#serious-discussion
1 messages · Page 492 of 1
Some do, some don't
But the ones who do would irritate me as a prof
So then it's on you as a professor to create incentives to learn over to nitpick for grades
Like in HS that was everyone
If you don't actually know what you're doing
True
People cheating always drives me up a wall
If you're graded on a curve, then you are hurting someone else's grade for your selfish unearned gain
Although, most of that fault lies with the incentive brought on by the prof./education system
The other issue is that there are standards to be upheld for a reason. Nurses, Doctors, Engineers, etc. need to have an education, and need to have an honest education
If they cheat their way through the system, then that can literally kill someone
Yeah
grades are the worst thing to happen to education
Have you found a way to mitigate their impact in the classroom?
It's very difficult to do so, even when the grades are essentially meaningless
I taught at Russian School of Math for 5th, 6th, and 7th grade - which is an after school program for ultra math nerd kids
Our internal grading and recommendation system meant almost nothing in reality
But the kids took it super seriously if they couldn't solve a quiz problem or something
I kept trying to tell them that this doesn't matter, but they kept getting stressed over it
Woah!
Russia is soo cool at that stuff.
Russian school of math is an american education company rooted in soviet union curriculum
So what was being taught for say 7th grade?
Just algebra & word problems
What level Algebra?
7th grade
some people in my department have been experimenting with doing mastery based grading the last few semesters
it's been interesting
Wait so how is it ultra math nerd?
im doing that right now
how's that going?
They are paying to attend extra math classes and enjoying it
yea that's the impression I get too
Kids that don't enjoy it leave the program quickly
I kinda want to work it into my classes
idk how to scale it up to like several hundred studenst though
I have heard that happened to the Chinese Math Olympiad team or something? Did it really?
which is what our calc classes are
How did you implement the mastery based stuff?
Did you give an oral exam? More open ended questions?
no i think oral exams are great though
thought about doing that as well but havent tried it yet, but mi ght do it next semester in my intro to proofs class
for me it was just weekly quizzes with one question per learning objective. if you get it right you get a checkmark, if you get it wrong, try again next week. no partial credit
students pick and choose which questions to attempt each week based on what skills they've been practicing
your goal is two checkmarks per objective
(i had some other components to the grade as well, like "application problems" which were multi-part applied problems that combined lots of learning objectives, but the weekly quizzes were the biggest component)
Buncho Bananas you are a professor?!!?
.
maybe
That's super cool
.
more people here than you’d expect seem to be professors
?
Buncho has tenure 
do you mean "someone who teaches collegiate math classes"? or "someone whose job title is Professor"?
hahahaha
no i do not
if you mean the former, then yes, basically everyone who is a grad student in their 3rd year or above falls in this category. if you mean the latter, then there's maybe like 1 or 2. there's also a middle category of "faculty at a university" in which case there are a couple more
1st.
I see.
yeah
That's cool!
so there aren't that many people here of that level
Oo.
Which books does the Uni use for proofs?
if you're like 15 years old and assume that discord is only used by high schoolers then it might be surprising lol
but there are twenty-somethings on here as well :P
you mean like intro to proofs?
depends on the person teaching the class
I see.
I will soon start proofs so I was asking for proofs books yesterday here lol.
So asked for your recommendations lol 😅.
i dont have any, sorry :/
the book my uni uses for proofs is a sentence that says "it's recommended that math spec students learn proofs in the summer before first year"

