#help-17
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Hey guys.
I'm having some difficulties starting a proof :
https://imgur.com/a/Gf4JDUO
My major difficulty is working with many conditionals like this.
Thanks in advance.
what's that C?
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Hi, this is applications of integration (with physics ish). does anyone mind helping?
.
<@&268886789983436800>
oh yeah theres only 3 questions left in this unit finally :D
then ill be done with the whole unit
and not just the "sub" unit
Are you familiar with W=mgh?
W = mass gravity height?
yes
somewhat
You need that
The general formula is $W=\int \vec{F}\cdot d\vec{s}$
SWR
But, for your application, this will reduce to $W=g\int h\cdot dm$
SWR
Hm, interesting
so how do i get the values necessary to compute this?
g, h, and dm
g, you should know
9.8
dm will be a (constant) function of h
You use the volume of a cylinder formula, along with the density of water
1000 kg/m^3
$dm=\rho \pi r^2 dh$
SWR
Where $\rho$ is density, and $\pi r^2 dh$ is the differential cylindrical volume
SWR
dh is dh
You use dh in $W=g\int h dm$
SWR
yes
Looks good
can you tell me if im right for this problem?
So first, i found the upper and lower limits, 0 to 8 which corresponds to the depth of the water
then, the gravity, 9.8 with the integral from 0 to 8
after, i found hdh, so
the area for a sphere is 4/3 pi r^2
h
the height is (16-x)
the radius is 8
so the ending of this would be
9.8(1000) (1000 is the density btw) times the integral of a upper limit 8 and lower limit 0 with an integrand of: 4/3pi (8^2) (16-x)
How are you getting 1000 for the density?
the weight is 50 (pounds)
it says per cubic feet though ._.
show me what you have in full
x? so
4?
oh wait
since its half of a sphere
should i just cut the volume in half?
i could do 4/6pi instead of 4/3
no
radius is a function of x, yes. But it is neither 4 nor x
Also, the 4pi/3 shouldn't be here at all
You're not doing volume of a sphere
You're integrating differential cylindrical volumes
what does that mean?
For a given x, what is the radius of the horizontal slice of the sphere?
Im not sure,
Use some trig and take some time to work it out
Here, your radius is CB
and CD is your x value
ok
Not trig, pythag
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video is uploading
Hey everyone, I'm a game developer and trying to complete my ocean waves which use 8 various sizes and speeds of Gerstner waves.
The problem should be solved with this concept (timestamped - about 20 seconds):
https://www.youtube.com/watch?v=kGEqaX4Y4bQ&t=802s
You can see in the video i uploaded, i have the goal of making the red part sit ontop of the ocean while not moving in x and y coordinates. The white cube shows the result of "testing" that x and y location. The Gerstner wave is deforming x, y as well as z of the ocean plane so this is expected.
math here:
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let me know if you need more info to answer, i've tried to say everything useful i could 
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how do i solve this?
please ping me
!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
ok
what have you tried
Try to eliminate the x term in 1 and 2
Then solve 3 and thing u got
From there ull get y and z
Then ull get x
how can you solve this?
if we take any values of x,y and z then you will get a,b and c respectively cause they are all different variables
im confused do we have to find the proof here?
how will it even have a proof
they are asking to solve in terms of a b c prolly
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how do i prove that the set of all rational numbers is countable
What's the definition of "countable"
Do you know?
no i know what it means, but not the "mathematical" definition
The mathematical definition is that, a set $A$ is infinitely countable iff there exists a bijective function $A \to \mbb{N}$
45
"infinitely countable"? arent these opposites?
No
Q is infinite
Thus infinitely countable
There are sets, like the real and complex numbers, that are "bigger" than the natural and rational numbers
And are called infinitely uncountable
okayyy..
I'm guessing this is your first time taking a discrete math class and you're learning about countability
I suggest reading about Cantor's diagonal argument if you're interested
In learning more
ive an exam tomorrow
But back to the question
You need to prove that there exists a bijective function mapping the rationals to the naturals
and youre gonna guide me how to do this, right?
