Mathematics - 2017-04-29 (page 3 of 5)

@SoumyoB Well what is so wrong about that? I don't see anything inherently wrong in working to get admission in a university which is better than most others. If I am given a choice between Ivy Leagues and some random college in rural Africa I'd obviously try for the former.

Benjamin

@SoumyoB I was just about to give that PSA.

Ran Wang

French election?

SoumyoB

5:05 PM

@blue the thing that's wrong with going into universities just for status is that it is, in my opinion lame

3

it's not just about being given a choice

people usually sacrifice a lot of sleep (some students sleep just 4 hours a day at such a young age when they should be playing outside and socializing and learning about life)

Anonymous

@SoumyoB Well, most students don't go to universities "just for status" .

Benjamin

Another PSA for anyone interested in the fundamentals and basics of calculus: youtube.com/playlist?list=PLZHQObOWTQDMsr9K-rj53DwVRMYO3t5Yr

Anonymous

They go for better education.

Balarka Sen

I don't sleep and I don't think I should be playing outside or socializing, @SoumyoB.

user123733

Danu

5:06 PM

eyyo @TedShifrin

SoumyoB

@ not here

user123733

Is the answer of this question as option D is correct . I am getting $\frac{20\sqrt 2}{\pi}$ .

Benjamin

@BalarkaSen I have to agree with this.

Ran Wang

HI @user123733

SoumyoB

@BalarkaSen obviously I'm talking about normal people

Balarka Sen

5:07 PM

Who are the "normal people"?

user123733

@RanWang ))hi

Ted Shifrin

heya @Danu

Daminark

I think the grievance is when people are using education at least partially as an avenue for prestige instead of education, and are very deeply competitive about it

SoumyoB

@blue not here, they mostly do it because their parents pressure them into doing it, who in turn are pressured by the greed for social status

Eric

lol @blue a significant portion the people I know at my school did in fact go here because of status considerations

Danu

5:08 PM

And can you blame them?

Anonymous

I find this to be an extremist view where you assume everyone goes to college for gaining status. You can't get into the top colleges unless you are passionate about the subject, in my humble opinion.

Balarka Sen

I just think your point against JEE that it eats up students' time for ""playing"" or ""socializing"" is moot. I do think JEE is bad for health but for different, much much more concrete reasons.

Danu

That kind of stuff matters in life

Ted Shifrin

Most US students aren't passionate about anything ... but their parents want them to be credentialed to make money.

3

Eric

@blue you can 100% definitely get into top colleges without being passionate about something.

Danu

5:09 PM

@blue Oh but that isn't true. Money buys entrance, for sure.

Benjamin

@blue I know many people who prove that this can not be true. They go to good schools, but aren't passionate.

Anonymous

@Danu Wut? Not here atleast.

SoumyoB

@blue I'm not talking about everyone; obviously there are going to be exceptions

Danu

Why do you think all of these dumb politicians have degrees from top places? ^^

Balarka Sen

I can give you 10 people who did JEE, went to IIT, and are not passionate about anything much.

Anonymous

5:11 PM

@BalarkaSen We need to see the ratio. I can give a 100 examples of people who are passionate. (and who qualifies the JEE advanced)

Balarka Sen

If you think JEE automatically makes people passionate about STEM you are wrong.

Benjamin

@blue Where are you referring to?

SoumyoB

@Danu I expect you're talking about our most honorable politician Rahul Gandhi? LOL

Anonymous

@BalarkaSen I don't think so. But without passion it is difficult to qualify the test.

Balarka Sen

@blue "You can't get into the top colleges unless you are passionate about the subject" This is plain wrong, regardless of the ratio :P

Eric

5:12 PM

In fact I would say the college admissions system in the US has been thoroughly gamed. People with the right resources know how to play the game really well and do not need to be passionate about something

SoumyoB

to be honest, I wish my childhood had been spent learning martial arts and fighting, with a little bit of math every now and then

I mean 90% of my time in school was pretty much useless

2

Anonymous

@Benjamin India (IITs specially)

SoumyoB

it boils my blood to think how those teachers at school made a waste of my entire childhood

Anonymous

@SoumyoB Who stopped you?

Benjamin

@blue Do they have a fully subsidized education system?

Eric

5:13 PM

@Daminark do you know a lot of people who actually like the core... I would say about half the people i interact with daily hate general education stuff here

SoumyoB

@blue the pressure of getting an education and the more tangible factor aka my parents

Anonymous

I used to do karate, swimming, everything in my childhood. That never was a hurdle to studies.

Daminark

More people I know are passionate but there are a lot of people who are not. It's tricky to tell since the way things are going, you can't feasibly go about college without worrying about career considerations, but genuine passion isn't required

Anonymous

@SoumyoB Well, I was never put under such pressure. I had enough time to do everything I liked. Can't comment...

