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00:00 - 18:0018:00 - 00:00

00:23
@anon You here?
@anon I am pretty sure that Martin is mistaken here
the quotient is not a domain
indeed
@anon What is this guy talking sense?
what?
@anon I mean that guy that posted the answer is talking nonsense
well, it's the absence of sense..
00:55
@Ethan What is it, man?
@BenjaLim Link or GTFO =)
nvm I got it figured out lol
@Ethan But what was it?
just help geting a book gustavo helped me
What do you do if your up votes are not giving you rep?
for an answer
you do not get rep for upvoting others. when you cap for the day you do not get further rep from upvotes until the system goes to the next day.
as for "what you do" in that situation, it's up to you
01:08
@anon
@cyclo
@anon I got two up votes for an answer and it didnt count on my rep page
@anon I deleted the answer and undeleted it, why?
you don't get rep on CW posts
community wiki
01:10
ok kewl
@anon thanks for the help
mmhmm
I got a math question for ya
Can we prove that there is a prime between (n^m, (n+1)^m) for any m greater than 1?
the case $m=2$ is an unsolved problem
legendre
@BenjaLim How is uni going?
anyone have a link that explains simply of how to find the slope of a parabola?
@JohnMerlino Do you know how to differentiate?
a little bit
I am able to find the y-intercept and x-intercepts of the parabola, just looking to find the slope now, and I know differentiation gives the slope of the quadratic equation
as long as its algebra solution
I used factorization for the x-intercepts
01:57
the slope of the line tangent to the curve y=f(x) at (a,f(a)) is f'(a). if f(x)=ax^2+bx+c then f'(x)=...?
@anon I am wondering why the cyclic groups were not called the polygonal groups.
they don't need to be thought of geometrically
@anon I know, I just wonder why, say, the Dihedral groups got their name like that and these didn't.
@Peter: Cyclic groups were discovered by cyclists ;-)
@amWhy chuckles
cyclos accounts for "circle", and tomos for "divide."
According to Wikipedia.
02:05
Polygonists have a fettish for $D_{2n}$, except for eccentric (odd) polygonists, who feel slighted by $D_{2n}$
I am sure the polygamists are not slighted by presenting their group's size though.
@anon hehehehe
02:22
@robjohn Hmm....ok. I didn't really think about the repercussions to other accounts...
I think I'll just stop logging in... (I'm trying to reclaim some lost time). I don't need my account actually deleted, I guess.
02:40
Evening all
Morning.
03:16
$$\sum_{n=1}^\infty\frac{\Gamma(n)^2}{\Gamma(n-x+1)\Gamma(n+x+1)}=\frac{1}{x^2}-\frac{\sin(\pi x)}{\pi x^3}$$
@anorton we all need to set priorities. Good luck :-)
3
@Ethan That's actually doable using the functional equation, I believe.
what do you mean
 