Guide yes, but I won't spoon feed you the answer
And it won't be easy
im ready
a function that is injective and subjective both
Yes
*surjective
yeah yeah
One sec, I'll show you something
I want you to consider an infinite grid @smoky trench, this is something I wrote a paper on back in high school, and it's being graded right now, so I can't send it here but I can send it in dms
What we want to do is show that $\mbb{N} \cong \mbb{Q}^+$ first
45
and I'll explain why
$\cong$ denotes that they're of the same size, or that a bijection exists
45
Yes, but it's used in different fields differently
e.g. isomorphism in Group Theory
Anyway
Here we will use it as a sign that two sets are of the same size
ok..
so what you want to do now is
consider the set $\mbb{Q} = \left{\frac{p}{q} : p \in \mbb{Z}, q \in \mbb{N}, \gcd(p, q) = 1\left}$
45
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
Are you familiar with gcd?
Actually, we can even do without that
consider the set $\mbb{Q} = \left{\frac{p}{q} : p \in \mbb{Z}, q \in \mbb{N}\right}$
whats gcd
Don't worry about it
45
q is not equal to 0
Yes, that's why q is in N
ok ok
I'm just thinking which proof I want to use here, since there's several
simples+easiest
do you know what you're allowed to use? Tool-wise
of my exam
yeah
what are you allowed to use
I have a neat proof for this but it's a bit technical
it's short though
so this is the syllabus
and I don't know if you're allowed to take for granted that the countable union of countable sets is countable
I think you're jumping ahead. Where does it suggest that you'll be asked to show that a set is countable?
This sounds like an introductory course in discrete math
its a pyq
Okay
2nd semester
?
If you state this, do you think they'll ask for a proof?
Let's assume that the (countable) union of two countable sets is countable. We'll take this for granted. Then we can define a function $\phi : \mbb{Q} \to \mbb{Z} \times \mbb{N}$, where $\times$ denotes Cartesian product. Define this function $\phi$ to be such that for all $r = \frac{p}{q} \in \mbb{Q}$; $\phi\left(\frac{p}{q}\right) = (p, q)$ where $(p, q)$ is a tuple with $p \in \mbb{Z}$ and $q \in \mbb{N}$. We can prove that this is an injection trivially. We use the following result: Let $X$ and $Y$ be sets and $f : X \to Y$ an injection. Then $X$ is also countable. This shows that $\mbb{Q}$ is countable.
And p and q have no common factors^^
Otherwise we don't have an injection
45
ok
Just memorize this tbh
You need to know two results
- Countable union of countable sets is countable
- If f : X \to Y is an injection and Y is countable, then X is countable
There's also a more "handwavy" way of showing this by constructing an infinite grid and showing that there's a direct bijection between N and Q^+, which is then extended to Q by showing that there's a bijection between Q^+ and Q^-
na this sounds hard
i'll use this
The only issue is
you're using two results not having proved them
Proofs can be found online tho
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Solution to the implicit derivative of x^2 + y^3 = cosx + lny. One is mine, and the other is from my teacher's material. Is one better than the other? Or are both equally valid final answers?
Acording to mathway, both are equal to the other, mathematically
Or at least that is what i interpreted from that lol
you just multiply the top and bottom of the left one by y and you get the right
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Please let me know how to solve this. I somehow got 67 but the correct answer was 8. Don't understand at all how
what is $\frac{124}{2}$
tobi
okay do you know what I mean with my question
what is it
calculator?
what?
did you use a calculator for it?
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How can I solve this integral?
,rotate cw
My first thought is factoring the denominator
What class is this for?
12th
I didn't understand
Are you able to photograph your solution and send it?
I‘m trying to know what techniques of integration you know, and therefore I can use with you
Ah, I think I see it now
So you have $\int\frac{1-\ln x}{(x+\ln x)^2}\dd x$ right?
ℑμΤ𝛄𝛗θ
I did this step, but after that I was not able to complete the solution
,rotate ccw
Right
So this form
Don‘t you think it looks like the quotient rule? $\dv{x} \frac{f}{g} = \frac{f^\prime g - fg^\prime}{g^2}$
ℑμΤ𝛄𝛗θ
So integrate both sides, you get f/g is integral of the big fraction, and you can compare the terms to find f and g
Yes, but I did not find anything suitable for the specialized derivative
Well, g is obviously $x+\ln x$, and $f\cdot g^\prime = \ln x$
ℑμΤ𝛄𝛗θ
So you can find f
can u speak arabic?
