#help-27

1 messages · Page 426 of 1

lusty sapphire
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comes with time

sturdy yew
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but B has to be real

lusty sapphire
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I may not even be right

sturdy yew
sturdy yew
lusty sapphire
# sturdy yew but B has to be real

This is why I thought n must be even. You can have imaginary numbers properties with even-sized matrices, like $A^2=-I$ is possible for $n=2$

woven radishBOT
sturdy yew
gritty terrace
#

ok i have an idea

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can i say it?

sturdy yew
#

yess

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but pls tell me its a high school level idea not a pg level one

gritty terrace
#

suppose $\lambda$ is an eigenvalue of $B$. then $\lambda^2 + \lambda$ is an eigenvalue of $B^2 + B$, which means $\lambda^2 + \lambda$ is an eigenvalue of $B$

woven radishBOT
#

Pseudo (Cat theory #1 Fan)

sturdy yew
#

yes yes

gritty terrace
#

in other words, $\lambda$ being an eigenvalue means $\lambda^2 + \lambda$ is also an eigenvalue

woven radishBOT
#

Pseudo (Cat theory #1 Fan)

sturdy yew
#

,.

gritty terrace
#

this is potentially bad becuase you're only allowed finitely many eigenvalues

lusty sapphire
sturdy yew
gritty terrace
#

like if 1 is an eigenvalue so is 2, and then so is 4 + 2 = 6, and then so is 36 + 6 = 42, ...

sturdy yew
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so we need cyclicity

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basically

gritty terrace
#

yeah

lusty sapphire
sturdy yew
gritty terrace
#

yeah i think you can use this to show that $B$ cannot have any real eigenvalues

woven radishBOT
#

Pseudo (Cat theory #1 Fan)

gritty terrace
#

i think this is correct

lusty sapphire
#

I suppose you can find cyclic eigenvalues by solving $a+b=\lambda$ and $a-b=\lambda^2+\lambda$?

woven radishBOT
lusty sapphire
#

No, that doesn't work

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I have it backwards

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hmmm....

sturdy yew
#

wait eigenvalues of B have to purely imaginary right?

stone stump
#

the obvious set of equations is x^2+x=y, y^2+y=z, z^2+z=t, t^2+t=w, ... until a^2+a=x. for some number of variables

lusty sapphire
woven radishBOT
lusty sapphire
#

for $n=2$, you can do just $\lambda_1^2+\lambda_1=\lambda_2$ and $\lambda_2^2+\lambda_2=\lambda_1$

woven radishBOT
sturdy yew
lusty sapphire
#

I think the right idea here is considering the eigenvalues need to be cyclic. Maybe the next question is to ask yourself is what happens to the cyclicity if n is odd

gritty terrace
#

well the thing is that if $n$ is odd

woven radishBOT
#

Pseudo (Cat theory #1 Fan)

gritty terrace
#

||B has to have at least one real eigenvalue||

stone stump
#

you should try to show that for n=2 you cannot have real solutions. that approach immediately generalizes

sturdy yew
gritty terrace
spiral moss
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which works in this example

stone stump
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B is invertible

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*nonzero real eigenvalue

spiral moss
stone stump
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given in the problem

spiral moss
#

oh i missed it

sturdy yew
stone stump
#

x^2+x=y, y^2+y=x. show that this has no nonzero real solution

stone stump
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preferably not by bruteforce computing and instead by something that might generalize

spiral moss
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||i think that using trace helps with showing no real numbers except 0 can be eigenvalues||

stone stump
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oh yeah thats also nice

sturdy yew
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using trace we get that tr(B^2) = 0

spiral moss
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trB is sum of its eigenvalues, right?

sturdy yew
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how 😭

stone stump
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diagonalize

sturdy yew
# stone stump diagonalize

yea when u diagonalize, the trace of the diagonal matrix is equal to the sum of the eigenvalues of the diagonal matrix right

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and since say D = PBP^-1

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D and B are similar

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but wait

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that still doesnt say anytg abt trB and the eigenvalues of B

vast zenith
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the trace is invariant! super nice property

sturdy yew
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so are the eigenvalues right?

vast zenith
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hmm

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what do you mean?

sturdy yew
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eigenvalues of D and B are equal

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i mean

vast zenith
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precisely

worthy raft
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Trace has the nice property that Tr(AB) = Tr(BA)

sturdy yew
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ok so now tr(B) is equal to the sum of its eigenvalues

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but this feels like its true for any matrix

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also how does it help in showing thhat B cannot have real eigenvalues?

vast zenith
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it is true for any matrix that is diagonalizable

worthy raft
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So when doing PBP^{-1} you get that Tr(PBP^-1) = Tr(BP^-1 P) = Tr(B)

vast zenith
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or actually for any matrix I think

stone stump
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well jordan form is enough

sturdy yew
stone stump
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so as long as you are working over a field or integral domain you are good

vast zenith
#

yes true

vast zenith
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symmetric, orthogonal

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but these are special cases

sturdy yew
vast zenith
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in general you have to find a full basis of eigenvectors

sturdy yew
#

it feels like we've digressed very far

sturdy yew
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riight

stone stump
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yes

vast zenith
#

this is an interesting problem

sturdy yew
#

for n = 2 the eigenvalues are imaginary

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and thats completely fine

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for n=3 if i show that there has to be atleast one real eigenvalue then this caase is not possible

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as then the entire set wud diverge?

