#help-49
1 messages · Page 269 of 1
is it
yay congratz
how would you apply the limits here
would i put it where it says 2a+1
u apply the limits only for the variable u integrated with which is x
a remains, because it's a constant
e^(2a+1) is a constant
and then u apply the power rule as usual
what is your question
is the 6k^2 meant to ne 12k^2
why do you have 6
idk
oh i see
yeah 6 remains
would you just expand and then square
you get only 6 because the 2 cancels
yea
and then
idk what then
ok yea
they've just written the decimal as 9/2
they are making use of symmetry
of the graph?
yes but that seems the wrong way
y is odd not even
so the integral just vanishes
someone thought the function was even and so they can integrate over half the interval but double the area, i guess?
by definition
you show this property holds then it's odd
yh i know this
yea and this is also not only necessary to know but also sufficient
ididnt know the graph would be symmetric tho
so
sometimes when the bounds are equidistant then it's worth to see first if the function is odd/even
is f is odd then the graph is symmetric?
about the origin
so if f(x) is odd then its symmetric about the origin?
Mr. Zzzzz
yes
alr ty
if u r done u may close this channel
hello
im not
o oki
i'll open another one tho
sure
.close
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sure
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how would you factorise this
i cant help with the integrating part but fpr the factoring part
try to factor between x^3 - 2x^2 and -x+2
you should end up with the same brackets.
you can factor out the x^2 from the x^3 -3x^2.
alternatively, you can use something like the rational roots theorem
how did you get -2x^2
it's in the cubic
Cheze is suggesting you group the cubic like (x^3 - 2x^2) - (x - 2) and factor each term separately
the cubic is x^3 - 2x -x + 2
you're missing the square on the 2x
it says 2x^2 on it
this
have you by chance read it wrong and it being the only reason yuo cant factor it?
i meant this
it is still 2x^2
ye
first two and the last two
take out the HCF between them
for eg. x^2 + 2x + x + 20
-> x(x+2) + 1 (x+20)
yeah
and hen?
now do the same thing to the last two numbers
-x + 2
wdym
what is the HCF of x and 2?
i should say -x and +2 for that matter but ye
what am i factorising
factor out something common from -x abd +2
the last term is only -x+2
yes it can still be factored
oh so 1(-x+2)
yeah but
since the x is negative
you can factor out a -1
instead of a 1
so what does the bracket inside become if i take out a -1 instead of a 1?
-1(x-2)
yh
now if i treat x^2(x-2) and -1(x-2)
as numbers in themselves
you see how they have a common HCF of (x-2)?
yh
so i can just
(x-2)(x^2 - 1)
because i took out common from x^2(x-2) and -1(x-2)
which is (x-2)
and the thing left is (x^2 - 1)
which is the last bracket
hmm
now if you want to take it a step furthur and factorise the x^2 - 1 bracket then do it but i dont know if it will help in integration because i havent even learnt basic trig yet
😭
im not doing calculus.
yeah. If it helps that is.
integrating part
?
welp anyways. im going now. Hope my part helped with ur factoring
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how hard is intro analysis 2 compared to intro analysis 1
hard to say. do you have a description of each?
yea but they are oudated
cuz
the analysis 1 description says we cover integration
but we ended with rudin chapter 5
differentiation
its prob a few more chapters of rudin
the general metric space stuff was genuinely cooking me a little bit
is that left behind
no two courses are the same
So do you have a list of the topics covered? That would help
e.g. analysis 1: sequences, series, continuity
analysis 2: lebesgue spaces, locally convex spaces
maybe i should js email the prof
yeah lemme see but its oudated
Convergence of sequences and series of functions, differentiation and integration in higher dimensional settings. Inverse and implicit function theorems.
how about from your own recollection of what they said or what problems you had to do
this is analysis 1?