I cannot
Because I started not understanding
I can ask if another helper speaks arabic in the helper channel if you want
Yes please
I asked. Can‘t guarantee anyone will respond, but fingers crossed 🤞
Arbitrary functions
Have you learned the quotient rule?
yes
but I did not find anything suitable for the specialized derivative
Yeah ok
I don't think it's obvious
But you have a differential equation for f
No cause you might have cancellation
In the numerator
I gtg shower but I think the ODE should be pretty straightforward..
@olive jungle Has your question been resolved?
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I don't get the "Whole work will be done in (3 × 5) = 15 days" part
Like
Why did 1/5 became 5 and where did the 3 came from?
how much work does A do in 3 days?
1/20+1/20+1/20+1/30+1/60
that equals to 12/60
or better said
1/5th
to do all 5 of the 5ths
A needs 3x5
Wait how did you konw that there are "five 5ths"
ohhhhhh
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no problem
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Can anyone help me at b)? I already solved a) but I am stuck
I feel like I dont get the task completely. Would I show that the long definition in b) with the "if and only if" implies, that the eigenvalues of BB^T are non-negative? Or how would you approach the question
<@&286206848099549185>
observe that BB^T is positive semidefinite
this helps out with one direction of the implication
if A = BB^T and BB^T is PSD, then A is PSD
the other direction of the implication to show the existence of B is definitely a lot trickier
Wait
Am I trying to prove the following two statements? \
- If $A$ is symmetric and positive semi-definite then there exists a $B\in\mathbb{R}^{n\times n}$ such that $A=BB^T$ \
- If there exists $B\in\mathbb{R}^{n\times n}$ such that $A=BB^T$ then $A$ is symmetric and positive semi-definite.
Mathmatix
And you basically showed the 2) direction correct?
well kind of
i showed that if A = BB^T then A is PSD
since BB^T is PSD
to show that A is symmetric is also simple enough, just show that BB^T is symmetric
a matrix is symmetric if it equals its own transpose
so what's (BB^T)^T?
If BB^T is symmetric then it follows BB^T = (BB^T)^T and so on
well yeah so that's your proof for 2
The only trouble I have right now for 2) is, if we are proving the direction 2) why can we use the fact that BB^T is symmetric? Because arent we trying to show that in the sentence:
If there exists $B\in\mathbb{R}^{n\times n}$ such that $A=BB^T$ then $A$ is symmetric and positive semi-definite.
Mathmatix
A is symmetric? For me its sounds a bit like we use the fact we want to prove as argument
you are using that
you want to conclude that A is symmetric and PSD
BB^T is symmetric
since A = BB^T, you can conclude A is symmetric
BB^T is PSD, since A = BB^T you can conlude A is PSD
this isn't circular reasoning
But our premise is "there exists a B such that A=BB^T". The conclusion is "A is symmetric and psd". But in the premise we dont know if BB^T is symmetric and psd? We just know that A is the product of B and B^T or not?
but you can prove that BB^T is symmetric and psd
And how would you proof that its psd and symmetric without using the fact that A is psd and symmetric?
and this is the proof for BB^T being PSD
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Okay somethings been bugging me
so this is a true statement i think
but
this
e^ix/2ix integrated from 0 to inf is undefined
sure
because Ei(0i) is undefined
just shows that you can't decompose it that way and still integrate
another simpler example,
$$\int_0^\infty 0,dx = 0$$
Bungo
but $0 = x - x$
Bungo
and $\int_0^\infty x ,dx - \int_0^\infty x,dx$ has the same problem
Bungo
i see
"integral of sum equals sum of integrals" is only true if the integrals are all convergent and finite
got it
@prisma stag Has your question been resolved?
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What does f:R—->R mean
you know how functions have domains and codomains?
