#help-49
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Yes, or cosx=1/3
And how would that work?
Sin is 0 for nπ, so you have -180, 0 and 180 as answers
yeah that makes sense'
For cos you need to use calculator as we don't know the exact value for cos inverse 1/3
Remember to equate this to 2x+30
yeah
Yes
It's just factors
If multiplication of 2 quantities is given to be zero, one of them or both of them could be zero
Glgl
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what methods do you guys use to factorize stuff like this
Find factors of 3
And sub those values in for x
If it adds up to 0
It is a factor
It’s like
Integral zero theorem I think It was called
P(x)=x^4 + 4x +3
Factors of 3 is +-1, +-3
So trial and error those values for x
And then you can do synthetic division
Lmk when u get there if u need help

i get everything about those but the problem is the videos only show x^2
dont go for rational roots or smth
these expressions are easy to evalutate you just need to make perfect square
Huh
wait
Wdym
Examples shown in youtube videos are usually x^2
i can't look up the technique for higher grade polynomes anywhere
Do you know integral zero theorem
https://www.youtube.com/watch?v=KziDD1hVEMI oh sec that's a hint
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 ...
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.
Where did you learn it like that
oh i have come across such problems many times during my oly prep
so i developed this technique myself but im sure more ppl know about this .
i also got one hammer method to factor polynomials of form
x^4 -16x-12
also there is one hammer method to factorize or solve biquadratic equation with cubic terms as well
(monic)
in the first one both +1 and -1 equal 0
so how do i know which of the 2 is the correct one
or both are directly factors
AH ok makes sense then
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Can someone help with this? Idk how to answer
Think about the relationship that acceleration is the change of velocity per unit time
And construct a differential equation
Velocity is the integral of acceleration
Wait wdym?
Yep
just intergate
So workout the integral with initial value 5
v(t)=t^2
Yep and you know the value for t = 0
v(t)=C
No c is a constant that is lost on the differentiation. So you are setting c to 5
Integrate t^2+5 from 0 to 5?
You can just plug in t for the end speed
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Please help me to understand this
Tried many times but cant reach the conclusion
AB = A, and BA = B. So you can multiply both sides by B or A to get ABA = A^2 and BAB = B^2.
However, AB still equals A, and BA still equals B, so you can probably use that
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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
is that all we need to say ?
Have u learnt calculus?
use the vertex
and put it into the equation
i found it using -b/2a
to get corresponding y value
its 25
its that easy ?
yep
its basically almost the same as the c)
i just needed to tell if it was max or min
and bc leading coeficient is - its the max
thanks for the clarity anyways
have a good day and ty for the help : )
wdym
How do u find max/min using vertex thinggy?
its just -b/2a to find x value and then plug it into the function to find the y value of the vertex
I didnt get taught it back then
-b/2a is also to find the axis of symmetry of the parabola
i have another question, when i completed the square i found 2(x+5/2)^2 -9/2
does the 2 mean a vertical or horizontal stretch ?
vertical
BRUH, why I didnt get taught this....
if f(x) = x^2 and g(x) = 2f(x) you are basically doubling y values of f(x) by 2 in g(x)
which means that your curve will be much steeper or closer to y-axis
theres another way to find it, when you completed the square a(x-b)+c, the b is also the axis of symmetry
bc to find it you do -b/2a
and it makes sense because b represents the horizontal transformation
Well, it probably I was taught quadratic equation in 9 grade and get taught precalc at 10
it will tell you if the axis of symmetry moved 2 units to the left or to the right for example
same here
My precalc was brutal
yes but on the complete the square form a(x-b)+c i dont know if a is af(x) or f(ax)
so if its a vertical or horizontal
i think precalc trig will be brutal for me
we just started it
what grade are u in now ?
undergrat
ig ur major is math ?
Engineering
Nope
im still not sure if i want to do enginerring or finance
so basically architetcure ?
the math and physics behind architecture
Totally different thing
Lowkey yes
it seems fun as well
well civil enginerring is pretty much buildiing roads, infrastructure etc right ?
whats ap ?
Applied Physic
ohhh
nice
physics is fun
you basically use math to solve real life problems
best of both worlds
My professor once said: "There's nothing fun about physic, only pain and suffering "
😫
do you still have time to change majors ?
lol
ig the physics i do is pretty simple compared to yours
@echo forge could you help with something ?