no one told me anything and my prof didnt know
but you know which problems you had to complete and hand in, right? So you could reconstruct a list of topics from that
from analysis 1 yes
then intro analysis 2, from your description, seems more annoying than intro analysis 1 if you aren’t using the Lebesgue integral
basically we just did metric spaces and compactness, sequences (convergence, cauchy, upper/lower limits,), limits, continuity (just from R into R really with mostly the standard metric, differentiation (mvt, lopital, taylor polynomials)
no series tho
so yeah it sounds like it still
so you haven’t done the Lebesgue integral
I don’t understand why people teach the higher dimensional Riemann integral
and they have to introduce “content zero”, whatever that is
i dont have to take analysis 2 i was just deciding between a few options
is it not good
It seems like you could just teach higher dimensional integration after the Lebesgue integral, but take my opinion with a grain of salt because I haven’t learned the higher dimensional Riemann integral
the Lebesgue integral is general enough to cover higher dimensions after you define product measure spaces, which you should do anyway
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one more thing. if i wanted to learn some of this on my own what book could be good
?
to me, the “integration in higher dimensional settings” seems like the annoying and unnecessary part of the course if you’re doing that rigorousl
everything else is important
hmm
I’m also going to try to learn these topics, and so far it seems like for differentiation in higher dimensions and the inverse and implicit function theorems, Folland’s Advanced Calculus and Boothby’s book Intro to manifolds (or something) could be good
ok ill check those out when im done covering the parts we skipped, thanks again
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You should ask in #book-recommendations , and ping me if you do, because I also want to know good books for these
In case the two books I mentioned aren’t the best
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Hi
I’m trying to find out how to find the range for this matrix A that defines a linear transformation
The book didn’t even explain how to find the range except show one example where they took the RREF of the matrix and used its row vectors as a basis for the range
Which also i didn’t understand
But it makes more sense to be the column space
Not row space
Oops
Never mind the book took the column space
Not row space
Dude 😂
My bad
But do we need to do RREF??
Is it because RREF ⇒ independent vectors and we need independent vectors because basis ⇒ independent vectors ?
^^
it's a computationally efficient way of just checking if a vector is LI from a set of others
it might be the most computationally efficient, even
@last slate Has your question been resolved?
it’s not really that
it’s just that RREF only requires calculators and not a brain, so it can be useful to reduce all problems to taking RREF using the right theorems
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not sure how to manipulate the end
this is a geometric progression in all but name
anyway, you may have better luck showing that
(1-r)(1+r+r^2+...+r^n) = 1 - r^(n+1)
,,\begin{align*} a + ar+ar^2 + \cdots + ar^k + ar^{k+1} &= \frac{a(r^{k+1}-1)}{r-1} +ar^{k+1} \ &= \frac{a(r^{k+1}-1)}{r-1} +\frac{(r-1)(ar^{k+1})}{(r-1)} \ &= \frac{ar^{k+1} -a +(r-1)(ar^{k+1})}{(r-1)} \&= \frac{a(r^{k+1} -1 +1)(r-1)(r^{k+1})}{r-1}\end{align*}
did i factorise wrong
yeah you messed up the numerator p bad.
what is it with my factorising today 
factor out just a for a start
Is this right?
well it's correct but you haven't done what i said to do yet
just a?
calvin
is this right?
no you are still messing up bad and probably overthinking it
$a(r^{k+1}-1)+ar^{k+1}(r-1) \ = a[r^{k+1}-1+r^{k+1}(r-1)]$
Ann
this is what i wanted you to do on the numerator
this and naught more
$a(r^{k+1}-1)+ar^{k+1}(r-1) \ = a[r^{k+1}-1+r^{k+1}(r-1)] \ = a[r^{k+1}-1+r^{k+2}-r^{k+1}]$
oh what
Ann
im stupid
there's not much of a way around it unless you're willing to cause a wind storm with your hand waving
was responding to ishmam
you got them r^(k+1) terms about to annihilate each other
wym
i cancelled them
im left with
,,\frac{a(r^{k+2}-1)}{r-1}
is this normal undergrad stuff
calvin
because i was just reading a number theory book
And proofs came up
what do i do from here
Is this proof sound?
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Elo
yes
Is this just a fancy wording for the gram Schmidt process ?
Interesting name
never heard of that before, can you briefly explain the context?
The gram Schmidt process is basically taking a basis and make it orthonormal through a process of using projection vectors
I just googled it, looks like you can apply that in this question
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What is 67+69
136
.solved
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#chill if you wanna troll or smth
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Hi can I get quick help
(1, 0,-2) and (2, -1, 1) span a plane right?
