#help-10
1 messages · Page 27 of 1
@rare oak Has your question been resolved?
@rare oak Has your question been resolved?
(c) This is the same as the circumference of an enlarged version of the original figure, with a rectangle of dimensions 84.39 by 77.88. The distance is thus $\boxed{84.39(2)+77.88\pi}$ \ \ (d) Find the diameter of the semicircle in terms of the number of lanes, and find the length ran using the logic from (c).
messy circle creation
So C is 413.4?
yeah
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✅
ummm
What
sorry
did I do it wrong?
It says its wrong and I followed the previous persons steps
im confused
ah
oh wait nearest meter
You would assume the person is running along the far end of the first track
did I round it wrong?
Nearest meter
actually this too
No decimals
imma just leave it to you lol
You assume the person is running along the far end of the first
yes
No because 413 is also wrong, idk how you got that
ok I get it now I messed up part c
I got 413 from messy circle , he showed me how to do it and that made more sense
They goofed up because 73 + 2(1.22) = 75.44
ah
84.39(2) + 75.44π
Nearest meter bud
Np
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@rare oak Has your question been resolved?
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What's the domain of sqrt(1-x^3)
You sure?
Plug in x=3
See if you get a real answer
Wdym FI?
Here's the thing. Your function has a domain restriction because of the $\sqrt{1-x^3}$. The domain of that is $x \leq 1$, so the domain of the function that you're taking the limit of is ALSO $x \leq 1$.
Umbraleviathan
Because of the domain restriction, as x approaches infinity you're gonna get complex numbers that don't exist on the normal XY plane
@wild matrix
@wild matrix Has your question been resolved?
No it doesn't change anything
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How would I find the limit for this problem?
Combine the fractions or use L'Hopital
Thanks!
@teal breach Has your question been resolved?
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im a little stuck
You might want to learn some algebra to do that
$\frac{1}{-7x - 5} = -1$
NEONPerseus
ive gotten this far, just figuring out this last bit
Can you show the whole process?
ignore the little top part that says u = 5x+6 , its from another problem
obviously
Thats correct, just continue
Biblicalwizardx
like, whats the next step?
Ok for simple, what fraction make -1
like, multipy both sides by -7x-5?
Yes, its true
so that'd be...
-1/-1 equal 1
so the answer is 1?
Just follow this
No
if i multiply both sides by -7x-5, wouldn't that cancel them out in eachside?
It cancels the left one, not exactly cancel, its like (1/2)*2
The right side is wrong
which right side?
This one
so up until here im good?
Yeah, and dont forget the other x too
exactly, sorry, but how does $\frac{1}{-7x - 5} = -1 (-7x-5)$
Biblicalwizardx
You have to multiply both side
?
$\ (frac{1}{-7x - 5})(-7x-5) = -1 (-7x-5)$
Rise
Biblicalwizardx
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
Yes
so x = -4/7?
and the other is -16/21?
Yes
omg thank you u r a saviour!
Np
p^4-26p^2?
would equal
26p^2?
actually 25p^2 because p - 26p = 25p
and 4-2 = 2
right?
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hi! im trying to find x in this question
the background of this question has to do with triangles but this is the part im stuck on
ive tried using elimination and substitution but it always ends on a dead end
im also not very sure on what you can "cancel out"
Row 2: $y^2 = (x + 5)^2 - 12^2$
Use this new row to subtract row 1, and y-terms should be gone.
how did you get (x+2)^2
did u mean 5?
ill try that
ok but after u subtract x^2 from x^2 u get 0
jimmy1234
Typo sorry.
nw but even if u use that one and subtract from the first equation dont the variables just cancel themselves out?