Gonna grad next month LMAO
oh
fuck
so you have done the entire four years even tho you dont like it
i feel sorry for u
this year is the first year i have biology and i cant have one more class of it
you had classes everyday for four years on smth you hate
thats ruff
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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?
🇵🇸Mína🔆
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
How can we say that that'll always exist for an arbitraty s?
if anyone has a different proof, I'll be happy to see it
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@frozen totem Has your question been resolved?
apparently it comes from the N/log(N) asymptote
thank you so much! Could you throw me an article to cite?
I won't prove it in the thing, I'll just quote it
it's from here https://en.wikipedia.org/wiki/Bertrand's_postulate
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how do I find the diamond and square
m8of48...
slayla 
or just plug -3 in
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I don’t really understand this problem can someone help
I assume length is getting the magnitude
But direction I don’t really know
Is it just finding the unit vector
they might want the angles
@minor turtle Has your question been resolved?
Like for example
This is a similar question with a cross product
Where it asks for length and direction
Would the direction just be the unit vector of the cross product/vector
?
Hell
Hello
<@&286206848099549185>
Direction is the angle of the vector from standard position
Arctan(y/x) gives the angle of direction
Why is the direction here different then
Not sure about this
Direction vs angle direction
So length is just sqrt of the sum of the terms squared
If you divide the sum of your vectors by their length you get direction
cross product*
So if the cross product evaluates to 0 there is no direction because if you divide by length it’s still 0
@minor turtle Has your question been resolved?
Alright
So the direction is basically the cross product divided by the magnitude
?
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<@&286206848099549185>
@raw owl Has your question been resolved?
<@&286206848099549185>
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does y^2+2y-1 simplify to (y-1)^2
no
you must've done something wrong
ah
i see
well im stumped on what to do then
I moved the 4x and 21 to the other side
and the only way to complete the square would be subtracting one no?
(y+1)^2 = y^2+2y+1
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,, f(x)=\sqrt{2{x}^2-3{x}+1}+\sin^{-1}x
yajat
we have to find its domain
stuff inside sqrt() cant be <0 right?
yea
wait let me just show u what i've done
i've come to this result- ${x}\in \left(-\infty,\frac{1}{2}\right]\cup [1,\infty)$
yajat
and also $x\in [-1,1]$
yajat
@last slate Has your question been resolved?
astar 💔
{x} means fractional part right
ok so to satisfy arcsin x
sin-1x x has to be between -1 to 1
factorise that polynomial
3+-1/4
1/2 to 1
so in range 1/2 to 1, the polynomial is -ve so regect
answer should be [-1,1/2)
@last slate
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sorry wait a min
but this is not the answer
fractional part is always positive
thaaats why
wait then
if we remove values from 1/2 to 1
we do it in -ve side too
-1 to -1/2
shouldnt we omit -1 to -1/2
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how would you do that
let's call that A so i dont have to write the whole thing
what do you get for sin A
yea
ok
i know you use cos(x+y) rule but i dont know why or how you determine it
this whole thing ill call A
ok
why do you do that
you'll understand why in the next step
(actually you can also use cos(x+y) but I was trippin and thought it was like tan sum formula)
so then sin A would be 38/65 right?
what
from that
sin A become 56/65 doesn't it
oh
pretty sure its 56/65
yes that
k
k
yeah
so you'd get cos A = 33/65
yeah
why at the start did you want sinA
.
my brain was not braining
how do you decide it's cos (x+y) then or is it trial and error
you could also do the same with cos (x+y)
cos(A) would be like 4/5 x 12/13 - 3/5 x 5/13
which gives the same result
so how do you decide to do cos(x+y)
wdym?
so why cos(x+y) not cos(x-y)
well u can use either sin or cos, just need to convert
because they're summing
k im stupid nvm
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3 squares of a chess board are selected at random, the probability of getting two squares one colour and one square another is
$\frac{2c\left(32,2\right)c\left(32,1\right)}{c\left(64,3\right)}$
ƒ(Why am. I here)=misery
would this be it
,w $\frac{2c\left(32,2\right)c\left(32,1\right)}{c\left(64,3\right)}$
16/21 should be right
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✅
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
so the sample space would be $(15)^7$
ƒ(Why am. I here)=misery
now what
since the max number on coupun can only be 9
the selection is made from coupons numbered 1 to 9
so total 9^7 ways
and one is fixed
hmm
ok
thanks
wait
my book says
$\left(\frac{3}{5}\right)^7-\left(\frac{8}{15}\right)^7$
ƒ(Why am. I here)=misery
I don't get this part
why isn't it just (9/15)^6
yes
also its not just 9/15 because
but one coupn has to be 9
{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
got it
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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
so total 6*5 possibilities
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
what are u trying to do
so there are 3 choices for the first number
1,2,3
and 3 for teh second
4,5,6
so 9/30
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!