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right?

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i mean

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if we have a real eigenvalue then the number of eigenvalues wud be infinite

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as if x is an eigenvalue then x^2 + x shud also be an eigenvalue

vast zenith
#

they must both have the same set of Eigenvalues,

sturdy yew
#

yess

devout snowBOT
#

@sturdy yew Has your question been resolved?

sturdy yew
#

<@&286206848099549185>

tribal leaf
#

Hi

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What's the question

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instead of typing csn you send like an image

frosty crescent
tribal leaf
#

yeah

sturdy yew
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so lemme explain

tribal leaf
#

I mean

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I read your explanation

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and checked the pin

sturdy yew
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ok'

sturdy yew
tribal leaf
#

okay

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soo

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P^{-1}(B^2 + B)P = B

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this is the question

sturdy yew
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ok

tribal leaf
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and you need to prove n can be written as any positive integer

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Correct?

sturdy yew
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i need to show that n has to be even

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it cannot be odd

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B is real and invertible

tribal leaf
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Ohh okay

tribal leaf
sturdy yew
#

mb

tribal leaf
#

without this I was getting n is both even and odd

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so are you familiar with eigen values?

sturdy yew
#

yes

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kinda

tribal leaf
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B is real and invertible
eigenvalues of B are real or complex conjugate pairs

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so

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We can say

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Lamda is an eigen value of b

sturdy yew
#

why complex conjugate pairs

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?

tribal leaf
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B is a real matrix

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so

sturdy yew
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ohhh because B is real and its characteristic eqn will have only real coeff

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yesyes

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mb

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oof

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wtf

tribal leaf
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Okayy

sturdy yew
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i think i got it

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thanks

tribal leaf
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okayy

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lmao good job anyways

sturdy yew
#

thanks @stone stump n @tribal leaf

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lmao

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finally

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😭

#

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stark mist
#

Hello, I have a question regarding my college algebra assignment. I tried to use the remainder zero formula or what it was and got these. I asked my professor about it and he said that I need to use synthetic division to find the remainders of zero, but after doing them in my head I can’t find any values that equal zero, so I just want to check on if I’m right on this

wise trout
stark mist
verbal wharf
#

you are correct yes

stark mist
#

But thank you for clarifying!

verbal wharf
#

synthetic division is good to test but if they don't produce 0 remainder -> no rational roots

stark mist
#

Ah I see, thank you!

winter patrol
#

note that rational root theorem by itself only identifies candidates.
IF there are rational zeroes, it will be within the list generated

stark mist
#

So do I just close this now

winter patrol
#

you can close whenever you want

topaz axle
#

you don't have to, it'll close eventually

stark mist
#

Ah I see

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Thank you for the help!

winter patrol
#

ideally you'd close when youre certain you're done

verbal wharf
#

welcome and gl with the rest !!

winter patrol
#

And don't require more assistance with the question

stark mist
#

Alright, thank you!

#

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gray prawn
#

Helo

If i assume that every infinite sequence doesn't have any infinite subsequence which is monotonic

What are the consequences of it

(I am trying to prove that every infinite sequence has an infinite monotonic subsequence so I am trying to prove it through contradiction

I somehow constructed that i can find 3 terms following defination of monotone given that sequence is non monotonic
( Because if sequence is monotonic it is trivial))

bronze void
#

<@&268886789983436800>

uncut crow
#

not (every object has property X) means there exists an object that doesn’t have property X

gray prawn
#

I want to prove that every infinite sequence has a infinite monotonic subsequence

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For the sake of contradiction
I assumed that for any arbitrary infinite seq there is NOT a single infinite subsequence which is monotonic

uncut crow
#

the negation of that would be
there exists a sequence that has no monotonic subsequence

gray prawn
uncut crow
#

hm both i guess

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you can lay out rules and make it procedural

gray prawn
uncut crow
#

or just practice and the ‘rules’ will be natural and make sense

uncut crow
#

instead of doing this you could try to construct a monotone subsequence of an arbitrary sequence

devout snowBOT
#

@gray prawn Has your question been resolved?

devout snowBOT
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noble mango
#

Are there any errors to my answer to part b?

noble mango
#

I'm sorry if the handwriting is a little hard to understand, i was writing fast.

trail eagle
#

Seems like a fitting counter-example

noble mango
trail eagle
#

Keep this one

noble mango
#

Alright, why did they use (x+5)^2 here for?

