Mathematics - 2018-10-20 (page 3 of 4)

6:01 PM

Corned beef is anisotropic. I remember my brother once cut it with the grain rather than against it before serving it, and it was weird to eat

Stan Shunpike

@TedShifrin Je suis heureux d'entendre que votre mère reçoit de l'aide.

Ted Shifrin

oh, meat in general is anisotropic. If you don't slice it against the grain, you get very tough eating.

Akiva Weinberger

Pretty sure it was corned beef, anyway. (I'm hungry now)

Ted Shifrin

merci bien, @Stan

Eric Silva

sup nerds

Stan Shunpike

6:02 PM

@TedShifrin i am trying to learn french

Ted Shifrin

heya Eric

Eric Silva

how goes it

Ted Shifrin

@Stan: If you say "je suis heureux que" you need subjunctive. You cagily avoided that. :P

I've spent 10 minutes trying to figure out how to open a private chat (because Jakes asked). I still don't see it from main.

Stan Shunpike

@TedShifrin I cant even do that in Spanish or italian let alone french 😂

Ted Shifrin

J'adore le subjonctif, @Stan :P

Leaky Nun

6:03 PM

@TedShifrin il n'y a aucun salon private

Ted Shifrin

@Leaky: privé ... But you always get notified "take this discussion to chat"

I don't mean private ... I mean targeted.

CaptainAmerica16

@AkivaWeinberger Now I've got a bit of pattern! I folded it in half and tore diagonally.

Leaky Nun

@TedShifrin chat.stackexchange.com/rooms/new

Ted Shifrin

How do you get to that conveniently?

In here, I click on your avatar and I have the link.

Leaky Nun

"all rooms"

Stan Shunpike

6:05 PM

@TedShifrin im taking machine learning. So far the math has been pretty reasonable. We did OLS first week and how to like use polynomials for fitting data sets.

Leaky Nun

and then scroll to the bottom

Ted Shifrin

Ugh, Leaky. That seems way too convoluted.

Leaky Nun

those are two steps

Lozansky

Or just change the URL :P

Ted Shifrin

Anyhow, I hope @jakes has read all of this.

Akiva Weinberger

6:08 PM

https://chat.stackexchange.com/rooms

Is there not a button somewhere there?

On the bottom

Ted Shifrin

DogAteMy: Ah, there it is. Nice 'n obvious.

Joe Shmo

ok, i see it ted

Ted Shifrin

wow, I thought you'd gone to sleep, @JoeShmo.

Joe Shmo

haha

well i did a few other things too. im not that slow

Ted Shifrin

IF you say so. :)

Stan Shunpike

6:11 PM

Hahahahaha

Akiva Weinberger

@JoeShmo How

Ted Shifrin

Well, I grumbled when someone closed as a duplicate a question I'd answered — as it really wasn't. And it's been undone. Miracles.

Stan Shunpike

Wit still sharp i see Ted.

jakes

Thanks guys

Secret

@AkivaWeinberger Pretty sure love transcends mathematics

Stan Shunpike

6:12 PM

@TedShifrin where r u keeping ur keys these days?

Hahahaha

Ted Shifrin

Huh? @Stan

I'm not the one with Alzheimers ... just yet, @Stan.

Bob

I was wondering if somebody here could look at my post: math.stackexchange.com/questions/2955619/…

Joe Shmo

@AkivaWeinberger write $x = \dfrac{z + \bar z}{2}$, $y = \dfrac{z - \bar z}{2i}$ and apply the chain rule to $\dfrac {\partial f}{\partial z}$, $\dfrac {\partial f}{\partial \bar z}$

Stan Shunpike

@TedShifrin That was always why I found it amusing you jokes about the keys so often.

My grandpa has just recently passed some threshold of no return

Ted Shifrin

I don't remember joking about it much at all, @Stan. My sympathies.

I have started making comments about my agedness, it's true.

Stan Shunpike

6:14 PM

C’est la vie I guess

Bob

Jokes are often subjective

Stan Shunpike

^ so true

Bob

@TedShifrin You do not seem old to me

Joe Shmo

jokes are surjective

Ted Shifrin

That too is subjective, @Bob :)

@JoeShmo: That's an example of a joke worth ignoring.

Stan Shunpike

6:16 PM

Yeah my other grandpa still goes to school.

Joe Shmo

:(

Stan Shunpike

And he’s 86

So u think its relative

Joe Shmo

there goes my career in comedy

Ted Shifrin

@JoeShmo: The beauty of differential forms is that the chain rule is built in to them. Avoid using it on the differential operators!!

