#help-49
1 messages · Page 93 of 1
It does?
rank(A) = rank(A^T)
actually this is even better for us i think because it tells us what V is gonna be
so we can get to full RREF
and we can swap around columns or rows
so we can for sure get to $\mqty( I & 0 \ 0 & 0 )$
jan Niku
I would never
I was in the toilet, hence I didn't respond
ah
sorry 
usually i only respond on the toilet
so cant relate
we can start with A
with some right multiplication
we can get to REF
then, some left multiplication
RREF
because A and B have the same rank, theyll have the same RREF
and, each individual elementary matrix is invertible
how do you feel about each of those pieces individually
feels alright to me
then good to connect? 
so eventually we can get it to $\begin{bmatrix} I&0\0&0 \end{bmatrix}$
Veni, vidi, perii
you've sent examples from your textbook doing this in the past
$A = E_R ^m \mqty(I & 0 \ 0 & 0) E_C ^n$
where R and C for row and column and 3 and 4 for square dimension
err
shit i should use m and n
jan Niku
That's using row reduction, we haven't done column reduction in class
no, you've definitely done this and last time you claimed the same thing
your textbook did row reduction on the transpose
which is just column reduction

its okay i believe you dont remember veni
no like we haven't done in in our actual classes
there's a lot in our textbook we arn't covering
IDK what you want us to say to that
nothing
first pre-multiply both sides by $(E^m_R)^{-1}$
Veni, vidi, perii
and then post multiply by $(E^n_C)^{-1}$
Veni, vidi, perii
lets just say like
geez im running out of letters
I kinda wanna change the notation
lets just know n means columns
and m means rows
I actually have a class in 5 minutes, shall I contniue this later. Also, I'll post in my thereads from now on
$E^m_A \cdot A \cdot E^n_A = E^m _B \cdot B \cdot E^n _B$
jan Niku
we agreed both would have the same rref
thats all this says
moving forward from here is very easy

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Have I done correctly
The mark scheme says correct working
But doesn’t show any working
Yup
@last slate Has your question been resolved?
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So my idea was let U be a m by m square matrix,which is a product of the elementary matrices that gets us form R to A
yes
is that enough?
yes
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can any one prove tan47/cot43=1
The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.
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let complex numbers $z_1, z_2, \dots, z_{2023}$ be the roots of $$P(x)=x^{2023}-x^{2022}+x^{2021}-\dots-x^2+x-1$$
find
$$(z_1^{4049}+z_1^{2024})+(z_2^{4049}+z_2^{2024})+\dots+ (z_{2023}^{4049}+z_{2023}^{2024})$$
Skill_Issue
bruh who tf made this abomination 😭
oh this one is actually fine
Omg
looks very ugly at first though
i.e. notice what happens when you try to factor this
what grade is this btw
no clue, olympiad
ye
wait which one do you want me to factor
oh the polynomial
$(x-1)(x^{2022}+x^{2020}+\dots+x^2+1)$
Skill_Issue
this?
yes that would be right
ig this was noticeable at the very start but now to proceed it is clearer that || the thing on the right is a geometric series||
it is unique yes i don’t think I’ve seen this setup appear specifically before
but the trick of rewriting polynomials using geometric series is a good tool to be familiar with
$$(x-1)(\frac{x^{2024}-1}{x^2-1})$$
$$\frac{x^{2024}-1}{x+1}$$
Skill_Issue
soo x=/=-1, x^2024=1?
ig that clears the ^2024 part of what were looking for
how bout the 4049 part
thank god tbh i thought there will be some root of unity bs
wait i think i see the idea
say the $z_1^{4049}=(z_1^{2024})^2z_1=z_1$
is this corrwct
so it becomes
$$(z_1+z_2+\dots+z_{2023})+(2023)$$
and the first part you can get from vietas or smth
its 1 right?
its the negative of the coefficient of x^2022
is it 2024?
whoops my dummy head used the wrong var :p
would say so
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✅
wait
am i stupid or is (x^2024-1)/(x+1) not equal to x^2023-x^2022+...
err ok stfu
.close im stupid asfk :p
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does this mean u see why it’s not
oh it was a typo
i meant to ask for (x^2024-1)/(x+1) cause using syntethic division i get something much diffrent, but i realized i tried to divide with x-1 instead
:p
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how do u do this
what are the domain and range of arccos(x)
what to i do next
u got the domain
now for the range
range of arccos(x) is 0 <= y <= pi
so what will be the range of arccos(x)/2
divide*
thats the range
how do i get the domain
u already got the domain
.
the answer says its -2 <= x <= 2
do i do this kind of method for arctan and arcsin as well
allg
also i tried finding the range of arctan(x-6) + 3pi/2 but i got the wrong answer can u help me
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Hey
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Is 1 = 0.999999999999... ?
yes
yes
But when u use lim it's not the same
wdym
W?
