#help-49

1 messages · Page 40 of 1

cosmic zenith
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apparently i need to make sinx = 0?

inner wolf
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Yes, or cosx=1/3

cosmic zenith
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And how would that work?

inner wolf
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Sin is 0 for nπ, so you have -180, 0 and 180 as answers

cosmic zenith
#

yeah that makes sense'

inner wolf
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For cos you need to use calculator as we don't know the exact value for cos inverse 1/3

cosmic zenith
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do you look at it as if both sinx and cos x are x?

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x(3x-1) as if its like this?

inner wolf
cosmic zenith
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yeah

inner wolf
cosmic zenith
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ahh okay

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thanks man

inner wolf
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It's just factors

cosmic zenith
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have a nice day

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im boutta have my exam

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next week

inner wolf
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If multiplication of 2 quantities is given to be zero, one of them or both of them could be zero

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Glgl

cosmic zenith
#

thank sman

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midnight plankBOT
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eternal pine
#

what methods do you guys use to factorize stuff like this

eternal pine
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or this

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i only know the methods for binomes

solid hornet
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Find factors of 3

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And sub those values in for x

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If it adds up to 0

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It is a factor

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It’s like

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Integral zero theorem I think It was called

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P(x)=x^4 + 4x +3

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Factors of 3 is +-1, +-3

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So trial and error those values for x

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And then you can do synthetic division

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Lmk when u get there if u need help

eternal pine
eternal pine
pallid juniper
solid hornet
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Huh

pallid juniper
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wait

solid hornet
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Wdym

eternal pine
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i can't look up the technique for higher grade polynomes anywhere

solid hornet
#

Do you know integral zero theorem

eternal pine
# solid hornet Do you know integral zero theorem

The integral zero theorem is great for factoring higher degree polynomials 😁, like cubic polynomials or quartic polynomials, when the leading coefficient is equal to 1 👍. The rational zero theorem, also known as the rational root theorem or rational roots theorem, is great for factoring polynomials when the leading coefficient is not equal to 1 ...

▶ Play video
solid hornet
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Yea try watching that

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If you don’t know synthetic division search for that too

pallid juniper
midnight plankBOT
# pallid juniper

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.

solid hornet
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Oh I c

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I never learned like that

eternal pine
pallid juniper
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i also got one hammer method to factor polynomials of form
x^4 -16x-12

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also there is one hammer method to factorize or solve biquadratic equation with cubic terms as well
(monic)

eternal pine
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so how do i know which of the 2 is the correct one

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or both are directly factors

pallid juniper
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+1 and -1

eternal pine
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AH ok makes sense then

midnight plankBOT
#

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amber abyss
midnight plankBOT
amber abyss
#

Can someone help with this? Idk how to answer

boreal belfry
#

Think about the relationship that acceleration is the change of velocity per unit time

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And construct a differential equation

amber abyss
amber abyss
boreal belfry
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Yep

sage helm
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just intergate

boreal belfry
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So workout the integral with initial value 5

amber abyss
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But it says initial speed

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s(t)

boreal belfry
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At t= 0

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It is 5

amber abyss
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v(t)=t^2

boreal belfry
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Yep. But there needs to be a +c

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For the constant initial speed

amber abyss
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Ohh

boreal belfry
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Yep and you know the value for t = 0

amber abyss
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v(t)=C

boreal belfry
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So what is c

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It's the initial speed

amber abyss
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Integrate it again?

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@boreal belfry

boreal belfry
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No c is a constant that is lost on the differentiation. So you are setting c to 5

amber abyss
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Ohh

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Do i integrate 5=C?

boreal belfry
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No

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You have the equation v(t) = t2+ 5

amber abyss
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Integrate t^2+5 from 0 to 5?

boreal belfry
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You can just plug in t for the end speed

amber abyss
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Oh ok

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Thank you

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simple falcon
#

Please help me to understand this

midnight plankBOT
simple falcon
cursive dawn
#

However, AB still equals A, and BA still equals B, so you can probably use that

midnight plankBOT
#

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round badger
#

hi, could anyone help me understand the 4th question, it dosent make sense as we just answered it in the last question, the vertex is -3,25 and bc the leading coeficient is a - the vertex is the maximum

round badger
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is that all we need to say ?

latent elk
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Have u learnt calculus?

round badger
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nope

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im in precalc rn

echo forge
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use the vertex

round badger
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yes

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i know it

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its -3,25

echo forge
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and put it into the equation

round badger
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i found it using -b/2a

echo forge
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to get corresponding y value

round badger
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its 25

echo forge
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which will be ur maximum

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which they have asked

round badger
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its that easy ?