Stan Shunpike

@JoeShmo you can always tell math jokes. Ive heard they’re quite popular with the general public

Ted Shifrin

6:17 PM

It's way easier to just use undetermined coefficients (or an inverse matrix) starting with the forms.

Stan Shunpike

Wow i never noticed that about differential forms

Joe Shmo

yes, i know. everything reeks (in a good way!) of differential forms here, but i haven't built up my technique well enough last semester

Stan Shunpike

Learn something new everyday

Bob

When you say undetermined coefficients are you referring to the technique for solving DE?

Joe Shmo

so im like doing everything right with them, but only sort of

Ted Shifrin

6:19 PM

No, writing $\partial/\partial z = a\partial/\partial x + b\partial/\partial y$, similarly for the other one. Now solve for $a,b,c,d$. It really is an inverse matrix ...

Joe Shmo

ill have to read differential geometry again in the summer. this rime properly

Ted Shifrin

Or watch a few of my lectures, @JoeShmo.

Joe Shmo

probably your book

Your lectures are really great, but i understand books better

Bob

@TedShifrin Do you have your lectures online?

Alessandro Codenotti

Hi @Ted

Ted Shifrin

6:19 PM

Yes, @Bob.

See my profile.

heya demonic @Alessandro

Stan Shunpike

Yeah Ted is an online superstar

Ted Shifrin

blah.

LOL, @Alessandro

I think for running me down so often ...

Alessandro Codenotti

I actually forgot how I became demonic too

My phone really hates editing messages for some reason

Ted Shifrin

Demonark is just demonark

Alessandro Codenotti

@TedShifrin I think you're right

Stan Shunpike

6:22 PM

«@TedShifrin what kind of music do u listen to these days?

Ted Shifrin

Now you have me scared to visit both Italy and Germany, @Alessandro

still classical, @Stan ... went to a vigorous piano recital the other night

Stan Shunpike

Ooo what pieces?

Leaky Nun

how vigorous?

Alessandro Codenotti

Germany is safe, I don't have a car here!

Ted Shifrin

Korean pianist ... at times he definitely was bangy, but other times very nuanced ...

OK, @Alessandro, I'll keep that in mind.

Akiva Weinberger

6:23 PM

Nov 21 '17 at 21:45, by Alessandro Codenotti

first demonark, now I am the demonic driver, we're gonna need an exorcist in this chat at this rate

Ted Shifrin

Can always count on DogAteMy to peruse the archives

Bob

@TedShifrin Thanks for telling me about your video

have a nice day

Ted Shifrin

take care

Stan Shunpike

@TedShifrin I just went to see a string quartet on campus

Ted Shifrin

which one?

Mary Star

6:27 PM

Stan Shunpike

Some local one I think. I didnt look carefully. My friend just invited me. But they were splendid. They played Haydn, Shostakovich, and Brahms. And for an encore Webern

Ted Shifrin

oh nice ...

Secret

@MaryStar This is identical to hobo's proof, because the definition of || is that there exists a bijection

Stan Shunpike

The contrast between Haydn and Shostakovich was a bit jarring because his piece was a bit darker. And the use of the instruments so radically different i feel like it would have been better to do Haydn Brahms Shostakovich

Joe Shmo

@MaryStar sure. this seems like the most straight forward proof of fact.

Stan Shunpike

6:28 PM

But the pieces were exceptionally executed

Mary Star

Ah ok! Thank you!! :-)

Ted Shifrin

The Brahms was probably the longest, so they left it alone for the latter half.

heya @MikeM

Mike Miller

hi

Stan Shunpike

Very true, maybe that is why

Akiva Weinberger

Heyo

Joe Shmo

6:29 PM

$M\subset M\cup N\Rightarrow |M|\leq |M\cup N| < \infty$

Stan Shunpike

@TedShifrin My friend wanted to go for her class so it was fun explaining some aspects of classical music she’d never experienced before. Its cool seeing someone enjoy it for the first time

Ted Shifrin

Very cool, @Stan. I'm sure you did a great job :)

Stan Shunpike

Hahahaha I try my best. @TedShifrin Im not tutoring math this quarter. I dont know if I should do it again. I felt like it was a waste of time last year. The kids like me more because I make them laugh and I seemed to make no impact on their actual love for math, even though they did perform better.

As a unit collectively they resist developing enthusiasm

Ted Shifrin

I know how you feel.

Akiva Weinberger

What grade/level?

