#help-10
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'sen' D:
Oh does the sen(x) mean sine of "x", considering your indeterminate form
mhmm np
I thought the 2 ways were acceptable
I think only in some languages it is written sen
$\lim_{x \to \frac{\pi}{2}} (\sin x - \cos x)^{\tan x}$
Ansh
tg is tan?
yes
That is new to me lol
Do you want to use this question as an example?
Yes that's alright
kay-
ahahha from "tangente"
so umm, first we start with this being a (+1)^infty form
exactly
that's where I got stuck
I tried L'Hopitale
But not the best way here for sure
since we're more familiar with other indeterminate forms, preferably 0/0 or infinity/infinity forms... or 0times infinity
we want to convert this form into one of them
'kay?
k
L'hopitale applies only in 0/0 or infinity/infinity forms. Unfortunately you don't have it here yet
Oh
so, our first step is to use log properties
Some other guy here at discord told me with was applied with any indeterminations
Remember $a^b = e^{b \ln a}$?
Ansh
a should be above no?
given.. the log of "a" is defined
hmm?
so "e" and "ln" they dissapear and we would get b * a ?
yes
what does $a = \ln b$ imply?
Ansh
e^a = b?
Ansh
a
Ansh
you might have to use exponent laws here as well
once you answer this, we might very well be able to start with your actual question
Ik it's supposed to be a^b
Yep
Just not clearly getting how
okayyy
So, you have: $e^{b \ln a}$ right?
Ansh
y
Ansh
Got it!?
hmm
let me try to use the bot
Ansh
$4^{6 \times \x} = (4^{\x})^6$
pinto
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$4^{6 \times x} = (4^{x})^6$
Ansh
Right ?
yes
that's what the exponent laws say
Got it
Ansh
$= a^b$
Ansh
Got it?
yes yes
100% sure?
Now, back to the actual question
If I hadn't got it I would tell
$\lim_{x \to \frac{\pi}{2}} (\sin x - \cos x)^{\tan x}$
Ansh
Right?
yes
We use the same trick to send the stuff inside the parenthesis to the exponent
okay?
hmmm
then you say if I got it right
okie
Just with this tip
okkkkk
tough
Cause it's so different
nope
@raven spire
Couldn't do it
oop
So we do the same trick and get
$\lim_{x \to \frac{\pi}{2}} (\sin x - \cos x)^{\tan x}$
Ansh
that's the same we had
$=\lim_{x \to \frac{\pi}{2}} e^{\tan x \ln (\sin x - \cos x)}$
Ansh
Makes sense?
yes
Ansh
Next, my question is: which indeterminate form do you want this to become... that will make it most comfy for you
That's a tricky question
π
Ansh
the ln part is 0 already, what would you do to make the exponent 0/0 form
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\ln(1 - \cot x) - \ln(\sin x)}{\cot x}}$
Ansh
make any sense?
Ansh
Yes???
Because cot I never used it before I'm being honest with you
But I guess it should be in my seventy
okay never mind cot..
Tell me one thing
Have you dealt with substitution method during solving limits?
Yep
yes
Ansh
Then, $y \to 0$ right?
Ansh
yes
great
now, we substitute y = x - Ο/2 in the expression
$=\lim_{x \to \frac{\pi}{2}} e^{\tan x \ln (\sin x - \cos x)}$
Ansh
but we don't have any x - pi/2 in the expression
yes
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \ln (\sin x - \cos x)}$
Ansh
Now, it's 0/0 form because $\cos x \to 0$ and $\ln(\sin x - \cos x) \to 0$
Ansh
I have one question
mhmm?
sinx is the one multiplying ln(sinx-cosx) right?
Yep
cosx is muliplying 1
yep
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$
Ansh
No.. wait... what?
0 * 0
how is sin x / cos x = 0 here?