echo forge
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yep

round badger
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its basically almost the same as the c)

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i just needed to tell if it was max or min

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and bc leading coeficient is - its the max

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thanks for the clarity anyways

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have a good day and ty for the help : )

latent elk
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WAIT

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Enlight me on the vertex thing

round badger
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wdym

latent elk
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How do u find max/min using vertex thinggy?

round badger
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its just -b/2a to find x value and then plug it into the function to find the y value of the vertex

latent elk
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I didnt get taught it back then

round badger
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-b/2a is also to find the axis of symmetry of the parabola

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i have another question, when i completed the square i found 2(x+5/2)^2 -9/2

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does the 2 mean a vertical or horizontal stretch ?

echo forge
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vertical

latent elk
echo forge
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if f(x) = x^2 and g(x) = 2f(x) you are basically doubling y values of f(x) by 2 in g(x)

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which means that your curve will be much steeper or closer to y-axis

round badger
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bc to find it you do -b/2a

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and it makes sense because b represents the horizontal transformation

latent elk
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Well, it probably I was taught quadratic equation in 9 grade and get taught precalc at 10

round badger
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it will tell you if the axis of symmetry moved 2 units to the left or to the right for example

latent elk
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Precalc offers a better way to find it then

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lol

round badger
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yep

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precalc is fun

latent elk
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My precalc was brutal

round badger
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so if its a vertical or horizontal

round badger
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we just started it

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what grade are u in now ?

latent elk
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undergrat

round badger
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ig ur major is math ?

latent elk
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Engineering

round badger
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nice

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do you like it ?

latent elk
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Nope

round badger
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im still not sure if i want to do enginerring or finance

round badger
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thats problematic

latent elk
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Mine is civil, i dislike it so much

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I should have choose CS

round badger
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the math and physics behind architecture

latent elk
latent elk
round badger
round badger
latent elk
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yep

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I hate it thats all

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CS or AP is way better

round badger
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whats ap ?

latent elk
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Applied Physic

round badger
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ohhh

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nice

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physics is fun

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you basically use math to solve real life problems

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best of both worlds

latent elk
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My professor once said: "There's nothing fun about physic, only pain and suffering "

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😫

round badger
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do you still have time to change majors ?

round badger
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ig the physics i do is pretty simple compared to yours

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@echo forge could you help with something ?

latent elk
round badger
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oh

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fuck

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so you have done the entire four years even tho you dont like it

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i feel sorry for u

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this year is the first year i have biology and i cant have one more class of it

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you had classes everyday for four years on smth you hate

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thats ruff

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#
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frozen totem
#

Suppose $s\geq3$ is an arbitary odd number, let $p_1<p_2<\dots<p_s$ be odd primes such that $p_1+p_2>p_s$. Show that such primes always exist.\[.5em]
We start by taking $\epsilon\in\mathbb{R}^+$ such that $(1+\epsilon)^{s-1}<2$. Let $p_1$ be a~prime large enough, that for any prime $q>p_1$ there exists a~prime $q'$ satisfying $q<q'<(1+\epsilon)q$. Then let $p_2,\dots,p_s$ be consecutive primes. It follows that $p_s<p_1(1+\epsilon)^{s-1}<2p_1<p_1+p_2$.\[.5em]
My question is, why does the afformentioned prime $q'$ always exist? What theorem on prime gaps do we use? Does this proof even work?

grand pondBOT
#

🇵🇸Mína🔆

frozen totem
#

specifically, we take p1 to be a prime, such that for a range of consecutive primes p2,...,ps, the number p1(1+ε) exceeds any gap in said range

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How can we say that that'll always exist for an arbitraty s?

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if anyone has a different proof, I'll be happy to see it

midnight plankBOT
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@frozen totem Has your question been resolved?

frozen totem
#

<@&286206848099549185>

midnight plankBOT
#

@frozen totem Has your question been resolved?

final monolith
frozen totem
#

I won't prove it in the thing, I'll just quote it

final monolith
frozen totem
#

tysm!

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last nebula
midnight plankBOT
last nebula
#

how do I find the diamond and square

novel herald
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x^2 + dx + 12 = (x+3)(x+s)

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distribute the right side and compare the coefficients

junior flower
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m8of48...

novel herald
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slayla froggerspy

radiant trout
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or just plug -3 in

midnight plankBOT
#

@last nebula Has your question been resolved?

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minor turtle
#

I don’t really understand this problem can someone help

minor turtle
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I assume length is getting the magnitude

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But direction I don’t really know

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Is it just finding the unit vector

novel herald
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they might want the angles

midnight plankBOT
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@minor turtle Has your question been resolved?

minor turtle
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Like for example

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This is a similar question with a cross product

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Where it asks for length and direction

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Would the direction just be the unit vector of the cross product/vector

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?

