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14:00
@Liad Compose with a rotation of $\Bbb C$ so that the line $\{\alpha z_0\}$ gets mapped to the real axis $\{\alpha\}$ probably.
i thought about it but i want to understand something else. if i use Cauchy–Riemann equations how do i differentiate $\alpha(z) x_0$ with respect to $x$ (or $y$) ? $\alpha$ is a function from $\Bbb R$ to $\Bbb R$ @BalarkaSen
Hey!
I don't understand the question but I have to leave now
I just wanted to ask whether we can treat functions like algebraic variables (adding subtracting and stuff like we do with variables)? Actually, I used functions like algebraic variables in a physics problem and got the right answer but I am unsure about my solution.
@LeakyNun Mind answering^ ?(Please let me know if more details required)
14:07
@Abcd yes, as long as the subtraction is well-defined
@LeakyNun well defined?
In mathematics, an expression is called well-defined or unambiguous if its definition assigns it a unique interpretation or value. Otherwise, the expression is said to be not well-defined or ambiguous. A function is well-defined if it gives the same result when the representation of the input is changed without changing the value of the input. For instance if f takes real numbers as input, and if f(0.5) does not equal f(1/2) then f is not well-defined (and thus: not a function). The term well-defined is also used to indicate whether a logical statement is unambiguous. A function that is not well...
uh oh
class is awesome :o
learning about sets atm
@Dodsy nice
@Abcd in particular, what does $f+g$ mean where $f$ and $g$ are real functions?
14:09
I was so nervous to go haha
@LeakyNun I am not sure. Haven't had much exposure to function algebra.
@Abcd how would you define $f+g$?
@LeakyNun I seriously don't know..
have you seen this symbol? $f \circ g$
@LeakyNun no
14:10
that's the composition of f and g, correct?
@Dodsy yes
@Abcd alright, $f+g$ is defined as a function whose value at $x$ is $f(x)+g(x)$.
i.e. pointwise addition of functions
would be $g(f(x))$ if $f \circ g$
@LeakyNun Will I get to know the reason for this ever? PS: There's a big chapter functions in class 12, will I get to know why f(x)+g(x) = f+g?
@Dodsy not really
sorry.
14:12
@Abcd let's look at $f(x)=x$ and $g(x)=x^2$.
What do you say $f(x)+g(x)$ is?
@Abcd I never said that.
g sends x to g(x), and then f sends g(x) to f(g(x))
@LeakyNun $x+x^2$?
@Abcd exactly
f(x)+g(x)=(f+g)(x) not f+g
so it would make sense if $f+g$ is a function that sends $x$ to $x+x^2$
14:13
Yes, right @LeakyNun
@semi
I wish I would stop doing that
I always think that by pressing enter, your name will just enter into my text bar
@Abcd so what would $f-g$ mean if $f$ and $g$ are real functions?
@Dodsy use the tab key instead
$f(x) + g(x)= value of f(x)+value of g(X)$. Please verify.
@Abcd ?
14:16
@LeakyNun I can't understand the concept clearly.
@Abcd you said "yes, right" above
let's do it again
@Abcd that makes no sense whatsoever
now, $f$ is a function that sends $x$ to $x^3+1$
$g$ is a function that sends $x$ to $x^2+1$
what should $f+g$ as a function send $x$ to?
@LeakyNun what do you mean by "sends x"? x is input right?
@Abcd yes
a function sends a value to another value
@LeakyNun What does $f+g$ mean mathematically, and non- intuitively? What is the definition of $f+g$?
7 mins ago, by Leaky Nun
@Abcd alright, $f+g$ is defined as a function whose value at $x$ is $f(x)+g(x)$.
14:19
all righty
notationally, that means (f+g)(x)=f(x)+g(x)
@LeakyNun Edit makes the post come down now?
@LeakyNun Hi again >< i know its been more than 30 mins =p
@Abcd ?
@Semiclassical Hello semi
14:19
so at least notationally it's as though one 'distributes' the x into f and g
@LeakyNun Understood.
one shouldn't take that literally, of course.
@LeakyNun x^3-x^2
5 mins ago, by Leaky Nun
@Abcd so what would $f-g$ mean if $f$ and $g$ are real functions?
@Abcd right, now answer ^
@KasmirKhaan what is your question?
