The h Bar

Bernardo Meurer

00:01

@vzn I want to do it all in LaTeX

@EmilioPisanty Halp?

@ACuriousMind How can I align these so that the first two are side by side, but the third one is in the middle on the next line

\begin{align*}
	E_n = \frac{n^2h^2}{8m_{e^{-}}L^2} &   & L=4\times d_{\text{c-c}}=5.64\si{\angstrom}\\
	&E_1 = \frac{1^2h^2}{8m_{e^{-}}5.46^2}&\\
\end{align*}

ACuriousMind

Uh

You better ask the nice people from TeX - LaTeX

Bernardo Meurer

I guess I will :p

Emilio Pisanty

00:28

@BernardoMeurer with that tikz abs thing above?

not a clue beyond: don't do it in tikz

Bernardo Meurer

@EmilioPisanty Why not? I'm using pgfplots

Emilio Pisanty

@BernardoMeurer whatever rocks your boat

but that's what people made nice plotting software for

Bernardo Meurer

It's not a real project, it's just me trying to learn LaTeX :P

Emilio Pisanty

for your other one, though, does

Bernardo Meurer

So I'm doing things for the sake of it

Emilio Pisanty

00:31

\begin{align*}
	E_n &= \frac{n^2h^2}{8m_{e^{-}}L^2} &   & L=4\times d_{\text{c-c}}=5.64A\\
	E_1 &= \frac{1^2h^2}{8m_{e^{-}}5.46^2}&\\
\end{align*}

work?

Bernardo Meurer

@EmilioPisanty I just used alignat and it worked

Let me try yours

Emilio Pisanty

@BernardoMeurer that's like heather writing a "how to do matrices without amsmath" tutorial

Bernardo Meurer

@EmilioPisanty That didn't work no

Emilio Pisanty

there's plenty of things that you can do in TeX but that does not in any way mean that you should

Bernardo Meurer

@EmilioPisanty No, because people (@DavidZ for e.g.) actually do plots in LaTeX

There is an argument for it

Emilio Pisanty

00:32

@BernardoMeurer yeah, I have strong differences of opinion with those people ;-)

Bernardo Meurer

There is not a sane argument for "matrices without amsmath"

Emilio Pisanty

@BernardoMeurer yeah, that was some usage of hyperbole on my part

DanielSank

@BernardoMeurer That's one person.

<3

Also, making plots in TeX is silly.

There, I said it.

TeX is a terrible programming language. Terrible. Use it for typesetting and nothing else.

Bernardo Meurer

@DanielSank <3

It's a very fun challenge though

DanielSank

I can't wait until you grow out of that.

Bernardo Meurer

00:39

It might take a while given that my notes are 109 pages long and I'm like 8 pages through

DanielSank

I mean grow out of learning tools by using them for not what they're for.

Bernardo Meurer

Oh, that will take a lifetime

It's what I'm all about man

Linux on a calculator? What's that about?

DanielSank

@BernardoMeurer That made slightly more sense to me.

Can sit in class and play Super Metroid, for example.

Bernardo Meurer

You just made me fail the next semester

I hope you realise that

DanielSank

Anyone around here ever release a TeX package and wanna hold me hand through it?

@BernardoMeurer How?

Oh.

Lol

Take that.

Bernardo Meurer

00:42

:p

The guy who wrote pgfplots is on TeX SE, maybe email him? he seems pretty sweet

DanielSank

Realistically, you should play that game in a room with the lights off and the sound turned up.

That game is all about atmosphere and the sound is really important.

Play with good headphones or something.

Bernardo Meurer

Get a 2000 dollar dac to hear that 8 bit music lel

DanielSank

Just make sure you don't play it on some god forsaken handheld with crap sound.

Crank this up and imagine you just landed your space ship on a deserted planet.

Bernardo Meurer

I'll wait until I can get a proper NES or something

Let's remaster the game and put that as the sountrack

DanielSank

SNES

n00b

Emilio Pisanty

00:48

does this one need protecting?

39

Q: How come neutrons in a nucleus don't decay?

I know outside a nucleus, neutrons are unstable and they have half life of about 15 minutes. But when they are together with protons inside the nucleus, they are stable. How does that happen? I got this from wikipedia: When bound inside of a nucleus, the instability of a single neutron to be...

Bernardo Meurer

I'm typing one handed, I can only focus so much

Gimme a brake

Emilio Pisanty

three (four?) terrible answers by <100rep users

over a multi-year timescale

DanielSank

Sounds like it, then.

Hey, @EmilioPisanty, my Spanish has gone to hell. What's a good Spanish movie I could watch to rejuvinate it?