Ues
the thing to the left of the arrow is the domain, the thing to the right is the codomain
Absolutely
so that's read as a function from R to R, or a function that maps real numbers to real numbers
So a function like that had domain R and codomain R
yeah
Mhm so
F:R(+)—->R means that the domain is positive real numbers and the codomain is all real numbers
And f:[-1,5]—->R means the domain is the interval and the codomain is R
(Just want to clarify)
yes
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anybody good at drawing those word problem vector diagrams with planes and ships and shit 😭 I cannot draw a single one properly
this is what I draw but idk how to figure out the rest/enough angles inside the triangle to solve the problem
@blazing sail Has your question been resolved?
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How could I solve for x here? $2xe^{x^2}=0$
dingypine
gotta find the critical points and this is my derivative
devidie both sides by 2x
I see
okay
first things first, e^{x^2} is well defined!
it's a function
the other thing is that, I would definitely not recommend dividing both sides by 2x
yeah i didnt know what else to do lol
to see why, suppose I have x(x + 2) = 0, and I divide both sides by x
then I am left with x + 2 = 0, so x = -2
which is correct, but clearly x = 0 solves our original equation too!
so we've deleted a solution
use the zero product law
whats that
if ab = 0, then either a = 0 or b = 0
just replace "a" with "2x", and "b" with "e^(x^2)" here
(2x)(e^(x^2)) = 0
so i see one of the solutions is just 0, for 2x
e^(x^2)=0, take ln of both sides and thats undefined tho
so can i just ignore htat one?
correct
that's correct, but we don't need to invoke logarithms to know that
e^x is always positive, not matter what x is
ohh
in general, e^(any real number) is positive
okay i see
x^2 is certainly a real number if x is
i see

.close
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why do i need to use lhoptials rule here
im not really sure why this is considered indeterminate
i know its indeterminate when its 0/0 or something, but not like this
you don't have to but if you do, it makes the continutiy part really easy
else do the lhs, then rhs and then fx
$0 \cdot \infty$ is indeterminate
cloud
it takes little time to solve lhs, rhs, fx
but if you do it with lhopital then it is really fast
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The answer is 1%, but I got 0.1/1.57 which is around 6%
@mellow wyvern Has your question been resolved?
0.01
between 1.565 and 1.575 difference of 0.01
you;re not given a number like 0.4 but a number like 0.32
isn't the uncertainty like 1.57+-0.1m^2
oh
oh ok that makes sense
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How can I complete this integration?
It's not possible
It works try it
ok
Here you mean by assumption؟
Wait, I want to think about it
I think you need to lower cos^5 first
Haha
i love to see this integral and will probably give you one of the best methods to solve odd powers of tan and cot ,
Only three steps doesnt matter how long the problem is
I hope
Do this
So cotx dx = -z dz
Now cosecx = e^z
Or cosec²x = e^2z
or 1 +cot²x = e^2z
You mean to make an assumption?
Or cot²x = e^2z - 1
i mean substitution
yes
So our integral will become int (e^2z - 1)² and if you know binomial expansion
Then expand it next step
And write answer on the last one
As the easiest integration is of e^ax giving e^ax/a
@olive jungle Got it ?
thank u
close.
Question, is this method possible for all odd exponents in cot and tan? @orchid wren
Ofc
Sorry for bothering you
Np bro
close.
@olive jungle Has your question been resolved?
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!status
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
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7. None of the above
Square both sides
done. now
You’re done?
x^2 +y^2 -2xy <= |x|^2 + |y|^2 + 2|x||y|
is this it?
just language now, right? that absolute value of x is greater than x and blah blah blah?
might be useful to notice that |x|^2 and x^2 are the same thing, you could simplify this inequality
You can simply remove the x^2 and y^2 from both sides
okay
-2xy <= 2|x||y|
might as well divide by 2
-xy <= |x||y|
now it's just a matter of casework for the possible signs of x and y
when x and y are both nonnegative, |x| = x and |y| = y
repeat this for x negative and y positive, x and y negative, and y positive and x negative
Sure, but I suggest you open a new channel
alsi
also
i just realized
you don't have to do the casework
it's much simpler
|x| is either +/- x
so divide both sides of this by |x|
then x / |x| is either 1 or -1
same thing when you divide both sides by |y|
so the right side becomes 1
and the left side becomes -1 * +/- 1 * +/- 1
which is always either 1 or -1
so your inequality just becomes 1 >= +/- 1
which is always true
yeah this is much shorter
appreciate it!
imma open a new channel now.