@KasmirKhaan heyo
14:21
@Abcd no, a function is not a value.
@LeakyNun well its better to reread the chapters so I know what to ask =p
@LeakyNun Ted and Semi helped me yesterday on that question, but still strugle to make a good proof
@LeakyNun $f(x) + g(-x)$?
@Abcd same problem.
@LeakyNun the question was how to show z/2 x z/2 and z/4 are the only groups with 4 elements
@KasmirKhaan I said I already scrolled through the conversation
14:23
Okay
Ehm what I have trouble with is
and I will refrain from commenting (on the conversation). Do not get me started.
What do you mean ?
I think him explaining his lack of commentary would count as commentary :)
@KasmirKhaan never mind. go on.
@Abcd do you know what the difference between a function and a value is?
the problem I got is , when i have 2 groups , and i know all their elements
also found a 1-1 correspondance between each element
14:24
@LeakyNun Function = Takes inputs and gives outputs; Value = Abstract quantity
in this case am talking about GL_2( Z/2 ) and S_3
@Abcd hmm, no.
both have 6 elements
$x$ is a variable, it isn't constant, but it isn't a function.
the dependent variable is also not a function.
and the value can also be dependent.
How to prove they are isomorphic, without listing all possible products
f(xy) = f(x) f(y) this holds for all, but should I write it out for all 36 possible products
14:26
you just need to find what the generator maps to, @KasmirKhaan
@Abcd that's better
@LeakyNun Why is that enough?
@KasmirKhaan because everything else is generated by the generators
@Abcd so $f(x)+g(x)$ is not a function, but a value.
@LeakyNun all righty , let me try to think for a while why that is true :D
@KasmirKhaan they're called the generators for a reason
@LeakyNun ok
@Abcd so what does $f-g$ mean?
I posted this to Facebook a couple years ago. ^^
> Been playing around with Fibonacci-style sequences on groups!

For both, I started with the Cayley Table. Then I traced out the paths that sequences take. For example, the second one is the integers modulo 4, or in other words, {0,1,2,3} (and 3+3=2 in this group). You can start with 0 and 1, and by repeatedly adding them Fibonacci style, you end up with the sequence 0, 1, 1, 2, 3, 1, 0, 1. For Z_4, there are four such sequences:

0, 0, ...
0, 1, 1, 2, 3, 1, 0, 1, ...
0, 2, 2, 0, 2, ...
0, 3, 3, 2, 1, 3, 0, 3, ...
you're right
@LeakyNun what are f and g?
@Abcd real functions
14:29
@LeakyNun You tell please.
@Abcd $f-g$ is the function that sends $x$ to $f(x)-g(x)$
@LeakyNun I said that earlier :( and I meant the same thing.
@Abcd no, you said $f-g$ is $f(x)-g(x)$
@LeakyNun I meant $f-g$ is a new function that returns output as $f(x)-g(x)$ for an input $x$. Is it correct now?
@Abcd yes it is
and I can hardly tell you mean that by simply "$f(x)-g(x)$".
14:32
@LeakyNun It's the same thing for the same $x$ inputs IMO
$f-g$ maps $x\mapsto f(x)-g(x)$
@Abcd that's a common misconception
@LeakyNun Please recheck.
which grade are you in?
If Leaky had said "what is $(f-g)(x)$?" then $f(x)-g(x)$ would be appropriate
14:34
@Abcd ok
1 min ago, by Abcd
@LeakyNun It's the same thing for the same $x$ inputs IMO
but he didn't. he asked what $f-g$ was. hence the answer should be a function, not the output of that function.
@LeakyNun No, a function is not the same as its value evaluated at $x$
@LeakyNun Grade 11, why?
@Abcd alright, then you probably won't need that distinction
@LeakyNun we dont have any generators on S_3
14:35
bull.
@LeakyNun When will I need it?
@KasmirKhaan of course we have.
the order of elements are 1 ,2 and 3
@Abcd when you get into university perhaps
@LeakyNun was referring to S3 not having generators.
14:36
@LeakyNun :0
@KasmirKhaan alright, I meant $S_3$ has generators.
@Semiclassical wrong ping
Well but generator by definiton must generate the group
S_3 is not cyclic
cyclic is when you have one generator that generates the whole group
this is what I was getting at earlier. generator (singular) versus generators (plural)
there's not one generator, no. but there is a set of generators.