ooo
and for (B) there are 2 cases
9 right
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})
so 18/30
18+6
you forgot to add this
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Hey
We have a system Ax=b
A and b however have errors in them
$\tilde{A}\tilde{x}=\tilde{b}$
Martin
$\tilde{A}=A+\Delta A$
Martin
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
This is what i got so far
I will work on something else for now, maybe i ask again later
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Hello I have probability-related questions I'd like to ask
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
Yeah use Gamma distrbution
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>
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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
$A^2=7A-4I$
ƒ(Why am. I here)=misery
multiplying across by $A^{-1}$
ƒ(Why am. I here)=misery
$A=7-4A^{-1}$
ƒ(Why am. I here)=misery
what if you did (A - 2I)^2 like completing the square
ƒ(Why am. I here)=misery
that is the idea yes
$(A-2I)^2=3A$
ƒ(Why am. I here)=misery
det that shit!
that feels unnecessary
hmm let $det(A-2I)=u$
ƒ(Why am. I here)=misery
$u^2=det(3A)$
ƒ(Why am. I here)=misery
$det(3A) is 3^3 det(A)$
ƒ(Why am. I here)=misery
should be
Yeah
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the question is if this matrix can even exist
not diagonal
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
?
det A is the value of the char pol at 0
oh right mb
Damn
no it means every answer choice is correct

wtf is gemini
bard
the google ai
i was never into astrology
it's ok
Bard is google's answer to GPT
wdym
dw i'm talking to layla
what’s that
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not really
why ?
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How to do this
I know that $A = PDP^{-1}$
Book Reader
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
Book Reader
$P = \M[ ? 0 ; ? 1]$
Book Reader
Book Reader
Book Reader
How did you get 14/4
$\M[0 0 ; 4 -14] \equiv \M[0 0 ; 1 -14/4]$
Book Reader
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
aye
Well you try and just wing it when you try and find your eigenvectors
$x = y \M[ 1 ; 14/4]$
Moral of the story : don't wing it
wiat
Book Reader
nah, i'm following the method that I learnt, not winging it
the first column has a pivot position and the second doesn't
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 
Yeah, I just put the 14/4 in the wrong row
Yeah seems like it
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How do I determine if a matrix is diagonalizable?
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
$A - 7 I = \M[3 -3 ; 3 -3] \equiv \M[1 -1; 0 0]$
Book Reader
So the only eigenvalue you got is 7 right ?
Book Reader
Ok yes
Well think of how many linearly independent solutions you can get from that
1?
$x = y \M[ 1; 1]$
Book Reader
Yeah so only one solution
So I'll just have to check each eigenvalue and see if it has a eigenspace dimension equal to eigenvalue multiplicity?
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
okay
But it's a bit of a special case here
In general you'd have to go for the long checks
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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)
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
(A,B) - (2A, 2B)?
why subtracting though
and in what order
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?
sorry my wifi cut out
but why can't you do (-8,2)-(-4,4)?
because vectors have directions
when you calculate a distance in the vector way, you first get the final point and subtract the initial point
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ok I couldnt type in the other channel anymore
damn channels
ok so why is [T] w respect to basis C, the inverse of the matrix formed by vectors in basis C?
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
yeah it also got me at first
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
if you want
@obtuse totem Has your question been resolved?
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?
they say that they have earlier shown these things for the dot product
(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)
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
@obtuse totem Has your question been resolved?
LMAO not me listening to clubbing music while doing math😭 😂
@obtuse totem Has your question been resolved?
I think theres a typo
should be [2t 3t]
Please let me know if there isnt... cause I really dont trust my thinking
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...
-did they use the dot for the dot product to instead represent the complex standard inner product 
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 
Complex conjugate (of all entries)
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 🙂
Goodnight
hope you rest well 
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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?
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?
Pythogaras theorem
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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?
yes, because cramer's rule requires det(A) =/= 0
Exactly. Perfect, just making sure to know what to do if I get det(A) = 0.
