#help-36
1 messages Ā· Page 274 of 1
HOW
You know the formula for cos2x?
LITERALLY HOW
now we're on like polar but we just did double angle formulas and stuff
sum and angle bla bla
??
WHAT THE ACTUAL FUCK
um
š„²
guys?
i know calc too! but im not in calc at school
anywayyy off topic, reading problem a sec
lols nw.
Do you know the formula for cos2x????
Gimme likeā¦2 minutes Iāll brb
:/
okay, we have an expression with a numerator that looks like (1-cos(2theta))
hey, wanna take it from here?
thanks š
true, but also cos(2x)=1-2sin^2x by extension
It's a standard formula, try to keep this in mind.
Yeah...
ur not
Yup!
^^ i used this one for the top, and 2cos^2x-1 on the bottom
Yes.
ditto
Iām trying to check my BP
I have blood pressure issues that flare when I get overwhelmed
Pretty cool thing but wherever you see 1-x or 1+x just put cos2theta in place of x.
Cuz this is so darn useful.
Especially while doing integration.
oh i see...
i haven't gotten far enough in my integration studies to know that tidbit, thats cool
I hate that Iām so bad at math that I have the active role now
Yeah now you know.
lmaoo i have active too
Here's nr. 2 (recap)
Yeah well youāre good at math
nahh i struggle too dwdw ive opened plenty of help channels
Iām only active here because I donāt know anything
Why do I not have it yet lol, I've sent like 300 messages. šš
lemme check how many i sent
first step to mastery..?
Iāve been in this server like all day everyday for the past 2 weeks
oh... uh.
Probably not
welp. perhaps more than 300.
It's a good thing, your dedication is really cool.
Eh it's a math server.
Not a bad thing.
You're spending your time here.
I'm crine
Itās not dedication Iām just so behind from being sick that I canāt catch up
Not helpful
lmaoo its okay growth isn't linear and imporvement is improvement
Why can't you catch up?
What's holding you back?
She keeps pulling me out of class to do tests I didnāt learn the material for which takes me out of class for more material
Hmm.
So she pushes back my tests to give me a chance to learn the material that i canāt learn because she doesnāt teach me
What grade are you in?
And the cycle repeats over and over and over again
did she provide you with like
I can try recommending books.
maybe
Iām a junior
To help you cover stuff.
practice problems or like notes or something?
She does but I donāt understand any of it
And none of my classmates like me enough to help me
And I donāt have time to go talk to her because I have class during her one free period
Im 17
Uh what's your portion like.
does your school offer free tutoring/after or before school help?
No
This assignment is like 2 months overdue because she keeps assigning shit idk how to do and I canāt do it
It's okay bro don't fret too much.
Just be patient.
And learn math slowly and stepp by step.
Slowly*
you can try khan academy or watching yt videos like organic chem tutor or others
I have 2 days to get 2 proof assignments done and one asymptote assignment or I fail the class
Yikes.
Sooo with proofs you have to keep the end goal in mind, asymptotes, ummm what asymptotes? like with trig or?
Thatās what Iāve been trying to do
See idk about your portion.
But like I can recommend sm called NCERT.
It's a very simple book for math basics.
Idk what youāre talking about
Hey Milo, I have to leave now, but i just wanted to say that I think it's great that you're taking the initiative to learn this kinda stuff even though you don't like math. It sucks when you have to learn and feel like you're behind everyone, and uhm, respectfully speaking, the other people talking about their own progress is not helping that. It takes a while to do math, and it feels like no progress is done sometimes, and it's okay. Just hang in there alright? Take some breaks when you need them too. Believe in ya! š
For 12th grade.
idk what it is either but if its a book u can probably find it online
Thatās not gonna help me
I'd just focus on the assignments first, then potentially if you want you can go to the reading.
Yeah exactly.
First assignments.
I canāt focus on anything rn
Then do the books.
I canāt see or breathe or anything
2 days is plenty of time.
Just relax.
You got this.
Use chatgpt or whatever to get this done for now.
Yeah! You got it. Take a step outside and a breath of fresh air. Then you can tackle it again.
I'd not recommend it but like this is the last resort.
I canāt do that I have to turn this in for her to grade
Chat gpt doesnāt show the steps
Sheās grading the steps not the final answer
I'd have helped you do the assignment out but I got a big exam on the 15th myself.