Stan Shunpike

6:33 PM

7th / 8th so 12-13 year olds

Their favorite things to do are eat gossip and sleep

Ted Shifrin

Sounds like college students :P

Stan Shunpike

Hhahahahhahahahahahahhaa

Omg

CaptainAmerica16

I like to eat.

I don't like sleeping though.

Ted Shifrin

We won't discuss your bad eating habits, @CaptainAmerica.

Stan Shunpike

@TedShifrin And I feel like there’s little point to tutoring at the high or middle school I attended because those students already have every advantage you could ask for, even if they would be more motivated

@TedShifrin so what motivates u to teach?

CaptainAmerica16

6:36 PM

@TedShifrin I told you I'm trying to change ;-; But now Burger King has 10 nuggets for a dollar. I didn't know what to do.

Stan Shunpike

Love for the subject?

Ted Shifrin

Stan, I tried to get a gig volunteering to help at-risk students, and no one would let me .... so now I'm teaching the very pampered AoPS kids. But at least they're interested in learning math.

Stan Shunpike

Yeah

Ted Shifrin

ROFL, CaptainAmerica. Just don't tell me.

Mike Miller

you must struggle every day to be the man you want to be

Stan Shunpike

6:36 PM

Thats kind of where im at

Ted Shifrin

To whom is that addressed, Mike?

Stan Shunpike

Wait no @MikeMiller lolol

CaptainAmerica16

I wish someone would be willing to mentor me. I love math, but I don't have anyone.

Ted Shifrin

The sarcasm level depends on whom.

Stan Shunpike

Hahahaha i should use the @

Ted Shifrin

6:37 PM

You have all of us, CaptainAmerica.

Lozansky

You can teach me, @TedShifrin

I'm at-risk... of failing

Ted Shifrin

Ha ha.

Stan Shunpike

@TedShifrin out of practice in math chat

Mike Miller

@TedShifrin captainamerica but it applies to every human being

Ted Shifrin

oh ...

CaptainAmerica16

6:38 PM

I have learned a lot here.

Alessandro Codenotti

@TedShifrin Where do the college students you know find time to sleep?!

Stan Shunpike

@TedShifrin who’s your favorite classical composer?

Akiva Weinberger

Hey, you know this geometric proof of the 2x2 determinant formula?

Ted Shifrin

@Alessandro: The ones who took my classes claimed I made it difficult. But most students at UGA partied an awful lot.

Akiva Weinberger

Also this

Conjecture: No such proof is possible in 3D.

Ted Shifrin

6:39 PM

DogAteMy: I've done similar things in my lectures. But my favorite for the $2\times 2$ determinant uses the dot product formula.

Mike Miller

@AlessandroCodenotti i slept 4 h every day for the past week. caught up with 12 tonight

CaptainAmerica16

Ooh, geometric proofs. The only one I've ever done was one of the Pythagorean theorem.

Akiva Weinberger

@TedShifrin How does it go?

CaptainAmerica16

@MikeMiller I've heard it's not possible to catch up on sleep.

Ted Shifrin

rotate one of the vectors $\pi/2$, DogAteMy, and use $a\cdot b = \|a\|\|b\|\cos\theta$.

Alessandro Codenotti

6:40 PM

@MikeMiller You're turning into Balarka

Akiva Weinberger

(And the reason I say you can't do it in 3D is related to that cutting-and-rearranging theorem)

Hilbert's 3rd, or maybe it was the 4th

Eric Silva

@AlessandroCodenotti if u sleep ur a cop dont @ me

Mike Miller

i don't know what that means. if you reliably undersleep you'll continually feel exhausted. if you sleep a good amount you will not feel exhausted any more the next day. i'm not claiming the last week was healthy, just that for once i no longer feel exhausted.

Ted Shifrin

DogAteMy: That's actually in chapter 1 of my book.

Akiva Weinberger

Ah, I see.

Also doesn't work for 3D :P

Ted Shifrin

6:42 PM

No, you need base times height for 3D.

CaptainAmerica16

@MikeMiller I guess I don't really know what it means either.

Alessandro Codenotti

4 hours is fine once, but for a whole week I need at the very least 6 hours per night on average

Ted Shifrin

But you can do the shearing argument fine.

Akiva Weinberger

That's true

Eric Silva

(for the record sleep is good and im bitter bc life makes it hard)

Mike Miller

6:43 PM

yes

Mary Star

@Secret @JoeShmo The statement with the intersection is false, isn't it?