Emilio Pisanty

@DanielSank oooooh, good question

Bernardo Meurer

@DanielSank Zorro

DanielSank

00:50

^ :|

Emilio Pisanty

off the top of my head, Amores Perros and El Secreto De Sus Ojos

Bernardo Meurer

That last one was great

Emilio Pisanty

but be sure to bring along a good bit of faith in humanity, 'coz they'll both take a toll on it

El Laberinto Del Fauno

(also taxing on the faith in humanity thing, but amazingly beautiful)

DanielSank

@EmilioPisanty I thought Amores Perros is horribly depressing.

I don't do horribly depressing.

Never heard of El Secreto Do Sus Ojos. Will check it out.

Emilio Pisanty

@DanielSank I'm not sure horribly depressing is quite the right way to describe it, but it isn't far, either

DanielSank

00:53

@EmilioPisanty Oh, or not.

Bernardo Meurer

That fauno one was horrible IIRC

DanielSank

Got anything on the lighter side?

Also, @BernardoMeurer, your opinions about all things Spanish are hereby void.

2

Emilio Pisanty

maybe Por La Libre, or Y Tu Mamá También?

DanielSank

...until you fall for the Spaniard as I have cursed you to do.

Bernardo Meurer

@DanielSank What? I liked Zorro

DanielSank

00:54

@EmilioPisanty Ok will look those up, thanks!

Emilio Pisanty

maybe Vampiros En La Habana?

haven't watched it in aaaaaaages but it was good fun

Diarios De Motocicleta was quite nice and non-depressing

Crimen Ferpecto was loads of fun, if you can get hold of it

DanielSank

@EmilioPisanty Is that what it sounds like?

Bernardo Meurer

Diarios de Motocicleta is for communists

DanielSank

@EmilioPisanty confirmed communist.

Bernardo Meurer

I always knew

His real name is Emarxio Pisengels

DanielSank

00:58

lolololol

Emilio Pisanty

Ahí Está El Detalle is really good but it takes some pretty strong Mexican Spanish skills

P1_VampirosEnLaHabana.wmv

►

DanielSank

Consider me an intermediate, i.e. I used to be relatively conversational at modest speeds, but it's been fifteen years.

Emilio Pisanty

I think the thumbnail says a lot

DanielSank

^ Indeed.

Ahhh, dangit, I have to close my eyes to not see the subtitles.

Emilio Pisanty

@DanielSank how well do you do with this one?

Cantinflas - El Juicio

►

DanielSank

00:59

But it's slow enough that I can understand. Thanks!

@EmilioPisanty Blocked in my country.

Emilio Pisanty

@DanielSank huh

DanielSank

(╯°□°)╯︵ ┻━┻

Bernardo Meurer

@DanielSank Drama

DanielSank

Nothing compared to you, broski.

Bernardo Meurer

I am the queen, nothing compares to me

DanielSank

01:02

Yo wait a sec... does TeXlive automatically download packages?

Emilio Pisanty

@DanielSank not in my experience, at least over linux

but I have a well documented hatred for tlmgr

DanielSank

ugh. This should be easy!

Contributions being hard is the bane of improvements in software!

grump grump grump

I'm using a git submodule for all my cool TeX stuff and I'd like to do something better.

@BernardoMeurer you're a computer person, fix everything for me.

I'm waiting.

Bernardo Meurer

Eh, I don't even know how LaTeX packages work

let alone how to publish one

It's all black magic

Ask on TeX SE

Like, make an actual question

DanielSank

I asked in the chat room.

DanielSank

01:35

Cool, I've written a TeX package.

Now I have to figure out how to distribute this thing.

I feel the need to point out that my avatar octopus is tipping his hat to you all.

Just, fyi.

user228700

Ello, everyone :-)

DanielSank

Hi, @Kaumudi.H.

How did you sleep?

:-D

user228700

:-) I slept well today! I will sleep for 8 hours tomorrow and let you know if that works.

DanielSank

great

Happy to hear it.

user228700

I've a "quick" question about the domain and range of a function. One of the methods to find the range of a function given in my textbook is to rewrite the given function in terms of $y$ (as opposed to $x$ being the independent variable) and then find all the values of $y$ for which this function will take real values.

user228700

01:47

Why does this work..?

DanielSank

Imagine a plot of y versus x.

The domain are all the values of x for which the result is a real number.

Right?

user228700

Right...

DanielSank

Ok, the range is the set of all possible y values.

So, flip the paper around so y is on the horizontal axis. That's the same thing as inverting the function, i.e. writing x as a function of y.