If that is the case, gauss-jordan resolution.
yes
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@thick grotto Has your question been resolved?
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whats the fastest way to find inverse matrix
or a simple way idk
a good way
like ik that A^-1 = adj(A)/det(A)
that will take forever to find
and theres this way
It’s a very hard task
where AB=I
wdym
There’s no easy way to find the inverse of a generic matrix
oh ok so only those 2 ways right ?
If there were we’d use it
There are others
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...
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Can someone please help me out with this?
Oh, C contains congruence modulo relations
but it's not something completely outlandish
Yeah, right
yes
The question itself is throwing me off though
now the question a) itself starts getting quite abstract yes
"Notion of refinement defines a binary relation on C"
they're defining a relation between congruence relations
That means that for all $m, n \in \mathbb{N}^*$, we must have $\equiv_m$ refines $\equiv_n$?
Omega
no
that would be like saying "a=b mod n for all integers a, b"
Which obviously isn't true
so no, not all congruence relations refine one another
For some values of m and n, I'm assuming they DO though
And that's the whole point of the problem
to give an example, $\equiv_4$ refines $\equiv_2$
aPlatypus
if a=b mod 4, you know that a=b mod 2
Really?
the idea for refinement essentially is that a=b mod 4 gives you more info on a and b than a=b mod 2
Yes
we're working with equivalence relations
Yeah
so embrace them fully, and don't think of mod as only the comp sci remainder operator here
I didn't even know we were allowed to write this
But that's besides point
well you don't have to reduce everything to the smallest representative all the time
7=3 mod 2, 7=5 mod 2, 7=54867434984771617 mod 2, ...
these are all true
Got it
so yeah do you get why =_4 refines =_2 ?
Yes, I do
That's fine
So the problem is asking me to show that the REFINEMENT relation is a partial order, i.e. reflexive, antisymmetric, and transitive on C?
yeah
So we go back to the definition of Refinement right
aRb implies aSb
Actually, I feel like I'm getting ahead of myself
I'm not sure
there's not a lot else you can work with anyway
if you want a graphical representation of the situation regarding =_2 and =_4 here it is
each of the equivalence classes from =_2 is neatly partitioned by some classes of =_4
Yes
and there's no equivalence class from =_4 that spans two classes of =_2
that's refinement
now if you took =_2 and =_3
There's no refinement
yeah
each of the =_3 classes is split between the two =_2 classes
so yeah it prolly won't help directly for the abstract question
but it's nice having some examples in mind
Yup
you can try solving the q yourself for a bit
Do we need to show that the congruence modulo relation is a "refinement relation"? How does that relate to the fact that the refinement relation is a partial order?
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
But as we said, that is not NECESSARILY the case
And I'm not sure how to use that fact to answer the actual question
Here's the start of my write-up
yeah so what
not all integers are congruent to each other mod n, but you can still talk about the "congruence mod n" relation
Yes, sure
the question a) isn't really specific to congruence relations mod n anyway
Indeed, which is what is confusing me
you should try to answer it without referring to the internals of the congruence relations
They're asking me a question that's pretty specific to the refinement relation, it seems like
I think they just said "ok let's look at congruence relations mod n" to make the problem more digestible
yeah sure
but it's not specific to C at all is what I'm saying
let's just get into it shall we
so yeah we want to show the refinement relation is a partial order
i.e. that it's reflexive, antisymmetric, transitive as you said
can you rephrase these three properties in terms of the refinement relation ?
like just write what reflexivity would look like in this situation
Give me a minute
$\forall \equiv_n \in C, \equiv_n [_{ref} \equiv_n$
Omega
It seems a little iffy notation-wise
yeah or "forall R in C, R refines R"
they're really insisting on the congruences mod n in the question for some reason
Yeah
For antisymmetry and transitivity, would be a similar thing
yeah, just state them so that we really know what we have to prove
Ok, let me write this down
Should I delete reference to the congruence modulo relations in my write-up?
Or does it not matter
it's gonna be easier to follow (and to write) if you don't refer to them
So, remove the first paragraph?
Isn't that going to be confusing
Ok, it's fine
I'll write up later
What we need to prove
ok yeah
pick one and try to prove it
the whole proof is gonna rest on the fact that set inclusion defines a partial order already
Don't we need to bring back the congruences to prove them
no, use the definition of refinement
So, if we use the definition of refinement