Then you need to find the vector u, projected onto this plane
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How to solve this without delta method? Factor?
what is delta method
it's not possible without the quadratic formula
Look it
well, you could complete the square but that's the same method
But the assignment does
Use quadriceps formula or not
have you seen this method before?
But otherwise the other method would be factoring. @lethal path
it's not factorisable
No wasnt taught
What condition can be factor able
that the discriminant $\Delta$ is a perfect square number
south
Okay so this number isn’t in real numbers
exactly
x /€/ R
$x \notin \mathbb R$
south
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I can't wrap my head around this solution
What sum of products do they mean here and why they're corresponding to the words of length n
Ping on reply please
if we multiply out eg (a+b+c+d)(a+b+c+d) we get aa+ab+ac+ad+ba+bb+bc+bd+...
so we get all words of length 2 in the letters a,b,c,d
similarly for (a+b+c+d)^n
@late rover
Oh wait yeah, I did thought about that but somehow I got lost
Wait letmme try to digest this solution
omg I get it now, what a brilliant
hang on I still want to make sure I don't misunderstand anything
@late rover Has your question been resolved?
I can ensure that I understand it fully now as I has written it down w/o looking at the solution
Thanks y'all
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Let's be honest, the question's more scared of me then I am of it but wth. How do I...what am I even supposed to do here? It's like my brain is lagging??
(also, sry, I accidentally sent the pics in the wrong order)
(this is why I'm incompetent or smth)
I suppose the price on the graph is quoted per quintal?
Yeah
Do you need help with all the stuff
so which part(s) are you confused by?
Isn’t this categorized under economics type of help? Or still allowed? Just asking just in case i might need help in economics things
well it's kind of math-adjacent I suppose, but the mods can determine if need be
you can ask for anything actually, at least it's science related like that one time a girl ask about biology meiosis process in help channel
we get people asking about stoichometry in chem here too
okay that's over the line
nothing to do with maths
-# But she did got help lol
Amazing
i asked for ochem twice or thrice btw
physics is very rare idk why
physics ain't rare from my experience but I'm not discussing this in OP's channel
Anyways, I'm losing it cause I have an entrance in like 2 days and my god am I scared, idek what to look for in this?? How do I study for this??
this looks like you need to know how to interpret the graph, and separately find the revenue per acre of both products.
(not profit, revenue. you can find the profit afterwards)
the idea is that given the yield per acre and the price per quintal, you can know how much money you'll earn from planting an acre of each product and selling all of the yield
then, you can subtract the cost of planting those products from the revenue to get your profit, and thus your ROI
a simple example
suppose an acre of paddy has a yield of 2kg, and the selling price per kg of paddy is $20.
that means, for every acre of paddy I plant, if I sell every last grain I get, I'll have $40
now, this is only the revenue, because there are costs involved in planting the paddy as well, of course.
so say that this cost is $15 per acre of paddy.
that means that for every acre I plant, I first spend $15 to plant them, then I get $40 of revenue, so my profit is $40 - $15 = $25, and my ROI is $25/$15 = 1.67
wtf
is this about the elasticity curves demand and supply?
alright thanks
this concept translates directly into your graph
except that you have to be careful, because the selling price of both products increase over time, and therefore the profits also increase over time.
if asked to calculate a profit, ensure you are looking at the selling price of the right product and the right time.
also, the yields per acre of each plant is different, so there's that to consider.
however, you can precalculate all of this, so not too big of a deal.
Hmmm, I see
Thank you for explaining, I'll give it another try
Wait uh, also, question number 45
What
(no, that's it. That's literally my question: what)
let me have a look at that
I see, so there's now an inventory cost
well the inventory cost I presume is a simple annual rate, so at 12% per annum and a holding period of 6 months (aka half a year), the effective rate charged would be half the inventory cost
so factor in the inventory cost, which I presume is based off the total item value
@tame summit Has your question been resolved?
I'm guessing I have to subtract inventory cost from the total thing?