2 hours later…
05:36
@GustavoBandeira can you help me'
I like cucumbers.
In terms of propositional logic
Would it be correct to say all formula are either atomic formula or can be construct from atomic formula through the use of the logical negation and conjunction connectives
$$
\frac{\Gamma(n)^2}{\Gamma(n-x+1)\Gamma(n+x+1)}=\frac{\sin(\pi x)}{\pi x}\frac1{n^2}\frac1{(1-x^2)(1-x^2/4)\dots(1-x^2/n^2)}
$$
I guess all formulas can't be atomic, let me check.
@robjohn haha you got it lol
05:38
@Ethan That's what I meant by using the functional equation for $\Gamma$
Wait, Kobo is loading
@robjohn $$1+\sum_{n=0}^\infty a_n\prod_{k=0}^n\frac{1}{1-a_k}=\prod_{n=0}^\infty \frac{1}{1-a_n}$$
Yeah, I believe that is correct. All formulas are either atomic or constructs of atomic formulas.
I'm just not sure about the end of your statement.
@robjohn ignoreing convergence and assuming no $a_i=1$
@GustavoBandeira thanks
I'm not sure if all formulas can be derived with only negation and conjunction.
05:46
well can't the other logical connectives be rephrased in terms of negation and conjunction
When I was building TECS (The elements of computing systems) - The only primitive give was a NAND gate, with it I built the NOT gate, then the AND gate, then the OR gate. With NOT, AND and OR, it is possible to derive all other formulas though canonical representation.
I'm not sure if this is connected to your problem though.
I am probably just confusing myself
I got out of school yesterday, I am now on summer break
Relax, me too.
I didn't go to school today though lol
:-)
I hated school.
The question you made helped me to elaborate one nice question. :-)
05:52
I was talking to someone outside on Wednesday during one of my classes, they said they had to go to the bathroom, they never came back
I guess some find me annoying
First time something like that has happened to me, I don't normally talk to people that much, but I was pretty bored.
What did you do? You shot 10 random formulas at them? :-)
No, I was just asking him standard questions, like what kind of music do you listen to, do you have any hobbies, what makes you happy etc
I think he was foreign or somthing, his name was Hovo if I am spelling it right, thats how it read phonetically
Oh, that philosophical probing you do sometimes?
It must have been that..
lol
05:56
@GustavoBandeira Lol my digital imaging teacher had us put down questions for a college recruiter sort of person who gave us a presentation
Buy a tablet, keep out with you to chart with mse people.
chat
lol
The one on types?
?
No at school
05:58
My digital imaging teacher brought in some college recruiter to give a presentation or somthing
I guess they don't life their lives
Like*
Sorry the typos, I'm on my cellphone, computer is not working.
Oh, where are you?
do you live by yourself?
@GustavoBandeira recommend me some movies or something you know any good ones
Were you the one that reccomended tree of life? or was that peter
Regaurdless I found it kind of boring
Nope, my mother agreed to pay my bills while I'm in university.
But I live in a separate house.
Tree of life? Want it isle of flowers?
06:05
No not that one lol though that one was sort of depressing and boring
Not that I don't feel bad or anything
Just not very enjoyable I guess
yep.
I don't know about movies, I didn't watch movies lately.
06:21
@Ethan This is just too funny :-D
The transcript. XD
@GustavoBandeira ROTFL !! You are right !
06:56
I guess there is a new ThePirateBay Laptop
07:34
@anon u there ?
yes
I need help understanding what slope of a line is
If I am not wrong, it means...
Change in Y when there is a change in X
That is, how fast / slow Y changes
so slope is, as a derivative, $\frac{dy}{dx}$
@anon correct ??
mmhmm
Ok great ! Just wanted to know if my understanding is right
Thanks
08:02
@anon derivative is all about slopes of curves ?
aaaand... the slope of a line is a tangent at that point ?
@anon Do you know about measure theory? I have a question
isn't it ?
@LittleChild yes
So, in case of a straight line the tangent and the line coincide and hence the slope is consistent throughout
@BenjaLim right ? :-)
 