Iām trying to collect myself and figure this out
alrighttt so i would def recommend just taking a break and then like, i can try to help and stuff
Ok thank you
Why don't you send the assignment for now?
Btw believe me or not I'm in a similar situation.
I barely know anything in organic chemistry.
And I have a huge ahh exam which has oc in it.
I'm trying out what I told you to do- just patiently learning it.
damn
i had an fbla competition and missed one day of math and i have math tues and i have to have my pages of homework done, but i dont understand what a limacon is or why those flowers form. so i guess im also a lil cooked lwk (i hate polar-)
š
What's fbla
future business leaders of america (club)
Oh damn.
had states so i missed fridays math lesson
I think I have an intellectual disability
like i really dont care what a dimpled limacon is-
My exam is like life deciding.
I'll get my college based on this.
i swear in all my studies of calc ive never had to use a limacon so does ts matter
š„
nuuu its okok you got this
Oh.
Time to lock in on organic chemistry tutor
Nah... My exam requires much more depth than what he teaches...
(if you're serious) have you tried reaching out to counselors? (if you're not serious) don't beat yourself up, its okay
Just memorizing won't help.
Iām half serious half not-
hi milo
its alright... i get it, dont worry you'll get throuhg it
KRISH MY SAVING GRACE
š š
Yea
im doing my own math hw rn lmao
YOU COULDNT HAVE SHOWN UP BEFORE I HAD A PANIC ATTACK
lmao i need to do my roses and limacons assignment- fahhh
perhaps i shall make my own help channel and beg someone to teach me ts
i needed to take a nap i was way too tired and then realized my hw is due tomorrow
Oh shit
Yoo send dat assignment?
Oh wait this was the assignment?
And itās just late and itās been a while since Iāve done this
oh i love proofs lol
Yeah
Is this the entire thing?
Send the pdf file then.
so number 3 now right?
Of the entire thing.
^do not send a pdf file. send screenshots of it
No-
Bro I'm not gonna lie.
I wasnāt gonna send a pdf
You just gotta memorise like 10-20 formulas for this one.
And you'll be able to do these.
oh
I have the formulas beside me
We were
And they are straightforward applications of the formulad.
We never got done with number 2-
so looking at like the end result i would think like which formula would be best
just making sure cause May said so lol. for future reference @tepid valley we don't like people sending files of any sort in case of viruses or anything of the sort that could possibly be on there
Thatās what I was trying to tell him earlier and then I got confused cus he was doing things weird
Oh didn't know, thanks.
Then send photos of all the pages. :p
Yeah.
nw, a lot of times screenshots work well enough or if it's a picture and its unclear we just ask to take a better pic lol
Ok let me find em on my phone so itās easier
heres my work for number 2
so basically like
i saw that in the end result on the RHS
.pin
there was a sin squared in the top and a cos squared in the bottom
Ok- can you walk me through that from the beginner
so i plugged in the cos2x formula that would work best (having those terms)
Beginning*
Hold on Iām not following
No Iām just lost at where we are
The numerator of lhs
I have the formulas guys š„² Iām just not- all there rn
This is a short, animated visual proof of the Double angle identities for sine and cosine. To get the formulas we employ the Law of Sines and the Law of Cosines to an isosceles triangle created by from a reflected copy of a given triangle.
If you like this video, consider subscribing to the channel or consider buying me a coffee: https://www.bu...
okay so like let's think just about the top half of the left side. and plug in for cos(2x) in a way that would keep a cos^2x in the top like the RHS
Guys the formulas is not my issue I promise you šššš
Ye we got that dw.
See is LHS there is 2x everywhere.
In RHS there is x not 2x
Soā¦. 1-2sin^2x?
So we gotta convert the 2x into x somehow.
That's why we did this.
Yea.
yup
(i said cos^2 earlier i meant sin^2 mbmb)
now, apply the same thought to the bottom of the LHS
hmm.. good thought. is there one thats better, perhaps with no sin in it and just cosine?
mmhm cus thatd make it easier to simplify later right?
one step at a time..
plugging back in... remember the original ones
plug in the formulas for cos2x
and see how you can simplify that
Alr then ima go study some OC, ping me if y'all need help!
All the best evelyn and milo.
