The h Bar - 2015-10-31 (page 2 of 3)

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8:00 PM

no

I remember the exercise with the arctan

our TA only had this terrible formula for the nth derivative of arctan

and I thought about partial fractioning $1/(1+x^2)$

what are you babbling about

and got a nicer formula

so he's the troll

just listen to the story kids

this is the story of how I met your mother

what the heck is 1/(1+x^2)

the derivative of arctan(x)

what

8:02 PM

even my students know that

why are you trolling me

because I can't factor $s^2-2s+5$

maybe you made some mistakes again

can I just give up

oh fine you tell me what the characteristic equation of $y''-2y'+5y=0$ is

only after 20 minutes

fukin LoL

oh are they complex or something

8:04 PM

well yea

you'll get some fancy sin and cosine

how do you know

do you know the joke with the sin and cosine

indeed

and e^x

I think the joke only works in German

they're all cousins in an incestuous relationship

8:05 PM

so I won't tell it after all

sag es auf Deutsch, dann

nein danke

bitteeeeeeeeee

bittebittebitte

no I'm not in a joking mood

maths is a serious thing

you're the troll around here

8:06 PM

no

oh! complete the square! I'm an idiot!

more like square the circle

if you know what I mean

not really, no

:(

It's easy to square the circle

8:07 PM

lies

just draw a box with side $\pi$, right?

do you even TeX

@0celo7 You and quadratic equations are not becoming friends, are you? :P

I don't see the issue

@ACuriousMind MIDDLE SCHOOL

well by Galois you can't construct rationals so it's impossible to draw a box with side $22/7$

8:08 PM

@ACuriousMind dude I can't even complete the square :D

@Huy uh lol of course I can

@0celo7 How the hell did you pass math in high school, then? :P

@ACuriousMind skin of my teeth!

No idea what that means.

German alert

it's a saying

deine Mutter

is a saying too

8:10 PM

The literal translation...makes absolutely no sense. It means "just barely"

but in German

My mother isn't German

but a saying ?

for the love of crap how do you complete the square

lol

8:10 PM

is it $b^2/2$ that you add?

or $(b/2)^2$?

so physicists really do only recall formulas and plug numbers in

I'M NOT A PHYSICIST

4

^that

what are the physicists working in the nuclear engineering department?

what are the engineers who do plasma physics?

isn't "physicist" the name/descpription of the job?

I figured out how to complete the square!

good for you

now you can finally derive the formula for solving quadratic equations all by yourself

8:14 PM

what :o

I thought you needed to be a grad student at least to do that

we did that in 3rd grade

alright I'm calling bullshit on that one

call my teacher

I went to German school for 6 years

2-8

I never went to a German school

8:15 PM

never saw the quadratic equation

we didn't even just see the teacher derive it

I don't even believe that you proved anything

we derived it ourselves

I must be literally retarded

our teacher had a very nice exercise sheet for it

which made the quadratic equation a little bit harder every time

8:15 PM

I think I have a mental handicap

I didn't see the quadratic equation in a math class until 10th grade

@ACuriousMind did you star those things

10th grade

rly?

yes

that's a bit late

did you never multiply something by itself before

what?

I seem to recall it was 8th grade when we treated it systematically.

8:17 PM

Well I took 8th grade math in Germany, and I didn't see it

@0celo7 If I answer that, THE ASTRONOMER will punish me.

it's telling that I was a C student in math in Germany

...why am I a math double major? what's the point, I'm not good at it

u can become

study functional analysis

would be a good start

I've tried becoming good

I asked a TA about that, and the book he said was a light intro is too hard

I have a headache

8:19 PM

telling me to study functional analysis is a troll meme at this point

you're the troll at this point

I bet you feel real proud about that one

very much so

@ACuriousMind well don't say his name so loud, goof!

I printed it out and am laminating it

8:22 PM

random factor of $5$ floating around

more sign errors

an odd number of them!

@Huy oh I'm sure

just know that if you're not actually doing that, you're just trolling :)

I know

pic?

I don't send my pics to strangers on the internet

you sent me pics of your room!

omg I bet it wasn't even yours

maybe that wasn't my room

8:26 PM

@ACuriousMind Seriously, are "physicists" only people who have degrees in physics?

I would say that that is the defining characteristic of a professional physicist, yes.

Is Dyson an exception?

