#help-28
1 messages · Page 274 of 1
Even without the bonus problem, I hope that was clear enough
Yeah that's super helpful
Ok so would the original students approach work for this version
I'll let you take a guess
what are the "problematic" points for this integral?
(the bound(s) which make(s) the integral improper)
Infinity and 0?
yes
in those integrals, the only improper bound was 0
in here, it was only infinity
to sum up, you've only seen what happens with one improper bound
so, the p tests that we used were around 0, or around infinity
there definitely isn't a p test that works with both
the values of p that work around 0 are p < 1
and the values of p that work around infinity are p > 1
so a single p test won't get us out of this
So do you just do multiple?
the question is, how are we going to do multiple p tests
we would need to have multiple integrals
for example, one where only 0 is the improper bound, and another one where only infinity is the improper bound
Do you see what we're gonna do?
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I am asked to find the area of the shaded region
i think there should be a plus there, is that true?
you are subtracting a negative, so yes there should be a plus
to find the area between these two, i have to do integration wrt x
but idk how to write the second function in form of y=f(x)
you can just rearrange the equation x = 2 - y^2 for y 
and choose the positive root since the graph you’re given has a y-intercept of 2
why do i have to choose the positive part?
the graph is going under the x axis too
because the graph here has a y-intercept of 2, not -2
hold on, they flipped the x and y axes
well, either way, you need to pick the function that matches the graph
use the x-intercept to do that
the intersection points are -2 and 1
so i just integrate now?
,w integrate root(2-x)+x from -2 to 1
is this gonna be correct?
@royal dew Has your question been resolved?
is this the correct integration for area between y = -x and x = 2-y^2 guys
ye\
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find volume of solid of revolution using shell method
okay guys for this one i used integral of 2pi y f(y) dy
,w integrate 2 pi y (2y-y^2) from 0 to 0.5
Why are you integrating up to 0.5 lol
Also its 2y- 2y^2 not 2y-y^2
Otherwise its fine
lmao i mixed up the x and y dimensions
its gonna be from 0 to 1
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Since there is no finite-dimensionality assumption, we must explicitly construct the isomorphism. I am looking for hints on how to do that.
@stone meteor Has your question been resolved?
We can at least begin by stating some basis of V/U, but either way, I'm not sure where to go from there.
to build a map U x (V/U) -> V, you can start by mapping (u, 0) -> u
how do you use the basis to map elements of the form (0, v)?
holo_morph
what are v1, ..., vn?
Let $v_1+U,...,v_n+U$ be a basis of $V/U$. We claim that
[
V = U \oplus \text{span}(v_1,...,v_n).
]
We know that $V = U + \text{span}(v_1,...,v_n)$ since for all $v \in V$,
\begin{align*}
&v +U = a_1v_1+\dots +a_nv_n+U\
&\Rightarrow v-(a_1v_1+\dots +a_nv_n) = u, \text{for some } u \in U\
&\Rightarrow v = u + (a_1v_1+\dots +a_nv_n).
\end{align*}
Moreover, suppose $v \in U \cap \text{span}(v_1,...,v_n)$.
\begin{align*}
&v = u = a_1v_1+\dots+a_nv_n\
&\Rightarrow v+U = 0+U = a_1v_1+\dots+a_nv_n + U\
&\Rightarrow a_j = 0\ \text{for each } j =1,...,n\
&\Rightarrow v =0\
&\Rightarrow U \cap \text{span}(v_1,...,v_n) = {0}.
\end{align*}
holo_morph
this is my current progress
this is pretty much the argument, but you should rephase it in terms of proving an isomorphism
but this isn't done
now I have to construct the argument
now I have to construct an isomorphsim from V to U x V/U
although I guess that is quite easy to see now
because I just decompose elements v into u + a_1v_1+...+a_nv_n
then send
you've described the map
yes
no I haven't lol
I just did here
but not in the proof
but I think I can do the rest anyways
.close
thanks
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.reopen
✅ Original question: #help-28 message
I'll keep this open actually
because I may find trouble with showing injectivity and surjectivity
or maybe i should instead opt for the possibly better method of just constructing an inverse
okay I am kind of confusing myself
Let $v_1+U,...,v_n+U$ be a basis of $V/U$. We claim that
[
V = U \oplus \text{span}(v_1,...,v_n).