Thank ya
glgl may
Which ones-
There are multiple that could theoretically work in this case
for the top and the bottom
That apply to cos2x
^^ for the bottom
^^ for the top
Right
Go find another help channel
Hgf6uhg
This one is currently being used
this is occupied... also this isn't even a problem this is just random pics lol
And there are about 5 other open channels rn for yourself
I was gonna say
None of that makes sense lmao
lmao its probably a generic math pic
Someone else is already using this help channel. If you need help with a question, please open your own help channel/thread (see #āhow-to-get-help for instructions).
lol
anyway off topic
Anywaysā¦
Iāve got 1- (1-2sin^2x)/1+(2cos^2x)
remember the -1 for the formula in the bottom
should be 1+(2cos^2x-1) but close
yesyes on the right track
yup...
?
So there are steps involved š
so heres the first step in going from the expression you built to the RHS
so i distributed the negative sign in the top
and reomved parentheses in the bottom
so far so good?
If you distribute the negative shouldnāt that first 1 go away?
Yup, it'll cancel
(left it like that so you could notice, and also for baby step work)
now on the bottom...
less noticeable perhaps, but, anything similar popping up?
Thereās a 1-1 on top and a 1 + (-1) on bottom?
0
2sin^2x/2cos^2x
Hi guys.
yes!
Oo still on first one.
and now how could we further simplify this... hmmmmm
2nd*
yup been working thru the steps
2/2 cancels to 1?
so now we are left with...
I see I see.
Sin^2x/cos^2xā¦..? With a 1 somewhereā¦.
err
well the 1 is like
invisble
sorta
1 Ć anything = anything
^^ yup this, the identity property
I am the lorax. I speak for the trees. For the trees have no tongues.
Ok- so just sin^2x/cos^2x
Hi the lorax
.... ||srsly gng, go to #chill ||
Ok this dudes just a troll
<@&268886789983436800> troll
Righttt!
And that's what we were looking for, right?
Noice.
We wanted the left hand side to be the right
and now it is
after we algebraically manipulated it, its equal
At the end of everything write LHS = RHS
Hence proved.
Btw Milo did you get the answer to 1?
Yes
Do not troll in help channels, keep shitposting in #chill
Trees are no joke man
Ok so number 3ā¦Iām thinking
If you can help idm to work w you
Hold on chat lemme think
I wanna give an attempt
You remember how you got sin2x in the first one?
Bet.
lmk if you dont get how to explain something im active just doing my hw alongside lol
lol sorry i was helping in another channel
Krish explains it in dumb dumb terms for me
while doing my math, chinese, and bio homework
I can do bio
Thanks lol I think I suck at explaining but I'll try my best.
Iām good at that
Multitasking final level. š„
OK IDEA
I thinkā¦.i think i wanna take 2sin^2 x and turn it intoā¦
Cos2x-1
Waitā¦that doesnāt seem right
Okay then?
Just trust the process in math. š„
You'll always get the right answer somehow.
No I mean I donāt think i manipulated the formula correctly
Yeah you didn't but you're close.
Cus itās cos2x= 1-2sin^2x
It's 1-cos2x
THATS IT
Alright then?
Lemme write it down
Right okā¦
Uhmmmmmm
Then I wanna turnā¦cot^2x to csc^2x -1
Which gives me 1-cos2x +csc^2x -1
So I can cancel the 1ās
And then move the negative cos2x to the other side of the csc
And itāll be equal
@tepid valley does that seem right?
YESSS
Wait I'm reading.
Yea thanks.
,rotate
Whoa- where did you get 2sin²x + cot²x?
Theā¦.original problem?
The question is 2sin²xcosx right?
Not number 3
Oh.
uh
And labeled it 3
oh well
Yeah that's right.
This is perfect.
Here's some tips tho- write every equality on a diff line pls. š
Fair enough Iām just trying to save paper
I only have this one page atm šššš
Is this rough?
Get more, all this is not gonna fit in a page bro.
Oh I know
But itās all in my locker rn
Iām just trying to get through 5 tonight
And then Iām gonna go to bed
Cus itās 11 pm
Ok actually for number 3 this time
Alright then.
I wanna do the same thing
Btw this is how catchpoints work.
Whatās a catch point
What you're doing is wherever you see 2sin²x, you're using this formula.
It's not an official word but my teacher uses this.
Ag
So yeah good.
??