It will gives u an epsilon when u use lim
Lim means that it's 1 but it's not
And here is correct too
I think you misunderstood what lim means
Can u explain it for me pls
what definition of lim have you seen
That there is a function near to our function that u never achieve it
Like lim of 0
are you confusing it with an asymptote?
(thats also not the correct definition of asymptote tho)
So please explain it
For sure not
while you not necessarily ever "reach" it, in the limit you are still actually equal to it
Unfortunately I can't explain lim in English I have to explain it in persian
cant help with that
Exactly so lim of 0.999999... is one but there is an epsilon
no
in the limit its equal
the ... itself stand for the limiting process
so we have the numbers 0.9, 0.99, 0.999, 0.9999 and so on
and you are right, they never equal 1
but we get closer and closer
and a limit is a way to make precise that "after infinitely many steps" we actually equal 1
I understand what u say but it's not okay that 1 is equal 0.999999...
why not
Due to its never reach it( the definition of lim) but u can say that both r same
so it is ok to say they are the same?
I say both are correct so we can say they are equal and they are not
But my idea can't be correct
so we have two numbers which are equal and not at the same time?
Exactly what I mean
Schrodinger's number
how could both of these be true at the same time
The problem is this
Or grassman number which said a×b=-b×a
Any idea?
No they aren't the same there is an epsilon between them
One another question is this interval correct? (0.99999...,1)
I think it has two answers
We can't because it's an epsilon
in the real numbers there are no such things
if you want to be in the hyperreals then go ahead
but you'll be lonely there
So maybe we have an imaginary number
thats another completely different thing
As ur talking about hyperreals num we can believe that it would answer for imaginary mums too
hyperreal numbers and imaginary numbers are very different things
hyperreal numbers are actually a way to have numbers "epsilon" like you want
But it can be it subset
Yeah when u have f(x)=f(ε+x)-f/ε
Is it correct?
well ignoring the typo and that we are ignoring any semblance of technical accuracy, sure
before you try to work with hyperreal numbers you should first actually understand what real numbers are
Just one question r u a math teacher?
no
however there are definitely faster methods to show that 1=0.999
by definition yes, this dot dot dot notation, or the way I prefer to write it using a bar $1 = 0.\bar{9}$, is just some notation that refers to the limit itself, not the sequence terms that lead to this limit
rbit
How?
It's the lim of x=>1
the limit of the sum 0.9 + 0.09 + 0.009 + 0.0009 + ...
Okay
to put it into more rigurous terms
Ah I got u
if you have a sequence of digits $a_1, a_2, a_3, ...$ and some integer K, you can then define the notation $K.a_1 a_2 a_3 ...$ to refer the limit of the sum $K + \sum_{n=1}^{\infty} a_n \cdot 10^{-n}$ (which can be proven to always exist)
rbit
in our case, K=0 and a_n = 9 always
exactly, plugging that into the definition leads to exactly that sum
Tnx man/madam
so yeah in the end its just true by definition, you may argue whether this definition makes sense or not, but seeing as this gets used by almost all mathematicians that may answer it
R u an mathematician?
anyone who does math
Aha in that case
but ok, maybe I should have stated professional mathematicians
theres a lot of unprofessional people that like to question it
Yeah
And ur not a teen I guess
well more than that I means, they question it and then refuse to believe any evidence that is presented to them
Coz I'm teen but I enjoy studying math and helping others but other teen that I know hate math
yeah, might have to do with the fact how math is being tought most of the time
Yep
it can be much more than just boringly manipulate some numbers over and over again
We are at the same page
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hey does anyone know how to define $\exists!$ with only $\exists$ and $\forall$?
wololo
I don't really need any help I'm just really curious
Do you want a solution or just a hint?