"x" isn't going to 0
It's going to Ο/2
cos x -> 0
the denominator goes to zero
and the ln term in the numerator goes to zero
cos(pi/2) is zero right?
yeah (γο½₯_ο½₯)γβ³ββ³
so sin x * ln(sinx-cosx) / 0 * 1
yep
wait
._. You ended that so vaguely I'm confused as heck
lemme write it up for you β
Lim is not really my strong, sorry if it gets annoying to you or so
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\fbox{\cos x}} \frac{\fbox{\ln (\sin x - \cos x)}}{1}}$
hmm lemme see how I can fix it (γο½₯_ο½₯)γβ³ββ³
Ansh
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@exotic oak Has your question been resolved?
help @raven spire
hehe
got hopefull that I was going the right way but solution is different
Isn't it 1/e?
Well, looks like someone forgot how to differentiate as well π
no
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$
Ansh
You had this?
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x = 1}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$
then
Ansh
You put sin x limiting value 1?
d/dx of sinx / cosx
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\fbox{\cos x}} \frac{\fbox{\ln (\sin x - \cos x)}}{1}}$
Ansh
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I told you only the boxed parts of the exponent are responsible for the indeterminate form
If you were gonna apply L'hopital, your numerator function should've been the log function
and the denominator must've been the cosine function
the sine x limiting value is 1 so forget it
not sure how you got an x in there
$=\lim_{x \to \frac{\pi}{2}} e^{\frac{\sin x}{\cos x} \frac{\ln (\sin x - \cos x)}{1}}$
Ansh
d/dx of ln
$=\lim_{x \to \frac{\pi}{2}} e^{ \frac{\ln (\sin x - \cos x)}{\cos x}}$
Ansh
yes
$=\lim_{x \to \frac{\pi}{2}} e^{ \frac{\frac{\sin x + \cos x}{\sin x - \cos x}}{- \sin x}}$
Ansh
why sinx + cosx / sinx - cosx?
:p
Have fun!
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on the topic of limits
can you apply l'hospitals rule to only the numerator/denominator repeatedly until you get to an answer for the numerator/denominator only
you can apply the rule repeatedly
so long as the conditions hold
so if you
turn the denominator
into a fraction of itself
and that is 0/0 or inf/inf
you can use it
ah
yea
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how do i check how many roots a quartic function has?
what is the method to do so
use formula
thats the quadratic formula
thats what u asked
how is that going to help
I said how do I check how many roots a quartic has
e.g. there is the discriminant for quadratics
what is there for quartics
nvm then
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Hi
<@&268886789983436800>
I donβt get how to do the puzzle
i think youre supposed to write the answer of each equation in the puzzle then i think you will see a pattern that will allow you to find the code
what are your answers
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Part E, I am missing something.
how did you get this answer?
should be a natural number
My first answer 4023 was from pluggin in 8 to the original equation. This current one was just me trying a difference/summation of the s(8) and s(11/4^1/3)
current answer has no real thought behind it. just plugging numbers in.
I wasnt sure if I had to only use numbers between (11/4^1/3, 8]
have you tried s(8) - 2 * s((11/4)^(1/3)) ?
Why * 2?
But no, havent tried. just s(8) - s(the other)
i dont think that worked, unless I typed it wrong.
calculated
Let $s(t_1, t_2)$ be the path travelled between $t1$ and $t2$, $T = \sqrt[3]{\frac{11}{4}}$
Then $s(t_1, t_2) = s(t_2) - s(t_1)$
Since the particle is moving in one direction for $t \in [0, T]$ and in the opposite for $t \in [T, 8]$, our answer should be:
[ \abs{s(T, 8) - s(0, T)} = \qty(s(8) - s(T)) - \qty(s(T) - s(0)) = s(8) - 2s(T) ]
rept1d
Thank you! That makes sense, but where does the value of s(0) go in the final equality?
yeah, that makes sense!
The prior one still applies
and ill try that
Thank you! The opposite movement part really helped me conceptualize, and that answer worked!