I mean " $M\cap N$ is finite $\implies$ $M$ and $N$ are finite sets " is not true, or not? To find a counterexample do we take one of M or N as an infinite set and the other one as a finite example that contains just some elements of the infinite set?

Akiva Weinberger

Sleep or weep

CaptainAmerica16

I've ruined sleep for myself. I've been on YouTube/Netflix until 3am every night for the past 4 days. Then I spend my day doing math. It's hard to break the cycle and it's cutting into to my time spent on my boring classes.

Joe Shmo

@MaryStar correct. counter example?

Mike Miller

I mean, in arbitrary dimensions you'll get an irritatingly large formula that seems to me to make geometric proofs unnatural, other than the usual "volume is an n-form" argument

Akiva Weinberger

6:43 PM

That's my slogan, I'm gonna spray paint it on walls now

Joe Shmo

ah yeah. you gave one. sure

Mike Miller

@CaptainAmerica16 i get this but now is the time in your life where you'll be able to stop yourself before permanently creating bad habits

Joe Shmo

@MaryStar can you give a concrete counter example?

Alessandro Codenotti

I'm actually sleeping way more and better now that I have no internet in the dorm

Akiva Weinberger

Nonnegatives, nonpositives

Mary Star

6:44 PM

For example $M=\mathbb{N}$ and $N=\{1,2,3\} then $M\cap N=\{1,2,3\}$, right? @JoeShmo

Mike Miller

though i understand because when i was a kid i hated sleep for how it cut into my doing things time

it's just, that's the wrong framing

Joe Shmo

@MaryStar sure. that's right.

Mike Miller

i just want you to internalize the important things now

like also never trust the police

CaptainAmerica16

@MikeMiller I know. You sound like Ted and my mom. I wish the sun stayed up longer...and I didn't have to take English.

Ted Shifrin

@Eric: You just like being bitter!

Eric Silva

6:45 PM

@MikeMiller hell ya bro

Akiva Weinberger

@MikeMiller ACAB?

Ted Shifrin

@CaptainAmerica: English is great! So are other languages. You can't do mathematics if you can't write decently.

Akiva Weinberger

(I suppose the question form of that is AACB)

Mary Star

So, to disprove the statement " $M\cap N$ is finite $\implies$ $M$ and $N$ are finite sets " is it enough to give a counterexample? @JoeShmo

Eric Silva

@TedShifrin ur not wrong

CaptainAmerica16

6:46 PM

Oh my gosh.

Perturbative

Hey everyone

Mike Miller

Sometimes I like to call A CAB

Akiva Weinberger

Hi

Ted Shifrin

@Eric: I'm more perceptive than I appear. :P

Joe Shmo

@MaryStar of course. the implication doesn't hold!

Ted Shifrin

6:46 PM

hi Perturb

Eric Silva

hot take: English is a better subject than math

Alessandro Codenotti

@MikeMiller That's a very american thing to say

Perturbative

Hi @TedShifrin :)

Akiva Weinberger

@EricSilva What about Portuguese

Eric Silva

portuguese is better than english

Joe Shmo

6:47 PM

@MaryStar, how do you prove $A \implies B$ is false?

Akiva Weinberger

@AlessandroCodenotti I'd imagine in Turkey you wouldn't trust the police either

for example

Ted Shifrin

@Eric: The guy who cuts my hair is Portuguese-American, and I promised to cook him his favorite dish.

CaptainAmerica16

@EricSilva I laughed. That is a subjective statement. English is one of my lowest grades right now and I spend hours on it every week.

Leaky Nun

@CaptainAmerica16 then focus your efforts on maths :P

Ted Shifrin

Spend more hours instead of goofing off here, @CaptainAmerica.

@Leaky: In the US that's very bad advice.

Mike Miller

6:48 PM

meh

Akiva Weinberger

I can't write essays… This will bite me when I'm in college

Eric Silva

i did preface w "take" but also english is good to learn well

@TedShifrin is his favorite dish a portuguese one

Ted Shifrin

DogAteMy: You can still improve.

Tobias Kildetoft

@CaptainAmerica16 What level of English? I mean are you learning the language or are you analyzing litterature?

Eric Silva

im a big fan of portuguese food

Ted Shifrin

6:48 PM

Yes, @Eric.

Eric Silva

is it one of the millions of cod dishes

Ted Shifrin

A pork, chorizo, seafood stew. I researched recipes and have a good idea of what to do.