]
We know that $V = U + \text{span}(v_1,...,v_n)$ since for all $v \in V$,
\begin{align*}
&v +U = a_1v_1+\dots +a_nv_n+U\
&\Rightarrow v-(a_1v_1+\dots +a_nv_n) = u, \text{for some } u \in U\
&\Rightarrow v = u + (a_1v_1+\dots +a_nv_n).
\end{align*}
Moreover, suppose $v \in U \cap \text{span}(v_1,...,v_n)$.
\begin{align*}
&v = u = a_1v_1+\dots+a_nv_n\
&\Rightarrow v+U = 0+U = a_1v_1+\dots+a_nv_n + U\
&\Rightarrow a_j = 0\ \text{for each } j =1,...,n\
&\Rightarrow v =0\
&\Rightarrow U \cap \text{span}(v_1,...,v_n) = {0}.
\end{align*}
Now, we define a linear map $T \in \mathcal{L}(V, U \times (V/U))$ by
\begin{align*}
T(v) = T(u + (a_1v_1+\dots+a_nv_n)) = (u, (a_1v_1+\dots+a_nv_n) +U).
\end{align*}
It is self-evident that this map is linear and well-defined; we now direct our focus to showing that it is indeed an isomorphism. Suppose $T(v) = (0,0)$,
\begin{align*}
&u = 0, (a_1v_1+\dots+a_nv_n) \in U\
&\Rightarrow (a_1v_1+\dots+a_nv_n) + U = 0 +U\
&\Rightarrow (a_1v_1+\dots+a_nv_n) = 0\
&\Rightarrow v = 0 + 0 = 0.
\end{align*}
This shows that $T$ is injective. Furthermore, for any $(u, v'+U)\in U \times (V/U)$,
\begin{align*}
&(u, v'+U) = (u, (a_1v_1+\dots+a_nv_n) +U).
\end{align*}
Thus, $\exists v \in V$ such that $Tv = (u, v'+U)$ since we can just define $v$ by
\begin{align*}
&v = u + (a_1v_1+\dots+a_nv_n)\
&\Rightarrow Tv = (u, (a_1v_1+\dots+a_nv_n) + U) = (u, v'+U).
\end{align*}
This shows that $T$ is surjective, establishing an isomorphism of $V$ onto $U \times (V/U)$.
holo_morph
How is this looking?
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im doing part e) and i honestly don't understand how to do it after sayin that f(-1) - integral (from -1 to -4) of f'(x) dx = f(-4), how do i go about it? i was thiking maybe find the area of the interval? How would you solve it?
this is where i am at
Good! Yeah this looks about right.
You don't know what f', so its reasonably difficult to find a precise value for f(-4). I'd say use any estimation that you like.
For example, you can create rectangles.
ok brb lemme try that
ok so now i have that f(-1) - 4.7ish =f(-4) and since f(-1) =3 that is 3-4.7ish = -1.7=f(-4)
is that good?
Yeahh 4.7 looks good since it does look over the x axis
Yep! Fine to me.
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@umbral dome can u explain here?
yes
tysm
so you said that the centroid of suape 2 is at y = 75
but that's not correct, it would only be true if the second shape went all the way to the left edge
I’m having a similar problem here 💔
So how would you go around that
the second shape as you defined it is a rectangle whose left edge is at y = 6 and whose right edge is at y = 150
And how can u tell if it is or isn’t
it's up to how you decide to split up the shape into rectangles
based on this information, what should the average y coordinate of this shape be?
So for Qyy I DONT include the first shape in my calculations?
Hmm
One sec
72 for the second shape?
not quite
remember we removed the left section, so the centroid should not be further left
R we talking about the vertical or horizontal for the second shape/ right side?