Or division
Yeahhhhā¦sheās weird
^^
?
No on the RHS
2sinxcosx/cscx
Perfect.
So this time instead of making the LHS the RHS
You made the RHS the LHS.
Which is absolutely okay
They donāt match thoā¦
What's cosec x?
Uhhhh 1/cosx?
Nope 1/sinx
Oh yeah
sec x is 1/cos
Yeah
Bro see.
In trigo.
We do discrimination.
We don't give a f about sec cosec and cot.
Always turn them into cos sin and tan.
Ok but they still donāt match šš
What did you get?
,rotate
Well see.
First of all whenever we're doing proofs.
You can't start by saying they are equal.
Iāmā¦not
Like you can't start with 2sin²xcosx = sin2x/cosecx
Thatās the problemā¦.
This means they are equal.
See start like this.
Go look at it
Oh wait.
I literally wrote what was on the assignment
Bro but still.
Wdym?????
Yeah
Yea that's the thing.
The question isn't saying those 2 are equal.
We have to show they are equal.
I know
You cannot write the first line.
?????
And without the first line you can't get the second line.
Dude itās just there to show which side is which
Thatās how Iāve been doing all of these
Ik but that's not how it works.
But it is????
You gotta start with something like.
Itās the same on the second question
Give me a second.
And the 4th
And the 1st
Everything is set equal to something else
I know that weāre proving theyāre equal
I know theyāre not rn
But there has to be a sign there
No
Iām just doing it the way my teacher taught me
Fine yk what I think this'll confuse you more.
Let's just carry on with the questions.
We'll talk Abt this later.
Sure.
But later.
First let's get these questions done.
Frame them all like your teacher wants you to later.
Iāll get a better pic of the top part too
um.. just came back from helping someone with a log question
idk my teacher says we wont get the proof questions on the ap exam, so she just has us simplify to the RHS or whatever, like, just tells us simplify the LHS and try to get it equal to RHS
Ignore how bad my hand writing is
First few lines are unclear.
Wdym
Oh
Yeah that's the thing.
This is da wae
i mean the notes (we do guided premade notes not made by my teacher) that she had us cross out had like
an equals mark
with a question mark over it
and at the end they put a checkmark over it when they proved it
but idk if thats how its supposed to be done or not cus like well, we crossed them off cus those dont come on ap exam
Yeah idk this is just how we do it
Hmm.
We use a little gray box at the end to signify that the problem is complete
Basically if you have to prove sin²x + cos²x = 1
You can't say sin²x = 1 - cos²x
Yeah.
Yeah
Oh I see what you're trying to do.
It has to be sin^2x + cos^2x = sin^2x + cos^2x or 1 = 1
As long as you don't bring stuff from one side to other side.
Then you can do whatever you want..
I guess..?
Alright anyways.
Can I add you and we resume in the morning?
Make the cosec x = 1/sinx
Les finish the 3rd one.
It's very simple.
Ok
Also idk if I'll be able to help.
I gotta do oc.
Ask evelyn.
She's a much better teacher than me. š„
Did you do this?
Oh btw if you didn't know.
a/b/c = ac/b
š„ im 14 im not that useful-
ill try
i finsihed my bio hw
I didn't even know double angle formula till I was like 15.
Wasn't in the syllabus till 16.
So you're already better. š„
i learned it in this online thing my district had
when i was er
13?
before i turned 14 in 8th
Damn.
You remind me of this kid in my calc class
er... i had... yeah id say exponential progress xd i started but never finished unit circle in 7th. gave up on roses/limas in 8th (but finished most other trig work). learning calc on own this year
He has no reason to be in there other than itās a requirement
Heās doing shit not even the teacher knows
Damn, all the best ping me if you need help with something.
lmao
tytyy
And heās likeā¦.15? At best
Np, calc is very fun.
No like he knows everything
Heās just in the class because itās a requirement for graduation
Heās way past whatās happening
according to the UC graduation req they gave us
Wish that was in my country too.
i have 6 years of high school math
He literally just sits in there and does his own level of math
but according to my school
i have 1 semester
so i need to take a second year
to graduate
Anyways goodnight guys I rly gotta get some sleep
even though college admissions says i have like half a decades worthhhh ackkk i hate my schoo-
Goodnight punpun.
Oh???
Uh nvm.
What does that mean šššš
Sureā¦
Take it ez.