Akiva Weinberger

"The Oxford dictionary defines 'essay' as…"

Ted Shifrin

not "assay" :P

Akiva Weinberger

("…Thanks for coming to my TED talk")

CaptainAmerica16

6:49 PM

@TedShifrin But...this is more fun ;-;

Ted Shifrin

uh huh

Eric Silva

@TedShifrin oh ho ho what's it called

Joe Shmo

i dont think ive ever had pork, chorizo, or seafood

Mary Star

@JoeShmo negation of B $\implies$ negation of A, right?

CaptainAmerica16

@TobiasKildetoft Language and Composition

Ted Shifrin

6:50 PM

Oh, he told me the Portuguese name, but I don't remember, @Eric. Maybe I can find it.

Akiva Weinberger

Like, vocab?

Perturbative

Never expected myself to say this but some of the exercises on classifying groups of finite order are really cool

Tobias Kildetoft

@CaptainAmerica16 Composition of what?

CaptainAmerica16

Basically how authors use language to convey meaning.

Ted Shifrin

@JoeShmo: If you keep kosher, most likely not.

Akiva Weinberger

6:50 PM

@Perturbative Careful, there's a monster

Joe Shmo

kosher-esque

Ted Shifrin

Not me, obviously.

Alessandro Codenotti

@TobiasKildetoft functions

Perturbative

@AkivaWeinberger Badum tss

Joe Shmo

no portugese dinners for me i suppose

Ted Shifrin

6:51 PM

@Eric: Alentejana.

CaptainAmerica16

@TobiasKildetoft Analyzing Nonfiction, I don't even understand the question. I have no idea what we're composing ;-;

Tobias Kildetoft

@CaptainAmerica16 I mean, are we talking English for people already fluent, or for beginners, or... ?

Akiva Weinberger

I guess the way you'd present your ideas

Rhetoric

CaptainAmerica16

@TobiasKildetoft Already fluent.

Tobias Kildetoft

Ahh, ok.

Eric Silva

6:52 PM

oh hell ya @Ted ive had it

quite gud

Akiva Weinberger

What do you get when you cross a joke with a rhetorical question?

Joe Shmo

@MaryStar not quite. what you have on there is the so called contrapositive statement; which is equivalent to the original statement.

Ted Shifrin

Well, come on over when I make it, Eric :)

CaptainAmerica16

@AkivaWeinberger A joke.

Joe Shmo

$A \implies B \iff \neg B \implies \neg A$

CaptainAmerica16

6:53 PM

with no response. (no one laughs)

Akiva Weinberger

I feel like you want parentheses there

Ted Shifrin

Agreed, DogAteMy.

Impossible to parse.

Eric Silva

@TedShifrin yaa

Joe Shmo

fair

Akiva Weinberger

$(A\Rightarrow B)\iff(\lnot B\Rightarrow A)$

Ted Shifrin

6:53 PM

oops

Joe Shmo

$(A \implies B) \iff (\neg B \implies \neg A)$

Ted Shifrin

I think the shorter arrows are better, too, @JoeShmo.

Eric Silva

i noticed @Ted, there were like a ton of portuguese/brazilian places in cambridge when i went there this summer

Joe Shmo

now youre just playing favorites

Ted Shifrin

That's new, @Eric. I don't remember much from the 60s and 70s.

Mary Star

6:54 PM

Ok!! Thank you!!

Ted Shifrin

Bitch to your heart's content, @JoeShmo :P

Joe Shmo

To prove $A \implies B$ is false, one ought to prove $A \wedge \neg B$

where $\wedge$ is the logical "and" operator

@TedShifrin :P

Ted Shifrin

Yup. Negating implications was one of the hard lessons when I taught Intro to Higher Math.

Eric Silva

@Ted en.wikipedia.org/wiki/Portuguese_Americans#Biggest_communities i think it was a mid 20th century thing

Leaky Nun

$$\sum_{n=-\infty}^\infty z^n = \sum_{n=0}^\infty z^n + \sum_{n=1}^\infty z^{-n} = \frac{1}{1-z} + \frac{z^{-1}}{1-z^{-1}} = \frac{1}{1-z} + \frac{1}{z-1} = 0$$

Eric Silva

6:56 PM

i always knew a lot of ppl from the boston area lusophone community growing up tho

Ted Shifrin

Well, @Eric: Huge Portuguese immigrant population in Rhode Island. ... But I don't remember restaurants back then.

Eric Silva

but im young so

Akiva Weinberger

@LeakyNun Alternatively: it doesn't change when you multiply it by $z$ :P

Ted Shifrin

In fact, my haircutter friend is from the Providence area originally.

Eric Silva