Or well no sorry
Subtract it from profit if I have to find a net profit
subtract it from the revenue separately, or add it to the cost to be subtracted from the revenue together
either way works and is the same
Okay, I see, thanks
nps
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why not 16? you would get T to be proportional to a^3/m
came here cause it was more of a calculus and proportionality question than physics
most of the solutions just assumed the masses to be with constant acceleration and got t^2 to be proportional to a^3/m
@slow thorn Has your question been resolved?
take hints from the standard irodov qn here (u can find its soln in hcv btw)
not the same question bro
i get what you're trying to say
but the particles are accelerating here
and the velocity depends on the side length of the triangle
i did try solving that way and got the relation that T is proportional to a^3/m
like i stated at the start
actually wait i think i made a mistake
oh godddddd
thanks for the support thoug
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am i interpreting this right
@rocky quest Has your question been resolved?
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do you mean why like "why do we do it like this"?
yes
well watch what happens to the shit inside the integral with every ibp application
the exponent on the x goes down
eventually to 0
and then it is just a raw sine or cosine term
,w integrate cosx
@leaden seal Has your question been resolved?
Integration of -sin give cos
The minus is actually with the sin not the 4x³
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anyone know why my answers are different?
what kind of website or software is that
how did you get this to the right of the calculator
oh thats just a document
i thought x=0 would just give 0
iys?
ans - (-18) instead
,w integrate dx
what are you doing
just checking smth
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G is finite. Let p be the smallest prime dividing |G|. Let H ≤ G of order p. Prove H ≤ Z(G).
!status
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
1, I can be sure this time that I truly have nothing
ok, so if p divides |G|, give me a list of things we can say
about the elements and or subgroups of G
for one I found a typo in the question I just sent, Ill change that
I know the H in the edited question exists
it would have to be the smallest nontrivial subgroup of G, maybe
its cyclic
nothing new has come up since then
ok
so you want to show elements of H are in the center of G
Do you know any characterizations of Z(G)?
well more than a definition
can we write it, for example, using a ||homomorphism||?
I couldnt find one
Ok, here's a hint
If h is such that gh = hg
Then ghg^-1 = h
Do you know a bit about group actions?
I couldnt have remembered anything about the derived group on the exam, so lets go with no
so far two of the 3 questions Ive been able to find an answer for with an existing trick Ive remembered from for example the homework
Does Fixators, orbits and/or stabilizers ring a bell?
dont know what a fixator is, the others Ive heard of them but dont know much about them
for one of the homework assignments we had to do quite a bit about the derived group, dont really know much about it though
lets go with sure
Raphaelisius Maximus MMIII
We can then look at the morphism that sends g to phi_g
And we notice that this morphism has kernel = Z(G)
Mmh let me think
if its any idea, ^p is the smallest power that turns elements into identities
but I cant ever get the elements of <q> or whatever Im calling it to stack up conveniently
heres something unrelated but interesting
5 of the questions I was able to answer during the exam involved stuff directly relating to the textbook or previous exam questions
that left 3 I couldnt answer, of those, 2 were answered using tricks that are both outside of the textbook
so if its any indication, I cant just do something textbook for this problem
to be honest all Ive been doing is raising things to ^p powers and then seeing they dont work
wait do you have sylow theorems
yeah ok
we got normal towers though
G isnt given to be solvable though
and theres no guarantee the first nontrivial group in that tower is <q>
let along whether Z(G) is in that tower at all, it could be a normal subgroup that just gets left out
ok, do you know about the normalizer
I heard of it once, does that count
elements n where nHn^-1 = H
follows that its the largest subgroup of G that H is a normal subgroup of
it might have been given during the exam that H is a normal subgroup, but I cant recall
we could just include that in the problem for convenience, but just to be sure we'll need to prove it
yeah, if H is not supposed normal, it's very hard
I'm pretty sure if it's not we can come up with counterexamples
oh wait it most likely was
oh yes that, I did find a counterexample during the exam that not all cyclic groups are normal subgroups of G
So, if we suppose that H is normal
and we'll have to, really
then let's define $\varphi_g (h) = ghg^{-1}$ for $h\in H$
Raphaelisius Maximus MMIII
$\varphi_g$ is an automorphism of $H$
Raphaelisius Maximus MMIII
(you might have seen written $\varphi_g \in Aut(H)$
Raphaelisius Maximus MMIII
I have, in a different question
ok
so that means we can consider $\varphi: \begin{cases}G\to Aut(H)\ g\mapsto \varphi_g\end{cases}$
Raphaelisius Maximus MMIII
what do you think this map is gonna be
as in?