2 hours later…
10:35
@Lord_Farin Your query still returns even more post for me than the other one.
I've responded here and not on the meta, so that we do not add too many off-topic comments to that question.
Anyway, I do not consider this to be important.
@MartinSleziak It also counts answers. It is not at all clear from the description of the badge which is correct.
@Lord_Farin: Hi friend.
I think both you and me can use our time better than trying to find out progress to some meaningless badge.
4
@BabakS. Hello there, my friend.
@MartinSleziak 't Was a good recapitulation on SQL for me :).
@Babak How are you doing?
Tell me @Lord_Farin, what is that Err... in your first comment at meta.math.stackexchange.com/q/9883/8581. Is that a code in Latex? I have thought many but couldn't find that?
10:40
@BabakS. No, it's just plain text. It indicates me not understanding what part of \cases was outdated, since it functions just fine.
@Lord_Farin: Ohh... I see.
How about the thesis? Does your thesis go well?
@BabakS. Sort of. It's coming together, albeit a bit slower than I would like it to.
How about yours?
@Lord_Farin: I am red-correcting some awful assignments, but mine goes good. In fact, I collect the results when I am off from my job.
Excellent.
Thanks.
10:48
@Babak Do you also correct the spelling and grammar errors? I always have fun with those, although it is usually not allowed to deduct points for them.
@Ethan Sorry, yeah. Multiply through by the right side, then prove by induction.
11:04
@Lord_Farin According to this meta.SO post the edits, where only tag were changed (and not the body) do not count to the archaeologist badge: Do tag edits count for Archaeologist?
This could explain the discrepancy between the data.SE queries and actually awarded badges.
11:46
@MartinSleziak It's irresistible to spend time on only moderately useful stuff, no? :)
@skullpatrol Muhaha. I defied the impulse to click that. :D
@Lord_Farin Congratulations :D
@MartinSleziak I've adapted my query to reflect this information. Thanks.
12:10
@Lord_Farin: the suggested edit was actually good.
@robjohn It changed a plus to a minus, no?
@Lord_Farin twice and it was right
@robjohn Well, thanks for catching it; it's so easy to mess these things up.
I agree with you, on a third look (I switched from "accept" to "invalid", and now back).
@Lord_Farin does that mean the person will get their suggested edit points?
Pardon the interruption, but shouldn't there be a +C on that?
12:14
@skullpatrol on what?
4 mins ago, by robjohn
@Lord_Farin: the suggested edit was actually good.
@robjohn
@robjohn Well, I'm afraid not. I rejected it in the review queue, and hadn't realised that was erroneous until now.
@skullpatrol I added it
@Lord_Farin :-( oh well, tis only a couple of points
@robjohn It happens. I don't want to know how often these things happen without getting noticed.
@Lord_Farin I have made an apology in the comments.
12:20
Good.
@robjohn Just out of curiosity would you take a mark away if a student wrote -C instead of +C?
@skullpatrol absolutely not. That is quite fine.
so is $+2C$ and $+\log(C)$
12:38
@robjohn any surjection at the end works pretty fine, so even $+\cos(\Gamma(C))$ should to the trick :D
I am not so sure about the surjectivity, maybe some points are missing
@Lord_Farin A right cancellative morphism doesn't need to have a right inverse right ?
@exitingcorpse Nice skull.
@DominicMichaelis Correct.
Just try and write a minimal example/counterexample, and you'll see.
the Hausdorffspaces should give a counterexample, as they have as epis every continuous function with dense image
@skullpatrol it's just the unicode one with a pantone background ☠☠☠
13:02
@robjohn Why is $\log(C)$ acceptable? Typically in beginning calculus courses, the domain is $\mathbb{R}$, so we don't have negative results from $\log(C)$.
@anorton $\log(C)$ can vary over all of $\mathbb{R}$
Oh. duh. I don't know what I was thinking. :)
@anorton $\log(\exp(-1))=-1$
@DominicMichaelis exactly. (oops)
my brain collapses usually are just arithmetic, but the biggest most recent thing was the time i said the rado graph has isolated vertices
thinking is hard, saying grammatically correct sentences is easy
6
13:28
From time to time I realise that it is much easier to prove something when you know the definitions :D
MJD
MJD
I'm ambivalent about moving my comment to an answer.
At least partly because I don't know what the guy is actually asking about.
It's tempting to try to close it for vagueness.
Anyone else here have any thoughts?
@MJD I join in on the close vote. OP is gone so can't clarify.
MJD
MJD
13:45
Well, if one solution to the problem is good, three solutions is three times as good.
I posted two answers and voted to close.
i would say you've covered all bases / interpretations to the question and closing is unnecessary
@MJD Excellent. For other old unanswered questions, you can post in this room.
MJD
MJD
14:03
Hmm, "revival" badge.
2
14:34
Notice that it has not yet been completed...
The most frustrating (not the first) experience in trying to contribute to this site.
 