solution because I feel like I wouldn't even be able to find it myself
$\exists! x P(x) \iff \exists{x} \forall{y} (P(y) \iff y = x)$
lmao
I hope it's correct
how many edits was that
hm
MæthIsAlwaysRight
now it should be correct
Now it guarantees that there exists x such that P(x) and that the x is unique
i need to get better at latexing
btw, interesting fact is that you can even write \exists with \forall
I think the for all mean that for every result you get with p means that the value used is x
so x is unique
at least that's how I understand it
Firstly, it gives us that if y = x, then P(y)
Or simply, P(x)
$\exists! x P(x) \iff \exists{x} (P(x) \land \forall{y} (P(y) \implies y = x))$
this would actually be equivalent definition
MæthIsAlwaysRight
or even this
and the second part, that is P(y) => y = x tells us, that if P(y) then y must be x
meaning that there are no other y's, except for x such that P(y)
If you recall that
\forall is equivalent to \not \exists \not, then you can further rewrite this as:
$\exists! x P(x) \iff \exists{x} (P(x) \land \lnot \exists{y} (P(y) \land y \neq x))$
MæthIsAlwaysRight
and now this literally translates to "There exists x such that P(x), and there isn't any other y such that P(y)"
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is $x^{\log_x m} = m$?
anjali
yes
ok
may I close?
.close
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Helloo
I need some help solving this
I have a solution although...
Not quite sure if its correct
Ooo ooo explain pleaseee
it was cube root of y not x
Try rationalization
Times the denominator and numerator by √x³ + √y³
Brain damage math
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how to solve without using period properties
[.] represents floor function
just wondering
if it is possible
since it was given pretty early in the book so there might be i guess
i tried making series kinda thing but the last term was ugly
Why the hell is x both a limit variable and the variable for the integral 
same question 💀
@slim eagle Has your question been resolved?
bro how are you gonna integrate a function THIS discontinous😭😭
i mean i guess if the difference within bounds is less than or equal to 1 and doesnt cross an integer then you could just take the part you care about and analytically continue the rest to get a continious function for which the fundemental theoreom of calculus applies?
but if the difference of bounds is more than 1 then i dont think you can do a definite integral on it
so in this case x cant be greater than 1 or less than 0
(since if it is greater than 1 we will have an integration bound that goes through one of these jumps/asymptotes)
so in this case that means the functions domain is (i think) 0<= x <=1
(domain of the function that is the solution, not the integrand)

so for all cases of x less than 1, the floor will just be zero, so itll just be an integral from zero to zero
but if x = 1 its gonna be the integral from 0 to 1 of 1 which is 1?
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i feel like im doing something wrong
real
(this is very much integrable)
i feel like theres something wrong with the question
well aside from the poor choice of bounds it’s fine
you can integrate a non continous function??
yes
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bro?
I am very confused how one would logically get to that conclusion.
are you trolling or what
I will do this for the rest of my life.
we did this like 3 times already
if it means I will understand.
alright, what do you want to understand
well its not as much that i dont understand
as much as it is
i dont get how someone would reasonably get to that conclusion
like
here ill format
also astar i dont think we did this even once honestly
the phrasing in prior questions was so broken that i dont even think you mentioned the real problem tbh
or you did but phrased it in a way i wouldnt understand

1. Ok so this hurts my head the fact that they took 2 which was multiplication and put it inside of the 2nd parameter in order to create an equality where because they all multiply and are technically equal so they then undo this somehow by just adding and ignoring everything?```
so once they created the true statement they undid everything by just ghosting ^2 and adding 2?
and remember the answer to erm
(x+1)^2
the entire answer was that there was no factoring there was no special operation that would solve (x+1) (x+1)
the only thing that mattered was that (x+1) is the sqrt of (x+1)^2
prior i also had not considered every logic state of the problem
i also did not take as much as a detail-oriented approach
so i mistook sqrt of each component as the same as the sqrt of the whole
leading to problems
you there?
do you agree that 2y + y^2 = y(2+y)?
Buddy are you sure you are not trolling? Multiple people explained this to you multiple times
You keep repeating same and asking weird questions
you seem not to understand thats how math is
You don't seem to understand that you don't want to understand
its not exactly easy for me to just interpret something like that so give me a second
believe that if you want shows how little you actually understand about students
i am
this is my practice
there is no other form of practice if you cant answer a single question
you cant practice solving it if you cant in the first place
you love to stray from the topic sigh
Take easy questions bro to practice
If you aren't able to get this exact question
i will ignore all responses from you guys and only take into account the problem from now on

i am finished responding to distracting information that will not assist me.
hm? What do you think that guy along with many others just presented?
what was i just doing
before you distracted me?