definitely not an isomorphism
oh alr
start smaller maybe?
no, but like weaker than isomorphism
homomorphism
that I can do
the kernel is not H, though h is part of the kernel
oh wait that doesnt do much for us, nvm
I meant to say H and Z(G) are in the kernel
kernel would be the elements where gh = hg
ok, so we have that the kernel contains both H and Z(G)
we really want to find what the kernel is, but the best we can say for now is that it's the centralizer of H
$C_G(H) = {g\in G:; \forall h\in H, ,gh = hg}$
Raphaelisius Maximus MMIII
because the elements in the kernel are sent to the identity of H
is it possible that Z(G) = C_G(H)?
that would be a juicy finding, wouldn't it?
if we had that, then using that H is in the kernel
then H is in Z(G)
it would if it wasnt that ghg^-1 = h could allow for other not-h elements not to do the smae
I don't think Z(G) = C_G(H) actually
C_G(H) is probably much bigger
we'll see why in a moment (I myself can also get confused xd)
For now, we won't be able to go further talking about the kernel
so what are we gonna talk about now?
did raising things to the ^p power repeatedly ever get anywhere?
I don't think so 😭
no way
let's go back to our lead of $\varphi$
Raphaelisius Maximus MMIII
the Aut(H) version right
Idk its surjective
yes this version
maybe, maybe not...
The image of phi is, in any case, a subgroup of Aut(H)
what is Aut(H)?
set of isomorphisms from H to itself
Aut(H) is isomorphic to Z/pZ
oh right H and Aut(H) arent the same thing
well now that we know that H is isomorphic to Z/pZ
Aut(H) is isomorphic to Aut(Z/pZ)
no big surprise out of that?
thats not even a theorem we have
I don't think it even deserves a theorem
if you have a morphism H -> H
you can create a morphism Z/pZ -> Z/pZ
and vice versa
oh alr
like, if you have a morphism f: H -> H
and an isomorphism g:H -> Z/pZ
then you can create a morphism g o f o g^-1
that goes from Z/pZ to itself
and vice versa
that makes sense
so this
any more questions on that assertion?
nope
ok
now, we want the automorphisms of Z/pZ
what do we need
if stuck, hint: ||to know a morphism f: Z/pZ -> Z/pZ, how many f(k) do we need to know?||
Solution to this question if still stuck: ||f(k) = kf(1), so we only need f(1)||
oh this is no good
question 3 on the exam says it should be (Z/pZ)^x
but testing says it should be (Z/pZ) instead
having a hard time keeping track of which is what
well... Aut(Z/pZ) is isomorphic to (Z/pZ)^x
oh right
there are p morphisms, because p possible values of f(1)
then is (Z/pZ)^x isomorphic to Z/(p-1)Z?
but wait
Are you still discussing the original question
but it's irrelevant
we won't use that (Z/pZ)^x is cyclic
all we need is its order, p-1
so, by morphism theorem
|G| = |Ker(phi)| |Im(phi)|
Ive never seen that before
we did see |G| = |ker(phi)| [G : ker(phi)] before so we can go with that
ok let's use that then
[G : ker(phi)] = |Im(phi)| btw
did you never make the connection?
Im(phi) is the image of the morphism phi
|Im(phi)| is its order
the index of G with respect to ker(phi) is precisely how many different images there are
to see that, just notice that $\varphi$ defines an isomorphism between $G/Ker(\varphi)$ and $Im(\varphi)$
Raphaelisius Maximus MMIII
$\tilde \varphi (\tilde g) = \varphi(g)$
Raphaelisius Maximus MMIII
idk how you write equivalence classes
ok
or with \pi
you can define a homomorphism $\tilde \varphi$ such that $\tilde \varphi(\overline g) = \varphi(g)$
Raphaelisius Maximus MMIII
and it's an isomorphism between those
in any case, we use this result
notice that |Im(phi)| divides p-1
but it also divides |G|
do you see what's gonna happen now?