2 hours later…
16:40
@robjohn you there?
@JayeshBadwaik or you ?
any1 ?
@anon hi there !
@LittleChild what's up?
Hellow ! ^_^
Derivatives using limits and I got stuck
@robjohn Here is the question:
$\frac{\sqrt x}{8}$
so I need to find its derivative using limits.
and I got stuck midway
@robjohn wanna see the steps ? :)
sure
so, I went by the definition of derivative using limits
$\sqrt{x+h}-\sqrt{x}=\frac{h}{\sqrt{x+h}+\sqrt{x}}$ is often useful
16:53
I guess I might wanna make a picture of it :-D
could you possibly use the equation I wrote above to get that limit?
$\lim_{h\to0}\frac{\frac{\sqrt{x-h}-\sqrt{x}}{8}}{h}$
rewrite it as $\frac{\sqrt{x+h}-\sqrt{x}}{h}=\frac1{\sqrt{x+h}+\sqrt{x}}$
why do you have two $h$s?
Numerator: $\frac{\sqrt{x-h}-\sqrt{x}}{8}$
Ah, it's an 8
16:56
I posted the numerator separately :)
so basically, I took $\frac{1}{8}$ common, sent it down with $h$
then got stuck
$$\frac18\frac{\sqrt{x+h}-\sqrt{x}}{h}=\frac18\frac1{\sqrt{x+h}+\sqrt{x}}$$
what do you get if you take the limit of the left side?
Undefined. Cause it is divided by 0
no, if you take the limit.
I still didnt get why you flipped it over and changed the sign.
In the limit you never let $h=0$
16:59
how does $\sqrt{x+h}+\sqrt{x}$ become zero?
$\frac{1}{16}$
Hello how to compute E[XY], if X and Y are two discrete random variable
@LittleChild multiplying numerator and denominator by the conjugate $\sqrt{x + h} + \sqrt x$
@blob same way: you compute sum a*b*P(X=a,Y=b)
@LittleChild multiply $(\sqrt{x+h}-\sqrt{x}) (\sqrt{x+h}+\sqrt{x})$ and what do you get?
17:00
wait, let me get paper adn pen
@robjohn Sorry, didn't mean to interrupt
why and how are two different questions. the "how" is "difference of squares," the "why" is because then neither numerator nor denominator tends to zero
that would be $a^2-b^2$
and that is?
$a^2-b^2=(a-b)(a+b)$ ... or, another way of putting it for nonnegative reals $a,b$ is $a-b=(\sqrt{a}-\sqrt{b})(\sqrt{a}+\sqrt{b})$
17:02
only $h$ and then $h$s cancel out and I am left with a conjugate in the denominator
@anon sorry how?
@LittleChild now do you see why $\frac18\frac{\sqrt{x+h}-\sqrt{x}}{h}=\frac18\frac1{\sqrt{x+h}+\sqrt{x}}$
@robjohn yes !
@LittleChild now take limits
$\frac{1}{16}$
17:03
@blob how do you compute E[X] for a discrete random variable X?
why is division by a variable not considered a polynomial?
sum_x of p(x)
@LittleChild what happened to the $x$?
polynomial is supposed to have multiple terms right ?
sum_x of xp(x)
17:04
@JohnMerlino why should it be?
it stays in the root right ? I was just writing the numeric part :)
yes and 2/x + 3 is multiple terms
polynomial means multiple terms
I just showed you multiple terms
$\frac{1}{16}\times\frac{1}{\sqrt{x}}$
@robjohn I remember how teachers taught us limits
We had like a sequence of pattern to math
@blob correct, sum_x of x*p(X=x). then E[XY] is sum_x,y of x*y*P(X=x and Y=y). If X and Y are independent then things are nicer.
does this problem contain polynomial identities ? trigonometric identities ? can you find a common factor ? etc etc
17:06
@JohnMerlino it means more than multiple terms
conjugate slipped out of my mind :-)
$e^x+(-1)^x$ has multiple terms, it is hardly a polynomial
@robjohn wanna gimme a sum to solve ? Derivative using limits ? :)
I am just trying to get a hang of it before going on to integration :-)
@anon I understand the "rules" of what makes it not a polynomial. But the question is why? Why the limitation?
thank you @anon
17:11
@anon Why can a polynomial only have constants, variables, and positive exponents and cannot by divided by a variable?
who decided on these rules and for what reason?
mathematicians cause they had no life
they could have made it easier
but they wanted us all to suffer
@JohnMerlino Kidding, ok ? :-D
I think it has something to do with putting math at different levels, like how you have linear equations, and all you have quadratic equations
and then you have logarithms and so forth
I think they are limiting it
so if that is the case, what can the graph of a polynomial look like and what cannot it not look like?
@LittleChild
I am the dunce guy here. I am only here for asking quick questions that do not fit the QnA policy of the main site. :-)
@robjohn This just popped into my mind, consider this $x+2 = y$
if I were to move $x$ to the other side , it becomes $-x$
what about matrices ?
$A + B = 7C$
where A, B and C are matrices
if I move $A$ to the other side of the equation
it becomes a -A or $A^{-1}$ ??
17:19
I am going to ask in the main section
I like to know the whys of things
not just the rules but the whys