I meant this along the Y axis so horizontal
Ohhh wait
Yeah I was gonna go for 72💔
Sorry🥹
I’m terrible at section properties😭
So when we split the shape we never include the other parts of the shape in our calculations?
your shapes should not overlap
yes
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Do u guys know someone's explaining How to solve a linear programming problem using the graphical method
I looked in YouTube but like no one's explaining it in a good ?way
I'd be thankful mate
@chilly kernel Has your question been resolved?
@chilly kernel Has your question been resolved?
I would much recommend you keep the assistance to this channel.
While not disallowed, it's more practically beneficial if you can get people to cross-check your work
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hi,
I am wondering if any tutors would be able to take a couple hours tonight and help me study in a call for my differential equations final exam. I am not sure if this is against the rules of your server but if it is please feel free to close the ticket. Id be willing to pay for the time as long as the price named isnt outrageous.
@stiff valve Has your question been resolved?
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I am having a hard time understanding why this is not closed using the S\A definition (the complement must be open). I understand that it doesnt include 0 so its closed via limit points but my book has not introduced this definition yet
More plainly, A^c is just the union of all sets (1/n,1/(n+1)) which is clearly open.
and also (-inf,0) for the first set which is also open, then (1,inf) for the last set with is also open
hense, the complement of A is open so A must be closed? am i missing something?
are you sure about that?
this part yes
but also
just realized
doesnt include 0
so thats the closed part
the complement includes the point 0. think about the open sets containing 0
Yeah
🤔
0 must be in A^c
so the complement is the union of empty sets?
so its (-inf,0]
🤔
no
right, are there any open sets containing 0 that lie entirely in A^c?
(1/n, 1/(n + 1)) is empty since 1/(n + 1) < 1/n
I ment the other way around 
but yeah its becase the first set would be something like
(-inf,0]
which is not open**** (whoops im just learning this lol)
and by alkamedian there is always some 1/N between 0 and 0+r which will be in the r neighborhood
if we just append 0 that would be a closed set right
this is the entire argument
i’m not sure i understand what your question is
did you answer your own question?
@celest fulcrum Has your question been resolved?
I didnt know how the complement was open but i figured out i made a mistake not including the 0 in the complement
which was the question
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this is beckmann rearrangement right?
go to other doubts mr pigeon
whats funi beckmann then?
Idk why this happens so frequently, people ask stuff other than math here
because it isn't against the rules to do so actually
Fr?
one guy asked 10/2 when 5*2=10 was written in the qn
yesh
This one?
yes
mb this one actually
Not sure if it’s what you’re looking for
ts one mate
im js asking whats its name
beckmann rearrangement or funi beckmann rxn?
Yeah it is
Was that all you wanted to ask?
yea
Couldve just googled it...
any ideas whats funi beckmann
Unfortunately I dont
ik that very well but wanted to do it specifically in this sv
i wish to make it a kinda norm
If you wanna learn more, theres certain exceptions too
Those reactions are called abnormal Beckmann
u hv sm material relating to it? if yes do dm me
Ah i used to do this a year ago
My notes are probably just crumpled up now
Ah yes i remember favorski
i learnt fetizon very recently
a highly chemoselective reagent
im in 12th grade
JEE?
ill also hv to understand chemoselectivity regioselectivity n enantioselectivity thoroughly
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If pipe A fills 9 hour faster than pipe B
What would be the equation?
A=B-9
A=B+9
Neither, afaik
you have to be clear first in what the letters A and B mean in your equations
cause if they mean the flow rates of the pipes, then yeah, neither
also just to make sure: you are saying pipe A and pipe B are connected to the same pool and we are comparing the fill times from each pipe open individually, yes or no? @summer creek
and, once again: in your equation, the letters A and B represent the flow rate of water through each pipe, yes?
@summer creek Has your question been resolved?
mb
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hi yall, I need help with this question. we solve it using taylor series method, I did it for sinx and got my answer as 1/6, for tanx and the denominator x^n idk how to deal with them, I tried puting tanx as sinx by cosx [which is 1], but that is not working
the method given in solution is insanely long compared to 60 seconds time limit we are given, so like anybody knows any short cut to solve it quickly?
