$ are the poles of $f'/f$.

skullpatrol

@robjohn Have you ever heard of the Zollner illusion?

robjohn

@skullpatrol Not by that name, but I have seen similar illusions.

Ben W.

Anyone know of any decent texts for cryptography?

skullpatrol

@robjohn Wow! "If the illusion is printed in green on a red background and the red and green are equally bright, the illusion disappears." according to Wikipedia.

That shows the power of the use of color.

robjohn

3:52 AM

@skullpatrol also, if you look at it reduced in size and slightly defocused.

skullpatrol

@robjohn This builds a strong case for the use of color in proofs ;-)

Orange Harvester

@Khromonkey van Lint is a good book for combinatorics. I have it too. Another good one is Alan Tucker.

robjohn

4:14 AM

@skullpatrol I tried the color thing, but it didn't work.

mika

4:26 AM

+1 @robjohn

robjohn

4:44 AM

@mika in reference to...?

skullpatrol

@robjohn Actually trying it gets a +1 from me :-)

awllower

I have a little question:
http://math.stackexchange.com/questions/296337/subgroup-of-order-11-lies-inside-zg/296910#296910
In one of the answers, it is said that, P is a normal subgroup which intersects trivially with G', so P is a subgroup of Z(G).
I fail to understand it. Can someone help?

anon

@awllower If P intersects trivially with G', then [P,G], being a subgroup of both P and [G,G], must be trivial.

awllower

I have tried to form the dirct product, which helps not.
I also tried to consider the orders, but it leads to my answer...

@anon Because P is normal?

anon

@awllower yes, normality tells us that P is a subgroup of [P,G].

awllower

4:59 AM

Hum, I guess you mean [P,G] is a subgroup of P.

Thanks very much.

anon