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Asking this question again: Show that any distribution function F can be written as $F = aF_c+(1-a)F_d,$ where $F_c$ and $F_d$ are continuous and purely discontinuous distribution functions respectively, and $0\leq a \leq 1$
MeowingLoudly
A function F is purely discontinuous if it equals the sum of its jumps, i.e. if F(x) = $\Sigma_{y\leqx} (F(y)-f(y^-))$ for all x
MeowingLoudly
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that's the definition given for this
This is the definition of convexity
Idk if that helps

maybe
any way to prove this using just tools from probability?
like baby tools
I'm not sure
I believe convexity would indicate that the entire line segment between any two outputs of Fc and Fd would be contained in the overall distribution space
@meager belfry Has your question been resolved?
So you can most likely prove this by showing that lim x-> infinity of aFc-(1-a)Fd = 1 and likewise for x-> 0 the expression is 0
Then you could show theyre increasing, bounded between 0 and 1 etc
Skid
Like this
You should be able to do this for all conditions of a distribution
As the set is said to be convex by that definition
If you prove the necessary conditions for any arbitrary combination of distributions it means there would have to exist some combination to be that of the distribution F
@meager belfry
@meager belfry Has your question been resolved?
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Currently working on situation 1
These are my equations Standard form:
Equation 1: -(2x) + y - 2z = 5
Equation 2: x + 3y - z = 9
Equation 3: 4x + 4y β 4z = 36
Bit stuck on how to then get my x y and z
@sage charm Has your question been resolved?
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Is it possible to figure out if 3^9 is greater than or less than 4^7 without using a calculator?
it's useful to have $\log_{10} 2 = 0.3010$, $\log_{10} 3 = 0.4771$ memorized
xdk1235
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How does Wolframalpha go from the summation to the alternate forms?
@dark charm Has your question been resolved?
not really, my hint is to ||try writing out the terms (also ignore the 1-p factor since you can just take it out of the sum)||
Yeah but I don't understand writing out the terms
like list them out
starting at i=0
then list the term for i=1
...
try to find things that cancel out or smth
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Hi
Can someone help with indices
Real quick
True?
Or
Help urgent
Whatβs the rule behind it
You have 2 different things on the papers
I am super confused
anyways this is elementary exponent rules
look them up
Ok
Are the all valid?
just confirming
Is this true?
Yes/No
Please π
Hello?
I want to make g have no indices
you'll want to square both sides
no
oh yes
$$\left(g ^\frac{1}{2}\right)^\frac{-1}{2}=g^\frac{-1}{4}$$
Shuri2060
You apply the same exponents to both sides
so one of your first ones just doesnt work out cus of this
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is the inverse of y=f(x) x=f(y)
no
y = f(x) makes no sense, they serve similar purpose
f(x) means function
@ruby oyster its x=g(y)
yes thats why i deleted it cause ik that
Ah ok
the inverse of f if f^(-1)
where f(x) = y and (f^(-1))(y) = x
and f^(-1) is just a notation for another function (like g(y))
ahh yes
why do we change all x to make y
like the inverse of y= 3/(x-1)
is x= (3+y)/y
but you chnage the y to x
but since you usually use x as an argument and y as a function's value
and say it is f-1
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How valid is this proof? "Suppose there exists $N_0$ such that $s_n \le t_n \forall n > N_0$. Prove that if lim$t_n$ and lim$s_n$ exists, then lim$s_n$ $\le$ lim$t_n$."
Proof:
\\
Let lim$t_n$ = t and lim$s_n$ = s. Let $\epsilon > 0$, and observe that $|t_n - t| < \epsilon$ $\forall n > N_0$, $|s_n - s| < \epsilon$ $\forall n > N_0$
\\
$s_n \le t_n$ $\Rightarrow$ $s_n - s - t \le t_n - t - s$
\\
Thus: $|s_n - s| - t \le |t_n - t| - s$ $\Rightarrow$ $\epsilon - t \le \epsilon -s$ $\Rightarrow$ $-t \le -s$
\\
$\therefore s \le t$
dulg
i will keep that in mind, thanks
you basically add - s -t to both sides
How does this follow from the above?
If s is greater than s_n or t greater than t_n
then ?
===
Something helpful for this proof might be to draw a rough diagram
And to mark epsilon
@frigid oracle Has your question been resolved?
