@NotNotLogical in any case, the short answer to your question is, many big-list questions are closed because they are seen as off topic by the community.

by nature big-list is off topic here, but exceptionally good ones are allowed to stay around as exceptions. the community didn't feel yours was well-defined enough.

Does anybody know why some questions are highlited on main?

@AlexanderGruber Could it be made more well-defined?

Or is it hopeless?

@skullpatrol I think those questions are the ones with a tag in common with your favorite tags.

@skullpatrol those are questions in your favorite tags

Thanks guys :-) @amateur @mike

@NotNotLogical to be honest i think it's just too broad

similar but more specific questions have been asked if you want to look around for them

i may be able to find you a good tag to look at, hold on one sec

@NotNotLogical

you see that your question essentially encompasses this entire tag and all questions in it

you will have to narrow it down to some specific technique you want to talk about, or some specific type of problem you want techniques for

To be blunt there is no hope.

ouch

Sorry

:)

@NotNotLogical if you want, there is a list of links i can send you with tips on how to write better questions

hello @AlexYoucis

@Mike How do I turn off the pinging noise?

Upper right corner

Mute your speakers.

Next to the "all rooms" button

Found it.

lol @ Mike

Nice.

@Mike Sup.

Just disconnect the electricity to your computer

Well, my suggestion works.

Guaranteed no noise from the computer

deafen yourself.

lol

@AlexYoucis A friend of mine is going to Berkeley next year.

@Mike Oh yeah? Did they talk to me at the open house, do you know?

No, they've been in Russia this semester, so they didn't attend.

Did you wear that mask to the open house?

Ah, I see. Well, that's cool.

Andrew Hanlon. You'd like him.

Nice

@Mike We'll see. First years are the scum of the earth.

Including yourself, I hope.

@Mike I'm the scummiest.

As far as I know, he knows a lot coming in, like you. Symplectic stuff, though, not algebraic.

@Mike I hope he likes big beards.

Because he's in symplectic geometry?

@Mike Because this may very-well be his future: math.berkeley.edu/sites/default/files/imagecache/photo_faculty/…

He spent his undergraduate career working with Russkies. I'm sure he'll be fine.

Hello.

@ParthKohli Hello.

@r9m Hi.

hey guys, what do you think about using \mathcal for vectors?

seems silly

Who is that in your avatar @vochmelka?

I only who is not that...

:D

sorry

Unconventional.

Somebody has to be the first one

Does anyone know what $n= \overline{1,\infty}$ means? I have never seen this notation before

Where did you see it @JessicaK?

The equation in question is a set of coefficients for a power series expansion $a_{n}$ used to solve a fractional differential equation

Maybe $[1, \infty]$

the closure of $(1, \infty]$

I would guess that^

Without further context.

I found a pdf copy of the book, it's equation 6.18 here math.unipune.ac.in/Downloads/fractional.pdf

@JessicaK probably just means $n = 1 \dots\infty$

Okay, I just wanted to be sure because I recently came across $\sum^{\prime}$ and thought the prime was just an artifact of some old typesetting, but I was wrong

@JessicaK what are fractional diffeqs?

Just differential equations with fractional derivatives

What are those?

oic

Then probably $\overline{1, \infty}$ means $[1, \infty]$ and $n$ can be a real number

Depends on the definition, but it generalizes derivatives so you can take the half derivative or other non-integer orders

Maybe it means complement of the open unit ball at $O$ in $\Bbb{C}$

Or the complement of $[1,\infty]$ lot of possibles

What does that gain you?

@JessicaK taking fractional derivatives?

I don't know

Why are you studying them?

6_6

I don't have a good reason if you're looking for one. I was studying the gamma function and just sort of ended up here

That's hot.

Let $E$ be a topo space, $A \subset E$ & let $a$ be a cluster pt of A. Then a map $f$ of $A$ into a Hausdorff spc $E'$ has at most one limit at the point $a$ wrt $A$.

What does wrt $A$ mean here?

with respect to, but what does that mean here?

Ah, the book says $\lim_{x \in A, x \to a}$

makes sense

In a Hausdorff space $E$ every finite subset is closed.

For any $x \in E\setminus A$, take the intersection of all open sets $U_i$ disjoint from $a_i \in A$.

that contain $x$

Then it's disjoint from $A$ and open so $E\setminus A$ is open

@Hawk Hey!

@r9m Here?

@Sawarnik Hi..

Hey, would one of you be able to help me solve an integral / point me in the right direction, please?