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I really struggle with these types of prove questions, because I don't even know where to begin when writing my answer.

trail eagle
#

The way they wrote the proof I think makes it clear what they want to show, but I don't think it's a very natural thing you'd think about right away when seeing the problem.
I think the easiest way to go about it would be to expand (x+6)^2 as x^2 + 12x + 36 and try to separate 2x + 11 from it, so that you get x^2 + 10x + 25 + 2x + 11.
Then you'd spot that the first three terms are just (x+5)^2 and go from there.

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Another way would be to show the equivalent statement that (x+6)^2 - 2x - 11 >= 0 for all x, which would probably even be more straightforward by expanding.

#

Again I think the solution you're given is kind of working backwards with the solution in mind already

noble mango
#

this is gonna sound weird but i'm not entirely sure what the question is asking

#

if (x+5)^2>0 hasn't that already proved that x is greater than 0?

trail eagle
#

Well (x+5)^2 >= 0 is true for any x. Anything squared is >= 0.

noble mango
#

yeah thats true

trail eagle
#

In general, one method of showing that a >= b is to show that a = b + (something)^2. This is what they're using in the proof

noble mango
trail eagle
#

Yes

noble mango
# trail eagle Yes

I see, do you have time for one more question? I don't wanna be a bother.

trail eagle
#

Go on

noble mango
#

where tf did a^2 come from in the answer sheet?

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They didn't ask to square anything or imply to square anything and the original equation didn't have any square or square roots in it

trail eagle
#

They multiplied both sides of the inequality by a

noble mango
#

ohhh

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to get rid of the fraction?

trail eagle
#

Yeah

noble mango
trail eagle
#

Yes

noble mango
#

Geninually thank you so much dude @trail eagle

#

You're a life saver

#

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bitter dock
#

This might not be a math question, but I need help searching for an article. The article I search for is "Jagers (1975): Branching Processes with Biological Applications". I somehow only found reviews to that article but not the article itself.
Additional: Do you have any general advice on finding articles like that?

vital edge
#

Are you sure about the author

#

The only article I can find with this name is Wu (2010)

bitter dock
#

I'm not, I just found it as reference in my professor's notes for possible bachelor thesis and wanted to check it

vital edge
#

The article you're looking for is simply titled Branching Processes

#

Or at least that's what it looks like

#

<@&268886789983436800> ??

bitter dock
vital edge
#

I know this says 2005 but

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This is the link I got from an article linking to the 1975 version

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Not sure what's up with that

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Maybe this is an updated version of the old article

bitter dock
#

Thank you very much

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unfortunately my institiution does not grant access to it

vital edge
#

The emote I'm about to send has nothing to do with this channel

#

🏴‍☠️

#

I just really like this emote

bitter dock
#

.close

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summer harbor
#

i genuinely have no idea how to evaluate this

mystic scarab
#

Change of variable

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(aka substitution)

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I mean, it's not necessary but I believe it helps you see what to do next

summer harbor
#

u = particular equation in the integral

last parrot
#

Is this just finding the limits

summer harbor
#

yes

last parrot
#

Can you use algebraic manipulation, no?

mystic scarab
summer harbor
#

i assume,

mystic scarab
#

Yep

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So now you have $\lim_{x\to ?}\ \frac{x}{\vert x \vert}$

woven radishBOT
#

Alberto Z.

summer harbor
#

x approaches -2

mystic scarab
#

Careul 😉

summer harbor
#

right

mystic scarab
#

t → -2, but x = t + 2

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So x approaches ...

summer harbor
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0

mystic scarab
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Awesome

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Therefore, the limit has become $\lim_{x\to 0}\ \frac{x}{\vert x \vert}$

woven radishBOT
#

Alberto Z.

mystic scarab
#

Can you see what we could do next?

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In particular, we have an abs value which means we will have to study two cases, do you agree?

summer harbor
#

omg slr, i had to eat a bit

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yes

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cause abs val a negative and positive results in positive

summer harbor
#

but how do we do that

thick lotus
thick lotus
summer harbor
#

i get why but i dont know how if that makes sense

mystic scarab
#

Well, the two cases will be right- and left side limits

thick lotus
#

evaluate the left and right limit as x-> 0^- and x->0^+

summer harbor
#

but wouldnt that be 0/0 ?

thick lotus
#

-# off to you alberto

mystic scarab
#

,tex .abs def

woven radishBOT
#

Alberto Z.

summer harbor
#

so lim x -> 0- = -x, lim x -> 0+ = x

mystic scarab
#

Somehow yeah

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$$\lim_{x\to 0^+}\ \frac{x}{\vert x \vert} = \lim_{x\to 0^+}\ \frac{x}{x}$$

woven radishBOT
#

Alberto Z.

mystic scarab
#

$$\lim_{x\to 0^-}\ \frac{x}{\vert x \vert} = \lim_{x\to 0^-}\ \frac{x}{-x}$$

woven radishBOT
#

Alberto Z.

mystic scarab
#

This is how you should write the two cases

#

And easily conclude, I guess

summer harbor
#

can we say then that the limit technically DNE because lim x -> 0- != lim x -> 0+ ?

mystic scarab
#

Exactly! That's the correct conclusion, very well 💪

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Because the limit is 1 from the right but -1 from the left

summer harbor
#

right

#

thanks !!