Try plugging and checking
Since it's multiple choice
but if I do direct substitution without cchanging the equation then I plug 0 in x, so in denominator any power of 0 is just 0, soo like how wld that work?
yes
wdym?, [I got introduced to limits tdy, I'm finding it difficult with terms]
2?
he's telling sub all the answers and check manually what works
For each answer they gave you, substitute n in and find the limit
its 4
yeah
i got it
expand and cancel
@desert sonnet sub the expansions of sinx , tanx , multiply the leading coefficient and that is = to ur n
Im not really used to this trig thing in algebra, but i'd be better with no trig
same
for the question to be satisfied , the condition is the denominators power shud cancel the power in the numerator
x^n = x^4
n = 4
so tanx is an odd function that we have to take odd values. got it thankss
A is someone B is someone
.close
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@onyx glen
.
@summer creek Can you add those descriptions to your original question?
those "A is someone B is someone" make no sense to me
A,B represent a name
if they represent a name then they are of type String at best & cannot fit into any equation!
!xy
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
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Explain me fractions
what about fractions are you confused, and what grade are you atm, if you don't mind me asking?
Status
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I need help with a lesson coming in my Geometry midterm
Just post your question
that's always fine
ok, so what have you tried for this one?
afaict, you are asked to merely describe the relationship of these lines. you're not told to calculate anything.
so a qualitative answer would do.
specifically, you should aim to describe the relationship of the escalator to the floors it passes.
i dont understand what they mean
which part?
the releationship of the lines
do you know what transversals are?
a line that cuts between two or more linrs
parralel?
there we go.
now look at the floors. they're all horizontal. they're parallel to each other, aren't they?
yea i do see that
and you see how the escalator cuts through those floors like a transversal?
yes
that is the relationship needed
and I believe that's all they are asking for - merely to describe the floors as parallel lines and the escalator as a transversal to all of them.
so the escalator acts as a transversal cutting through parralel lines?
cutting through the floors*, which are parallel to each other
no permission needed mate. go ahead.
wish I had pin perms to pin each question as they come though, but welp
... this is an English question.
oops
got a math one for the math server?
by accidemt
nps
right, so what have you learnt about angles formed by transversals and parallel lines?
though I will give you a spoiler: you don't need any knowledge of transversals whatsoever to find x.
you do need some knowledge to find y, however.
i think that there are diffrent types of angles
not wrong. but what kinds?
specifically, there are three main kinds of angles you should look out for when dealing with transversals
can you name all three (or more/less depending on how your syllabus phrases this) and the corresponding properties?
if you can draw a diagram for each, that'd be best!
like corresponding alternate interior/exterior interior
ok that is cool, but do you know the properties of each?
linear pair vertical angles consecutive interior/exterior
let's first separate those to make them easier to recognize.
go in order of: corresponding angles, alternate angles, interior angles.
i think all of them are equal except linear pairs and consecutive interior which equal to 180
linear pairs and vertical angles have nothing to do with transversals directly
idk but my geometry teacher said some questions will have them.
oh ok I was a bit confused as to what consecutive angles are, but I see what you call consecutive, I call cointerior.
yes, no doubt questions will have them.
in fact, it is used in that very question you shared
but it is not exclusive to transversals. linear pairs exist any time a straight line intersects another straight line
oh ok
i dont think so
why not?
the 40 and the 5x have one very straightforward relationship
in fact, I was just talking about that specific relationship
because idk how to know what the angle relationship is from figures like that, and my mind goes blank...
well, going blank should be the last thing on your priority list, but let's make it this way
is line B a straight line?
i think so
well you don't have to think
they are straight
and so is C
there's not a single curve to be found here
Alright
more importantly, B and C are straight lines
and they intersect each other.
what kind of angle(s) did we just say is/are created by two intersecting straight lines?
linear pair?
mhm. and what are the properties of two angles in a linear pair?
supplement
apply it here.
28
,calc 140/5
Result:
28
good. one down, one more to go
now there are two ways I can immediately see to find y
but I want to hear your ideas first.
ok
note that lines A and B are parallel. use that to your advantage
so what attack plan do you have in mind?
first to find the angle
ok for this one, you should probably mark the angles you want to find
wdym?
since there are no letter names to help describe the angles you mean
well you said find the angle
there are literally eight angles in this image, and even excluding the three marked angles there are still five of them
so find which angle?