Idk if youāre flirting with me or insulting me orā¦babying me
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Could somebody explain this to me itās from an answer key and I donāt understand it at all
do you know the theorem that $\log_a(b) = \frac{\log_c (b)}{\log_c (a)}$
Annie Maqionde
No
its called the Change of Base Formula.
OHHH
then yes I do
Ok this is easy then lol ty
For this one Iām not sure how to finish a and b
do you know $\log(ab) = \log(a) + \log(b)$
Annie Maqionde
and what is $\log(a^x)$?
Annie Maqionde
Yea
Xlog(a)?
I dknt know how to do those with a tho since itās multiple in one
use both of these.
yea I know I should but I donāt know how to combine them
Cus I want the ^3 to only impact the 2 not the 3
first this
then this.
why is there a $\log 3 \log_5(2)$
Annie Maqionde
its just $3 \log_5(2)$
Annie Maqionde
remove the log in the front.
Whoops forgot I put that there
For 3 j donāt know what to do. Iām assuming Iām not doing change of basses since the base log has the base of 5 already. But I donāt know how to do multiplication cus no squared , ^3 etc will make 2 into ten. Or make 5ā¢6
i cant see 3j
rewrite 30 into the suitable factors
as in, 30= 6x5=2x3x5
And then simple do what you did before
Yea but I have to make them into a and b and I canāt figure out how to make 2 and 3 into 6 and 5
like 2^4,2^3 is 8
2 and 3 into 6?
They are js multiplied no?
3^2 is 9
yeah so here you have 2^1 x 3^1
no need for exponents of 2 and 3
If you are confused as to what to do with 5,
observe closely after splitting the log term as a sum of three log terms
ā
Yea I know how to do that with 2 not 3
oh its the same with any number of terms
log(abcdefā¦) = log(a) + log(b) + log(c) + log(d) + ā¦
I also donāt know how to know what to add it to make 30 there are to many options
yeah which is why we only use the favourable options
Sorry Iām just very confused I was out for the lesson before this and my teacher was out for this lesson
okay lets start over again
Was this clear tho?
no?
not really
okay thats fine
Cus I just donāt undestand how Iām supposed to know what to add with
What abt this
That wrong!!
abcd indicates product
We can only split the product!
When you add logs with same base you mutiply
I think I copied the first part of the review guide I donāt remeber it was on Friday

I just donāt know whatās going on cus I missed class
and I donāt understand it at all
okay uh, we need terms like xlog(2) , ylog(3) right
wait hold it there!
Good job
6ā¢5 can become 30 but 3 canāt become 5
can you do this step first?
But that doesnāt work
yeah ik, but we are making progress
But I canāt do it as the first step since it doesnāt equal that so itās untrue
?
why not
Use this, keep a as 3 and b as 10
Is this step clear?
Sorry Iām confused
And yes yes ik we have a 10 but, still we got a log3 term
But 2 canāt become 10 with ^2 or ^3
Donāt we need a log2 term not log 3?
Thats fine, you forgot about the thing that log_5 (5) = 1
Whatā¦
so what i mean is that, log_5 (10) = log_5 ( 2ā¢5) = log_5 ( 2) + log_5 (5)
Iām so lost
Okay observe this for now, lemme know if this was straight
It makes sense but I donāt understand how log5(5) is 1
Well its the definition of logarithm
log _a (a) = 1
5^1 = 5
So log5(5) = 1
It may feel like a lot, but just know that its all a play based on logarithm formulae
Have a list of them by your side while you solve future Qsns
Idk I just feel screwed for the rest cus I feel like it makes sense when people explain it after a while but I canāt do it myself
you can find the list anywhere on web by js searching it up
yeah i feel you, which is why it would be better to have a list of those formulae with you
dw, log is extremely simple
I feel like I may even get one on the test I got smth similar for the last unit cus on my iep I get a small reference sheet on tests. Tho most of them are useless besides lasts units
Honestly, I get a lot of mileage out of "taking the log of both sides" or "taking the exponent of both sides"
wdym by taking the log of both sides? Like change of bases?
log5(5) = 1
Take the 5^ of both sides:
5^log5(5) = 5^1
5 = 5^1
That's a way to go from "log view" to "exponent view" without having to memorize how to rearrange
Yeah that's exactly that formula, but I got from (1) to (2) by doing a 5^ on both sides
Maybe useful to you, maybe not. I find that can be useful often
Donāt I have to get rid of the extra 1?