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how did i create this venn diagram.
Let's say that the number of people in the intersection is x
Then what kind of equation do you think we can create
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prove that every equation of the nth degree has n roots and no more
correct
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hi,guys I'm new to here.😁
I heard from other students, that there is lot of masters that will help with my question.can you guys help? thank you so much!!!😆
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part 2
i tried u=(1-t^2)^(n+2) and dv=1 for F_{n+1}(x)
$F_{n+1}(x)=\int_0^x\frac{\dd t}{(1+t^2)^{n+1}}=\frac{t}{(1+t^2)^{n+1}}|_0^x-\int_0^x-(n+1)\frac{2t}{(t^2+1)^{n+2}}\dd t=\frac{t}{(1+t^2)^{n+1}}|_0^x+(n+1)\int_0^x\frac{2t}{(t^2+1)^{n+2}}\dd t$
pirateking0723
oh wait i will continue maybe that will lead to something
$=\frac{x}{(1+x^2)^{n+1}}+(n+1)\frac{(x^2+1)^{-n-1}}{-n-1}-(n+1)\frac{1}{-n-1}=\frac{x-1}{(1+x^2)^{n+1}}+1=(x-1)\frac{\dd F_n(x)}{\dd x}+1$
pirateking0723
yes
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✅
but this leads to some problems
for part 3
$I_1=\lim_{x\to\infty}F_1(x)=\lim_{x\to\infty}(x-1)(\frac{\dd F_0(x)}{\dd x}+1)=\lim_{x\to\infty}\frac{x-1}{x^2+1}+1=1$
pirateking0723
$I_0=\frac{\pi}{2}$ so using 3)a) $I_1=\frac{2(0)+1}{2(0+1)}\frac{\pi}{2}=\frac{\pi}{4}\neq 1$
pirateking0723
wait i have a mistake here the integral that i used is F_n(x)
not F_{n+1}(x)
all of this is wrong
i messed up
$F_n(x)=\int_0^x\frac{\dd t}{(t^2+1)^{n+1}}=\frac{t}{(t^2+1)^{n+1}}-\int_0^x-(n+1)\frac{2t^2}{(t^2+1)^{n+2}}\dd t=\frac{t}{(t^2+1)^{n+1}}+(n+1)\int_0^x\frac{2t^2}{(t^2+1)^{n+2}}\dd t$
pirateking0723
is this correct
if yes then what to do from here
i dont see anything that can be done from here
<@&286206848099549185>
<@&286206848099549185>
@onyx marsh Has your question been resolved?
<@&286206848099549185>
anyone willing to help I am not finding a way to solve part 2
<@&286206848099549185>
ive just taken a course on this. my best suggestion is that you should try subbing, or try the A B C method. not sure if it the method A B C is its actual name (ps i should probably remove my helper tag as i am now struggling with the same thing you are)
by ABC do you mean decomposing a rational function into a sum of rational functions??
yes
<@&286206848099549185>
exactly thats what i thought about
thats true
and the terms that i am summing will be products of many factors too
so i dont think thats the way to go
<@&286206848099549185>
t^2 = (t^2 + 1) - 1
for this ^
but i will have the dF_n/dx in the expression too right
yh
also here for the first term which is not the integral t should be replaced with x
but i would just leave it explicit rather than writing as dF/dx
yh
so something like $F_n(x)=\frac{x}{(x^2+1)^{n+1}}+(n+1)F_n-2F_{n+1}\implies F_{n+1}=nF_n+\frac{x}{(x^2+1)^{n+1}}$?