Like
x²+3x+2 = 0
Factorize this
also one last thing before i answer this
i want to understand, likely even more than you ever have
all i do all day every day is focus on eliminating all thoughts within my mind in order to focus entirely on math
math is everything to me
i spend every day focusing every single one of my thoughts trying to achieve 90% of the possible efficiency a human can output

chill bro, its not that deep
if you have an idea for an alternate route provide it and dont talk about me
carry on with your question
it is that deep
people get depressed when they dont care as much as i do because they live lives they hate
Buddy I care about people who are not able to solve things, that's why I am in this server 😅
no way you arent trolling
correct, now stop mentioning me or what im doing.
that will be all i will not respond to any other such topics
I dont know maybe I mentioned that earlier somewhere.
making a new channel lets try this again
.close
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Hi
hey
yo
a
question?
How do I get a y=kx+b+c/x-x'
hi
From
Hii
Earth
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
y=(x^2-4x+3)/x+1
The original is in Russian but I can rewrite it if u need
So long division polynomials
NP
Do polynomial division bro 🙂
I need to check out what is this
| x
----------
(x+1) | x²-4x+3 |
-(x²+x)
-----------
-5x+3
Like this continue
Understood 🫠
?
I guess I understood, will try to do this on paper rn
Will be back with a result in a sec
Division with polynomials (done with either long division or synthetic division) is analogous to long division in arithmetic: we take a dividend divided by a divisor to get a quotient and a remainder (which will be zero if the divisor is a factor of the dividend). More formally, given a dividend ...
There is also a faster way , look into it 🙂
Like that?
Damn
I think I wrote the last one wrong, it should be 8/x+1 instead
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i've got the base sorted but i'm unsure if i carry out the induction as i would normally if the summation term was something like k^2? i'm mostly getting lost with the k2^k part 😭
,rccw
A minor point: we don't need the base case to be true in order to assume the inductive case (you just need it to be true in order for the inductive case to be useful).
oops, lol thanks for the correction
So can you show your work on the inductive step?
well that's the problem is that i don't know where to start
like my main confusion is whether the 'k' in k2^2 is just disregarded (?; pretty sure i'm wrong 😭) and i would continue on with the induction or if there's a different procedure
well, you assume it's true for n = k. And then you try to prove it for n = k+1. So any place where you have (k) you replace it with (k+1)
wait sorry
k is the summation variable.
well, you have it holds for n.
So you show that it also holds for n+1
which means every place where you used to have an n, you now have an n+1
\begin{align*}
\sum_{k=1}^{n} k 2^k &= (n - 1) 2^{n+1} +2 \
\sum_{k=1}^{n+1} k 2^k &= (n) 2^{n+2} +2 \
\end{align*}
OmnipotentEntity
The top line is what you already have (from the inductive assumption), the bottom line is what you need to show
okay so i sub n+1 wherever n is but then what do i do with the k? is it not important?
the k is just the summation index, you don't need to touch it.
it's not not important
it's just unaffected by the substitution n -> n+1
ahh okie
so i just leave it and then continue with the induction and it's still proven?
yup
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Did I do something wrong
,w int log(x) / x^2 dx
I don’t see where I did it wrong
Ok I forgot to add the negative sign from the front but how is the 1 positive
because of this
no
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does this factorisation rule apply to function x^2 - 4
factorisation rule of polynomial?
sure
woah
can you see what x1 and x2 should be?
yep
wrong?
because
is true
yep
it gets trickier if you have x^2 + 4 instead of x^2 - 4
because x^2 + 4 has no real roots
but
so it can't be factored as (x-x1)(x-x2) unless you allow x1 and x2 to be imaginary
beats me, i don't know your test maker haha
What do you mean with "test maker"?
the person who makes a test
in university
for mathematics
which i write in 2 days
if i pass im on top of the world
so currently i am working 24/7 9/11
around the clock
to maximise mental capacity and performance
Still don't understand...
Yeah (I'm Italian though)
But I don't understand the context here
Yeah, and so?