#

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silk panther
#

hello, I need help in doing this Q

devout snowBOT
silk panther
#

so far, I already proved that the sequence is increasing, andd i just need to prove that it is bounded above

willow helm
#

Hello!

silk panther
#

then I can say the sequence converges

silk panther
#

im stuck in proving its boundedness from above

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any idea?

last parrot
#

Use lim?

willow helm
#

Have you found possible limits?

silk panther
#

what

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but the expression is like f(x+1) = (f(x) + 2) / 3

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how to find limit

last parrot
#

If x_n converge L then x_n+1 also converge L

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Let L=(L^3+2)/3

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Then find from here

silk panther
#

but I wanna prove its boundedness first

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from above

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then find limit

last parrot
#

No

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You find possible Limit first

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Then you will find the boundness

silk panther
#

but shouldn't we prove that it converges first

last parrot
#

Thats what im saying

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Assume it converge toward a limit

silk panther
#

are we doing induction

last parrot
#

Yes, but not now

silk panther
#

so ur saying

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we find the limit L first, then find out its convergence...?

last parrot
#

Ye

silk panther
#

erm

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if we already got the limit L, it must converge right

last parrot
#

No

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Just find lim first lol

silk panther
#

im doing it

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(L+2)(L-1)^2 = 0

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so L = (-2,1)

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oh wow there are 2 limits

willow helm
#

We don't find the limit

silk panther
#

what does this mean

willow helm
#

We find the possible values for limits

silk panther
#

yea its -2 and 1

willow helm
#

We haven't figured out that the limit is -2 or 1, and most definitely not that it's both

silk panther
#

okay

willow helm
#

To prove boundedness

silk panther
#

so L must be 1

willow helm
#

No

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We don't know that

willow helm
#

You notice, as proven, they are increasing

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But it seems like they are always above 0

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And this is where we can use the possible limit 1

silk panther
last parrot
#

They are above 0 for xn

willow helm
#

Yes

#

My bad

silk panther
#

the thing is, I have proven that the sequence is increasing, and given the possible limits are 1 and -2, and x_1 = 0.4, limit must be 1

last parrot
#

So it wont reach 1

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You need to show 0<xn<1

silk panther
#

hmm I see

last parrot
#

Since for the first terms of x you see it go positive

last parrot
#

Induction use here

willow helm
#

All that can be true, but still limit wouldn't necessarily have to be 1 (or -2)

silk panther
last parrot
#

Base case is 0.4

silk panther
last parrot
#

You find 2 L values, one is -2 other is 1, by intuitively find some x values, you see the sequence tend to go up positive, therefore, try to show 0<xn<1

#

Then by inductive, use the given formula

willow helm
# silk panther ok hold on now im confused

You have proven it is increasing. You have found two possible limits, one of which must be the limit if the sequence converges. You haven't proven boundedness yet, hence you haven't proven convergence, hence the existence of a limit is still not proven

#

All you have to do is prove boundedness from above, you have proven boundedness from below by proving it is increasing and that x_1 = 0.4, hence all are > 0

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The reason why we find possible limits is to prove this boundedness

willow helm
#

We find two values, -2 and 1

silk panther
#

I understand it now

willow helm
#

And what they mean is if the sequence reaches them, it stays there

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So from that we know if the sequence ever reaches 1, it stays there

silk panther
#

wait lemme share my answer

willow helm
#

We don't pick -2 because see know all terms are > 0

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So we work with 1

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To show it is a good upper bound

silk panther
willow helm
#

Once we do that, we have shown convergence

silk panther
silk panther
last parrot
#

Why dont you let possible limit be solved first?

silk panther
#

I haven't swapped it

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does it matter tho?

willow helm
#

In practice you expect it to work

silk panther
#

I see I understand

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yea need more practice

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need to get used to this

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sooo any suggestion for my answer? i will be diving to the last question

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ill ask for help later haha

last parrot
#

Looks fine to me i think

willow helm
#

Yeah

willow helm
last parrot
#

My first year doing calculus too

willow helm
#

Best of luck! 🙂

silk panther
last parrot
#

Yes first year uni

silk panther
#

woahh dope

#

alr thanks yall, ill see u in a new channel 😏

#

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willow helm
last parrot
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silent hawk
#

which method do i use to find the range of this thing

last parrot
#

Have you found domain yet?

silent hawk
#

i guess it will be R - {0}

slow junco
silent hawk
slow junco
#

x^2+1/x^2>=2

#

Now add 4 both sides

#

It's [6,infinity)

shy osprey
devout snowBOT
# slow junco It's [6,infinity)

As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.