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Hell

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Hello

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<@&286206848099549185>

hasty mantle
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Direction is the angle of the vector from standard position

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Arctan(y/x) gives the angle of direction

minor turtle
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Not sure about this

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Direction vs angle direction

hasty mantle
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So length is just sqrt of the sum of the terms squared

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If you divide the sum of your vectors by their length you get direction

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cross product*

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So if the cross product evaluates to 0 there is no direction because if you divide by length it’s still 0

midnight plankBOT
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@minor turtle Has your question been resolved?

minor turtle
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So the direction is basically the cross product divided by the magnitude

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?

midnight plankBOT
#

@minor turtle Has your question been resolved?

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midnight plankBOT
#

@raw owl Has your question been resolved?

raw owl
#

<@&286206848099549185>

midnight plankBOT
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@raw owl Has your question been resolved?

raw owl
#

<@&286206848099549185>

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torn geyser
#

does y^2+2y-1 simplify to (y-1)^2

midnight plankBOT
quaint lily
#

no

torn geyser
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how come?

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i factored it and got (y-1)(y-1)

quaint lily
#

you must've done something wrong

quaint lily
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and you'll see

torn geyser
#

ah

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i see

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well im stumped on what to do then

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I moved the 4x and 21 to the other side

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and the only way to complete the square would be subtracting one no?

quaint lily
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(y+1)^2 = y^2+2y+1

torn geyser
#

ah

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i see

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thank you for the assistance!

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last slate
#

,, f(x)=\sqrt{2{x}^2-3{x}+1}+\sin^{-1}x

midnight plankBOT
grand pondBOT
last slate
#

we have to find its domain

novel lion
#

stuff inside sqrt() cant be <0 right?

last slate
#

yea

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wait let me just show u what i've done

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i've come to this result- ${x}\in \left(-\infty,\frac{1}{2}\right]\cup [1,\infty)$

grand pondBOT
last slate
#

and also $x\in [-1,1]$

grand pondBOT
last slate
#

since domain of arcsin is -1 to 1

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{} is fractional part btw

midnight plankBOT
#

@last slate Has your question been resolved?

last slate
#

astar 💔

obsidian merlin
obsidian merlin
#

sin-1x x has to be between -1 to 1

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factorise that polynomial

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3+-1/4

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1/2 to 1

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so in range 1/2 to 1, the polynomial is -ve so regect

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answer should be [-1,1/2)

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@last slate

obsidian merlin
#

intersection

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you got it

midnight plankBOT
#

@last slate Has your question been resolved?

last slate
#

sorry wait a min

last slate
obsidian merlin
#

wtf

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ohhhh wait

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no

last slate
#

it says -1 to -1/2 union 0 to 1/2

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[] []

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idk why cant we take -1/2 to 0

obsidian merlin
#

does

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fractional part

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be always +ve

last slate
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fractional part is always positive

obsidian merlin
#

thaaats why

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wait then

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if we remove values from 1/2 to 1

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we do it in -ve side too

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-1 to -1/2

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shouldnt we omit -1 to -1/2

last slate
#

but why?

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u seems to be confused

midnight plankBOT
#

@last slate Has your question been resolved?

last slate
#

.close

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gritty holly
midnight plankBOT
quaint lily
#

evaluate sin of the whole thing

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then you'll get a number, then draw a triangle

gritty holly
quaint lily
#

what do you get for sin A

gritty holly
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the second one right

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what

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sorry but i dont follow

quaint lily
gritty holly
#

ok

quaint lily
gritty holly
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i know you use cos(x+y) rule but i dont know why or how you determine it

quaint lily
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this whole thing ill call A

gritty holly
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ok

quaint lily
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evaluate sin A

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using the sin(x+y) rule

gritty holly
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why do you do that

quaint lily
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you'll understand why in the next step

gritty holly
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ok ill take your word

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3/5 * 12/13 + 4/5 * 5/13

quaint lily
#

(actually you can also use cos(x+y) but I was trippin and thought it was like tan sum formula)

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so then sin A would be 38/65 right?

gritty holly
#

what

quaint lily
gritty holly
#

sin A become 56/65 doesn't it

quaint lily
#

oh

gritty holly
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pretty sure its 56/65

quaint lily
#

yes that

gritty holly
#

k

quaint lily
#

so then if you draw a right triangle with angle A, you get this

gritty holly
#

k

quaint lily
#

from that you can then get cos A

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by pythag

gritty holly
#

yeah

quaint lily
#

so you'd get cos A = 33/65

gritty holly
#

yeah

quaint lily
#

then A = (ii) = arccos 33/65

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done

gritty holly
#

why at the start did you want sinA

gritty holly
#

how do you decide it's cos (x+y) then or is it trial and error

quaint lily
#

you could also do the same with cos (x+y)