Yeah, I understand all of this
But I don't get how this has to do with the "test maker"
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I'm trying to think about this problem, and I'm stuck trying to figure out how to approach it. It feels familiar to Hensel's lemma as it's earlier discussed, but I'm not totally sure what to make of this problem
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show that the limit of the function in the origin doesn't exist.
choose two paths that converge to different limits
yeah that works
yeah
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Im confused on how to put the positive part of the graph into notation
I was thinking maybe (-inf, -1)U[-1,2]
Im assuming so, because the question is asking to find what part of the graph is positive and put it into notation
But is the function positive at those values, -1 and 2 included?
It would be neither because its at zero youre right
Like the same thing as this but without -1 and 2
I could just not include them and do (-inf,-1) but then how would I mark the relative maximum on that side of the y axis
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so U would be a 2 by 2 matrix here and V would be a 3 by 3 matrix ?
so U for instance would be
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A bit stuck, not sure how to integrate that RHS and not sure if what im even doing is correct
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bacc
Solve these instead
Then y(x) will be a piece wise solution and don't forget the IVP
how do I make sure that the solution is continuous at x=4?
You consider the LHS and RHS limit and equate them
You will need to find a constant C for your IVP and constant K for the continuity part
Both after integration
as in equate the first equation and the second equation after writing it in the form y= ?
Kind of
Plug in x = 4 basically and find K
what would y be at x=4 ?
idk
can I plug something like 3.99999 into the first equation to find it?
or is that wrong
bacc
Thats why you consider limits
Yea one piece is undefined at x = 4 still you can see what would the limit be
and then determine a suiting constant K
if I plug something like 3.999 into the first equation I get -9 but how would I find the limit from the right if I dont know what C is?
since y(0) = -6 say constant C would be used for that in eq. 1 and constant K would be 2nd piece, so you would need to adjust the 2nd piece for continuity
so would I be equating the 2 equations at x=4 ?
basically
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The first one wants justification too
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maybe a question that's a bit abstract, if I have X = X_1 + X_2 + X_3 + X_4 + X_5 (random variables, not necessarily i.i.d) and Y = X_1 + X_2, and I would like to add Gaussian noise(0, sigma) to X and Y (Y containing the sum of only a subset of X_i), would it make sense to just scale the respective noises?
That is, X = X_1 + X_2 + X_3 + X_4 + X_5 + Noise(0, sigma) while
Y = X_1 + X_2 + Noise(0, sigma * 2/5)
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@left rover Has your question been resolved?
Is there any more context to this?
(Note that, if this approach does make sense, you should scale the variance, not the standard deviation: sigma^2 and sigma^2 * 2/5)
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i dont understand what's a minor here
why minor Ai=1,2,3 , j=1,2,3 = 0?
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how do i solve
yes and what should you get if you differentiate F?
xsin(x)
but how do we find the constants
alr
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find the largest natural number such that its divisible by 36, all digits are even, all digits are diffrent
is this 8640? thats the largest found
well it is a 5 digit number at most
yeah but i couldnt find one where the digits sum to 18
you also know the last digit can only be 0, 4 or 8
yep exactly
if you use all 5 digits, then the sum is 20
so can only be 4 digits
8642 is the largest 4 digit number you can make with "all digits even, all digits different"
since it's not divisible by 36, 8640 is the one
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let S(n) be the sum of the digits of n, find all k that fulfills k+S(k)+S(S(k))=2025
2013 1995 1989
i got these from just guessing, are there any i missed?
Did you check all n in 1959 to 2025?
not all, just ones that make sense
im pretty sure there isnt any less than 1989
for 199x 1995 was the only one, 201x it was 2013, i couldnt find one for 202x
Ik 1959 was a pretty rough lower bound. 1985 is better.
That's smart
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.No
Is it generaly advised not to calculate the (x-1)^3 with the rule a^3 + 3a^2b+3a....
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✅
sorry i thought i understood it
but now i see like yo
i thought this cant be cancelled
cant comprehend this process
how cancel it just like that
is this all false?
Cancel what? The (x-1)² you mean?
yesy
That's completely legal, since it's common both in numerator and denominators
yes but im under arrest
this is how i did it
it not good?
starting from
so this was first derivative
and my solution is up
I think you applied wrong the cube formula
(A - B)³ = A³ - 3A²B + 3AB² - B³
hmmmm
but
generally
i should not have gone that way
calculating the cube right
cos could just have easily cancelled it
with the denominator?