$\log_a({a})=1$
KB
But I have to rewrite things only in a and b so idk what to do š
I think adding 1 is acceptable. An unacceptable answer would include a log
kk
For this one sorry I canāt out the question itās simplifying smth I understand how to do it but I donāt know how they got rid of the log3(2)
Ohh ok Ty
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is there any way to solve this equation without using the Weierstrass substitution?
Hmmm, couldn't you do sin^2(x) + cos^(2)(x) = 1, solve for either sin(x) or cos(x) and then sub that in and solve it? perhaps treat sin(x) as y and cos(x) as x (unit circle), just for purpose of substitution until you have done the algebra and reach an and result then plug them in?
the left hand side can also be rewritten as Rsin(x+a)
wouldn't that yield a ± which could be troublesome? also i didn't understand the second part of your message
in polar form?
no harmonic form
Rsin(x+a) = Rsin(x)cos(a) + Rsin(a)cos(x)
so if you can find R and a s.t.
Rcos(a) = 3
Rsin(a) = 4
then youre done
im unfamiliar with harmonic forms. perhaps you could teach me something about it?
Divide both sides by 5
@versed cargo Has your question been resolved?
if we take a circle of radius 3 and a circle of radius 4, these 2 lengths give us sin(x) and cos(x)
notice that the orange circle is rotated 90° compared to the red one, thats the phase shift between sin and cos
is it clear why those 2 lengths are 3sin(x) and 4cos(x)? x is this angle
yes, sinx would be y-coord, and cosx is x-coord but you said it's rotated 90 deg just like in unit circle
the largest circle shows adding those 2 movements
if you add this red and orange rotating stick, they will rotate in a bigger circle - the purple one
and the sin on that bigger circle will be blue + green, 3sin(x) + 4cos(x)
and then find x s. t. blue + green would equal to 3 (or red stick in our case)?
Yeah, sure, that would work
but for our purposes, lets solve it by instead finding what that purple circle is
that way we will be able to describe 3sin(x) + 4cos(x) with a single sine coming from that purple circle
if we look at x = 0, notice that the purple radius can be computed by pythagoras
red = 3, blue = 4
yep that's 5
damn my labels are wrong on the purple circle, should be the opposite
perfect
and there is also some angle shift
this angle
dw i'll change them myself
arcsin(4/3)?
Great, so
3sin(x) + 4cos(x) = 5 * sin(x + arctan(4/3))
ofc its a bit difficult to do it geometrically every time, so ill show you the algebraic way to do it
it works whenever you're adding multiply sines / cosines with same period but different phase shift
Firstly, from the geometrical insight we know that it can be rewritten as a single sine like this:
3sin(x) + 4cos(x) = Rsin(x + a)
now we use the identity Rsin(x+a) = Rsin(x)cos(a) + Rsin(a)cos(x)
3sin(x) + 4cos(x) = Rcos(a) * sin(x) + Rsin(a) * cos(x)
now we can match the coefficients of sinx and cosx
3 = Rcos(a)
4 = Rsin(a)
and now we need to solve this system
we can divide those equalities and get
Rsin(a) / (Rcos(a)) = 4/3
sin(a) / cos(a) = 4/3
a = arctan(4/3)
and we can square them and add them
9 = R^2 cos^2(a)
16 = R^2 sin^2(a)
25 = R^2 (cos^2(a) + sin^2(a)) = R^2 * 1
R = 5
so this is the algebraic way to solve it
i see
and once you rewrite it with a single sin, its pretty simple to solve
it becomes a fairly standard trig equation
and then sub these value back into here?
yep
and we get that it equals 5sin(x + arctan(4/3))
so the equation simplifies to
5sin(x + arctan(4/3)) = 3
and this can be solved by normal trig
looks correct 
np
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\subsection{Problem 6.} \textbf{Suppose that $(X, \leq)$ is a partial order. A subset $A \subseteq X$ is \textit{pairwise incomparable} if, for all distinct $a, b \in A$, $a \not\leq b$ and $b \not\leq a$. A pairwise incomparable subset $A\subseteq X$ is \textit{maximal} if there is no pairwise incomparable subset $A' \supseteq A$ with $A' \neq A$. Choose your favorite equivalent of AC (i.e., (ZL), (HMP), or (WO)) to prove that every partial
order $(X, \leq)$ has a maximal pairwise incomparable subset}
toast
hi
If X denotes a linear order
Then what would a maximal incomparable subset look like? Just a singleton?