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cos(A) would be like 4/5 x 12/13 - 3/5 x 5/13

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which gives the same result

gritty holly
#

so how do you decide to do cos(x+y)

quaint lily
#

wdym?

novel lion
#

ig

gritty holly
#

so why cos(x+y) not cos(x-y)

novel lion
#

well u can use either sin or cos, just need to convert

quaint lily
novel lion
#

because there's + sign between them

gritty holly
#

k im stupid nvm

midnight plankBOT
#

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twilit field
#

3 squares of a chess board are selected at random, the probability of getting two squares one colour and one square another is

twilit field
#

$\frac{2c\left(32,2\right)c\left(32,1\right)}{c\left(64,3\right)}$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

would this be it

#

,w $\frac{2c\left(32,2\right)c\left(32,1\right)}{c\left(64,3\right)}$

twilit field
#

my book says it's 8/21

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what am I doing wrong

sage helm
#

16/21 should be right

twilit field
#

thanks

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.close

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twilit field
#

.reopen

midnight plankBOT
#

twilit field
#

seven coupons are selected at random with replacement from 15 coupons numbered 1 to 15, the probability that the largest number appearing is 9 is

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so the sample space would be $(15)^7$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

now what

novel lion
#

since the max number on coupun can only be 9

#

the selection is made from coupons numbered 1 to 9

twilit field
#

there are 9 choices for 6 coupns

#

rught

novel lion
#

so total 9^7 ways

twilit field
#

and one is fixed

novel lion
#

but that also includes when number isnt 9

#

which is 8^7 cases

#

so (9^7-8^7)/15^7

twilit field
#

hmm

#

ok

#

thanks

#

wait

#

my book says

#

$\left(\frac{3}{5}\right)^7-\left(\frac{8}{15}\right)^7$

grand pondBOT
#

ƒ(Why am. I here)=misery

novel lion
#

split the numerator

#

9^7/15^7 - 8^7/15^7

twilit field
#

why isn't it just (9/15)^6

novel lion
#

where did 6 come from

#

its 7

#

you're selecting 7 coupons

twilit field
#

yes

novel lion
#

also its not just 9/15 because

twilit field
#

but one coupn has to be 9

novel lion
#

{1,2.......9} -> 9^7

#

this is sample space when any seven coupons from these are selected

#

it could be nine or seven or one

#

u need probability for coupon number 9

#

so the sample space of {1,2........8} is 8^7

twilit field
#

got it

novel lion
#

!done

midnight plankBOT
#

If you are done with this channel, please mark your problem as solved by typing .close

twilit field
#

.close

midnight plankBOT
#
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twilit field
#

Two numbers are selected at random from s={1,2,3,4,5,6} without replacement , find the probability that the minimum of the two numbers is less than 4

novel lion
#

so total 6*5 possibilities

twilit field
#

yeah

#

the numerator is confusing me

#

3 choices for the first one

novel lion
#

u can count all the cases where the minimum number is not less than 4

#

which would be 6

#

4,4
4,5
4,6
5,5
5,6
6,6

#

so favourable cases are 30-6 = 24

#

so probability = 24/30

twilit field
#

hmm

#

I don't get why my emthod fails

novel lion
#

what are u trying to do

twilit field
#

so there are 3 choices for the first number

#

1,2,3

#

and 3 for teh second

#

4,5,6

#

so 9/30

novel lion
#

you're missing some cases

#

the minimum of two numbers is less than 4 when:

#

(A) both numbers chosen from {1,2,3}
(B) one from {1,2,3} and one from {4,5,6}

#

total cases for (A) would be 3!

twilit field
#

ooo

novel lion
#

and for (B) there are 2 cases

twilit field
#

9 right

novel lion
#

1st number chosen from A and second from B
1st number chosen from B and second from A

#

so 9+9

#

(A = {1,2,3} and B = {4,5,6})

twilit field
#

so 18/30

novel lion
#

18+6

novel lion
twilit field
#

ah

#

ok

#

thanks

#

.close

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#
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plush prism
#

Hey

midnight plankBOT
plush prism
#

We have a system Ax=b

#

A and b however have errors in them

#

$\tilde{A}\tilde{x}=\tilde{b}$

grand pondBOT
#

Martin

plush prism
#

$\tilde{A}=A+\Delta A$

grand pondBOT
#

Martin

plush prism
#

Same for x and b

#

For ease of use i will write At for A tilde and dA for delta A

#

Using the maximum norm, we are given:
|dA|, |db| <= 1/100

#

Using this upper limit, we want to get a limit for the relative error in x, which is |dx|/|x|