17:31
@JohnMerlino there are already many different named objects: (a) R[x], (b) R[x,x^-1], (c) R[[x]], (d) R(x), (e) R((x)). in order: (a) polynomials, (b) polynomials in x and x^-1, (c) formal power series, (d) rational functions, (e) formal laurent series.
asking why the word "stone" applies to various types of rock but does not apply to trees is very strange. we already have different words for them both - rock and tree - and that's exactly as it should be.
polynomials are the most basic and ubiquitous: algebraic relations in commutative rings (structures with addition and multiplication) can be encoded as polynomials. all of the other things are built from polynomials. it makes sense, both pedagogically and conceptually, to distinguish the foundational type of object from the more general types of objects that are made out of them.
17:44
If you already have the broader class of "rational functions", why indeed would you still need to expand the definition of "polynomial" to include negative powers of the independent variable?
@LittleChild If it's reversing addition, it's $-A$. If it's reversing multiplication, it's $A^{-1}$
When using truth tables in propositional logic, would it be an abuse of notation to substitute the bits $\{ 0, 1 \}$ in for sub formula appearing in formula, when attempting to evaluate there truth value.
can someone help me
evaluating the truth value for yourself or for others to see? (barely such a thing as abuse of notation in the former case). of course the subformula has to evaluate definitely to either true or false to put a constant value in for it.
I know but would it be ok to write somthing like $0\wedge 1 = 0$
yeah
17:52
not sure if equality is the right relation here
when saying two formula have the same truth value in prop logic is it correct to say $A=B$?
@Ethan If this bugs you, you can consider the set $\{0,1\}$ as being endowed with operators $\wedge,\vee,\to,\neg$.
Hell, one can do 1 && 0 in C anyway... :D
@anon various types of stone look different and that's why they are grouped differently. In a polynomial you can divide a constant like so: 1/2. But in polynomial you cannot divide by variable like so: 2/x. Look, what causes the fabric of the two expressions to be different? Is it the graph looks different? What makes it look different: a green stone from a red stone, to use your analogy.
(P. S. consider using \land, \lor, \lnot for logical operators...)
@Ethan It can be made to be correct, but I'd prefer $A \iff B$ or $A \equiv B$.
17:54
@JohnMerlino With $2/x$, we have a singularity at $x=0$, while usually we want polynomials not to have singularities like these...
@Ethan Have a look at the Lindenbaum-Tarski algebra.
in addition to polynomials not having singularities (a graphical way of seeing a striking difference with reals or complex numbers), as I said earlier polynomials encode algebraic relations, and the things they encode the relations for need not be invertible. note that the coefficients of polynomials don't even need to be invertible depending on the underlying ring...
If we're going to admit $2/x$ as a polynomial, we would then need to rephrase the fundamental theorem of algebra...
@Lord_Farin to complex for me sorry lol, can you help me with one more thing though
@Lord_Farin The book I am reading defines the sub-formula of a formula as follows,

Definition $1.4$, The following rules define the subformulas of a formula.
Any formula is a subformula of itself.

Any subformula of F is also a subformula of ¬F.

Any subformula of F or G is also a subformula of (F ∧ G).

-----

But then later goes on to say,

Example $1.5$,

Let A and B be atomic and let F be the formula ¬(¬A∧¬B).
The formula A ∧ ¬B occurs as a substring of F, but it is not a subformula
of F. There is no way to build the formula F from the formula A∧¬B.
wait, so you are using the division by 0 argument
17:59
one way to bridge the algebraic and geometric understanding is through the "evaluation maps": you can evaluate a polynomial anywhere, not so if you have negative powers of variables. so polynomials are more universal.
you are using the division by 0 argument to justify why 2/x is not a polynomial
...as you will see, it's a house of cards: tweak the definitions of the most basic objects you're dealing with, and you will need to adjust all the theorems built on top of those definitions.
"justify"? dude, we're talking about naming things
@robjohn similar to regular arithmetic then :-)
sorry I was AFK
00:00 - 18:0018:00 - 00:00

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