SoumyoB

you guys should some day sit and do an arms wrestling match with your grandfathers, I guarantee every single one of you will lose

Daminark

5:15 PM

@Eric I'd say so, yeah, most of my friends and people in my house at least like the idea of the core

Balarka Sen

I generally think being or not being passionate about a subject per se has pretty much nothing to do with qualifying in whatever exam. "passionate about math" and "passionate about qualifying a math exam" are related, but distinct ideas (though never, ever mutually exclusive, I concur)

SoumyoB

@blue you're very fortunate then

Danu

@SoumyoB rofl

Eric

@Daminark I go through periods of liking it and feeling like it's the worst. I like the fact that they make you write a lot, but first year humanities was inane because everyone gave crappy arguments constantly

Danu

100% I'd win.

SoumyoB

5:16 PM

there was a study I had read-it said that the gripping strength in American males had dropped from about 121 pounds some time in the 1980's (I think) to 98 pounds today

Eric

but I guess that's growing pains

Danu

Even if he gets to be my age

Why'd you even think this? :P

Eric

@SoumyoB I have done this with my grandfather and have won.

Daminark

Some people felt like they didn't get much out of individual classes in the core, and wish they could skip in favor of other things they liked. But few are just against it entirely, at least as far as I've seen

SoumyoB

because modern males are extremely weak, physically in comparison to men from previous generations

Eric

5:17 PM

but to be fair my grandfather wasn't american I guess so that stat doesn't apply.

Balarka Sen

Speaking from a personal point of view, I rarely got 90% in my high school math exams. But I am, of course, very passionate about math. Now, it is a valid argument to say I am not good at math :P

Danu

@SoumyoB lol, why do you think that?

SoumyoB

@Eric I am genuinely surprised

Eric

@SoumyoB I've also beaten my father many times, and he works a job that requires a lot of manual labor :)

SoumyoB

like I said @Danu, it is proven by multiple studies

Eric

5:19 PM

also who cares if people are weaker now lol

Danu

@SoumyoB That surprises me

SoumyoB

@Eric you're perhaps a really great exception

Ted Shifrin

I'm weaker in one arm since I had cancer and my biceps muscles were removed :(

Balarka Sen

wth are we even talking about

from JEE to judo, seriously?

SoumyoB

@TedShifrin you're from a previous generation, so obviously this doesn't apply to you :P

Eric

5:20 PM

@Balarka genuinely I have no idea

Anonymous

Obviously we are weaker than the cavemen who lived thousands of years ago. We don't need to go hunting :P

Ted Shifrin

Oh, I'm antique. Sorry. :D

Balarka Sen

@TedShifrin I like antiquity.

SoumyoB

@blue personally to me it is the biggest insult-of being weak

I mean I don't care about people calling me skinny or balding etc

Anonymous

@SoumyoB We are mentally stronger ;)

SoumyoB

5:21 PM

but it really puts me off when I find myself not being strong enough

I really don't think so

the only thing we're better in than our forefathers is knowledge

useless knowledge (mostly)

Anonymous

I am getting the pessimistic vibes now :P

Anonymous

Should leave

SoumyoB

I'm leaving too, see you guys later

Ted Shifrin

Bubye

Balarka Sen

@SoumyoB This is an oversimplification which is both true and false, like every simplistic opinions in earth :P

user123733

5:27 PM

21 mins ago, by user123733

Is the answer of this question as option D is correct . I am getting $\frac{20\sqrt 2}{\pi}$

Ted Shifrin

@user123733: I don't know where you get $\pi$ from. But I get $500\sqrt2$, offhand.

user123733

@TedShifrin I got that to find time

Ted Shifrin

Oh, I found my mistake. Duh.

It is $5\sqrt2$.

I misread the speed for angular speed. Duh.

You know calculus, right?

user123733

yes

Ted Shifrin

So write down the distance as a function of $\theta$.

Then differentiate with respect to $t$.

user123733

5:35 PM

@TedShifrin $\theta$ from where

Ted Shifrin

From where the dad is.

user123733

I think your dad is from this world

Leaky Nun

It's an unusual scenario to see Ted doing high school mathematics

who on earth flagged Ted's message?

Ted Shifrin

Flagged? Seriously?

Leaky Nun

yes.

Ted Shifrin

5:37 PM

@Leaky: You should see me tutoring elementary school kids in arithmetic.

Leaky Nun

@TedShifrin :o

Daminark

Using this book: springer.com/us/book/9780387900407

Danu

lol

Daminark

A lot of French books have confusing titles

I remember when I saw a book called "Basic Number Theory" by Weil, I was like "Oh, I should check this out!"

Ted Shifrin

Hardly, Demonark. That's an extremely famous book.

arctic tern

5:40 PM

not sure if whoosh

Daminark

Then I read the title of the first chapter and said "Yeah... Maybe not yet"

Ted Shifrin

tern !!

So why am I flagged for doing high school calculus?

arctic tern

iunno

Daminark

Turns out there's one called "Number theory for beginners" which is actually reasonable

Anonymous

I don't think calculus is needed for this problem. It asks for rate of change of displacement (away from father). That is just radial velocity. You can get it by $10\cos(\pi/4)$.