why is that
because in the next part youre going to take the limit as x -> infinity
this is not quite right
your coefficients infront of Fn and F(n+1) are wrong
pirateking0723
no
right
this is right
but the coef of F(n+1) should be the same
ohh yes you are right
but with different signs
the coeff of F_{n+1} is -2(n+1)
the coeff of F_n is 2(n+1)
yes
$F_n(x)=\frac{x}{(x^2+1)^{n+1}}+2(n+1)F_n-2(n+1)F_{n+1}\implies F_{n+1}=\frac{2n+1}{2n+2}F_n+\frac{x}{(2n+2)(x^2+1)^{n+1}}$
yh
pirateking0723
now as x goes to inf F_{n+1} goes to kF_n where k is the above coeff
which proves 3a
yes
but with the lim for kF_n too
is there another way to figure part 2 without this trick
i mean probably
but that is the definitely the intended and easiest way i would say
yes that was neat
also a very common trick (adding 0 i.e. adding and subtracting something in order to allow your to rewrite the expression in a more favourable way)
you also see this with multiplication
multiplying by 1, for example when you rationalise the denominator
yes it didnt come to my mind this time although ive seen it alot before
$$\frac{1}{\sqrt{3} + 1} = \frac{1}{\sqrt{3} + 1} \cdot \frac{\sqrt{3} - 1}{\sqrt{3} - 1} = \dots$$
is the same principle
Acman
yes but with multiplication instead of addition
yeah it can be tricky to spot sometimes
yeah
for 3b $I_0$ clearly satisfies what we are trying to prove, now suppose that $I_k=\frac{(2k)!}{4^k(k!)^2}$ where $k\in\mathbb{N}$ then using 3a $I_{k+1}=\frac{2k+1}{2(k+1)}I_k=\frac{(2k+1)(2k)!\pi}{4(k+1)4^k(k!)^2}=\frac{(2k+2)!}{4(k+1)^24^k(k!)^2}\frac{\pi}{2}=\frac{(2(k+1))!}{4^{k+1}((k+1)!)^2}\frac{\pi}{2}$
pirateking0723
and this proves it
now i still have 3c
let me think about it for a sec
ok i figured it out
nice
ill leave a small hint ||its easier to use the result from 3a than 3b||
i am trying to reach something like (2n)!<2^n(n!)
i didnt see the hint yet and i will try more before seeing it
do you mean not to have the square on the RHS ?
yes
is this wrong
yes
(2n)! = (2n) (2n-2) (2n-4) ... (4) (2) (2n-1) (2n-3) ... (3) (1) = 2(n) 2(n-1) 2(n-2) ... 2(2) 2(1) (2n-1) (2n-3) ... (3) (1) = 2^n n! (2n-1) (2n-3) ... (3) (1)
so (2n)! is much bigger than 2^n n!
oh yes
i can rewrite (2n-1)(2n-3)...(3)(1) as (2n-1)(2(n-1)-1)(2(n-2)-1)...(3)(1)=2^n(n!)-c<2^n(n!)
so (2n)!<4^n(n!)^2
and $\frac{(2n)!}{4^n(n!)^2}>0$ so $\lim_{n\to\infty}0<\lim_{n\to\infty}\frac{(2n)!}{4^n(n!)^2}<\lim_{n\to\infty}1\implies 0<\lim_{n\to\infty}\frac{(2n)!}{4^n(n!)^2}\frac{\pi}{2}<\frac{\pi}{2}$ so $I_n$ converges
pirateking0723
$\lim_{n\to\infty}I_{n+1}=\lim_{n\to\infty}I_n$ but that doesnt prove convergence
pirateking0723
i was going more for I(n+1) < I(n) and I(n) > 0 for all n
is this correct
hm im not convinced tbh
k
how does that help
what didnt convince you
maybe i can convince you unless i did something wrong
what have you actually done on convergence
like what have you been taught to do for questions where you need to justify the convergence
if you have done monotone convergence theorem then that is suffficient to imply convergence
to show that as n goes to inf I_n goes to a constant ?