Good point. I kind of assume it since the textbook already went through it. Because of how absolute value is defined, where $|a| = a$ if a > 0, and $|a| = -a$ if a < 0, it follows that $-|a| \le a \le |a|$, since either $a = |a|$ or $a = -|a|$.
Thus: $-|s_n - s| \le s_n - s \le |s_n - s|$ $\Rightarrow$ $-|s_n - s| -t \le s_n - s - t \le |s_n - s| - t$
\\
Repeating the same process: $-|t_n - t| \le t_n - t \le |t_n - t|$
dulg
.
@balmy mortar ok wait
i am a bit stumped
realized something is a bit off halfway thru my last latex post
wait for me while i post this idea on how to prove $|s_n - s| - t \le |t_n - t| -s$
dulg
Consider case 1, where $s_n - s -t = |s_n - s| - t$. $s_n \le t_n$ implies $|s_n - s| - t \le t_n - t - s \le |t_n - t| -s$.
\\
Case 2, where I got stuck because I am not sure :(. Following the same process leads us to $s_n - s - t = -|s_n - s| - t \le t_n - t - s \le |t_n - t| - s$
dulg
The ambiguity comes from where $|s_n - s| - t$ would fit in Case 2
dulg
I would say to restart your proof
Because there really is no need to split cases
What you need to do
is draw a rough diagram
and indicate what you want to show with epsilon pictorially
what would that look like?
I have never imagined real analysis using pictures
hmmm
the entire proof? or this absolute value thing?
Maybe all, cus there wasn't that much progress
I'm just saying restart in terms of ideas
Stuff will be reused
In particular, like you said
We will take this
Using this, we need to prove s <= t
idk if the picture will help you see what you need to do with these 2 inequalities
not sure about the picture
i suppose they are converging to a set number, and one is def greater than the other
Try to draw your own
and mark an epsilon, basically
@frigid oracle ah actually, I see an error in your inital proof
$$(\forall n > N_0)(\abs{s_n - s} < \varepsilon)$$
$$(\forall n > N_0)(\abs{t_n - t} < \varepsilon)$$
Shuri2060
You make these claims.
They are not necessarily true --- think carefully why.
This does not follow from the defn of limit.
what is the difference between this and the defn of a limit?
where N is used, instead of N_0
recall the defn of limit
Limit of sequence
$$(\forall\varepsilon\in\bR^+)(\exists N\in\bN){a_n:n\geq N}\subseteq(L-\varepsilon, L+\varepsilon)$$
Shuri2060
Or
ah, N is a set of numbers in \bN, and N_0 is a one particular number?
$$(\forall\varepsilon\in\bR^+)(\exists N\in\bN)(\forall n\in\bN) (n \ge N\implies \abs{L - a_n} < \varepsilon)$$
Shuri2060
No, you misunderstand
You have probably seen this definition, correct
yep
Personally, I think this one is easier to visualize
The (L - e, L + e) represents an interval
In either case, you should realise the N_0 in the original question does not correspond to N
how come?
Let me write.
$$(\forall\varepsilon\in\bR^+)(\exists N_1\in\bN)(\forall n\in\bN) (n \ge N_1\implies \abs{s - s_n} < \varepsilon)$$
$$(\forall\varepsilon\in\bR^+)(\exists N_2\in\bN)(\forall n\in\bN) (n \ge N_2\implies \abs{t - t_n} < \varepsilon)$$
You should realise that the N's for different sequences are not necessarily the same
And moreover, then N0 in the original question has nothing to do with them
In fact --- the epsilons don't have to be the same either
But in this particular case, you can choose them to be the same if u like
I see
Shuri2060
π
(N1 and N2 depend on epsilon)
So you the answer says you should take max(N0, N1, N2)
yes?