So what you're telling me is that you could talk to a professional but not be able to say that he is a physicist without looking at the diploma?

Yes, because that's how I chose to define "professional physicist" in the sentence above :P

seems like you're trying to bar me from kinship :'(

19 mins ago, by 0celo7

I'M NOT A PHYSICIST

You did that yourself.

8:31 PM

I'm not anything.

I have a high school diploma.

laminated?

probably not

then it's worth nothing

lol @ 3rd order ODE

so much writing

hullo

8:33 PM

hi danu whats up

not much

agar.io

what?

a stupid online game

that I play when I'm braindead

I proved some stuff about the "topologist' sine curve"

which was pretty great

@ACuriousMind Do you have Hitman: Absolution?

that it's not path connected but connected?

or is there something else I must know about it

8:35 PM

are the games after blood money good?

yes

@0celo7 No. I've not heard good things about it, either

@Danu dunno, just started and I'm pretty terrible at it

@ACuriousMind Too "mainstream"?

@0celo7 Those games are pretty hard

(I know them up to part 4)

Young me was unable to "properly" complete most levels.

for one I just shoved the guy down a steam vent and stabbed everyone while making my escape

I intend to replay that one :D

@0celo7 No, it just has bad writing/story and not excellent enough gameplay to gloss over that

8:37 PM

the story is incredibly confusing

I have no clue what's going on

I'm about an hour in.

er, anyone know how to inverse Laplace transform an reciprocal cubic?

................................................................................‌.............................

what's that for?

Have you played the old Hitman games though, @ACuriousMind?

@Danu No, heard good things about them, though

I got Silent Assassin for a buck and change

8:42 PM

@ACuriousMind Pretty friggin' awesome.

Most epic games I think I played as a kid

@0celo7 Oh man... That first mission...

I spent so many hours lurking in the outside hills hahaha

I feel like you just have to wait a lot

I was way too young to be really good

@0celo7 Guess what real hitmen* do

for a hole to open in the guard patters, etc

@Danu nice edit :D

@0celo7 brainfart :D

Real hitmen = Sam Fisher

8:44 PM

haha

yes, I have a mancrush on him

Keep on dreaming

Sam Fisher is real!

You're telling me real hitmen don't clear a room while hanging upside down from a pipe on the ceiling?

pls

Just rewatching the first mission of Hitman 2 is giving me mad nostalgia :D

you can't just say Sam Fisher is a joke and not explain

he will cut you up

8:50 PM

As Leeb likes to say: "Proof: Clear"

Leeb can go f*ck his proofs

Agent 47 vs. Sam Fisher vs. Solid Snake

@ACuriousMind How does one factor a cubic polynomial?

With math

For example $3x^3+5x^2+x-1$

Seriously, that's not hard to figure out

@ACuriousMind why do you troll me

@ACuriousMind what?

I've never been taught how to do it

is there a way to find one zero and divide it out?

8:56 PM

Wikipedia

-1 is an obvious one

my students love doing this kind of stuff

ok, we get it, you have smart students

no

but that doesn't help me one bit

I'm just trying to emphasize your middle school maturity

8:57 PM

@Huy hehehe

rational root theorem? what is this madness

user image

wow

Wolfram knows what level I'm at

I never know when to use "evaluate" or "compute" or "find"

@Huy I didn't see it

9:03 PM

usually you start by checking 1, and afterwards comes -1

never would have guessed

yes because the measure of a singleton is 0

huh?

Calculate?

oh I remember that

ahhhh

yes, it's coming back

9:05 PM

measure

probability

anything ?

you really are a troll, you know

:(

you guys are so mean you'd probably just laugh if I asked how to factor a quadratic

ask in the maths chat

we're used to trolls there

dude I seriously can't factor $3s^2+2s-1$

the best I can do is see $-1$ is a root and long divide

9:10 PM

Use the quadratic formula

u can factor -1 even twice

and then you're done

I used to be able to just write it down

I've never learned long division

Lel

@Danu wat

@Huy what

9:11 PM

means u can divide by $(x+1)^2$

@ACuriousMind Never needed it, either

and not just by $x+1$

the cubic, yes

but not the quadratic

lol

hint

$(x+1)^2 = (x+1) (x+1)$

stop trolling

9:12 PM

I don't understand your confusion

how do you factor that quadratic

@0celo7 I do not see what you find so difficult about this. Just compute its roots!