Alternate exterior
so which angle is the alternate angle here?
(that's why I told you to mark the angle you're referring to!)
40 and 3y-1 are alternate exterior
no, unfortunately not
40 is not an exterior angle when considering the perspective that allows 3y-1 to be an exterior angle
then idk...
but now that you mentioned that alternate exterior angles are available to you, I see three ways of doing this
the first way is to indeed use alternate exterior angles, but not using 40
you'd use the 5x angle instead
140?
yes
,calc 141/3
Result:
47
so that you don't get hopelessly stuck as you do here
ok
the second method is to use the fact that 40 and the blue angle are interior angles. find the blue angle, then 3y-1 is vertically opposite that. and boom.
the third method is to use the fact that 40 and the red angle are corresponding angles. find the red angle, then 3y-1 is a linear pair with that. same shit.
but from what I can tell now, it seems like you need more exercise on identifying corresponding, alternate (interior or exterior), and cointerior angles, as well as maybe linear pairs, in any given diagram
you should probably get a few diagrams to practice this
I immediately see two attack plans
I'll give you a hint on what types of angles are involved in both
I'll give you the harder one to spot first then
ok
the method I'm talking about involves forming a system of two equations: one with a linear pair, and the other with cointerior angles
that being said, it is the harder method. there is a way easier method. try finding that.
(or surprise me with another method)
by what property?
wdym
they are alternate enterior angles
since you're not that hot in identifying angles, I want to make sure you get this right, so you can explain your steps if you are asked to.
and trust me, you do not want to not explain your steps in an exam.
you mean interior?
then yes
proceed
yes my bad
so 8x=7x+10
i subtract 7x from both sides to get x=10
cool. keep going
6y=20 and 7x are linear pairs
hope you meant a + there instead of an =
yes i forget sometimes to click shift
so 6y+20 +7x=180
Good
i think i substitute x with 10
I'll leave this channel to 1/0 then
bye and thanks for ur help @next cedar
ok so 6y+20+70=180
6y+90=180
6y=90
division
so 15
anyone here
😭
Yes
at least ping me for that 😭
alr thats all
!done
If you are done with this channel, please mark your problem as solved by typing .close
why should I if you were watching
thank you @next cedar and @delicate torrent
I mean I said I got this, yet you insisted on jumping in
Im hopping into a load of other channels too
.close
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Really struggling with this one and not sure where to start
remember that switching bounds negates an integral
Since $f$ is odd, what is $\int_{-a}^a f(x) \dd x$?
Nel
0
0
but what does that have to do with it?
cassie can i try with my tools?
sure
Can you split $\int_{-4}^2 f(x) \dd x$ for example?
Nel
why is ur name invisable
the problem is the tool i use has a watermark you have no issue with that?
hi 
this feels weird
you give off weird vibes
I like Nel
sorry, what is splitting it?
Like transform it into a sum of two separate terms
Ohhh
I mean
would that be f(2)dx - f(-4)dx
You might want to learn a bit of LaTeX
Cassie on a scale of 1 to 10 how much would you rate my preformance!
The notation to render these
commit alive not /10
Oh
Uhhh maybe eventually?
I'm going into chemical engineering so I might have to learn it eventually
idk
I have to learn coding and whatnot
I'm saying that because I'm not sure what this means
Oh
it's the second fundamental theorem i think
Nel its okay you tried!
I'm not really sure how to do this problem
and thats what truley matters..
Feel free
<@&268886789983436800> There's some weird bot here, @real vector
Do you understand that $\int_a^c f(x) \dd x = \int_a^b f(x) \dd x + \int_b^c f(x) \dd x$ ?
Nel
sybau
Intuitively that should be obvious if you look at areas under the curve
anyways
......
yea sybau
like atleast look at it///?