#

,rotate

grand pondBOT
plush prism
#

This is what i got so far

#

I will work on something else for now, maybe i ask again later

#

.close

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whole jetty
#

Hello I have probability-related questions I'd like to ask

whole jetty
#

Since there are 100 printers, I'm thinking that the problem represents a sum of 100 exponentially distributed random variables

#

which I think means it follows a gamma distribution

stiff pollen
whole jetty
#

I just don't know how to incorporate the payments

#

I was thinking of using the shortcuts for the mean which is just 100 times the mean, however, i think that isn't the case here

#

Should I solve for the expected payment using the integral formula? If so, does the given imply that there will be no refund for years 3 and above?

#

<@&286206848099549185>

midnight plankBOT
#

@whole jetty Has your question been resolved?

midnight plankBOT
#

@whole jetty Has your question been resolved?

midnight plankBOT
#

@whole jetty Has your question been resolved?

whole jetty
#

<@&286206848099549185>

#

Help me please

whole jetty
#

.close

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twilit field
midnight plankBOT
twilit field
#

so I know I've posted this before

#

But I would like to try it again,( I work better in these channels)

#

so to start

#

$A^2=7A-4I$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

multiplying across by $A^{-1}$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

$A=7-4A^{-1}$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

hmm

#

maybe I factorise the OG equation

#

nah

#

that won't work

#

oh

north ridge
#

what if you did (A - 2I)^2 like completing the square

twilit field
#

I think I got something

#

$(A-2I)^2-3A=O$

grand pondBOT
#

ƒ(Why am. I here)=misery

strong lava
#

that is the idea yes

twilit field
#

$(A-2I)^2=3A$

grand pondBOT
#

ƒ(Why am. I here)=misery

sage helm
#

det that shit!

twilit field
#

yeah

#

let me TeX it, just a min

strong lava
#

that feels unnecessary

twilit field
#

hmm let $det(A-2I)=u$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

$u^2=det(3A)$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

$det(3A) is 3^3 det(A)$

grand pondBOT
#

ƒ(Why am. I here)=misery

twilit field
#

which is 81

#

do the answeris 9?

sage helm
#

should be

north ridge
#

Yeah

twilit field
#

thanks!

#

.close

midnight plankBOT
#
Channel closed

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hard umbra
#

the question is if this matrix can even exist

strong lava
#

not diagonal

hard umbra
#

the min poly needs to divide x^2 - 7x + 4

#

that doesn't leave a lot of choices for the char poly

#

and then the det can't possibly be 3

strong lava
#

since it's X(0)

hard umbra
#

?

strong lava
#

det A is the value of the char pol at 0

hard umbra
#

yeah

#

the char poly divides the min poly^3

#

and the min poly divides x^2 - 7x + 4

strong lava
hard umbra
#

so this matrix doesn't exist

#

question is nonsensical joyspin

twilit field
#

Damn

junior flower
hard umbra
junior flower
#

snow wtf is this name

#

change back

hard umbra
#

lex asked gemini a question and it replied with broseph

#

so now i'm snoseph kekehands

junior flower
#

wtf is gemini

twilit field
#

bard

hard umbra
#

the google ai

junior flower
#

i was never into astrology

hard umbra
#

it's ok

twilit field
#

Bard is google's answer to GPT

hard umbra
#

if you make an api key i'll add it to the server

#

it's free

hard umbra
#

dw i'm talking to layla

twilit field
#

oh

#

sorry

junior flower
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last slate
midnight plankBOT
#

Please don't occupy multiple help channels.

last slate
#

different question

#

can't i just use the infinite G.P formula to find f(x)

fresh sparrow
last slate
#

why ?

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#

@last slate Has your question been resolved?