I think the new Row 2 will have like x^2 + 10x + …, and substracting Row 1 should still leave you an 10x term to solve for 🙂
omg i just realized my mistake
im so dumb
TYSM JIMMY
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how will you find the total surface area of this shape
can you help@on it
Find the area of the sector, then multiply by the height
Oops
That's volume.
to find the total surface area
you have to take out shapes
two sectors
don’t know what the yellow shape is
they have said in the question you have to find the total surface area of the slice of cheese
so i think you don’t have to consider other areas
does that make ssense
can you explain
Sure I can.
So you find the areas of all the figures that make sense.
First, the sector on the top.
thanks and they said in the question that you have to find the area just of the slice of cheese one
I mean, that means the area of the entire thing lol.
oh even though they said that you still have to find all the areas individualli oh
Right
OAB is where I'm getting at.
like they are obvious
the bigger ones
the green
but if you see doesn’t it look like a different kind of a rectangle
because of the top line it’s not straight a bit
length into width
Okay so the area of the rectangle in red like I mentioned, what would that be?
6 looks like the length
That doesn't matter lol.
So let's recall, we have the area of 2 sectors and 2 rectangles.
Now we have the right most curved area remaining.
it looks like a rectangle
can you tell that how@do@you figure that out
sometimes the shapes are like very complex so@how can you get it
AB is an arc.
i have found it
Always break the figures down into simpler fundamental figures.
in part a
Good what would it be?
right ill practice that for later shapes
it is 39.26990817 cm
,calc 25/180pi6
oops
Result:
2.6179938779915
for arc lengths you’ll use 25/360 * 2 pie (6) square
Yeah.
because you are finding out the arc length
Yes.
it would be this one
four areas and one arc length
The area of that curved shape would be arc length* height. . .
So that's your fifth area.
For total surface area, add them up.
can i ask you one question that the bigger rectangle that you highlighted will that be at the back too?
Yes, that's why 2 rectangles.
okay also the teacher said you can take out shapes if you want to got for easy working
the confusing thing here was that of the fifth shapes that was the arc length one
2 sectors.
2 Rectangles.
And one curved surface area of the cylindrical segment.
that’s only one
That's the area of a pizza slice.
Yes, now you know.
maybe the shape wouldn’t make sense if you said that curbed surface would be at the left side too
it’s only one hence
If you can think of a shape, it always makes sense.
Someone tell that to me. 
You're welcome.
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Why does 1 satisfy the conditions of a prime? If a prime is a number only divisivle by 1 and itself, isn't 1 divisible by both 1 and itself despite the fact that itself is indeed 1? Is the primacy of 1 mathematically refutable?
Please don't occupy multiple help channels.
Apologies. I had a new question lol.
You still don't open multiple channels so you should close the other channel you have
If I have a second question unrelated to the first, then why "don't" I?
Why don't you open multiple channels? Is that what you are asking?
First one is closed. Any further issues or are am I free to go?
You're good now, it was mainly because there's limited amount of channels and many people here could have multiple questions and if people opened multiple channels each,.. one people wouldn't know which one to help you in because you're in multiple channels and two because the server would run out of channels
Okay.
1 is not a prime, which is really just by definition/convention
take the fundamental theorem of arithmetic, which says every natural number greater than 1 has a unique factorization of powers of primes. it's not as fun if 1 is prime, bc then it's not unique anymore. eg. 6 can be written as 2 x 3, or 2 x 3 x 1, or 2 x 3 x 1 x 1 x 1... not unique anymore. so maybe it's easier to just say 1 isn't prime rather than exclude 1 as a factor in that theorem
actually iirc the greeks didnt think 1 was a number at all lmao
So, they say that every number can be made from primes in one and only one way. But what about 3? Without one, three cannot be made from two primes but itself.
I kinda feel that lmao
3
1 + 1 + 1 = 3
2 + 1 = 3
1 + 2 = 3
but that is all
we're talking about factors here, not sums
But every prime composes itself. Naturally.
yes!
No, you were talking about factors and I was talking about sums. Lol.
What is a factor, again? Numbers that can be multipled to make another number?
yep, those would be factors of a number
I am trying to understand the mindset of those individuals who consider primes to be sacred.