silent hawk
#

but just wondering how to reach there

slow junco
shy osprey
#

jaisa ki @ daredevils_ldoe ne bola

silent hawk
slow junco
shy osprey
#

since x^2 cancel ho rha hai

#

wo apply karlo

slow junco
#

Multiply both sides by 2

silent hawk
#

oh

slow junco
#

Then add 4

shy osprey
#

AM>= GM for any two no.s is
(a +b )/2 >= sqrt(ab)

silent hawk
#

OHH

#

got it

shy osprey
#

Yahan par if you observe, tumko dikhega ki x^2 and 1/x^2 wala term multiply hokr cancel hota hai

#

But suno!

shy osprey
#

AM GM inqequality is only for +ve numbers

#

We were able to apply this cuz x^2 and 1/x^2 (both are square isiliye postive)

silent hawk
#

ngl i never thought of using am-gm ineq

#

im 100% failing maths

shy osprey
#

Almost every qsn mein try karke dekha kar

#

Weighted am gm bhi works sometimes!!

silent hawk
#

whats weighted am gm

shy osprey
#

Abhi ineqality ka chapter nahi hua?

silent hawk
#

ill learn it myself

shy osprey
#

Oh okay then

#

aur kuch?

silent hawk
#

nothing for now

#

thanks

#

.close

devout snowBOT
#
Channel closed

Closed by @silent hawk

Use .reopen if this was a mistake.

silent hawk
#

.reopen

devout snowBOT
shy osprey
#

sure!

silent hawk
#

so this was the original q

#

and range of h(x) is [6, infinity)

#

then why is the smallest positive integer taken as 7

#

and not 6

shy osprey
slow junco
shy osprey
#

open bracket hai 6 ke liye

slow junco
#

Am gm mei closed aata bracket

#

Kya hogaya

silent hawk
#

na

slow junco
#

Kuch glt kra hai

shy osprey
#

one sec i think catch hai

slow junco
#

Lagta hai

#

Aapne

silent hawk
#

100% sure sab correct hai

slow junco
#

Huh?

vestal surge
# silent hawk na

inequality ki condition ke according tabhi 2 hota hai jab numbers equal hoge

slow junco
#

How is that possible

vestal surge
#

idhar equal nahi hai

#

toh vo exactly 2 nahi hoga

slow junco
#

Are haan

vestal surge
#

2 se jyada hoga

slow junco
#

Kya baat hai

#

He got the point

vestal surge
#

isiliye open bracket hoga

silent hawk
vestal surge
shy osprey
vestal surge
silent hawk
#

crap

slow junco
silent hawk
#

i missed the minor detail

#

that x is in the base

#

of log

slow junco
#

Broo

silent hawk
#

ye i missed that detail

slow junco
#

log(base x) (e)

#

Hai isme

#

To na hi 1 aayega na hi -1

vestal surge
silent hawk
#

tysm

#

yall

silent hawk
vestal surge
silent hawk
#

thx also btw if i keep this open for a bit is it okay

vestal surge
slow junco
#

Dera abhi

silent hawk
#

gl

slow junco
#

Thx

silent hawk
#

april attempt ya adv?

slow junco
#

Jan mei percentile acchi ni aayi

shy osprey
#

#chill

silent hawk
#

umm....

#

actually 1s

#

how do i find the range of this thing

slow junco
#

√(x+7) > 0

#

Now add 4 on both sides

#

And then change them to denominator

#

The inequality changes

silent hawk
#

got to this part

#

forgot to update it

#

mb

slow junco
#

It becomes 1/√(x+7) +4 < 1/4

#

Multiply by pi

#

Yea

#

Correct

silent hawk
#

now how do i find range of sin

#

tho

#

i basically found f(x) and 2f(x)

slow junco
#

The value of index of sin must be from (-π/2,π/2)

#

As it is it's principal branch

#

So -π/2< 2fx < π/2

silent hawk
#

whts principal branch

#

we've prob been taught by a diff term

slow junco
#

Huh?

silent hawk
#

cuz ive never heard/seen it anywhere before

slow junco
#

Maybe

#

Ho skta hai

#

Kuch alag batay ho

#

Range aagai ab -pi/4,pi/4

#

Sry closed

vestal surge
#

thats your answer

silent hawk
#

ok wait brb

slow junco
#

To y belongs to -1/√2,1/√2

thick lotus
#

so f(x) is never negative

slow junco
#

Yea

#

Missed that pt

vestal surge
#

i take that back, im wrong

thick lotus
vestal surge
silent hawk
#

um guys

#

i got this

#

but slight issue

#

the 0 should be in open bracket

#

why tho

#

umm what?

thick lotus
#

<@&268886789983436800> hope you good

thick lotus
silent hawk
#

as x gets larger

#

?