Bam.

user228700

Yeah, that makes sense, but gimme a second to make sure that it does...

user228700

So this is under the assumption that the range of a function $y=f(x)$, is the domain of the function $x=g(y)$, yes?

user228700

01:57

But why should that be true? (I'm sorry if I'm being dumb. It makes 100% intuitive sense but I'm still not really clear)

DanielSank

Range: All values the function attains.

ACuriousMind

@Kaumudi.H What do you mean by "the range of a function $y=f(x)$"?

DanielSank

Domain: All values you can input to the function.

In other words, range is all values you get on the vertical axis and the domain is all the values you get on the horizontal axis.

@ACuriousMind She means the range of a function $f$.

And of course, $g \equiv f^{-1}$.

Although the original statement she's trying to prove works for non-invertible functions.

ACuriousMind

Ah. Yes, if an inverse exists, then the domain of the inverse is the range of the original.

user228700

@DanielSank Right, but what ACM just said is what has been confusing me.

DanielSank

02:02

@ACuriousMind That's not the statement she's trying to prove.

She's proving a weaker statement.

Take any function $f$.

$f$ might be defined by the equation $y = f(x) = \text{some expression involving }x$.

@Kaumudi.H wants to prove that if she solves for $x$ in terms of $y$, then finds all values of $y$ which yield real values for $x$, then that set is the range of $f$.

Bernardo Meurer

Draw it

@Kaumudi.H Draw it, it should make it easier to see

DanielSank

^ Yes, as I suggested, draw a function (start with an invertible one), and then flip the x and y axes.

Then afterwards try a non-invertible one.

user228700

Gimme a minute...

Bernardo Meurer

@DanielSank sine and arcsine?

DanielSank

@BernardoMeurer For example, yes.

Bernardo Meurer

02:05

Those will do a nice plot

DanielSank

Arcsine is a wonderful non-invertible function.

It's so non-invertible.

Bernardo Meurer

Well, it is invertible on a small domain, no?

ACuriousMind

In many definitions, the arcsine is invertible (because it's the inverse of the sine on an interval where the sine is invertible). It's the sine that's non-invertible.

Bernardo Meurer

@ACuriousMind Always saying things more eloquently than I do

DanielSank

@ACuriousMind That's what I meant.

user228700

02:09

OK, I'm just gonna ignore all this about the invertibility of the sine and arcsine functions but are you telling me that my textbook method works even for functions that aren't bijective?

Bernardo Meurer

Well, if it's not injective it doesn't have an inverse

So no

DanielSank

The book isn't asking for an inverse!

@Kaumudi.H yes

Bernardo Meurer

@DanielSank No?

DanielSank

You just have to make sure that when you solve $x = f^{-1}(y)$ you get all the solutions.

user228700

But I don't get how!

Bernardo Meurer

02:10

Ah

I see

user228700

I don't :-/

DanielSank

Let's do an example.

$\sin$ is a good example.

Bernardo Meurer

@Kaumudi.H Daniel with explain, he's the master explainer

DanielSank

Actually no it's not because we can't write the inverse easily.

Let's do $y = x^2$.

Solving, we get $x = \pm \sqrt{y}$.

What values of $y$ yield a real number?

user228700

Greater than or equal to 0

DanielSank

02:13

Correct.

Done.

Why did this work?

Well, first draw $y = x^2$.

It's a parabola.

user228700

Uh huh...

DanielSank

Now flip your paper to swap $x$ and $y$.

Bernardo Meurer

Instructions not clear, I cut my eye with the paper

DanielSank

You no longer have a function (i.e. the parabola is not invertible) because you have $x = \sqrt{y}$ and $x = - \sqrt{y}$.

But it doesn't matter! You can still look at what values of $y$ give real numbers for $x$ taking into account both the + and - parts.

That's just saying that you take into account the curves that go up and down.

I wish I could point at a picture...

Here's a more interesting example

fooplot.com/…

That is not an invertible function at all, but you can still flip it and look at what values of $y$ give you values of $x$.

user228700

:-| Gimme a minute...

Bernardo Meurer

02:18

Just because you can't define a general rule of invertibility doesn't mean you cannot look at particular cases and take meaning from them

user228700

(Is there any way for you to explain this without the graph flipping thing?)

DanielSank

@BernardoMeurer Invertibility simply has nothing to do with Kaumudi's question.

@Kaumudi.H Sure.

Consider a function $f$ defined by $f(x) = \text{some expression}$.

Bernardo Meurer

@DanielSank Hmpf

DanielSank

The range is, by definition, the set of values that $f$ can spit out.

user228700

Right...