Then you can compare the inequalities
π€
Your textbook doesn't even use epsilon-N to show
and uses some result instead
I mean it's honestly not hard to use epsilon-N
Yeah, but atleast he proves the results in a more pedagogical way
$$(\forall n\geq N_0) s_n \leq t_n$$
$$(\forall\varepsilon\in\bR^+)(\exists N_1\in\bN)(\forall n\ge N_1)(\abs{s - s_n} < \varepsilon)$$
$$(\forall\varepsilon\in\bR^+)(\exists N_2\in\bN)(\forall n\ge N_2) (\abs{t - t_n} < \varepsilon)$$
Shuri2060
You have these 3 things
You can combine them into one statement by setting a new N = max(N0, N1, N2)
$$(\forall\varepsilon\in\bR^+)(\exists N\in\bN)(\forall n\ge\bN)$$
$$(\abs{s - s_n} < \varepsilon \land \abs{t - t_n} < \varepsilon \land s_n \leq t_n)$$
Shuri2060
what does the wedge mean?
$$\abs{s - s_n} < \varepsilon$$
$$\abs{t - t_n} < \varepsilon$$
$$s_n \leq t_n$$
logical and
Shuri2060
Shuri2060
Shuri2060
$$(t_n - t) - (s_n - s) \leq \abs {(t_n - t) - (s_n - s)}$$
Shuri2060
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How do you solve this question?
Trigonometric stuff aren't really my thing
which side will the largest angle be opposite
I don't understand?
So you're saying the opposite will be the largest angle?
never mind this question
do you mind explaining what SOHCAHTOA this is?
is it sin or csc? <@&286206848099549185>
if i'm wrong please correct me.
first, draw the figure
^^^^
great
Complementary angles
Or that
alternate interior angles*
tan
oh
there's nothing to do with hypotenuse here
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What "otherwise" approach could be taken to express the quartic as a product of quadratic factors
KurtDee
But it's going to be uhhh pretty hard
yh
Sheesh thats a nightmare
So I mean like
if you know you have whole numbers
that makes it a lot easier
for example, a,d is pretty simple
and c,f would also be trivial
I'm not sure how unique this equation is
I dont think it is
I would start with those two assumptions
a,d is a pretty easy one to address
you can just factor by a,d
so you would get
$ad(x^2+\frac ba x+\frac ca )(x^2+\frac ed x+\frac fd)$
KurtDee
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I need some help whit this
@harsh phoenix Has your question been resolved?
You'll more likely get help if you translate it to English
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help pls
A product is 0 whenever one of its term is 0, which is the case here
Can you see why?
I gave you a hint that one of the terms in this product is 0
(Try expressing nth term using n and then looking for its zeros)
what is nth term
For example here the first term would be considered to be (1 - 9/2)
The 2nd term then is (1 - 9/3)
And so on
Clearly the nth term in this case is (1 - 9/n)
ok
Now, what happens when n = 9?
geometric series problem?
0*anything = 0
fun
This doesn't seem to be a geometric series tho
thx
Np
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Hello
Here, I do not understand third step:
You use the result from (1) and put it into (2)
@timid silo
Okay. Thank you π
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I'm trying to work on 8
Have you tried defining a homomorphim from <a> x <b> to G using the obvious generators of the former ans showing that it is bijective?
How do you define isomorphic then?
A slight idea about it but I'm not too sure
I usually find it helpful to use small examples
Say C_3 and C_5
Then what does the direct product look like
Just to get you thinking in the right direction of what the question is asking
I think the hard bit is seeing what the group <a> x <b> looks like if you're unfamiliar with direct products
@wraith gazelle Sorry that was a bit badly written by me π
yh well...
Basically yes
My example is
m = 15
a has order 3
b has order 5
so <a> is the same as C_3
<b> is the same as C_5
if that makes sense? same structure/isomorphic
I'm a bit confused about cyclic groups
I have a slight idea but not well explained
Shuri2060
This is what C_3 looks like
in general
The structure will always be the same
$C_n = {e, a, a^2, \cdots, a^{n-1}}$
Shuri2060
You get this part?
a is just any 'object', it doesn't really matter...
The group operation tells you how to handle multiplication between elements (making it work like 'normal multiplication')
Oh I see
What's different is a group might not be abelian
But all cyclic groups are abelian
Since you've just got powers of the same element
So <a> represents the cyclic group generated by a
if a has order m (from the question) and b has order n
$$\langle a\rangle={e, a, a^2, \cdots, a^{m-1}}$$
$$\langle b\rangle={e, b, b^2, \cdots, b^{n-1}}$$
If a has an order m, does it also mean a^m=e?
right.