Yes
Alright
I am not sure if I am stupid
Would the idea be like
Find chains of X
Then take the complement?
I have to think about it a bit more
if you take a complement of a chain, it wont necessarily be pairwise incomparable
take a poset like this, then the middle chain's complement is just the other 2 chains, and some of the elements of those are comparable
Ur right
Personally, i'd try to use ||zorn's lemma|| here
hmm
I have an idea
What if I take the set of maximum of every chain
wait
oki this doesnāt work because there can be a lot of chains
it would work, if the chains had a maximum
oh
but they dont necessarily have it
so this is where zones lemmas come in
for example the Z chain doesnt have a maximum
What jf we consider chains with an upper bound
what if there are no such chains?
for example take a poset that consists of many Z chains
hmm
Can you just restate what zorns lemma says?
If X is non empty and if a every chain has an upper bound in X, then X has a maximal element
yeah, so zorns lemma allows you to prove existence of maximal element, under some conditions
this problem asks you to prove existence of a certian maximal thing
my hint is to focus on the goal and not on the poset you have, zorn's lemma wont be applied directly on the poset you have
Hmm could I consider a set of maximal pairwise incomparable sets
Maybe order them by length
a small issue is that it could be empty (the fact that its nonempty is what youre trying to prove afterall), and the length isnt necessarily a natural number, so idk how would you define that
but you're not that far
Ah
ill let you work on it and if you want another hint, lmk
Kk
ok ngl
Is it possible for a set to look like this
to look like what?
the set itself
It would just be the set itself
Ic
So thatās why we canāt rlly use length easily
I want to be able to generate a set
With incomparable elements
Until I cannot anymore
Yeah, you want the maximal incomparable set wrt to the subset ordering
do you get what im hinting at?
bc that works for infinite set
cuz the biggest subset is the set itself
so you never have to worry about avoiding an upper bound
Well, I essentially just re-read the problem
they ask you for a maximal pairwise incomparable subset and they tell you wrt what ordering
do you know to what poset you should apply ZL now?
wait I am a little confused about subset ordering though
the blue circle and green circle are both examples of incomparable sets right
yes
Is it true that the blue set is a subset of the green one?
no
and the converse isnt true either
neither is a subset of the other one
because they contain completely different points
ah I guess they donāt need to be subsets of each other then
indeed they dont. Zorns lemma works on any poset satisfying the conditions, not just on total orders (you dont even need AC for those)
Oooh okay I see
Cuz zorns lemma says nothing about comparability
Every chain has an upper bound means in this case itās just the āwidestā extent of something
Zorns lemma just needs it to be a poset, and all elements of posets arent necessarily comparable
This widest extent will always be bounded because at most it can contain elements of the original set itself
oh btw im not sure whether we're on the same page already
do you already know what poset with what ordering you should apply zorn's lemma to?
I think we might be, I think we consider the set of incomparable subsets of X with respects to subset ordering
exactly, because you want the maximal element of that poset, you're essentially forced to apply zorns lemma on that precise poset
the biggest possible comparable subset of X wrt to subset ordering is X itself
comparable or incomparable?
Incomparable*
that was only the case in here
yeah
but regardless itāll always be upper bounded
hmmm
because X isnt necessarily an incomparable subset of X, its not even part of your poset (the one of incomparable subsets ordered by subset relation)
consider we have some set
uh
we start by adding incomparable terms to this set
every time we generate a new chain
If we cannot add a new incomparable term
We are done
And we found an upper bound
Otherwise we keep adding elements until we reach X itself
if this worked, you wouldnt even need zorns lemma, because once you cannot add new incomparable term, you've found a maximal incomparable subset.
Hmm
you're describing some vague possibly infinite process (or even transfinite one could say, since even after e.g. countably many steps, you still wouldnt necessarily be done)
Maybe I need to select an arbitrary chain in our new posey wrt subset
And show it must have an upper bound
If X is non empty and if a every chain has an upper bound in X, then X has a maximal element
have you already shown that its nonempty btw