#

but never becomes 0

thick lotus
#

yes

silent hawk
#

ill take a break now

#

.close

devout snowBOT
#
Channel closed

Closed by @silent hawk

Use .reopen if this was a mistake.

thick lotus
#

np

devout snowBOT
#
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obtuse shell
devout snowBOT
obtuse shell
#

@dry robin

cyan rose
uncut crow
cyan rose
obtuse shell
shy osprey
#

@obtuse shell you there?

cyan rose
#

Yes, he is with us.

obtuse shell
shy osprey
#

Okay do you still require help in this one?

obtuse shell
#

Please

cyan rose
# obtuse shell

What is the scale here? Is one face of the square equal to one unit? Then AB would be two units?

shy osprey
#

Right so first things first, could you send a cropped img of the qsn so as to protect your privacy!!

obtuse shell
#

I got this

#

I might be Wo]wrong tho i kinda suck

cyan rose
# obtuse shell

You need to crop it, and only show the question part. Remove everything else including the browser tabs and else.

shy osprey
#

-# for your privacy!

obtuse shell
cyan rose
#

Alright, this is good enough.

shy osprey
#

you cant just do 8*4

obtuse shell
#

Okay

shy osprey
#

Since the left part doesnt have that small chunk in the corner included

obtuse shell
#

Okay

shy osprey
#

so you would have to subtract the area of that small chunk BCD from the 8*4 area

obtuse shell
#

So 6 x 4 maybe?

#

is my triangle calculations fine?

shy osprey
shy osprey
#

okay lets do this step by step

#

whats the area of the chunk that you need to subtract?

obtuse shell
#

The little square?

shy osprey
#

-# i hope u understood which chunk am talking abt

shy osprey
#

with three vertices BCD right?

obtuse shell
shy osprey
#

Right well whats the area?

#

!nosols

devout snowBOT
#

As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.

cyan rose
shy osprey
#

But no

shy osprey
cyan rose
#

Am I allowed to give them the approach by which I got the answer or do we need to do it in a step by step teaching way?

shy osprey
shy osprey
cyan rose
#

@obtuse shell are you with us?

devout snowBOT
#

@obtuse shell Has your question been resolved?

devout snowBOT
#
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devout snowBOT
#
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late cave
#

x^2 + y^2 = r^2 the equation of a circle centered at the origine.

For a circle of a radius 1 , determine the components of a vectr that origine is at the coordinate point of (0,0) and the extremity is at the trigonometric point P(pi/3)

late cave
#

P(pi/3) = (1/2 , sqrt3/2)

#

(1/2 - 0 , sqrt3/2 - 0) ?

#

Am i supposed to subtract (1/2,sqrt3/2) by (-1/2, -sqrt3/2) or (0,0)

winter torrent
#

P(pi/3) = (1/2 , sqrt3/2)

This is your answer. Points are vectors.

devout snowBOT
#
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devout snowBOT
#
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#
Channel closed

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last parrot
#

<@&268886789983436800>

devout snowBOT
#
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lost laurel
#

I'm having trouble in (b)

devout snowBOT
lost laurel
#

$f_n(x)$ = $\begin{cases} \left(\frac{3}{2} \right)^n x & 0≤x≤1/3\ \left( \frac{3}{2} \right)^{n-1} x& 1/3≤x≤2/3 \ \text{ something} \end{cases}$

woven radishBOT
lost laurel
#

The issue here is as n-> infty, doesn't the function on [0,1/3] diverge

lunar harbor
#

isn't $(3/2)^n x$ only valid for $[0, 1/3^n]$

#

or am I misinterpreting what your question is

lost laurel
#

like uh it's all defined on [0,1/3]; [1/3,2/3]; [2/3,1]

lost laurel
woven radishBOT
#

Civil Service Pigeon

lunar harbor
#

edited

lost laurel
#

I see

#

well, that would work for the middle segment, but what about the first bit

lunar harbor
woven radishBOT
#

Civil Service Pigeon

lost laurel
#

Noted

lunar harbor
#

tbf it's quite late but I'm very confused on what your question is

#

is "first bit" referring to [0, 1/3]

lost laurel
#

yes

lunar harbor
#

$f_{n+1}(x)=\frac{1}{2}f_n (3x)$ is basically inheriting the entire "step" structure of $f_n$ then

woven radishBOT
#

Civil Service Pigeon

lunar harbor
#

just scaled down to half the height and one third of the width

#

This is the graph of $f_1$, which has one "flat middle"

woven radishBOT
#

Civil Service Pigeon

lunar harbor
#

when you construct $f_2$ from that, the original part stays flat (aka the middle $1/3$), but the recursive rule creates \textit{new} flat parts in the middle of the first and last thirds

woven radishBOT
#

Civil Service Pigeon

lunar harbor
lost laurel
lunar harbor
lost laurel
#

mhm

#

I suppose I'll work on this

#

thanks, this is harder than I expected lol

wicked turtle
#

ooh cantor's function, one of my favorites

lunar harbor
#

I think you're trying to juggle too much rn

lost laurel
wicked turtle
#

hey Wai!

lost laurel
#

I'll close this for now while I work out the details

#

.close

devout snowBOT
#
Channel closed

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devout snowBOT
#
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solid osprey
#