Yeah I've just been doing math homework for 5 hours now so I'm a bit lost in the sauce if you get me
....ong
@real vector do not use AI to answer other people's help channels.
you should ban it fr fr
hmm how do i explain it
And @lunar creek has made it clear enough that she doesn't want you to help her, so please just leave the channel 
do yk what html scripts are?
cool
in either case i do not think cassie wants a canned response
oh okay!
you’re not fooling anyone when you say that it wasn’t ai generated
whats a canned
- its not?
- if its incorrect its my fault
thats insane nel back me up here bud
For $\int_{-4}^2 f(x) \dd x$, given you know $\int_{-a}^a f(x) \dd x = 0$, you should be able to figure out appropriate bounds to split and simplify
Nel
I'm not your bud, and you are annoying
-
my personality does not matter this is a professional chat to explain mathematical concepts
-
is my explaination wrong? i want to know for my understanding
@real vector this channel is for helping cassie. since she does not want your help, please leave rather than continuing to argue about what your response is or is not
alright
but if my explaiantion is wrong do tell me cuz i attempted it and my bad if thats the case and stuff ok byes
I'm gonna get some paper and pencil
and try and work this out with those guidelines
brb
fourth from the top is correct
and sixth from the top
and second from the bottom
Not sure what else tho and there has to be something else
.
oh I know
that's why it's second to last one
okay so
I got the correct answer
but why is the third from the top correct
Right let's just go through them one by one
I mean I understand why it's the last one
if it's the third one
or vice versa
just not sure why it's one of those
you get me?
Oh
can you just negative both a and b
So like you're no longer sure about this?
I mean I think i get it now
You can negative the upper and lower limits
and then if you can do that
the bottom one makes sense
I got the question correct
So, the first one equals the opposite, because the bounds are swapped
The second one equals the opposite again, but this time because the function is odd
Third one is the opposite of the second one, so valid
Fourth one is just the original + a part centered on 0 that equals 0
Fifth is that but bounds are swapped, so the opposite
Sixth is from -4 to 2 but with swapped bounds, so the opposite of going from -4 to -2, plus a zero part
which is the opposite of the second one, so it's valid
Seventh is the same as sixth but the bounds are swapped (or like sixth has swapped bounds and this one doesn't)
so it's the opposite of sixth, so not valid
Eigth is the opposite of seventh, so valid
And finally ninth is the opposite of second, so valid
yep
thank you
I get it now
that should be all for now, I've been doin homework for a bit over five hours so I'm gonna finish one more quick assignment then take a break
have a good rest of your day!
I fuckin hate that tilde is so close to exclamation mark istg
.close
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Do 9 and 10 imply that all isomorphic graphs have euler & hamiltonian circuits?
Isomorphic is not a property of one object
Two objects can be isomorphic, it's a relation
An object can be isomorphic to some other reference object, that would be a property
wat do 9 and 10 mean then
They are invariants for graph isomorphism
If some graphs are isomorphic, they either all have the given property, or none of them have it
so if one has euler circuit then the other shuld hav it too?
Read the definition again: for example, if G has an Euler circuit, and G' is isomorphic to G, then G' has an Euler circuit
Just replacing "has property P" with "has an Euler circuit"
well then all of the listed invariants are satisfied by these 2 graphs
does that mean that the two graphs might be isomorphic?
Yes, they may be
Yes, might
If one satisfied some invariant and the other didn’t then you know they are not isomorphic
That's kind of the point
Well the point is that if you can show two graphs are isomorphic, then you can prove one of them has some property, and that property automatically translates to the other
(If the property is invariant)
An invariant is like one part of what makes an object. You can have 1000 different invariants, but if the object requires 1001 to be completely defined, then you can't say that another object with the same 1000 invariants is actually the same object
kinda handwavy, but in general, 2 graphs are isomorphic if they can be drawn in a way, they look exactly the same (just with different labels at vertices). So for example this graph would be isomorhic to H (it's the same thing, just rotated)
and so would this graph be isomorphic to H
yeah but using the invariants doesnt even help
G, H and these two graphs satsify all listed invariants btw
They can sometimes help
and yet G is not isomorphic to H but it is to your graphs
Invariants can make disproving something a lot easier
If 2 graphs satisfy all the invariants, then they might be isomorphic
If they dont satisfy just one, then they are 100% not isomorphic
No, H is isomorphic to @grave elm 's graphs, G isn't
okay well if i am given a question to determine isomorphism, should i start satisfying these invariants?