DanielSank

02:22

Therefore, it is the set of values that $\text{some expression}$ can take.

user228700

Yeah...

user228700

(BTW, I've been trying to figure this out using these diagrams:)

user228700

DanielSank

Good. Those diagrams are excellent.

user228700

Yeah, okay, gimme a moment...

user228700

02:27

No, nvm, I thought I was onto something :-[

DanielSank

If I can solve $y = \text{some expression}$ for $x$ in terms of $y$ (which is not always possible) and find a value of $y$ that gives a value of $x$, then that just means we've found a value of $\text{some expression}$ that $f$ spits out for some value of $x$.

i.e. that value of $y$ is in the range.

user228700

Yeah, I guess that makes sense...

DanielSank

That's all there is to it.

user228700

Hmm, but why does this have nothing to do with invertibility? I mean, we are filliping the function...

DanielSank

Yeah but this process works even if the function is not invertible, like with the parabola!

I shouldn't have said it has "nothing" to do with invertibility. That was an overstatement.

user228700

02:33

Dammit, I still don't quite get that.

DanielSank

Draw your diagram for $y = x^2$.

0 --> 0

1 --> 1

-1 --> 1

etc.

That is not invertible, but the fact that 1 is on the right side is true anyway, i.e. 1 is still in the range.

user228700

In some cases, the flipped one won't even be a function, then!

DanielSank

@Kaumudi.H Correct.

user228700

Oh, and that's okay..? I see...

DanielSank

For example, if you have $y = x^2$, then $x = \pm \sqrt{y}$, which is not a function.

Don't worry about things being functions. That's just some thing your book told you to worry about for some stupid reason. All you care about is what values map to what other values.

user228700

02:41

Right, yeah, for it to be a function, it has to be bijective tho, which means that the original function will be too, which means it'll be invertibile, which is why I was confused before...

DanielSank

That's why I like your diagrams very much.

@Kaumudi.H Ok, so you get it now?

user228700

I think I do!

user228700

I'll spend some more time with this, figuring out if my brain's not just tricking me into believing that I do, tho.

user228700

But thank you!! :-D

DanielSank

sure

user228700

02:46

Okay, yeah, I think I've understood this properly now. Yas, that's one goal accomplished today, thanks so much, I've been struggling with this for weeks. I mean, it's been awhile since I revisited it but yeah. I asked some people over at MSE first and they didn't think that my textbook was correct so I spent a crapload of time learning about asymptotes :-|

DanielSank

asymptotes wtf?

Also, it's always funny to me when foreigners use swearing and related slang properly.

I applaud your use of "crapload".

user228700

Lol, okay, thanks..? :-P

DanielSank

The MSE people probably got caught up with invertibility instead of actually paying attention to the question you asked.

user228700

Yeah :-/

Pissed off layman

A function is a relation in which different ordered pairs have different first coordinates.

user228700

02:49

@DanielSank :-P I almost feel like English is my first language so I probably don't deserve the applause.

DanielSank

@Kaumudi.H English is one thing.

American slang is another.

user228700

Oh, right :-P Well, I used to watch YouTube. A lot. I also listen to podcasts. And most of my favorite creators are American, so it only makes sense that I'm kinda comfortable with American slang...

DanielSank

groovy

Oh I meant to ask, have you reduced world suck recently?

user228700

@DanielSank Yeah, I think I contributed some when I spent like, 3 hours b/w 2:30 AM and 5:30 AM writing an elaborate love letter to my mom on her birthday, the other day <3 :-)

DanielSank

@Kaumudi.H awwwwwwwwww

<3 <3 <3 <3

user228700

02:53

:-D She loved it. It made her cry and everything! Totally worth the effort.

Pissed off layman

are you an only child?

user228700

Nope, I have two younger sisters who are twins.

Pissed off layman

pardon me asking

user228700

Huh? Is no problemo :-)

Pissed off layman

so an only son

user228700

02:55

Sigh. Daughter and no, not "only".

Pissed off layman

sorry

DanielSank

lololol

user228700

Common mistake. I think I'm gonna change my avatar to my actual face so I don't have to correct people so often and make them feel kinda bad.

DanielSank

@Kaumudi.H Didn't you undo the face picture for reasons?

user228700

@DanielSank Yeah, but the creep's gone...hopefully. Besides, just googling my name yields a photo, so.

Pissed off layman

02:58

I come from an all boy family.

ACuriousMind

@Kaumudi.H Imo, you shouldn't be the one worried about people feeling bad when you correct people that just assume you're male when you've given them no reason to believe so.