Find the sum of all positive integers $n$ such that $1^3+2^3+\dots+n^3\equiv 17 \mod n+5$

woven radishBOT
#

ihave<skissue>

solid osprey
#

ok so
n^2(n+1)^2/4=17 mod n+5
(n-(n+5))^2×(n-(n+4))^2=68 mod n+5
400=68 mod n+5
n+5|332
332=2^2×83, so >5 solutions are n+5=83, 166, 332 or n=78,161,327

#

n=78 and 161 works, but why does n=327 suddenly fail?

lunar harbor
#

Consider what you need mod 4(n+5)

solid osprey
lunar harbor
#

when n=327, 332 is divisible by 4

solid osprey
#

hmm

#

but why does n=161 still work

#

is it like it just so happens to work

lunar harbor
#

This one is infamous for trolling people because you had to plug back in to check

solid osprey
#

eugh thats terrible

#

actually can the check just straight up be 400/4=17 mod 332, and noticing that it just doesent work?

#

huh then why in the world does 161 work

lean crater
solid osprey
#

yeahhhhh

#

ok i forgot inotation doesent work in text and not all people have the same humor as my friend group

lean crater
#

unfortunately C will turn out to be the most useful in applied maths

solid osprey
#

ew

lean crater
solid osprey
#

thats what im saying

#

what the fuck is wrong with modular aritmethic

lean crater
#

for n = 161 the modulus is 166 right

#

4S = 400 + 166k
k is an even number represented by 2m
2S = 200 + 83(2m) => S = 100 + 83m

#

if m = 0, S is congruent to 100 mod 166
if m = -1, S is 17 mod 166

#

voila 161 works

#

@solid osprey

solid osprey
#

ok i think i see

#

thank you pigeon

#

thank you nefer

#

.solved

devout snowBOT
#
Channel closed

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lunar harbor
devout snowBOT
#
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lost laurel
devout snowBOT
lost laurel
#

Very confused here

#

So the ideals are sets sets of cosets here, right

#

so I'll first want to find something this is isomorphic to , in order to make my life easier

#

.close

devout snowBOT
#
Channel closed

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faint gorge
#

Wai wait for other when Wai can help themselves

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#
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noble mango
#

Why did he substiute -2 into the equation when there was already a x value inside it?

noble mango
#

There are two y values in this equation and one x value

#

thats kinda confusing me

#

If any of the helpers need context here's the video https://www.youtube.com/watch?v=7zkCj4vgBos&list=PLquyU_6YLv6di-RCY0DD_xbrkcD_TJuMO&index=5 the time stamp is around 5:00

Check out the links at the end of the video to find playlists for questions on this same topic
You can find my AS and A Level material here:
https://drive.google.com/drive/folders/1NdcJdjkNy67kIYZiCZ_Ze5xY78SAlYJt?usp=sharing

An index of IGCSE Questions arranged by topic as well as papers can be found here:
https://drive.google.com/file/d/1iOMB...

▶ Play video
#

oh nvm

#

he made a mistake

#

i kept watching and he realised it then

#

.close

devout snowBOT
#
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last parrot
devout snowBOT
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summer harbor
devout snowBOT
summer harbor
#

how do i derive absorption law?

#

it just puts me back in a loop

inland carbon
#

v and ^ mean gcd and lcm? in which case p | p v q so p ^ (p vq )= p

summer harbor
#

no...

#

thats logic...

inland carbon
#

damn mb

summer harbor
#

v is disjunction and ^ is conjunction

young spade
#

btw when youre on paper, write v and "^" as:

$p \vee q \wedge r$
woven radishBOT
young spade
#

They go in line

summer harbor
#

right

inland carbon
#

maybe distinguish the cases p / not p if that's allowed

inland carbon
#

like a truth table

young spade
#

Yeah, proof by truth table is pretty straight forwards

#

given that you only have 2 variables

summer harbor
#

yeah

#

is it possible tho

#

to derive absorption law such that it is reduced to p?

young spade
#

I dont think you can do it with formal logic without appealing to itself

#

More like, with propositional logic or set theory

summer harbor
#

i see

#

so its inevitably

#

gonna be circular if i do it with js logic

polar chasm
#

it depends on what your axioms are

#

what laws can you work with?

summer harbor
#

im using

#

distributive

#

and idempotent

polar chasm
#

hmm then you probably cant do much

summer harbor
#

yeah

devout snowBOT
#

@summer harbor Has your question been resolved?

devout snowBOT
#
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#
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mellow mulch
#

Need help,

devout snowBOT
mellow mulch
#

this questions seems to be solved with help of products of determinant but how?

dull parrot
mellow mulch
#

ohhh... i thought i have to make a1 a2 and so on.

#

thanks bud.

devout snowBOT
#

@mellow mulch Has your question been resolved?