I dont know what thats good for
I forgot what ker(phi) even was equal to
is ker(phi) = C_G(H)?
yeah, it's not important how it's called
all we know it's some potentially big subgroup of G
maybe bigger than Z(G)
well if C_G(H) = G, then gh = hg and so H < Z(G)
if C_G(H) < G, then p is still the smallest prime dividing |C_G(H)| so H < some smaller subgroup
that second assertion is not true
at least I don't see how you'll prove it
Though if C_G(H) = G then yes you hit the jackpot
Are you trying to translate the idea G conjugate acts on H, each orbit has to have length 1 or p, to a more elementary language for him?
particular case, not really needed but why not check it out
p-1 is then 1
so what is |Im(phi)|
and so what is |ker(phi)|
oh p still divides |ker(pi)| then
well, sure, it comes from the fact that H is in the ker(phi)
but it doesn't have a clear impact on the divisors of |Im(phi)|
Let's try to find |Im(phi)| only using those two infos:
notice that |Im(phi)| divides p-1
but it also divides |G|
I thought p - 1 divides |Im(phi)| instead?
I don't know how you got that
💀
ok, let's take it back
First of, we had $\varphi_g (h) = ghg^{-1}$ for $h\in H$
Raphaelisius Maximus MMIII
To say that $H\subseteq Z(G)$ is the same as saying $\varphi_g = Id_H$ for all $g$
Raphaelisius Maximus MMIII
any questions from those two facts?
no
ok
consider the map $\varphi: \begin{cases}G\to Aut(H)\ g\mapsto \varphi_g\end{cases}$
It's a morphism, and we want to prove that $Ker(\varphi) = G$
(that way we get H is in the center)
Still ok?
waiting for your confirmation btw
phi(H) = identity
phi(Z(G)) = identity
phi(C_G(H)) = identity
ker(phi) = C_G(H)
phi(G) ≤ G
Aut(H) isomorphic to Z/(p-1)Z since H is prime cyclic
so |Aut(H)| = p - 1
phi is homomorphic,
ker(phi) normal subgroup of G
|G| = |ker(phi)| [G : ker(phi)]
however there are only p - 1 elements of the output of phi
so [G : ker(phi)] | p - 1 and [G : ker(phi)] | G
so [G : ker(phi)] = 1
so |G| = |ker(phi)|
so G = ker(phi)
as such the only phi possible maps everything to the identity
so ghg^-1 = g for all g in G, h in H
so gh = hg
yeah that's it
how did you even think to define phi in the first place
it mapped Z(G) and H to the same thing
Whenever there's center/commutativity questions, we tend to think in "group actions"
I didn't explicitly say it but this "phi" acts on H using elements of the group G
so you have to think about "commutativity <=> conjugation doesn't do anything"
so you look at some conjugation group action
and you had it act on H only, because we only needed H < Z(G) and not G < Z(G)?
you definitely won't have G <= Z(G) (unless you wanna show G is abelian)
in group actions, there are things called stabilizers (which group elements' actions do nothing)
there are also orbits (which elements from H you can attain from another by acting on it)
and fixed points (which elements of H don't change with actions)
here, we were looking to show that every element of G is a stabilizer
and we have results that link the cardinals of all of those between each other
it's a big step to make if it was only used to discuss a single exercise
but it's not easy to talk about the intuition without talking about this tool
how much of the intuition only predicts what a tool can do for us?
i feel like you can do this fairly low tech 
I didn't understand that question
if H = <a>, then gag^-1 = a^k for some k
and g^o(g) a g^-o(g) = a^(k^o(g)) = a
so k^o(g) = 1 mod p
but o(g) has no common factors with p-1
k * o(g)?
no
so k=1 mod p
pretty low tech indeed
where does g^o(g) a g^-o(g) = a^(k^o(g)) come from
so gag^-1 = a^k
then you do it again on a^k
g^2 a g^-2 = g(a^k)g^-1 = (gag^-1)^k
etc
(a^k)^k is a^(2k) though not a^(k^2)

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i need help with this i’ve forgotten alot about polynomial long division
well, if -2 is a root of the equation, then (x-(-2)) = (x+2) divides the polynomial
try writing out the setup for the polynomial long division first, then we can continue explaining 
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What does it mean to find spherical area with a non-euclidean method, not using integrals?