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last slate
#

How to do this

midnight plankBOT
last slate
#

I know that $A = PDP^{-1}$

grand pondBOT
#

Book Reader

last slate
#

and that D is a diagonal matrix with the eigen values

#

$D = \M[ 7 0; 0 -7]$

#

and P

#

would be the corresponding eigenvectors

#

so

grand pondBOT
#

Book Reader

last slate
#

$P = \M[ ? 0 ; ? 1]$

grand pondBOT
#

Book Reader

last slate
#

II thought it would be

#

$P = \M[ 1 0 ; 14/4 1]$

grand pondBOT
#

Book Reader

last slate
#

but its not apparently

#

$\M[7 0 ; 4 -7] \M[ 1; 14/4] = \M[ 7 ; 4-7(14/4)]$

grand pondBOT
#

Book Reader

last slate
#

bruh

robust isle
#

How did you get 14/4

last slate
#

$\M[0 0 ; 4 -14] \equiv \M[0 0 ; 1 -14/4]$

grand pondBOT
#

Book Reader

robust isle
#

Ok

#

So that means an eigenvector (x,y) satisfies the equation x - 14/4 y = 0

#

Never forget what your matrix represents

#

A system of linear equations

last slate
#

aye

robust isle
#

So if you fix x=1 as you did

#

You get y=4/14

#

y=2/7

last slate
#

that works

#

how come my way didn't work tho

#

it has worked all the time before 😭

robust isle
#

Well you try and just wing it when you try and find your eigenvectors

last slate
#

$x = y \M[ 1 ; 14/4]$

robust isle
#

Moral of the story : don't wing it

last slate
#

wiat

grand pondBOT
#

Book Reader

last slate
#

idk

last slate
#

the first column has a pivot position and the second doesn't

robust isle
#

Well either your method doesn't work

#

Or you're not following it correctly

last slate
#

so the second is a free variable

#

and everything can be written with respect to the free variable

#

idk

#

the top and bottom of fraction is swapped in my answer

#

oh wait

#

I see why ICANT

#

Yeah, I just put the 14/4 in the wrong row

robust isle
#

Yeah seems like it

last slate
#

ty

#

.close

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#
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last slate
#

How do I determine if a matrix is diagonalizable?

last slate
#

I tried to diagonalize it but couldn't figure it out so i just said it couldn't be done and got the right answer

#

$A - 7 I = \M[3 -3 ; 3 -3] \equiv \M[1 -1; 0 0]$

grand pondBOT
#

Book Reader

robust isle
#

So the only eigenvalue you got is 7 right ?

last slate
#

yeah

#

because characteristic matrix is $x^2 - 14 + 49 = (x-7)^2$

grand pondBOT
#

Book Reader

robust isle
#

Ok yes

robust isle
grand pondBOT
#

Book Reader

robust isle
#

Yeah so only one solution

last slate
#

So I'll just have to check each eigenvalue and see if it has a eigenspace dimension equal to eigenvalue multiplicity?

robust isle
#

Yes

#

That's the criterion for diagonalizability

last slate
#

Was hoping there would just be a "it doesn't look right" method

robust isle
#

It's not too bad frankly

#

You'd expect A-7I to be all zeros if you want a matrix with that char poly to be diagonalizable

#

So it doesn't look right yea

last slate
#

okay

robust isle
#

But it's a bit of a special case here

#

In general you'd have to go for the long checks

midnight plankBOT
#

@last slate Has your question been resolved?

midnight plankBOT
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last slate
midnight plankBOT
last slate
#

I'm trying to find the components of AB

#

how would that work?

#

I don't understand the addition or subtraction

#

I just know it has to do with the points of (-8,2) and (-4,4)

weary jetty
#

i think that what the text means where it sayst to find the related position vector, it means to "move" the vector so the point A is in the center

#

if its that the only thing you have to do is just the x component of B minus the x component of A and the y component of B minus the y component of A

last slate
#

why subtracting though

#

and in what order

weary jetty
#

what you have to think is that you dont care where the vectors are

#

you just care about the distance between the components

#

that in this case whould be (-4,4) - (-8,2) = (4,2)

#

do you understand it?

last slate
#

sorry my wifi cut out

last slate
weary jetty
#

because vectors have directions

#

when you calculate a distance in the vector way, you first get the final point and subtract the initial point

last slate
#

final - initial = distance travelled

#

okay that makes sense

#

thanks

#

.close

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obtuse totem
#

ok I couldnt type in the other channel anymore

robust isle
#

damn channels

obtuse totem
#

ok so why is [T] w respect to basis C, the inverse of the matrix formed by vectors in basis C?

robust isle
#

and what I was saying in my answer is that the typography sucks in your pic

#

you have to parse the statement like this

#

so they're just doing a change of basis here

obtuse totem
#

ohh

#

lmao I thought they were two seperate equations

robust isle
#

yeah it also got me at first

obtuse totem
#

ahh thank you!

#

thank you so much

#

can I stay in this channel

#

just in case more questions

#

cause theres other available channels anyways, so I dont think it matters whether I occupy this one or not

robust isle
midnight plankBOT
#

@obtuse totem Has your question been resolved?

obtuse totem
#

I thought you have to prove its inner product by showing these properties..

#

you can just state dot product is an inner product?