#
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#
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crystal pumice
#

how do i answer b

devout snowBOT
willow helm
#

!status

devout snowBOT
#
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
slow junco
crystal pumice
#

u get the variance of the original mean, 185. so u can get the Standard deviation of 190

#

nd its easy from there

#

idk how to close this thread

supple knot
devout snowBOT
crystal pumice
#

.close

devout snowBOT
#
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night rune
devout snowBOT
night rune
#

i am having a hard time translating this

#

Elentis has produced 31 times the world average for the number of professional tennis players per 100,000 residents.

thick lotus
#

yh i also do not understand what is statement 1 and 2

devout snowBOT
#

@night rune Has your question been resolved?

small geyser
#

I suppose the question asks you to pick statement 1 such that it implies a chosen statement 2.

#

at least, that's what a cold reading tells me.

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#
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topaz axle
#

it's 3→5

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fair canopy
devout snowBOT
fair canopy
#

Can someone help me solve this?

small geyser
#

,rccw

woven radishBOT
fair canopy
#

No idea what to do

shy osprey
#

Any specific part or all?

fair canopy
#

Well I suppose all r same how abt we do 4th part?

shy osprey
fair canopy
#

Ye

shy osprey
#

r would indicate the max value of the expression right?

fair canopy
shy osprey
#

since sin() terms max value can only be 1

fair canopy
shy osprey
fair canopy
#

Then square both sides and add both eq

#

Then take r Sq common

shy osprey
#

Okay yeah!
So what did you get r as?

fair canopy
#

10

shy osprey
#

Good!

fair canopy
#

Do we let - 6 equal r sin fi or 6= r sin fi

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?

shy osprey
#

You can take anything

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doesnt mattwr

fair canopy
#

Alr

shy osprey
fair canopy
#

So wait lemme show u what I tried

#

Lemme send pic

shy osprey
#

Sure!

fair canopy
#

So if I let - 6 won't that change my answer in terms of sin (theta plus fi)

#

?

shy osprey
#

but

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phi would be negative

#

so it would become theta + (-phi)

fair canopy
#

-phi? How

shy osprey
#

You can try!

fair canopy
#

Look

shy osprey
shy osprey
fair canopy
shy osprey
#

Am saying when you calc phi!

fair canopy
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When calc tan fie equal b over a will I take b as - 6 or 6

shy osprey
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<@&268886789983436800>

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wow

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tf is going on tdy

fair canopy
#

💀

#

This is not the solution bro

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😂

fair canopy
#

B is minus 6 or 6 idk what to take

shy osprey
#

So see

fair canopy
#

Ye

shy osprey
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if you take -6cos(theta)

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then you would get a tan-1( -3/4)

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which is same as -tan-1(3/4)

#

so thats how you get a negative phi

shy osprey
fair canopy
#

I solved this without using negative as

shy osprey
#

you just get a positive tan-1(3/4)

fair canopy
shy osprey
#

Yup correct

fair canopy
#

So calculation is fie is important here?

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As the question jst asks for the sin theta plus minus fie form

shy osprey
shy osprey
fair canopy
#

Calculation of fie is needed?

shy osprey
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phi is important yes

fair canopy
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As the question does not ask for it

shy osprey
#

i mean you do need it for the answer no?

fair canopy
#

If I want to put it in that form

shy osprey
#

Oh u mean like exact value of phi?

fair canopy
#

Ye

shy osprey
#

Idts

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but as far as i remember

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3/4 gives 37 degrees

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and 4/3 gave 53degrees

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one of the somewhat standard values

fair canopy
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Well thanks for clearing the doubt tho

shy osprey
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Well now would you like to try the others on your own first?

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Or should we start with the others asw?

devout snowBOT
#

@fair canopy Has your question been resolved?

devout snowBOT
#
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white pawn
#

I dont understand conceptually vector lines and planes

dull parrot
white pawn
#

Like when do I use a point as a vector to descirbe it

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its better in a differentq uestion

dull parrot
#

not sure what you mean

white pawn
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why do they use A as the r vector

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wtj

dull parrot
#

<@&268886789983436800>

white pawn
#

Anyway

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in that question above

dull parrot
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i think you mean direction vectors

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which is different

white pawn
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yeah why do they use A as the ditection vector

dull parrot
white pawn
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yep why cant they use b or c

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to describe the plane

dull parrot
#

well it specfically notes it as $\vec{AB}$ and $\vec{AC}$

woven radishBOT
dull parrot
#

so what we're saying is how do we get from point a to point b

white pawn
#

but above it has 3 points

dull parrot
#

and how do we get to point a to point c

white pawn
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so cant tehy use bc and ba?

dull parrot
#

you can if you want to

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but you'll get a different answer

white pawn
#

oh so its incorrect to describe the plane that way

dull parrot
#

ah no i meant, you get a different normal that's scaled differently

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but it will be right

white pawn
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ohhh I okay so yiu can use any of the points to find a normal and describe the plane

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and each of the normals if used other points would have a scalar factor difference betwene them

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not scalar factor difference like they are scalar apart

dull parrot
woven radishBOT