You can see that must be the case in these 2 groups.
Note the group operation is 'borrowed' from G
If we're going by the question
We have the same operation, but just different domain
I see
Shuri2060
looks better
Alright, so now you want to think what the direct product of those 2 look like
You are familiar with the definition of direct product?
Not really
Shuri2060
Shuri2060
But in this case, we're doing this with order m and n?
yh... but first of all you need to be familiar with how the group operation works
it turns out exactly how you expect in some ways
$(a, b)(c, d) = (ac, bd)$
Shuri2060
Note there are 3 different group operations going on here (but all 3 are referred to as 'multiplication)
$(a, b)\left(_{A\cross B}\right)(c, d) = (a\left({A}\right)c, b\left(*{B}\right)d)$
hmm that's ugly π
If that makes sense?
These are 3 different binary operations in general.
I'm a bit confused, which are from which?
I am using usual function notation to show
Or I could use different symbols if that makes it clearer
Yeah
$_1:A\to A$ \
$_2:B\to B$ \
$*_3:A\times B\to A \times B$
Just treat them as any symbols
Shuri2060
$(a, b)_3(c, d) = (a_1c, b*_2d)$
Shuri2060
This is an important thing to note
So $a *_1 c$ makes sense because a and c come from A
Shuri2060
And these are the operations of the three groups?
Yes
Because of how we defined A x B
a, c come from A
b, d come from B
And by closure, ac is in A
bd is in B
so (ac, bd) is still in A x B
So I'm going to use a small example
$$C_2\times C_3 = {(a, b):a\in C_2, b\in C_3}$$
Shuri2060
$${(e, e), (a, e), (e, b), (a, b), (e, b^2), (a, b^2)}$$
Shuri2060
Can you see how this is the entire group?
How come there's no a^2?
Ah yes
So let's stick with this example
So in the original question let's say m = 6
So I now have <a> x < b>
a = 2, b = 3
and they are relatively prime.
You now need to show this group must be isomorphic to the original group
I'm still confused how you get the whole thing
Well I understand {e,a} in C2 and {e,a,b} in C3?
$$C_2 = {e, a}$$
$$C_3 = {e, b, b^2}$$
Or is it e b, and b2
Shuri2060
Oh
C_n is the cyclic group of order n
There is only 1 generator
for cyclic groups
You are familiar with that right?
A finite group of size n is cyclic if one element has order n. If that is true, then all the elements must be some power of that element
Then everything must be generated by it.
Oh okay
Mhm
Written in this way? Or?
(a+a,b+b)?
That all depends on the group operation
but we usually prefer to write like multiplication
$(a, b)^2 = (a, b)(a, b) = (a^2, b^2)$
So like this.
Shuri2060
For the general case it will be written like this (the multiplication sign is omitted, but they are different)
Oh okay
(e,b^2)
Mhn
For clarity, sometimes it might be written like this
$${(e_A, e_B), (a, e_B), (e_A, b), (a, b), (e_A, b^2), (a, b^2)}$$
Shuri2060
Because e_A and e_B are not necessarily the same
They are just the identity elements from A and B
This is used when it is clear from context or doesn't matter.
So which of these is the identity element of A x B ?
(e,e)?
I do now
So the question...
You need to show this thing is isomorphic to G
Do you remember how an isomorphism works, roughly?
Just the main concept
Show it's bijective and morphic
yah but the main concept is
If we have 2 groups
X and Y
and they are isomorphic
I can 'relabel' the things in X with some things in Y
And the group will still behave exactly the same
Just different labels (and group operation)
f(xy)=f(x)f(y)
Yes, that is homomorphism. And then you also need bijection
So this isn't an easy question, there are several steps to it
You could focus on group G first.
It tells you $\gcd(m, n) = 1$
Shuri2060
a has order m
b has order n
Hmm
Thinking π
Do you have any idea what this could tell you about G?
I'm no sure
Shuri2060
If this helps, these are the problems that the question hints about
Shuri2060