no
we didnt do stuff like this just the def of convergence
yea mb
ive studied these alone but i didnt use them in a very long time so i am starting to forget them
but even if i still know them quite well i cant use them in the school rn
because its not something that we have covered in class
yeah thats the issue with questions like this, you dont actually have the machinery to do what its asking
so you have to be very hand wavey
and here this is probably insufficient i mean maybe the sequence isnt approaching a number
although is it bounded
here's how i would do it then
just like the lim of sinx as x goes to inf for example
although sinx is bounded but it doesnt converge
so this doesnt prove anything probably
yeah
you havent really shown that it converges
youve said if it converges this is the range it would converge in
so how would you do it
i think you just have to write something vague like '(2n+1)/(2(n+1)) = (1 - 1/(2(n+1)) and so the ratio of successive term is getting closer and closer to 1, meaning the change in size of I(n) gets slower as n increases' or smth like this
i dont think there is a satisfying way to answer that question given the content youre allowed to use
hmm but also that doesnt prove it because it depends on the convergence of I_n in the first place
so we are letting -I_n/(2n+1) go to 0 as n goes to inf although we dont know anything about I_n as n goes to inf
well we know that 0 < I(n) < pi/2
so it is true that I(n)/(2(n+1)) -> 0
it just also isnt a real proof of convergence
but neither is that what theyre asking for or what is achievable
they just want to you to say something along these lines to justify it
ohh ok
i think best to ask your teacher about it, they will have a much clearer idea on what is an expected response to that type of question
yes you are right about this
tysm for your help and sorry if i wasted your time
have a nice day/night
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yw and not at all :)
you too
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!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.
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7. None of the above
Between 1 and 2 ig
essentially $\frac{4 \pi r^3}{3} \rho=k$
ƒ(Why am. I here)=I don't know
makes sense ?
This was the only question for which i had to see solution and i still dont get it
differentiate this please
no, differentiate the LHS
wait
$\frac{dr}{dt}$
ƒ(Why am. I here)=I don't know
Begun and got stuck
as you differentating wrt time
Ohh
What to do of cube
so 4πr^2 dr/dt
let me write the entire thing out in TeX
wait a minute
$\frac{4 \pi r^2 dr\rho}{dt}+\frac{4 \pi r^3 d(\rho)}{3dt}$
ƒ(Why am. I here)=I don't know
But why is it not dr^3/dt
I differntiated that using the chain rule
What method is this ig my teacher didnt teach me
do you know the chain rule
can you do it from here?
no
i only knew i have to differentiate
dunno further
ok, should I help ?
$4\pi r^2\rho\left(\frac{dr}{dt}\right)+\frac{4\pi r^3}{3}\left(\frac{d\left(\rho\right)}{dt}\right)=0$
ƒ(Why am. I here)=I don't know
yes
$4\pi r^2\rho\left(\frac{dr}{dt}\right)=-\frac{4\pi r^3}{3}\left(\frac{d\left(\rho\right)}{dt}\right)$
ƒ(Why am. I here)=I don't know
yes?
$\left(\frac{dr}{dt}\right)=-\frac{r}{3}\left(\frac{d\left(\rho\right)}{\rho\ dt}\right)$
ƒ(Why am. I here)=I don't know
makes sense until here?
yes
now what?
now integrate or wha
velocity
and what is constant ?
f/a
wait
but will have to differentiate accereleration
$\frac{d\left(\rho\right)}{\rho\ dt}=k\ ;\ k\in\mathbb{R}$
ƒ(Why am. I here)=I don't know
yes?
yes
😭 im clueless
do you follow until here?
yes
and this?
if so, simplify this for me
how
i only know basic differentiation
this is very new to me
ty for helping ill ask my teacher
you wont be able to on text
okay
cause this is very new to me
I think you've almost got it
what is velocity in terms of derivatives
dv/dt, right?
I mean dr/dt
no
dx/dt
x is r?
yes
damn
so can you do it now?
i do get it but im def having problem while differentiating
everytime i get stuck in physics its cause of complicated calculation 😭
what is "inner" in our problem
here, nothing, but I thought you may want to brush up on derivatives
I could be wrong though, I'm pretty bad at maths
But worse at other subjects 
how does chain rule apply here then
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,w that is the solution of ×^5-x^4+1=0
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Xpower5-Xpower4+1
,w x^5 - x^4 + 1
Thanks!
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is this congruent
or no
would it be sas ?
because it can't be HL
because we don't know the hypotenuse side length
and for HL you need to know that
so it has to be congruent through sas right?
ok
thanks
🙂
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Brain can not compute.
f_y = 3(x) - 3x
That's what I got from plugging equation 5 into 4.
Where did they get y^4 = y?
i am pretty sure that when you substitute the equation 5 in 4 they get y^4 but im pretty dumb
yeah but how?
x = y^2
sub that into 3y^2 = 3x
you get 3x = 3x