You can start by looking at some easy invariants
Like a different number of vertices is easy to spot
well yeah the starter ones are easier
But if you can't show two graphs are not isomorphic that way, then you need to look deeper
but after i check all 10 properties and then end up satisfying all of them
If they are given by a picture and u dont need to prove it, then I'd say just use your eyes.
If you are supposed to prove it, then looking at invariants can help (saying "it doesnt satisfy this invariant" would be certainly lot easier than the proof they did in ur pic)
If the graph isnt given by picture, but perhaps by a more abstract definition, then invarians are probably a good idea
I wouldn't bother checking these 10 properties
wat would u check?
wym use ur eyes 💔
wat if i get a complicated shape
then use the invariants
Easy ones would be: number of vertices, degree of each vertices (like, number of vertices with degree k for all k), number of connected parts (just 1 if the whole graph is connected)
but e.g. here it's pretty clear that they are not the same graph, that they are not isomorphic
aight wat next
yea ig
Next you try to find a way to move the vertices of one graph around to match the other graph
💀
i forgot to use my eyes
how do i use my eyes on this one
i think they are
Both graphs have two vertices of degree 3
if i shift the v2
Show a correspondance between vertices of both graphs
Like u4 - v5, u2 - v3, and then for example u3 - v4, u1 - v6, u5 - v1, u6 - v2
Yeah if you write it that way then f is your isomorphism (from G to H)
so i start reshaping them to look the same in my head?
Yes
ts kinda hard 💔
It might help to see that they are both made up of a triangle and a quadrilateral
just move b outside
Doesn't matter
it doesnt really matter what is inside and outside in graphs (at least not here)
it only matters how they are connected
A graph is defined by vertices and edges, specifically which vertices are connected by edges
It's not defined by how it's drawn
does a->b not work
No, on the left a is connected to b and e, but b and e are not connected
On the right, b is connected to a and c, and these are connected
i was going thru the slides and discovered some adjacency matrix method
is that useful in this case
Graph isomorphism is a complex problem: https://en.wikipedia.org/wiki/Graph_isomorphism_problem
but you did these questions in like 2 min
Because they are small graphs
Just look at vertex degrees
v3 and v5 are degree 4
So are u2 and u4
v2 is the only other vertex that connects only to v3 and v5
u3 for the other graph
v1 and v4 are connected, so are u1 and u5
It's really not that hard once you classify the vertices into degree classes
It becomes hard when there are many vertices in the same degree class, or when there aren't enough degree classes (both things usually happen together)
at how many vertices does it become hard
That depends entirely on your ability and on how you define hard
Give me two graphs with 10 vertices and 30 edges and I'm giving up
okay well can you teach me this method
.
look and then what
Classify them
Wrong
ok
u2 got 4
u4 too
ok now i do the same with graph 2
ok
v1 v4 got 3
v3 v5 got 4
v2 got 2
now wat
Well if the graphs are isomorphic then vertices of degree k in one must correspond to vertices of degree k in the other
Right so v1 and v4 must correspond to u1 and u5
damn
v3 and v5, to u2 and u4
aight lemme do da mapping
Two options for v3,v5,u2,u4: either v3 is u2 and v5 is u4, or v3 is u4 and v5 is u2
Same for v1,v4,u1,u5
So 4 options total
At this point you can just check them all
Yes
how do i make a graph with this info
Take the second graph, redraw it to look like the first one
using the vertex correspondance you found
Do I have to spoon-feed you
I just chose v3 to be u2 and v1 to be u1
Then you actually draw the edges from the second graph
If it gives you the same graph as the first, then it's an isomorphism
This is one option out of the four, but FYI all four options work in this case
yea
i did dis
is it okay to just write the correspondences
without showing any working on how u found them
it would look like u did hit and trial to get there
Depends on what the question is and what your teacher expects
wat do i even write in the working
I would just write, for each vertex of the first graph, which vertex of the second graph it transforms into, and maybe list all the edges to show they are the same after transformation
If you fancy drawing a bit more, you can draw what the first graph looks like after moving one vertex, and repeat until you're actually drawing the second graph
So for example if you take the bottom graph here and move just v1, you can get this, which is already pretty much what you drew on paper
wow
but i would go with the correspondence trick
that's quite nice
@queen crater lmao
let me do this one
@queen crater what is this supposed to mean
That this one is tricky
should i go for invariants
You already know all vertices have the same degree, so probably not
I would try to gradually morph the graph on the right because it looks uglier
there were also some euler path invariants
morph mean change the shape?