And still failing, unfortunately.
I mean they are just numbers
but it's neat that there are numbers with that prime property, and there are infinitely many of them
lots of math involves the distribution of these primes among all the others, and you can do pretty neat stuff with all that
(disclaimer i am not a number theorist)
Funny, I just began reading an article about this same thing.
the riemann zeta function is well known example of something related to primes, obv a lot more advanced than what we were touching on, but it's famous (maybe in part bc of the small cash prize associated w it)
@wraith bane Has your question been resolved?
Just read about that as well.
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How do i extract the square root of a quadratic equation
please elaborate with you question. What do you mean by "extract"
do you mean completing the square?
@jovial plaza Has your question been resolved?
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if theres a root number in stuff like cost, should i find the root or just leave it as it is?
like if they ask "find the cost of laying grass in 105 root 50 m^2 at the rate of some $ per m", the cost would have a root
No, keep it as 105√50, don't approximate
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I need help with the second one
I know how to calculate the equation of planes with a line and point but idk how with a line and vector. Are vectors just points?
Can I treat them the same
I was thinking I could subtract the vector by the initial points of the direction vector but idk what that would give.
They probably mean it as a point
There's a chance they mean "if the plane contains x, it contains x+the vector"
In my other homework it said point
Which is why I’m confused that it says vector here
We can wait for another opinion
Alright
I'm voting point but not too confident
@timid silo Has your question been resolved?
,rotate ccw
Thanks
@timid silo Has your question been resolved?
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i need help andrea
from this question i got -9 and -2
when i write the equation by adding those 2 replacing -11x
does it matter which one i put first
-9x or -2x
no
(6x)^2 -9x^2-2x^2+3
or
(6x)^2 -2x^2-9x^2+3
ok so i shouldnt care which one i put first
just do whatever
addition is commutative
a+b=b+a
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a friend sent me this proof he was doing, i thought it was correct at first but after i re read it, it seems to have an error, is this step valid? we are supposing true (n k) not (n+1 k) so in theory we shouldn't be able to replace it, right?
@coral junco Has your question been resolved?
ok i think it is wrong, i'm gonna redo it and send it to him
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If AB, BC, AD, and AE are parallel to a line l, then show that A, B, C, D and E are collinear points.
Please don't occupy multiple help channels.
.close
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@brisk arrow Has your question been resolved?
<@&286206848099549185>
@brisk arrow Has your question been resolved?
@brisk arrow Has your question been resolved?
No
All remaining angles can be stated in terms of x
And we can find multiple values of x that all work
If you squash the top of the triangle down the point on the right just gets closer, that's all
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What is the difference between a field, a ring, and a group?
You may want to check other lecture notes on web or wikipedia. They must already make very clean explainations on these jargons 🙂
a group is a set closed under an operation like addition or multiplication (with a bunch of other properties)
a ring is a group under addition, that's also closed under multiplication
a field is a ring that's commutative under multiplication with multiplicative inverses and an identity
Thank you both
Do the operations of fields and rings have to be addition and multiplication
Or are the operations just called addition and multiplication
Based on this page it sounds like there can be other operations
they are just called addition and multiplication
because they "behave" like addition and multiplication behave for integers
@mossy ibex Has your question been resolved?
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hey every1, this year i got unlucky and got the math teacher who isnt pationated about math and doesnt know how to explain things properly so im already confused and lost my way in the forest, can someone explain everything to me in detail pls. thxxxxxx
..
You sound like you're looking for a dedicated tutor. That's not what this is for
This is for answering individual questions
What's the question
yeh im downloading the things into the channel, but its in dutch so ill need to translate
how to leave the forest
Downhill until you find water. Then follow it upstream.
LMAO SENDING ME TO THE MOUNTAINS!!
You got out of the forest
😉
there we go
i dont understand a single damn thing
i know its very much
Translate that first q
without using a calculator give the exact value of...