Ted Shifrin

5:41 PM

True. You can do it without calculus. I never said you couldn't.

arctic tern

@TedShifrin woah

Anonymous

@TedShifrin I'm just giving an alternate solution :)

Ted Shifrin

I like that solution. If user139... had said no calculus, I would have done that.

Anonymous

(It's more physics-y type solution :P)

Ted Shifrin

I like it.

Daminark

5:45 PM

@Ted Just wondering, what's your favorite argument?

Ted Shifrin

This is starting to sound like Monty Python.

Danu

hahaha

Semiclassical

hi chat

Daminark

Maybe I should've said proof instead of argument, lol

Semiclassical

The specific coordinates that I got from Mathematica were {{-1.458757076997436, 1.3682206657955056}, {-1.4587570778432628, -2.6214552805344944}} @TedShifrin

Ted Shifrin

5:47 PM

wow, @Semiclassic. So it makes you wonder if you can prove that's a vertical line w/o computation

Semiclassical

not numerically exact agreement, but pretty durn close

yeah.

Danu

Hey @Ted, do you know any place where I can learn about symmetric spaces (and in particular why $G_2/SO(4)$ is one)?

I tried looking at Cartan's classification paper but nope.jpg

Ted Shifrin

Didn't I send you my lecture notes? I did the basics in there.

arctic tern

$G_2/SO(4)$, is that the quaternionic subalgebras of $\Bbb O$?

Ted Shifrin

You need an involution.

Sha Vuklia

5:49 PM

Would anyone know how to write the condition "otherwise" for a piecewise defined function in Mathematica?

Ted Shifrin

You leave the spot blank, @Sha when you do the If[] construction.

Sha Vuklia

Danu

@arctictern Yes

@TedShifrin Which ones? :P

Sha Vuklia

I don't have an If[] construction, I think

Ted Shifrin

Oh, I haven't used Piecewise in a while.

Danu

5:49 PM

@TedShifrin I realize ^^

Ted Shifrin

Maybe I didn't send you the Riemannian geometry course, Danu.

Danu

I don't think you did

Semiclassical

If I'm honest, I always need to look up the syntax for Piecewise

Sha Vuklia

I know I could write: $x\neq 0,y\neq 0$, but I was wondering about a general "otherwise" option

Danu

I have complex stuff, vector bundles

and G&P stuff

Ted Shifrin

5:50 PM

@Sha: You can always use Mathematica help.

Semiclassical

Sha Vuklia

Yea I did, but they don't treat the multivariate case. And online it seems so complicated.

I'll ask there then (at Mathematica stack)

Danu

I always have a terrible time trying to make Mathematica work for me :P

Sha Vuklia

even though their chat is dead:P

Ted Shifrin

Piecewise uses the condition "val" if none of the cond_i apply.

Semiclassical

5:51 PM

That's the same contour plot as before, but now the red lines are the contour $2\cos \theta=3\cos \phi$.

Ted Shifrin

Oh right. I had that condition when I was trying to solve by hand.

Semiclassical

And you can see that it passes right through the max/min.

Ahh.

Daminark

@Danu I've found the perfect solution to most of my mathematica problems

Ted Shifrin

@Sha: Just put your complicated formula after the first brackets, without brackets.

Semiclassical

Once you've got that it becomes simpler to optimize.

Back later.

Daminark

5:53 PM

The solution is to not use mathematica :P

Ted Shifrin

@Sha: I gave you the syntax up there, but didn't ping.

Sha Vuklia

yea I read it! @Ted

Ted Shifrin

Oh, actually I did.

Sha Vuklia

sorry I was trying out some stuff on Mathematica

Ted Shifrin

But the higher-up one I didn't.

Yeah, now that you remind me, I've used this. Don't even bother with the x=y=0. Just do the plot without piecewise.

Sha Vuklia

5:54 PM

but I don't want to plot?

Ted Shifrin

Oh, what do you want to do with it?

Sha Vuklia

i want to check continuity I think

or

differentiability

Ted Shifrin

Mathematica isn't a substitute for thinking. It can't do such things.

Sha Vuklia

yea the latter

lol of course not :P

Balarka Sen

I have to decide what I want to do.

Ted Shifrin

5:55 PM

You should know this from other examples you've done.

Sha Vuklia

I've already shown it by hand

but I wanted to practice using Mathematica

Ted Shifrin

shown what?

Sha Vuklia

to see if I can check it there

well, I think $f$ is differentiable at $\vec 0$

Ted Shifrin

Mathematica can't do theoretical stuff. You can plot it and see it's not continuous.

Sha Vuklia

oh? whut

I thought it was both continuous and differentiable

but mathematica can calculate a limit, no?

Ted Shifrin

5:56 PM

Guess again.

Sha Vuklia

it's obviously continuous?

i'll write it out:

Ted Shifrin

I don't think Mathematica does multivariable limits.

I suggested it's not continuous.

Sha Vuklia

I went too fast there

Ted Shifrin

uh huh

Transcript for

$Mathematics$ Mathematics