Askaway

ok, the integral is $$\frac{1}{\left(z^2+x^2\right)^(3/2)}

and I have to integrate it w.r.t x

I tried differentiating it first and a few substitutions but couldn't get it to work.

I tried substituting u = z^2+x^2; u=x^2 and some others but neither of them worked. And I also tried differentiating $$\left(z^2+x^2\right)^(1/2)$$ to see if I could sort of "work it backwards" but they didn't work out, and I am a bit stumped how else to approach it.

anyone got any ideas, or advice on how to handle these types of integrals

@Aesir have you tried trigonometric substitutions like $x = z\tan \theta$

No I haven't tried anything like that

let me have a go now

@Sawarnik :-)

@r9m I have an inequality question.

@Sawarnik good .. :)

@Sawarnik my roomie solved it on AoPS a few days ago :P

@r9m Oh ho.

ok so I tried substituting $$x=z\tan\theta$$ and the integral reduced to $$\frac{1}{z^2\left(1+\tan\theta\right)^{3/2}}\frac{1}{1+\theta^2}d\theta$$, am I on the right track?

ah wait I see where I went wrong

let me try again

If $G = R \times H$ where $H$ is the multiplicative group of the ring $R$, then $R$ seems to be isomorphic to the subset $\{(\phi(r), \psi(r))\}$ where $\phi(r) = (r, 1)$ and $\psi(r) = (0, r)$, except $1 = 0$ in that set.

it's weird

actually doesn't work, nvm

alright now I reduced the integral to \frac{1}{z^2}\int \frac{1}{\sqrt{sec^2\theta}}d\theta

Have you thought about posting it on main @Aesir? In the mean time.

@skullpatrol Aesir did it on his own :)

I thought it might be too basic a question to post on the main site

Just a suggestion :-)

and I get $$\frac{x}{z^2\left(z^2+x^2\right)}$$ as the answer

which wolframalpha says is correct. Thanks for the help!

latex won't work without dollar signs around it

^thanks

Hello Everyone

What is the difference between differential geometry and differential topology

Hey, @r9m

@BalarkaSen hello

I have two subjects at my desk this moment, which I'd like to sit on and read but I can't decide which one to pick.

which ?

They are (i) Sieve theory and (ii) Sextic forms.

Both are equally interesting, IMHO.

And I know very little of either of them.

both are equally unknown to me .. so IDK

Which part of math do you like, @r9m?

@BalarkaSen I think we had this conversation before :D

My memory is not very good but I remember you like number theory.

But if I recall correctly, you also like some thing else which I forgot.

Thus my question.

Hello, @Karl.

@BalarkaSen Hi

@KarlKronenfeld I just learned the proof of independence of Euclid's 5th postulate. Enjoying Hyperbolic geometry!

@BalarkaSen Ah :)

I am digesting the Poincare $\Bbb H$ model now. Are the other models essentially beasts of the same forest?

At least, $\Bbb H$ got a complex analytic interpretation.

And I loved the connection with fundamental region of modforms.

=)

Wait, has Marvis left the site?

@ParthKohli What is happening to your avatars?

puberty?

Hi all

yo, wazzup?

I need some help on how to learn maths

askaway

I'm finding stuff like limits hard to grasp, I don't know why.

@ParthKohli Yes. No wonder, now it's an every Tom, Dick and Harry Eternal September "community".

I am putting community in quotes to emphasise that given that it's basically everyone, it's not really any sort of community anymore.

My maths is fragmented I would say. I know bit here and there. I'm not finding a good approach to studying maths to get good at it.

And proof-writing. I'm having problems with that as well. Induction/Contradiction.

@Sab what textbook do you use?

Plus a ton of people who post wrong answers.

@Sawarnik Hi.

Stewart Calculus, its aweful

@Sab find something more to your liking.

I like Spivak but I can't find a copy.

There is a copy in the library but I can't take it for more than a week

@Sab Photo copy it.

Now I got a test in like 15 days and I'm not sure how I'll learn limits, derivatives and differentiation etc

I guess I will do that

I once photo copied an entire Physics book.

First year book?

high school

Which one was it. I'm having the same problem with physics. We use a book which is totally random

It

It's like everything is slapped at you. It's not chapter wise, well detailed

hey guys!

Hi

@Sab How about PDFs?

I prefer physical books.

hey @Sab

Me too.

are you looking for books on induction/contradiction??? specifically???

I was looking at these fancy graphs of superman, or batman

Ya, a good book on proofs

and one on calculus

I'm reading Daniel Solow, but Proof by Induction comes later in the book.