2nd
is cos -ve or +ve in 2nd quadrant
it does
so cos120 = cos(90+30) which is -sin30. do you follow?
and what is sin30
well yeah but im asking for the value, thats what the q is asking you to do
yes
yehh
so your answer would be -1/2
why -?
ah yes yes
you yourself said negative
ok i hope its clear, now try the other parts
i got the 1st 1
where did you get these formula
cus i recognize them from somewhere previous year
but dont really have a paper or something with them
when its 120
the x coordinate will be negative
that is, cos will be negative
since its the x coordinate
so cos120=-sin 30
yes
and is that a formula or
how are those equal to each other
man im just asking questions because i dont understand it. sorry
issokk!
yesh those are formulas
there’s more
if u want to know why there are equal u can watch a vid on YouTube! it explains pretty well
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@bronze moth Has your question been resolved?
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Hi everyone, would like to know if it is possible to use the method of differences to find the general formula for the summation of an arithmetic sequence.
Would appreciate any assistance with this, as I have tried and failed to generate the formula so far.
Thank you
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@mellow igloo Has your question been resolved?
@mellow igloo Has your question been resolved?
idk about that, but there must be some yt videos about deriving that formula
@mellow igloo Has your question been resolved?
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How am I supposed to find a counter example for 9.?.
Im confused on what this paper is asking me
replace x and y
For 9?
yeah
How do I know when to replace x and y
If there is an even power exponent doesn’t that automatically make the function not invertible
I have x = y^5(2y+3)(3y-5)
How?
By replacing x and y
oh damn you factored already
multiple y-values for 1 x-value => not inversible (not a function)
Oh so then how do you find a counter example
lets say x=0
Ok
yh
So for the rest of these questions should I replace x and y
Or if I see just one exponent that is even
I should rather just go and find a counter example
Okay thanks for your help
gl and good work
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Can you change the signs of an equation without flipping it
without flipping it?
Like moving all the variables to the other side
you can just multiply -1
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Can somebody help me with this problem?
take a pic
im not tryna install that
oh you cant view it
yeah
yeah, this is an inequality though, does that matter?
no
im just stumped
basically you have to find the equation of the two lines
lets say equation of company A is A, equation of company B is B
ok
sweet, i'll try it
I'm confused how to find the slope of the line without any coordinates
i think just by the graph
choose points that are on intersections of the x and y axis
because they are easiest to tell what the coordinates are
(50, 32.5)?
@novel crystal Has your question been resolved?
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can someone explain this
post the definition and then we'll see where |x-2| comes from
what do you mean
like a screenshot of the definition of a limit
do you see where |x-2| could come from?
well I understand that you factor x^2 - 4 into
x -4 and x + 4
2*
not 4 sorry
but I don't get how it ended up being multiplied to the ϵ
I can't tell what's confusing you 
so we have |x^2 - 4| < ϵ
and then we turn that into
|x-2 * x +2| < ϵ
I get that
but then
a 5 comes out of nowhere?
and the |x -2| pops up too
this part
I thought it was supposed to be in terms of ϵ
but it just decided to dip
how you think to do this might be tricky but in order to accept this part of the answer you just need to agree that if |x-2| < 1 then |x + 2| < 5
I know it looks like it comes out of nowhere
that's just scratch work
hm?
the proof outline continues below
and presents more of the argument
the point of that is just to show that with an appropriate delta, if |x - 2| < 1, then |x^2 - 4| < 5|x - 2|
5|x - 2| is easier to work with
It might help to look at it like this
sorry but why 5
because... it works
so if I am doing a question by myself how am I supposed to find that
😭 🔫
ig I will have to keep practicing until I get it
ok actually I found another method
oough kinda hard to read sry
where does the 5 come from in this one
just the sqrt 25?
also this doesn't have absolute values
<@&286206848099549185>
Well it was originally 75
Or wait hang on I'm misinterpreting your question
They subtracted 5 from all sides
Because they wanted the center to be x-5, not x
oo I see I see
we want to find δ such that |x-c| < δ etc
Indeed
🤨
Think about it
We're proving basically that the limit as x->5 of x² is 25
It's not just a coincidence here that 25 = 5²
But yeah it's not too important
and then after that?
yes
so that F(x) is always within ε of L
the problem is the range isn't of the form |x-c|<δ
because it's in the terms of ε?