#

thats sufficient?

runic hamlet
#

they say that they have earlier shown these things for the dot product

tribal temple
#

(Yea in this case you’d have shown the dot product satisfies the inner product properties, and with the inner product defined here [on those polynomials], it’ll be exactly the same steps as showing the dot product [on R^3] is an inner product)

obtuse totem
#

ok

#

I think lin alg this semester has made me realized that

#

I do not want to research linear algebra lmao for the rest of my life

#

no wayy

#

one semester is enough trials and tribulations

#

nah nah I just wanna jump intto a lake or ocean or whatever and call it a day

#

cliff jumpiing

midnight plankBOT
#

@obtuse totem Has your question been resolved?

obtuse totem
#

LMAO not me listening to clubbing music while doing math😭 😂

midnight plankBOT
#

@obtuse totem Has your question been resolved?

obtuse totem
#

I think theres a typo

#

should be [2t 3t]

#

Please let me know if there isnt... cause I really dont trust my thinking

robust isle
#

@obtuse totem looks like a typo yes

#

2+3x should work

obtuse totem
#

ok

#

thanks!

obtuse totem
#

studying is surprisingly going well

#

sweet

obtuse totem
#

I think answer to a is wrong

#

I got 4+7i

#

if someone can cross check that'd be great

#

Im pretty sure its right...

tribal temple
#

-did they use the dot for the dot product to instead represent the complex standard inner product catAngery

#

If you use the “normal” (real) dot product definition I agree you get 4 + 7i

#

Though it seems they’re using the complex inner product (defined by bar{u}.v) which works out as they have bastard

obtuse totem
#

ohh

#

what does the bar do?

#

ontop

tribal temple
#

Complex conjugate (of all entries)

obtuse totem
#

so it negates only complex numbers?

#

i bar would be -i

#

but reals keeps the same

#

alright

#

okie

#

thank you

#

I think I'll call it a day today

#

thank youuuu

#

gn 🙂

tribal temple
#

Goodnight SCgoodnightcya hope you rest well LanLove

obtuse totem
#

.close

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forest karma
#

no one is answering my f question

#

please help me

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sage helm
#

Consider a rectangle of length 4a and breadth 3a. If a circle of radius 1, completely inside the rectangle, is drawn, what is the probability that it does not touch nor intersect the diagonals?

sage helm
#

Kind of confused on how I'd even start with this one

#

i think it has to do with area

#

maybe a 1 cm clearance around the diagonals?

#

1 - that area/total area?

vague reef
#

Pythogaras theorem

sage helm
#

.close

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sullen scaffold
#

Quick question for understanding a concept

Cramer's Rule for the resolution of a linear equation system.

Say we have a matrix A that is not inversible. We will have to use the usual resolution with Gauss-Jordan?

crude pier
#

yes, because cramer's rule requires det(A) =/= 0

sullen scaffold
#

Exactly. Perfect, just making sure to know what to do if I get det(A) = 0.

#

If that is the case, gauss-jordan resolution.

crude pier
#

yes

sullen scaffold
#

Perfect. Thank you.

#

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thick grotto
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thick grotto
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.reopen

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thick grotto
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.reopen

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topaz wolf
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whats the fastest way to find inverse matrix

midnight plankBOT
topaz wolf
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or a simple way idk

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a good way

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like ik that A^-1 = adj(A)/det(A)

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that will take forever to find

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and theres this way

subtle blaze
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It’s a very hard task

topaz wolf
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where AB=I

topaz wolf
subtle blaze
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There’s no easy way to find the inverse of a generic matrix

topaz wolf
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oh ok so only those 2 ways right ?

subtle blaze
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If there were we’d use it

topaz wolf
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ye but like those r the only 2 ways

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?

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or there r others

subtle blaze
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There are others

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In linear algebra, an n-by-n square matrix A is called invertible (also nonsingular, nondegenerate or —rarely used— regular) if there exists an n-by-n square matrix B such thatwhere In denotes the n-by-n identity matrix and the multiplication used is ordinary matrix multiplication. If this is the case, then the matrix B is uniquely determined by...

midnight plankBOT
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@topaz wolf Has your question been resolved?

topaz wolf
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appreciate it

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.close

midnight plankBOT
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last slate
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Can someone please help me out with this?

robust isle
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it's a set containing relations inside of it

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so sure you don't see that everyday

last slate
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Oh, C contains congruence modulo relations

robust isle
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but it's not something completely outlandish

last slate
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Yeah, right

robust isle
last slate
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The question itself is throwing me off though

robust isle
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now the question a) itself starts getting quite abstract yes

last slate
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"Notion of refinement defines a binary relation on C"

robust isle
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they're defining a relation between congruence relations

last slate
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That means that for all $m, n \in \mathbb{N}^*$, we must have $\equiv_m$ refines $\equiv_n$?

grand pondBOT
robust isle
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no

last slate
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Are we taking this as a given?