So I'm wondering if I can just skip the parts before that and go directly to induction.

@Sab : the graphs of "batman" form I saw once on a book of Fouries series...

Guys, do you think it's reasonable to study maths, if I'm mediocre at it? I always loved it, but now at college I've realized how much I suck at it and I am not sure if my life is going in the right direction, which kinda depresses me :(

Are these taught in first year?

but i don't think it is a good idea for you to read this kind of book for first year

@mirgee I'm in the same situation. Aced A-level Maths like a breeze nearly failed first test at uni

@Sab Ah, welcome to the club :)

Well, now even if I get 100% for the rest of all my tests, I will never get 100% in my class

I'll get max 97.3%

That's not bad, is it

Well, I need to learn my stuff first

I got a test in 15 days

Tests don't always show your real ability anyway

Dude a guy last year got 100% ]

His final grade

Which means that his 7 class tests and his 4 exams were all 100%

How is that even possible O.O

Well, some students are just stellar, I know :D Try to not compare yourself with them

Well. I'm sure if I get the right way of learning I can do it.

Reading ahead and being self-motivated.

Its funny how I got a 95% in applied maths though. Never had any experience with the kind of stuff.

Normally, how many hours should I dedicate to math everyday?

And.. stop thinking about A-level. They are just.. too different.

I'm like 5 weeks behind. I'm scared.

They say you can do anything, which is quite true until you reach your limit (forgive the pun)

xD

As much time as you need to understand whatever is taught on that day.

I understand math fast, I just can't sit straight and do it

and I don't have good resources if I need help

And, it really depends on what you intend to do after your BA.

Well I'm majoring in CS and Maths

@BoniTea is right

I want to do AI or Quantum computation which both require extensive math

So, going into an academia. Then the "lack of resource" might work in your favour.

Well,for a first year it's not

Really need to get used to finding and figuring things out on your own.

@BoniTea I spent many hours studying series, and in the test, I made a sequence of stupid mistakes failed it. Some people are natural, on the other hand. I am not. Those thing are very demotivating :/ How do you stay motivated?

^

Have a clear goal in mind and dedicate yourself to it.

Sometimes you just forget a lot during the test even if you know them

don't know if it's stress or fear or both

@mirgee Because if it's what you want to do then you gotta just take it. Think what would you do instead.

@BoniTea... the fact is that by seeing you ouwn fail does not seem to be very nice

Ooh, I've seen plenty of my own failures. Just need to learn how to learn from them, which is cliche, but true.

@Aesir You're right! I mean, math is so beautiful. I can't imagine studying anything else.

Some people get it first time, others take longer. But a good work ethic will pay off. If it's what you want to do then it is worth your time.

Some good advice here. I'll keep these in mind

And.. as for the first year tests, don't worry about them too much, unless your topic of interest depends on it.

When I came to uni, I thought I would be getting 80+

Now I'm finding myself late by 5 weeks

For example, my calculus was and is an utter mess. But it really doesn't matter much in what I do.

@BoniTea Well, calculus is quite essential, no matter one's topic of interest, isn't it :)

Later on, yes. For now, no.

@BoniTea how much time were you dedicating to maths on average?

Not enough. I almost failed my BA.

damn

I'm dedicating 4 hours/day to math now

I hope this would help.

Counting hours is pointless.

It is the quality of your understand that counts.

Aha.

Time does come into it, in that you definitely should take breaks here and there.

It's true. I find that just working when you feel motivated to learn is best for me.

@BoniTea... and what do you do now?

Also I find the best way to revise / learn is to teach. I teach an empty room explaining concepts out loud to myself infront of a whiteboard

Salvaging what I can and trying to get into a MA programme.

^This.

I miss my huge whiteboard. I couldn't take it with me in the plane

@Aesir Exactly. I spent so much time teaching calculus to my little sister, I believe she understands it better than me now.

ok

It's funny how some times you teach someone and they ace it and you fail it

:D

@Sab Well it's so sad it's funny :D

@Sab Glad to see smn has the same experience

@migree Yes, and I had the advantage of being the younger one :D Me and my sister studied together for her exams and that helped me immensely :D

Ah, may be you can do some A-level Maths tutoring in your area.

I did a-levels last year, I;m in uni now

Calculus :{

Oh, A-level, how much I miss you. You were so easy

ya

I don't remember learning for a-levels to get A

I guess that's why I'm struggling now, not used to studying or practicing

Don't know why they make you believe you are talented by making high school maths so easy to dis allude you at uni :D

That's the A-level system.