Sorta
Your final δ is actually gonna end up being in terms of ε if that makes sense
But try converting the range in the third to last box into the form |x-5|<δ
You'll end up running into a certain problem
?
Yeah that one
ok gimme a sec to think
I don't get it
|x - 5| < δ
δ = E/5?
idk what to do w the stuff on the side
the sqrt stuff
|x-5| < 3
ok
so then doesn't the rest of it play out like
sorry if I am a little slow rn it is kinda late
don't worry
ok so what is the significance of δ = 3 in the example
Just a random value I chose
yes but what does that change
To show how to go from inequalities on both sides to one side
So in general the process is
-δ < x-5 < δ
which is the same as |x-5|<δ
Forget the 3 here, this is true for any δ
What do you mean by that?
well
δ=3 is in terms of ε
again that was just an example and not the value you should actually use
ok so are we going back to the original q then
yeah
so δ = -5 sqrt 25 + e/3?
Well, that's the unfortunate part
If that's δ
The thing on the left isn't -δ
They're not negatives of each other
So that's good thinking, but we run into a problem
does it have to be +5 instead of -5?
It's like if I asked -3 < |x-5| < 4
The bounds are correct as is
We haven't made any mistake in getting to them
They're sadly just not useful as is
yes but for me to do the δ = -5 sqrt 25 + e/3
the -5 has to be +5 on one of the sides
so that they are true opposites right
is that why it doesn't work that way in this question
I am not questioning -5ing everything
Ah ok
Yeah in order for them to be negatives you would need the left side to be like 5 - sqrt (25 + ε/3)
ok
in the meantime
Something important to note
We have a range, that includes 0, but is not centered about 0
On that range, we know |f(x)-L| < ε
That's all the work that's been done so far
Now we need to find a range that is centered about 0, for which |f(x)-L|<ε
Just by visualizing the problem, do you think that's possible?
Don't worry about the δ,ε part for now
We have a range that contains 0 but isn't centered about it
Every point in that range satisfies an important property (the ε thing)
Can we find a range that's centered about 0 (any range!) such that every point in it also satisfies the important property
wdym centered about 0
the range is -a < x < a for some a
actually let me help you understand my situation a little bit
I'm not sure what is going w prof but we are using calc early transcendals textbook
we went from section 1.5 to 2.9
ah hmm
like in one day to the next
what class is this?
so I have 0 clue
calc for math and stats 1
Is it 300 level?
this be the cover
worth full course marks yea
never heard of it
ah as in like a 3rd year of college course
is what I mean
no
see my uni we do each course is worth x amount
like most courses are worth 3.0
I thought that's what you meant
nah it's university year 1
ah
it's the first calc course I can take
😨
so went from grade 12 to this
uh oh
Calc 1 is a normal first year course
Rigorously proving limits of quadratics was more of a 3rd year thing though
🤷♂️
Definitely a difficult topic
2 days ago we were talking about inverse functions
Have you taken courses on logic?
and function notations? or smth like that
the day after that
we just went to a completely different unit
no this is my first semester
it is like my 3rd day
I haven't done any courses
ah all right
that's brutal ooof
👍
not like this is a class I can drop either
it is literally the core of my major
there is calc for math and stats 2 next sem
so if I mess up foundations I gonna have a tough time
I would tentatively suggest that unless you see otherwise there's a chance you don't need to rigorously prove limits
The way to solve (finite) limits for most functions is to just plug in the value
like lim x ->2 plug in 2.0001 kinda thing?