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Oops

robust isle
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that would be like saying "a=b mod n for all integers a, b"

last slate
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Which obviously isn't true

robust isle
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so no, not all congruence relations refine one another

last slate
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For some values of m and n, I'm assuming they DO though

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And that's the whole point of the problem

robust isle
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to give an example, $\equiv_4$ refines $\equiv_2$

grand pondBOT
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aPlatypus

robust isle
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if a=b mod 4, you know that a=b mod 2

last slate
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Really?

robust isle
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the idea for refinement essentially is that a=b mod 4 gives you more info on a and b than a=b mod 2

last slate
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(7 = 3) mod 4

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(7 = 1) mod 2

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Is that incorrect

robust isle
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you still have 7=3 mod 2 tho

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their difference is a multiple of 2

last slate
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Yes

robust isle
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we're working with equivalence relations

last slate
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Yeah

robust isle
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so embrace them fully, and don't think of mod as only the comp sci remainder operator here

last slate
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Ok

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Sure

last slate
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But that's besides point

robust isle
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7=3 mod 2, 7=5 mod 2, 7=54867434984771617 mod 2, ...

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these are all true

last slate
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Got it

robust isle
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so yeah do you get why =_4 refines =_2 ?

last slate
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Yes, I do

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That's fine

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So the problem is asking me to show that the REFINEMENT relation is a partial order, i.e. reflexive, antisymmetric, and transitive on C?

robust isle
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yeah

last slate
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So we go back to the definition of Refinement right

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aRb implies aSb

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Actually, I feel like I'm getting ahead of myself

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I'm not sure

robust isle
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there's not a lot else you can work with anyway

last slate
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Yeah

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True

robust isle
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if you want a graphical representation of the situation regarding =_2 and =_4 here it is

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each of the equivalence classes from =_2 is neatly partitioned by some classes of =_4

last slate
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Yes

robust isle
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and there's no equivalence class from =_4 that spans two classes of =_2

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that's refinement

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now if you took =_2 and =_3

last slate
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There's no refinement

robust isle
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each of the =_3 classes is split between the two =_2 classes

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so yeah it prolly won't help directly for the abstract question

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but it's nice having some examples in mind

last slate
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Yup

robust isle
last slate
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Yeah, I'm thinking

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I'm confused

last slate
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Naturally, with all the information we have at our disposal, we are inclined to show that congruence modulo relations can be refinements of each other

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But as we said, that is not NECESSARILY the case

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And I'm not sure how to use that fact to answer the actual question

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Here's the start of my write-up

robust isle
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not all integers are congruent to each other mod n, but you can still talk about the "congruence mod n" relation

last slate
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Yes, sure

robust isle
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the question a) isn't really specific to congruence relations mod n anyway

last slate
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Indeed, which is what is confusing me

robust isle
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you should try to answer it without referring to the internals of the congruence relations

last slate
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They're asking me a question that's pretty specific to the refinement relation, it seems like

robust isle
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I think they just said "ok let's look at congruence relations mod n" to make the problem more digestible

robust isle
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but it's not specific to C at all is what I'm saying

last slate
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But I need to refer back to C though

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The question is asking "on C"

robust isle
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C could have completely other relations inside it

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the proof would be the same

last slate
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Okay, noted

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So wrong write-up

robust isle
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let's just get into it shall we

last slate
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Shouldn't refer to what's inside C

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Sure

robust isle
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so yeah we want to show the refinement relation is a partial order

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i.e. that it's reflexive, antisymmetric, transitive as you said

last slate
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Indeed

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That I'm okay with

robust isle
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can you rephrase these three properties in terms of the refinement relation ?

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like just write what reflexivity would look like in this situation

last slate
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Give me a minute

last slate
grand pondBOT
last slate
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It seems a little iffy notation-wise

robust isle
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yeah or "forall R in C, R refines R"

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they're really insisting on the congruences mod n in the question for some reason

last slate
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For antisymmetry and transitivity, would be a similar thing

robust isle
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yeah, just state them so that we really know what we have to prove

last slate
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Ok, let me write this down

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Should I delete reference to the congruence modulo relations in my write-up?

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Or does it not matter

robust isle
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it's gonna be easier to follow (and to write) if you don't refer to them

last slate
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Isn't that going to be confusing

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Ok, it's fine

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I'll write up later

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What we need to prove

robust isle
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ok yeah

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pick one and try to prove it

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the whole proof is gonna rest on the fact that set inclusion defines a partial order already

last slate
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Don't we need to bring back the congruences to prove them

robust isle
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no, use the definition of refinement

last slate
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So, if we use the definition of refinement