14:37
IIRC there's a theorem that every finite (simple?) group can be generated by exactly two elements.
definitely not.
@LeakyNun But now I am eager to know. Can you explain the difference sometime later (because I am busy with Physics right now)?
@Semiclassical Is that in response to my statement? What about this? mathoverflow.net/a/59216/57164
15 mins ago, by Abcd
@LeakyNun Function = Takes inputs and gives outputs; Value = Abstract quantity
I may have been too hasty.
14:40
you already explained it
i'm a bit shocked if it's true
@LeakyNun okay.
@El'endiaStarman yeah, looks like I was wrong. huh.
@Semiclassical To be fair, it's certainly a shocking result in general.
<123> = {e , (1,2,3), (132) }
but how does this help us?
14:43
@KasmirKhaan, your group needs to be generated by 2 elements.
I allready found the 1-1 correspondance between each element of Z/2 X Z/2 and S_3
as we've been saying, one generator isn't going to cut it here.
you need two.
@KasmirKhaan a bijection is not an isomorphism.
14:44
two elements
(i'd have said at least two, but it turns out we don't need more than that.)
@LeakyNun okay >< I was thiniking limited to one element =p
this idea opens the door to more glorious ideas then :D
let me think =p
okay, so what two elements generate the group?
(123) and (23)
Semiclassical, let me show you a cute identity of sequences I derived and proofed:
Let $A_n=\sum_{m=1}^na_m,B_n=\sum_{m=1}^nb_m$. Then:
$$\sum_{m=1}^na_m\sum_{k=1}^mb_k = \sum_{m=1}^n(A_n-A_{m-1})b_m$$
14:49
Yup, it's indeed possible to generate any finite simple group with two elements...
$A_n-A_{m-1}=\sum_{k=m}^n a_k$.
Though, as far as I'm aware, every proof of this relies quite heavily on the classification :/
so this is just a special case of swapping the order of summation of a double sum.
(along with swapping the summation labels)
Ah I see, I guess that's why I saw this weird triangular pattern:
\begin{align}
\sum_{m=1}^na_mB_m & = a_1 (b_1)\\
& + a_2 (b_1+b_2)\\
& + a_3 (b_1+b_2+b_3)\\
& + a_4 (b_1+b_2+b_3+b_4)\\
& ...\\
& + a_n (b_1+b_2+b_3+b_4+\cdots +b_n)\\
\\
& = (a_1+a_2+a_3+a_4+\cdots +a_n) b_1\\
& + (0+a_2+a_3+a_4+\cdots +a_n) b_2\\
& + (0+0+a_3+a_4+\cdots +a_n) b_3\\
& + (0+0+0+a_4+\cdots +a_n) b_4\\
& ...\\
& + (0+0+0+0+\cdots +a_n) b_n\\
& = \sum_{m=1}^n(A_n-A_{m-1})b_m
\end{align}
@LeakyNun so by that logic , i should just show the homomorphism , 1-1 and onto on the generator elements?
14:53
@KasmirKhaan yes
neet :d
but how to argue formally that all the groups structures are "inside" the generators?
Do you mean "neat"? :P
yes ><
I learned that word by hearing it
NEET actually is web slang, amusingly enough
Not sure if we have many neets here
14:55
@KasmirKhaan no idea
okay I guess its time to keep reading the book
I wish I could find some good lectures on this
anyone know good lectures on abstract algebra?
on youtube or something?
15:15
If $x+y=2$, then how do I find the minimum value of $x^2+y^2$?
Is it even possible to find it? I don't think so...
@Abcd I have never seen anyone giving up in a shorter time
@LeakyNun Hey! I tried it for 10 minutes already. Using AM, GM. Possible inequalities but in vain
what are your tools?
what topic is it under?
@LeakyNun Part of a physics problem's solution. :p
@Abcd any further constraint on $x$ and $y$?
15:19
Have you tried using that $x + y = 2$ ...?
have you tried interpreting the problem geometrically?
(it becomes trivial)
Hint: $y=2-x$.