Uh, that sentence's structure became more awkward than I intended :P

DanielSank

Being in a physics chat correlates to being male. Like it or not.

Pissed off layman

that^ too

:-)

DanielSank

That said, I wouldn't assume someone's gender to be one thing or another in any case.

@ACuriousMind You are German, right?

user228700

:-) I guess that's true. But I'm tired of correcting people over and over. I've done it about a zillion times till now.

user228700

02:59

And sometimes, they forget and use the wrong pronoun again.

Pissed off layman

Don't let it bug you.

It happens.

ACuriousMind

@DanielSank Yep, still can't quite shake off the German tendency to make run-on sentences

user228700

Them being wrong doesn't bug me all that much but I don't wanna keep correcting people.

Pissed off layman

Just don't correct them until absolutely necessary.

If you know what I mean ;-)

DanielSank

@Pissedofflayman wtf why not?

English has gendered pronouns. Help people use them correctly.

Gendered pronouns are dumb, but we have them. Oh well.

Pissed off layman

03:03

Is this the English room?

Sorry

:-)

DanielSank

No, it's not the English room. However, in this room, we use English to exchange information with one another.

Pissed off layman

Indeed, hence

3 mins ago, by Pissed off layman

Just don't correct them until absolutely necessary.

Be more relaxed, I guess.

ACuriousMind

@DanielSank At least you can use 'it' for all inanimate things without having to remember grammatical genders ;)

user228700

^ Exactly.

user228700

There. Done and done.

Pissed off layman

03:08

imo, in this context, it doesn't really matter

*imho

user228700

Well, a) I want people to stop assuming that literally everybody here is male and b) My face doesn't look all that bad (:-P)

Pissed off layman

:-)

user228700

Say, why did u ask all that about me being a single child or not?

Pissed off layman

I wanted to find out why the tears.

of joy

user228700

Um, what does that have anything to do with me (not) being an only child?

Pissed off layman

03:13

Like I said I come from an all boy family and we're not that emotional with each other.

user228700

Oh, I see. Well, we're all an girl family :-) (And also, it might just be your family. My best friend is from an all boy family and they're even more emotional than us!)

Pissed off layman

Don't you think parents would be more emotionally attached to a single child?

user228700

Of course, but like I said, I have two sisters as well, so I'm not their only daughter. Anyhoo, breakfast time, toodles!

Pissed off layman

cya

You do have a perfectly valid point @DanielSank l just expressed my opinion :-)

@ACuriousMind why do you think that is so?

Individual German words certainly are long too :P

Pissed off layman

03:33

@JohnRennie in the match of University Challenge that I watched Timothy Gowers came through at the last minute and basically won the game for them.

David Z

@DanielSank I did once, if you have questions maybe I can dig it out of my memory

Pissed off layman

Hi @DavidZ

David Z

@BernardoMeurer that works fine for me. I'm not sure what's going on with your output.

@Pissedofflayman hi

user228700

03:50

@DanielSank: Yello again, want to see what I just had for breakfast? Bet you've never even heard of it.

Pissed off layman

>.>

<.<

user228700

Pissed off layman

:O

user228700

^ That is Medu Vada and Sambar.

Pissed off layman

An Indian breakfast?

user228700

03:55

Yep, although it's not very typical of "breakfast".

Pissed off layman

cool

yep, looks kinda oily for "breakfast"

DanielSank

@Kaumudi.H omnomnom

Pissed off layman

Nice quality photograph.

iPad?

user228700

@DanielSank :-D Have u heard of it before?

user228700

@Pissedofflayman Yep. Usually, it is had with something called Idli but we were satisfied with just Vada for now.

user228700

04:00

@Pissedofflayman Thanks! No, Lenovo Vibe p1m :-P

DanielSank

@Kaumudi.H I don't think so.

Looks a bit oily for me.

user228700

Yep, it is pretty oily, but what the hell, we have it like, once in three months :-P

user228700

Usually, we just have the standard: dosas.

DanielSank

@Kaumudi.H those are good. Very open ended.

user228700

Haha, yes. Of all the tasty food (even including the North Indian curries) that I've had, I like dosas best and that's surprising not only because it's not much but also because I have it every single morning.

Pissed off layman

04:05

Have they elimated the 100 rupee bills yet?

user228700

Nah, that they cannot do.

Pissed off layman

I see.

I'm hungry now too, later peeps :-)

Balarka Sen

Who's to say what a fascist government can't do?

Also we -have- started getting new 100 rupee notes out. They just haven't eliminated the old ones.

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