It just means you are working in spherical (curved) geometry rather than flat Euclidean geometry.
Thank you @silent dock ⼼

Do you know a method to look up?
The most classic one is the Girard’s Theorem
awesome, thank you so much, I'll look into this
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.reopen
$\begin{enumerate}
\item Perform the division in increasing powers of $1 - X^2$ by $1 - 2X \cos \theta + X^2$ to an arbitrary order.
\item Deduce the value of $1 + 2\sum_{k=1}^n \cos k\theta$ for $\theta \not\equiv 0 \pmod{2\pi}$.
\end{enumerate}$
Darky
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i need help
i don't know where to start from
i tried doing division couple times but i couldn't find any pattern to make a conjecture
@last slate Has your question been resolved?
You can deduce that sum by using geometric progress and e^iθ thing. But no idea what you were talking about in the beginning
Isn't there just a formula for $\sum_{k=1}^n\cos(kx)$?
Nico
Yeah, geometric progress
Right
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it's division by increasing powers
yeah but i guess i need to solve it with the results from the first question
Isn't this just Bézout's theorem for polynomials?
@last slate Has your question been resolved?
@last slate Has your question been resolved?
what is the first question?
Perform the division in increasing powers of $1 - X^2$ by $1 - 2X \cos \theta + X^2$ to an arbitrary order.
Darky
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@last slate Has your question been resolved?
@last slate Has your question been resolved?
are you sure this is the right statement
should be
do you have any example of similar questions
this forexample
in this question
the division of 1 by (1-X)^2 to an arbitrary order came out to
You're handwriting is very aesthetic but also completely illegible
You should become a math professor
@last slate Has your question been resolved?
i write better on paper 💔
i can't write with a mouse
$1 = (1 - x)^2 \left( \sum_{k=0}^{m} (k+1)x^k \right)
- \left( (m+2)x^{m+1} - (m+1)x^{m+2} \right)$
Darky
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is this right
then i just substract
yh sorry
which is the same thing as adding n^2 actually
so how do i do it
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write things in a less "disorganized chicken scratch i thrive in chaos but then wonder why i get nothing right in math" way tbh
Xd
so i do 5-1=4 then 3-4=-1 then -9-1=-10
?
yh ok
is this right
as u said just continue
this error came purely from the fact that you wrote your work in a way that you yourself can't read and understand.
wouldnt 3--4=-7?
thanks
also any tips to keep my working tidy
yes ok
because writing with your finger or god forbid a mouse over a digital image
is just a road to disaster
tip #1 is to write SLOWLY
it is a mouse lol
ok
badbad. bad. BAD!!!
mousewriting bad. bad.
tip #2 is to write WORDS to SAY what you're doing\
to yourself AND the grader
try your best to separate arithmetic workings from your main/planning work
uhhh do questions that you know how to do without focusing on time but with a focus on neatness
you know sometimes i feel like ik how to do the question but when i start i get stuck
then i just leave the question do others and reread the question which wastes time
sorry, not what i meant
i meant that you should practice types of questions that you otherwise know how to do
like not as part of a mock
but just on their own
and then write your work out neatly for those
oh i see
how about mock
ig something like
- first pass: do the questions you can take to completion there and then. if a question poses doubt, skip it for now
- second pass: go over the questions you skipped but give each one some more time. if you see a route to completing it, then do it; otherwise save it for the third pass.
- third pass and onwards: do the hard questions one at a time
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- In a certain right triangle, the sum of the two legs is 10 cm. Determine the smallest possible length of the hypotenuse
Im clueless
hint: pythagoras
also, perhaps drawing a random right triangle to help you visualize the question may help
Ye I figured that much out but idk how to proceed
What's your resultant equation
Sure
yes, please show your work
Literally just a+b=10 😭
then minimize a^2 + b^2
so you know you should apply pythagoras. can you apply that first?