@AkivaWeinberger I thought $x+y-2=0$ is also one of the standard forms
Er, sure, I guess, that's also a true equation
I was thinking of writing $x^2+y^2$ as an equation in terms of $x$, using substitution
also follows from (x-y)^2 >=0 and (x+y)^2=4
15:25
I mean, I can recognize $x+y=2$ by itself.
oh, @AkivaWeinberger you weren't following my approach
I really like my approach :P
I think at Abcd's level, the standard approach is reducing to a single variable and differentiating :P
All of the approaches we've all said are more or less equivalent
@SteamyRoot I doubt there's calculus.
I mean, technically you're intersecting a paraboloid with a plane to get a parabola, but, yeah
AM-GM theoretically works as well
@SteamyRoot nah, you don't need differentiation to find the minimum value of a quadratic polynomial
you only need to express it in the vertex form
15:27
You don't need it, no
I mean I dunno, the thing that you feel should be the answer turns out to be correct, so
But it's the standard approach for any "minimise this stuff" question
use lagrange maximization and nuke the whole thing off the galaxy
@BalarkaSen right
Incidentally, given that this is a quadratic in $x$ and symmetric about $x=1$, you don't even have to calculate anything, you just know it's either the endpoints or the middle
('Cause there can be only one extremum)
15:28
we have already like tons of approaches
and here goes Abcd "I don't think it's possible"
@LeakyNun "except mine is the best"
@BalarkaSen come on, isn't mine beautiful?
I definitely don't think my solution is the best or most beautiful :P
@Steamy Is that your bragging line? Being a normie?
Haha, no.
It's just that I've been TA'ing a crapload of first year bachelor courses
So for easy question I default to whatever solution requires the least tools and/or insight
However sad that may be
15:31
@LeakyNun No
@LeakyNun -_-. I said that after tryinggg.
@Abcd read the conversation ensuing
try out every approach suggested
(except Balarka's)
@SteamyRoot who?
Balarka's approach
I have been working on a problem for a year and a half now
You can't give up after 10 minutes
15:36
If we want to continue with the theme of ridiculous ways to solve this problem
Here's another one
@AkivaWeinberger Are you sure?
@Abcd Like 80%
Haha Balarka got banned
I wonder who reported him
Another way is to say $(x-1)^2+(y-1)^2=x^2+y^2-2(x+y)+2$${}=x^2+y^2-2(2)+2=x^2+y^2-2$
Wait seriously?
15:37
It's you for sure
so $x^2+y^2=(x-1)^2+(y-1)^2+2$
In that case, RIP Balarka
@MikeMiller It's Not Nice to discuss suspensions (however short they may be).
2
so if we want to minimize it we need both those squares to be as small as possible (i.e. zero)
@MikeMiller me?
15:38
@El'endiaStarman Sorry, who is this not nice to?
How the hell is whatever he said even offensive, anyway?
I'm asking him what it was lol
Some joke about normies or so
Maybe people don't like the F-bomb. Curiously enough, though, search it in this chat and you'll find a lot of use
15:40
What is the the function $f: R \times M \to M$ that accompanies a module usually called? Would it just be a ring action?
[Waiting's harmonic reciprocal series]
wp @Leaky
@MikeMiller The user that was suspended. They can't say anything about it while they're suspended.
Reduction formula:
\begin{align}
\sum_{n=1}^m\left(\frac{H_n}{n}\right)^r = \sum_{n=1}^m\frac{H_n^{r-1}}{n}\sum_{s=1}^n\frac{1}{s} = \sum_{n=1}^m\left(\sum_{s=1}^m\frac{H_s^{r-1}}{s}-\sum_{s=1}^{n-1}\frac{H_s^{r-1}}{s}\right)\frac{1}{n}
\end{align}
Pffffft
15:41
@Semiclassical I was suspended
Totalitarian chatroom incoming
where the individual sums can be computed in terms of harmonic numbers (to be done later)
@MikeMiller :)
@LeakyNun Please suggest a method.
@El'endiaStarman Nah, they can say plenty. I'm having a lovely discussion with him on gChat about normies. I also posted the "offending" message up there. That way we all know the context!
15:42
just a second ago
@Abcd We gave like 10 brah
@Abcd mine :P
@MikeMiller I am confused because of so many messages.
well, the substitution is probably the most straightforward
@LeakyNun Permalink please
@LeakyNun Permalink please
15:43
@MikeMiller I was suspending for saying a variation of "oh my god"
@MikeMiller Wait what's gChat?