Apparently the help channels weren't the right place for my question, so hopefully this one is?
It's about a user review system and I'm looking for a better solution than the x/10 rating system.
Like having relative comparison and let the maths/system do the ranking and possibly assigning x/10 values.
Here is the link to the detailed problem, along with the few follow up posts.
#help-17 message
I can move it also to one of the specific channels - if I know which one ...
This really isn't a math problem. I feel like "out-of-10" questions on surveys come up a lot in social sciences; maybe a social sciences server would be helpful to you?
I got an extremely good education at berkeley but it was in large part due to getting myself out of my comfort zone to find resources, support systems, and basically never taking anyone else's advice to take it easy (always doing the most amount of work humanly possible for me at that time). It got kinda nightmarishly awful in my 3rd year for a number of compounding reasons. I still loved my experience there and it definitely is the reason I feel very prepared for my grad program now, but I think if I were less willing to take on a lot of anxiety and just deal with it, then I would have come away from it with a more sour perspective.
Berkeley is a school where you can do pretty much anything you want, but you might have to fight tooth and nail to make it happen.
Also as an out of state student it was definitely not cheap for me. I managed to reduce the price pretty significantly by working part time and by endlessly appealing for fin aid, but normally that stuff is very hard to make work.
I feel like I'm making it sound like a nightmare, it was actually a lot of fun, the math community is incredibly supportive and lovely, there are so many groups outside math that are also wonderful, the staff in the math dept were lovely, almost every professor I had was super friendly and loved teaching, etc. It's just easy to get caught up in a whirlwind of taking on too much work at Cal cause nothing is gonna stop you.
also Berkeley math tourney
Yeah I was involved with that a little, it was fun. Great group of people
anyone got an example of a homomorphism that's not bijective?
the zero morphism
sure. the map from Z to Z which is given by phi(n) = 3n is a homomorphism.
any non isomorphic homomorphism? 
That's what I was asking for
Thanks folks
it's injective, but it's not surjective. on the other hand, the map from Z to Z/3Z given by phi(n) = n mod 3 is a homomorphism. it's surjective, but it's not injective.
I'll check both of these by hand, but why the
?
as a 3rd example, the map from Z to Z/6Z given by phi(n) = 2n mod 6 is not only nonsurjective, it's also noninjective.
so both can happen.
slim is mad that his answer to this question was just a rephrasing of the question and that i actually gave an answer
i just did it coz i have an impulsive nature to react
lmao
Just so I'm sure I've got this right, these maps preserve the structure of these groups under both addition and multiplication?
oh
umm
i was giving group homomorphisms
if you want them to be ring homomorphisms
uhhh
ok then it's just preserving addition
what if you have a bijective homomorphism that is not an isomorphism 
but group mapping dont preserve both, no?
Z is not a group under multiplication

dont tell me that is possible
I was thinking of Z once under multiplication, once under addition
Z cant be under multiplication

4/6
in terms of ring homomorphisms (respecting both multiplication and addition), only this is does both
Yeah I just realized lol, my bad
that's because 3*n * 3*m does not equal 3*(mn)
well, continuous and bijective does not imply homeomorphism
trying to decipher if you sent this seriously or if you're baiting me into responding 
are u making stuff up

i should do a lot of algebra soon 
but in groups and rings you have a bijective homomorphism, the inverse map is automatically a homomorphism as well
in more general settings you need homomorphisms in both directions such that their composition is the respective identity
topological spaces as i mentioned
ah 
in even more general settings (categories in which the underlying objects arent sets), it gets worse
Grp

just pretend they dont exist youll be fine
Oh shit i got an email from courant tech support
this
Lets see if they'll change my website url to something not idiotic
Thats what i try to do
but you brought them up
i doubt if i can do that for long tho

Nope! Lol
i just wanted to sound smart
Alright fuck me I guess
u are smart tho
debatable