Exactly, with the quotient rule you should always try to see if there are possible cancellations, so that calculations become easier
But of course if you don't simplify you still get the correct answer, but in a "heavier form" with higher exponents
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I am not convinced with any choice
i believe it's c
since the graph of the derivative is < 0 for x<0 and >0 for x>0 therefore the graph should have the trend
downward for x < 0 and upward for x > 0
the answer is indeed "c" but i dont get it , would u explain further
what do you know about a derivative?
don't worry about it
i see that the shown graph is 1/x
thus dy/dx = 1/x
then y = ln(x)
i'm not the best at explaining math things so just tell me if i confused u
first of all you can't decide f(x)=ln(x)
there are many other complicated functions that also have this derivative
now why is it c
a derivative shows the slope of the tangent of a function at x0
so if the derivative is positive then the original graph also have an upward trend
dy/dx
in a graph x also goes forward
so dx is always positive
now we have dy
that's great 
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,w 4000*pi/6
erm
how did you got this result?
Is it not (4000tan(30))
no
it is 4000 times the theta(in radians)
NOTE: Assuming that earth is spherical
Oh because we’re speaking in terms of (theta equals s/r)?
yeah
Oh ok. I thought it was talking about sin cos and tan
I guess it never defined it as a right triangle
distance between cities is generally surface distance
not the straight distant through the earth
(if my words are confusing then ignore it)
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let $x\pitchfork X$ be a relation that says if point $x$ lies on line $X$. prove that their exists a isomorphism between $S^3$ in which we define a point as a pair of antipodes, and a line as a circle through them, and define a point as a line, passing through 0, in $\mathbb{R}^3$ and a line as a plane in $\mathbb{R}^3$.
bigpufik
I mean clearly both spaces are proejctive, but I do not know what to do next
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Oof this looks nasty
First instinct wld be to write it in summation notation and see if smth pops out
Doesn't seem like it 😭😭
Maybe there's some sort of combinatorial argument?
Spit balling rn
Wait wait wait
Maybe u can use pascals identity here
I thought we can take like (1+x)^30 and (1-x) ^30
Write the binomial expansion
And multiply them
But i don't know what to do next
It is an IIT JEE PYQ
Yeesh
Bro can you try
I'm trying 😭😭
And dm me if you get the soln
🤭🤭
I have to go sleep
Aight gn gn
Evening for me
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How can i prove that for image taken of a sphere (from far away such that rays incdenct on camera sensor are essntially parallel) half of the sphere's surface area is visible?
Verbally, you can say that images are 2D pictures only, so whatever clicked in a camera will be a 2D plane with 2D shapes only, and a sphere looked from any angle is a circle in 2D space.
Experimentally, you can color half the surface of the circle and then.....
Idk if there are even more methods...
well sure but that doesn't prove that half the area is visible
if you are close to the sphere you will only see a portion of it
how so?
?
not quite
What's calc 2...?
Calculus 2?
its for a math paper
Ok....
In calc 2, u learn how to project a sphere
AKA describe by f(x,y,z)
onto a plane f(x,y)
im cool with calc
Then use that to prove this
Can't we use the fact that for finding a sphere's volume in 1 octant, we use integration in such a way forming a quarter of circle on the XY plane then?
Since all point on the sphere (not inside) say with coord x1,y1,z1 when project onto the plane call xp,yp,zp always share the same xp,yp,zp with another point on the sphere with coord x2,y2,z2 except the ring
Thus, half the sphere is visible
Pretty sure for sphere only
but for any closed surface a ray will intersect it at two points except for a curve where it is tangent
take a cone for example with its tips towards the camera
any ray will intersect two points except for the circle on the base
Correct, but not "Half" of the surface area are visble
For the cone
exactly
The majority is visible then
so thats why i dont think thats a valid proof
The only hidden part is the circle
Well
U then can prove the area?
i guess i could that yeah
U need 2 parts
From the ring
U can prove the ring diameter = sphere diameter
Then thats pretty much it
To be more careful, prove that ring divide the shape into 2 equal parts
Thats easy
inversion, reflection, etc
Or, easier
Prove that the plane contain the ring, is the reflection plane
Thats way easier
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how
surely $\sum_{n=1}^{\infty}|b_n|^t$ converges for all $t\geq 2$
Flip
if that's true, then maybe that helps?
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