@Abcd you just need to substitute the first one into the second
but with just the letters
google
and not actually written out.
15:43
oh
he's the only reason i have one of those
everyone else in the world just uses facebook
@LeakyNun ? What do you mean?
I didn't know it still existed
Also, the fact that Ted gets extremely annoyed of my (accidental??) flooding of the chat room means posting frequency will decrease in maths chat and then increase again in h bar
@Abcd $x+y=2$, express $y$ in terms of $x$, substitute to $x^2+y^2$, find minimum.
15:44
Ok
@Secret It doesn't feel very accidental tbh
Have you ever, like, considered keeping a blog?
Nobody wishes to discuss my suspension sniff
That would probably also get rid of your problem of finding your old messages
@Secret you might want to just open a room
@Dodsy Tell me about it
15:45
@MikeMiller he wrote "omfg" and got suspended
@MikeMiller Not in this chat. The Not-Nice part is a group of people talking about person A in a public space where A cannot say anything. They can't defend themselves, make an appeal, etc.
without the quotes
Oh my god, you were suspended for something non-vulgar? :o
yes.
yes
@El'endiaStarman Great! Unban Balarka so he can. :)
2
15:45
[redacted]

Steamy: I have started the blog, but things are still slow...
@El'endiaStarman please unban him
saying "omfg" gets you banned?
I was also banned today for no reason
Find a single person who could possibly have found that message hurtful, lol
@MikeMiller The system will unban him soon enough.
15:46
that's right
well it's not fair
my suspension was also not fair.
My temporary blog before moving to wordpress
http://secretlabsultraviolet.blogspot.com.au/
Well, it seems mean not to let him defend himself.
If the "system" bans people for those messages, I'm losing faith in the system.
NB No maths yet
Well somebody reported my message.
15:46
Is the minimum 0 @LeakyNun?
We're not allowed to talk about bans, but neither are the banned! It makes good sense.
@Abcd why?
interesting development
Ooh, which one?
@MikeMiller Yeah, exactly. That's why suspensions should not be discussed while they're in effect.
15:47
my lin alg class was terrible
I can't see on mobile.
@El'endiaStarman okay but bans should be discussed.
@El'endiaStarman Hahaha. Do you not understand how nonsensical that is?
@LeakyNun Minimum of "$(2-y)^2+y^2$" can be minimum 4 as y can be minimum zero.
What's the point of continuing to come to a place where I can't even say "omfg" without being banned, and mods join the chat and just let me be banned.
15:48
So if a ban was nonsensical, you have to just sit it out anyway?
That's not fair.
I'm pretty sure, in any case, there was a long series of mods coming in here for a while telling people to stop reporting.
yes there were.
Yup...
I guess now we're down to mods coming in here to have us stop talking about the reporting.
3
15:48
@LeakyNun The problem of rooms is that they are too many to keep them from frozen. Seriously, if the chat rooms don't get auto deleted or frozen when not in use, I am ok to open as many rooms as I want
If we don't talk about a problem, there's decent odds we don't have one, right?
It's that maintainence bit that annoys me about making new rooms
@Dodsy For what it's worth, I probably would have dismissed (or not taken action) on that flag if I had been around to see it.
I understand.
Hey daminark.
:D
Ooh, what about the one from 10 minutes ago? Can I get your thoughts on that in 20?
I understand that for the next 20 you did sign a sworn affidavit not to talk.
15:50
first day of class was cool, already learning about sets. Then in lin alg teacher decided to "motivate us" and ended up teaching vectors very poorly and calling magnitudes velocities and confusing people. But it was very boring and grade 9 level content.
eh this is boring now
math time zoom zoom
@Abcd How would it be zero? For what value of $y$?
@AkivaWeinberger It would be 4 for y =0
Oh I see
You can get it to be smaller
Expand out $(2-y)^2$
@AkivaWeinberger come on
let him think.
15:53
8 mins ago, by SteamyRoot
That would probably also get rid of your problem of finding your old messages
@MikeMiller what are you working on Mikey?
(To be thinking)
anyway, heading to sleep
night secret
I'm just reading this morning. I don't want to do actual research. I have to do a bunch of lame symbol manipulation
@AkivaWeinberger I got $y^2+2y+2\ge0$. But that doesn't take me to a minimum value.

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