@ACuriousMind I can do that

There's a trick for just writing it down, but I've forgotten

zweiklammeransatz?

what?

9:14 PM

idk what trick u mean

I'll give you two parentheses

Computing the roots is not hard. I don't see why a "trick" would be needed

because it's hard for other people

what other people are you talking about

You are not "other people", are you? :P

9:17 PM

ok I know I told you guys to be meaner, but this isn't what it was supposed to be like :(

@Huy I have to do partial fractions on this now

If you can't factor it then its prime :P

@Danu I would indeed have answered that question, but now someone else did it with "sandwiches".

I f*$#@%g hate those stupid food analogies.

I never heard that one

But the bounty is about explaining it without sammiches

@Danu orly?

food analogies are the best

a black hole is really a donut shop

you get so fat you never leave

9:20 PM

@0celo7 zomg that hurt.

Ba dum tss

it's funny because rotating black holes have ring singularities

and donuts are products of rings

wat

$\mathrm{donut}=\mathrm{ring}\otimes\mathrm{ring}$

don't tensor me

9:23 PM

::cringes::

^ should I turn on chatjax for that?

for your own safety don't

just some engineering math

I see engineers misuse the $\otimes$ even worse than physicists :P

Hmm, I think the people of this chat forget that I have two majors

oh well

I doubt it will ever matter, anyway

So I wrote down the problem wrong. That's fun.

9:25 PM

classic 0celo7

I can't do anything right.

@ACuriousMind It's funny that BBS sometimes uses $\times$ and sometimes $\otimes$ for the group product :D

dear lord

I'll try to cry myself to sleep now

thanks for the nightmares

good night and good luck with your remaining exercises

they also make no distinction between algebra and group

...............................................................

please stop the torture

mercy

wonder what else they do

@ACuriousMind You surely have a list of offenses committed by BBS, right?

9:30 PM

what is bbs anyways

amazon.com/String-Theory-M-Theory-Modern-Introduction/dp/…

bible of bs ?

pretty much, although I think GSW/Pol is more standard

ok

i sleep now

bya bya

bye

sweet dreams

9:31 PM

thx <3

$\mathrm{SU}(2)\otimes \mathfrak{so}(5)\times E_8$

@DanielSank Yush!

@Danu I see. I was confused by the fact that there's already an accepted answer.

@DanielSank Note that the question is four (!) years old.

@DanielSank Note also that the bounty is from dmckee, not the asker.

9:38 PM

maybe he is the user

dun dun DUN

@ACuriousMind Indeed.

@ACuriousMind what's the biggest abuse of notation in physics?

probably some QM or QFT thing, right?

@0celo7 Actually, one of the worst offenders is the constant conflation of functions and variables.

please elaborate

Similarly, there is a very frequent conflation between vectors and representations of vectors in a particular basis. This confusion is made worse by the fact that representations of vectors are themselves vectors!

9:49 PM

are you saying like $v^ie_i$ vs. $\{v^i\}$

But those errors are mostly problematic for beginners, at graduate level that type of stuff doesn't really pose any problems.

@Danu I wouldn't agree with you there.

@Danu Self-consistent notation really helps me understand what I'm doing. This was a huge issue in GR.

lol, you'd love wald

abstract index notation is the biggest scam

@0celo7 What? No it's not.

Abstract indices are a very good idea IMHO.

dude it's just index notation but the indices aren't indices!

9:52 PM

@0celo7 Right! They're labels on function arguments.

and it hurts when he writes partial derivatives or Christoffel symbols in abstract index notation

@0celo7 I wouldn't know about that.

as far as I understand it, the abstract indices should only be on tensors

but Christoffel symbols aren't tensors

I think one can make the partial derivatives make sense

@DanielSank Meh---I think most people seem to get by just fine.

Also, AFAIK the tensors-not-being-their-components is done in most graduate courses.

@0celo7 Yes.

@0celo7 Oh.

9:57 PM

(neither are partial derivatives)

@Danu True, but most people don't understand what the hell they're doing.

@Danu Yeah, I'm trying to think how he defined $\partial_a$

but I don't have the book with me and my iPad is at home, too

Well, now that I think about it, Hawking-Ellis uses the same notation

So neither makes sense.

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