only when you get 0/0 or something as a result do you need to dive deeper
Just plug in 2 lol
oh what
It'd work for this problem
It's not a proof
But you'll usually notice when the method doesn't work because you'll get 0/0 and then you'll have to work harder
Like lim x→0 of x/x
I think we do have to prove limits like that though sadly
like as shown in the textbook
all this stuff
ah that's brutal
what time zone are you in
is it est by chance
ok an hour behind
nice
do you mind if I ping you again tmr
won't be at like 5am or anythin
Not at all go ahead
Although you might get in trouble you can tell them you have my permission
I'll be on around 10:40 est probably lol
9:40 central
am
no problem, good luck with your class
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Am I allowed to do this with limits?
no
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if cot(a) = 4/5, find sec a
Yes. You may want to draw a right-angled triangle to figure things out.
ok
Notice that you may have to consider all 4 quadrant 🙂
wdym
Say if A is in quadrant 1 and 3, cot is positive, but cos can be positive or negative there.
oh ok
so i got sq root 41
So what do i do after i got √41
<@&286206848099549185>
@restive sapphire Has your question been resolved?
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So I know 4 is a factor
and then I did quadratic to get complex roots
But it's just +/- 5?
,w solve x^3 - 4x^2 + 25x - 100 = 0
Oo
did you get x^2 - 25 or x^2 + 25?
I'm a tad rusty so maybe I just needed to include the i
I used quadratic formula
So I used synthetic to get (x-4)
Which leaves you with x^{2}+0x+25
Using quadratic, you get +-sqrt{100}/2
ohhh wait
It's sqrt{-100}
My bad
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How would you solve \sqrt(3)tanx=1 for 0<=x<=2\pi ?
Tan x is equal to 1/root 3
but i'm not sure how the rest of the 0<=x<=2\pi comes into it
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have you made any progress?
this problem yields quite easily to applying the definition of linear independence and the definition of kernel
so i know if v is in the kernel and we let v be a linear combination, that combination is 0
nyeh? what?
btw for this cant u just factor 25 from 25x-100 so 25(x-4)
and x^3-4x^2 factor x^2 so x^2(x-4)+25(x-4)=(x^2+25)(x-4) then zero product rule
@lone blade would you like me to give you the start of a proof for you to continue
@lone blade Has your question been resolved?
Ya
We wish to show {v, w} is linearly independent.
To this end, let a, b ∈ R be scalars such that av + bw = 0.
...
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Hello
How do I do number 6
Wo I opened up in the formula : (a+b)(a^2-ab+b^2)
Then
What should I do
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ohh u don’t need to use that formula
can use triple angle formula instead
ohh okie good job (:
Thx
another instance of
helping someone inadvertently starting a new channel
@tidal hawk
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so i just started studying matrices and this question came up
can someone please tell me how to do this question
use induction i guess
there is a good geometric visualization for this
ooh what is it
A is the matrix for a clockwise rotation by alpha
yea normally geometric is just to visualise
oh cool
but like how to prove that
i haven't studied induction yet so can someone teach me
@wild swallow uve a template right
LOL
i didn't understand anything when i read that 🥲
well first observe that your formula works for n=1
which should be obvious
then from the formula for A^n deduce that it works for A^(n+1) too
i.e. verify that $$\bmqty{\cos(n\alpha) & \sin(n\alpha) \ -\sin(n\alpha) & \cos(n\alpha)} \bmqty{\cos(\alpha) & \sin(\alpha) \ -\sin(\alpha) & \cos(\alpha)} = \bmqty{\cos((n+1)\alpha) & \sin((n+1)\alpha) \ -\sin((n+1)\alpha) & \cos((n+1)\alpha)}$$
that line break
Ann
better
i can fix my own tex if needed
yes indeed
ok i put n=2 and got the RHS