The day they start changing questions and make you think, people will start failing it

I hate this system, because it didn't teach me how to think

I know this is maths forum, but anyone into physics here??

i am on physics

i am not mathematician

I'm doing physics as well

So hardcore :'(

Poli, any good first year physics book?

@PoliTolstov Great, would you mind explaining to me some electromagnetism concepts, please? :)

I'm struggling hard :|

Everything is dealt with vectors now.

@Sab... are you first year, right?

@mirgee... i wish i can

I study physics

everybody is studying physics here? haha

Ya

I'm doing Maths, Applied Maths, Physics and COmputer Science

;-;

I thought Physics would be easy

mirgee the best electromagnetism concept are on MIT ocw

i used th book by Alonso and Finn @Sab

I'm using matter and interactiions by chabay

it's a weird book

The problem is the chapters are not like normal physics books

amazon.com/Physics-Marcelo-Alonso/dp/0201565188

It tells you something in chapter X and then 2 chapters later tells you why

I like Introduction to electromagnetism by Griffiths

:O that book should be perfect

@Aesir i like griffiths too

I'm finding mechanics hard

Poli what's the best way to learn physics?

I haven't actually read it but every time I need clarification it hasn't failed me

i feel halliday is superficial

There was Halliday in the Lib. it's 2nd edition

I didn't take it

Many people recommend Halliday, but I don't see lost of vectors in it

we did like 9 chapter in 7 weeks

in Matter and Interactions

:/

@PoliTolstov I'm sure you can :) I have two balls (you know what I mean) made from different materials. Induced electric dipole in one is 1.5 times smaller than in the other. I am given electric permitivity of one of them and am supposed to find permitivity of the other... So I guess the question is how is polarizability connected with permitivity

test in 15 days

@PoliTolstov All I know is $\vec p_{ind} = \alpha \vec E$, where $\alpha$ is material constant

Boriing question, I know :)

yeah @mirgee... i dont think i can... i have to take the book and make some readings..

i am not at this topic yet... i did not get this section on electro... i am starting to see this

i dont know much on polarization

:(

@mirgee i really would like to help you...really

@PoliTolstov Well, I also found $\vec P = V \vec p_{ind} = \epsilon_0 (\epsilon_r - 1) \vec E$, but I am missing something, this doesn't work

@PoliTolstov Well, never mind :) Thanks anyway :)

@PoliTolstov What year are you in now?

@chris'ssis can you mention two series expansion of $$log(2)$$¿

@Sawarnik where did you get the inequality question from, the one you asked me today ?

@r9m From an online pdf on inequalities. And I asked it on the main too, and the genius Macavity answered.

@Sawarnik can you link it?

@Sawarnik hou .. !! titu's form !! (my solution too involves it :P )

@Sab math.stackexchange.com/questions/760759/…

@r9m What is titu's form? :D

@Sawarnik titu andrescuu :P (the first line he used is popularly known as titu's form .. for holder or CS ineqs)

Ty

Is that a year 1 question O.O

?

@Sab Which?

This inequality?

Maths is starting to freak me out hard!

@Sab these are more like olympiad oriented questions ..

@Sab Nobody can solve all kinds of problems! So don't worry.

But what to say, higher maths is freaking me out as well!

@r9m Right.

Ok, I have to go.

I'm still in year

1

@Sawarnik @Sawarnik I want to know how to handle initial conditions like $a+b+c+abc=4$ .. where do you find these questions ? :P

@r9m Lagrange.

Oh wait, the problem is something else.

hi guys

@r9m This one in particular is from artofproblemsolving.com/Resources/Papers/… :D

And inequalities is my on of my weakest portions, I can hardly solve any that require more than AM GM.

@Sawarnik thanks :D

@r9m Do you know what all that Holder's and Schur's are?

@Sawarnik yas

@r9m Ok, did you see this math.stackexchange.com/questions/750614/… ?

:15057867 you know Cauchy Schwarz right ?

@Sawarnik freaking yes .. tried it .. but miserably failed to get anything remotely useful

@r9m Oh :D :D

@r9m Not really :(

Simple geometric shapes are getting popular in avatars.

Greetings

@GabrielR. well, think of the series expansions of $\log(1+x)$ and $\tanh(x)$.

I didn't want to create too much stuff today, but finally a thought stroke me and I produced something marvellous.

Hi, any physicists in here? :)