Find a 5-cycle in that second graph and draw it like the outer regular pentagon of the first graph
ima just satisfy all the variants and conclude that they might be isomorphs
Then draw the other vertices inside
i mean you arent 100% sure that they are isomorphs rigth
I am
It still expects a yes or no answer
i'd say might
That's neither yes nor no
dang
do u think that adjacency matrix thing is gonna help
but i feel it is the same as finding the perfect correspondence
trying all combos
Not sure what you're refering to
you have not heard of that?
like when you draw the adjacency matrices of two graphs
and if they are the same then graphs are isomorphs
you have to manipulate the matrix in some way to make it look like the other
idk bout that in detail
Sure, you can try
It's not really easier than just gradually morphing the graph by drawing
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With respect to $n\in\mathbb{N}$ find using $\mathcal{Z}$-transformation sum of this finite series [1\cdot 2+2\cdot 2^2+\cdots + n\cdot 2^n]
Slowaq
so far i have this but i got stuck because if i try to plug z=1 its outside of region of convergence so this doesnt hold
kappa is series whose sum im trying to find
<@&286206848099549185>
@iron sand Has your question been resolved?
<@&286206848099549185>
What's the definition of z transformation
You are not allowed to simply directly calculate it? Have to use this transformation thing?
@iron sand Has your question been resolved?
Anyway, write one 2 first row
two 2^2 second row, three 2^3 third row … then sum each columns and add up. No idea what this transformation is you are talking about
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For a ring for multiplication, does identity hold
Can you reformulate that?
Uh
In a ring,
Does the set with the multiplication operation only
Have identity property
I mean... by definition of the ring (R,+,x)
there is a neutral element for x
so there is a neutral element in (R,x)
but it doesn't make it a group
Why not
well, many things
inverse most notably
(I gotta stop saying things hastily, it's 3AM I have to give myself more time to think)

Anyways
So it does have identity
0 doesn't have an inverse
in a ring, you always have a "0" and a "1"
so in (R,x), "1" is your identity I would presume
1 is in R, because it's a ring
wait, are we talking about the same rings
does ring for you not mean unitary ring
Never heard the term unitary ring before
ok, what's your definition for a ring
That's what I'm trying to figure
Some places it's mentioned that identity exists
Some places not
well Ig it depends on the places then

some sources are gonna say a ring is (R,+,x) where (R,+) is a commutative group and x is associative and distributive with +
and those first sources are gonna say "but when there is a 1, we call it a unitary ring!!!!!"
so very tough luck. Use the definitions you have in your own book/lectures
I may be wrong, so check this: So (R,+) is a commutative group
And (R, x) is a monoid or semigroup depending on source
yep,
"(R,x) is a monoid" means "there's a 1"
"(R,x) is a semigroup" means "there's not necessarily a 1"
F as in field?
(F \{0} , x) is a commutative group
Yeah
that is true
Yeah so what about (F, x)?
(F,x) is only a monoid (there's a 1 because F is a field, but no inverse)
Okay
but (F \ {0}, x) is a group
(F,x) in this case is a commutative monoid
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hi
so i was learning abput AP
and there is a property where the sum of terms equidistant from starting and end are equal
like 1,2,3,4,5,6,7 be an ap so it says 7+1=^=2=5+3.....
now my doubt is like is it applicable to 3 terms also like let a1,a2,a3,a4.....an be ap is a1+a7+a8=a9+a5+a2