Who needs categories anyways
I'll just keep using my berkeley website for now until someone decides to have respect for me
homology?
but like the topological spaces example is worth to keep in mind
i see, yeah i will try to keep it in mind
Whats your website
Not gonna self dox that easy 😇
ryc i won’t dox you
You guys have like, secret identities on discord?
I'm secret
you say that as if its abnormal?
has social media normalized posting your personal info publicly nowadays
when i was a kid, we were always told to not share anything personal on the internet
even saying my university here gives me weird vibes even if i know its fine
I was told that too
But I was never told the reasoning behind it
So ig I just shrugged it off as superstition
Well if everyone promises not to dox me, I guess I could just tell everyone.
Isn't the recording of my talk enough??
shyshu of the golden doxx
gdoxx
Lol yeah
Is there a way to check for myself if this is a homomorphism? Or do I take this for granted
Oh wait I cropped it out
Eddy don't do it
I know it's unbearably tempting but you are strong
Thank the lord this book uses the D_2n notation and not the other common one
what is the common one?
Say for example I have an element rr (r^2), how do I know what this is mapped to in D_2k?
just check the conditions for all elements of the homormorphism
group homomorphism condition so phi(rr)=phi(r)phi(r)=r1r1
i feel like it doesn't really matter
like i like my privacy and i would not share more than needed but if i tell someone online i'm in uni x or my real name is x
its like...ok? and? how is that different from introducing yourself in public
what am i missing
Your privacy is gone if you're superstar X, but if you're not, then your privacy has non-zero (and presumably non-negative) worth
Well, not all aspects of privacy are gone for superstars, but having a Wikipedia page detailing aspects of private life (even in line with WP:BLP - that policy also only protects against contentious details - and ~2yrs after death) will make privacy disappear, just about forever
im just skeptical about everything
like I share as little as possible
y'know
bc I feel like if people have my info then they will come to my house and murder me irl
which I know won't happen
but if I keep that in the back of my mind then I won't post anything out of stupidity
yeah it's too late gmod i already doxed you to the whole server
someone’s already coming to your house to murder you
😳
How do you prove this
The book proves stuff about presentations at some point, I don't remember what exactly
Oh this is just a definition
I was thinking this was saying any group that is finitely generated has its relations also being finitely generated
Wait, how can you generate relations?
I think that's a difficult problem in general
I forget the technical phrasing for "how bad" it is lol
Oh, I thought it mightve been something I missed in the book, definitely not then
I guess you can get a presentation by starting with the cayley table and mucking around there and boiling down stuff idk
I think this has something to do with the definition of solvable groups, I'm sure someone knows more than me here
So if you have a set of generators of a group, that's essentially specifying a group homomorphism from the free group on that many generators to your group, sending the i'th generator of the free group to the i'th generator of your group. The relations will be the subgroup of this free group which is the kernel of this homomorphism. What i meam by saying the relations are finitely generated is that this kernel is finitely generated .
I'll save this and reread it later because I still have a while ahead of me before I even get to free groups lol
Hello guys, I need to do a research for the noise reduction in acoustics, and need to find a probabilistic method for it. Any recommendation?
I firstly thought of Kalman filtering, but it is way too hard for my actual level
Free group is just a group without any relations. The free group on n generators is the group whose elements are finite strings of letters from an alphabet of size n (you also need the inverses of each letter). The group operation is concatenation.
free groups and words are cool
Nothing in life is free 😡
🤔What about the cosplayers who walk in fairs with a sign that says free hugs.
No new avatar 😭
nope i can’t find any
Hey all
hi corra
Hope you're doing good, thought I'd hang out while I prepare some lessons for when teaching starts up again
I find lurking and doing some chatting here gets me motivated
@rapid folio what are your lessons on
Is Year 7 and Extension 2 the equivalent to a senior in high school
Right now I'm taking it a bit easy, I'm planning for Year 7, which is 13 y/o's coming into high school from primary. So after doing some number line stuff, it goes into place value and then comparing numbers with >, < and =
year 7 is 6th grade 
Year 7 is the youngest year of high school, Extension 2 is a course you can take in Year 12, which is the final year of high school
Australia
So you teach 6th grade, 9th grade, and 12th grade?
Primary school: Kindergarten, then Year 1 to Year 6. Students start kindergarten around age 5 and finish Year 6 at age 12.
High School: Year 7 to Year 12. Students start Year 7 are 12/13 years old and finish Year 12 when they're around 18
interesting
I really enjoy it, it's got its tough times. But I know the content, so what really interests me is answering the "How do I teach this to you?", which changes year to year depending on what students you get.
I find it fascinating that with my job I can introduce someone to something that's foreign to them, that they've never encountered and get them to a point where they understand and it's familiar to them. It's a good process for them to appreciate.
in the uk we have:
Primary school:
Key Stage 1: Foundation Stage/Year 0-2 (starts at 4, unless your birthday is very early september)
KS2: Year 3-6 (starts at 7 with same caveat)
Secondary School:
KS3: Year 7-9 (starts at 11 with same caveat)
KS4: Year 10-11 (starts at 14 with same caveat) (at the end you do most of your GCSE exams, although some schools do some earlier)
KS5: Year 12-13 (starts at 16 with same caveat) (you don't necessarily need to be in school at this point, just some form of full time education. most people do A Level exams at the end, but others may do BTECs or otherwise)
I'm thinking of being a professor eventually, so it sounds interesting
I sometimes peak at your A level tests and other senior ones, I'm always keen on seeing how they compare to what we have. You find the questioning technique is slightly different, it's a nice change from what we do here and I sometimes use some of the questions in my own topic tests. The Irish was another one we looked at in the staff room, they set theirs out slightly different again.
the further maths a level papers are interesting
they give you a lottt of space
I'm currently in year 11
I got asked at uni if I wanted to do a PhD and lecture, with the idea of going on to do research, but I have a problem with the lecturing part, because it's not quite teaching. By definition, it's lecturing.
And I can always do any research or learning I want in my own time because my university give alumni access to the library and academic paper
Good to hear! If you're in this discord, that's reassuring as a teacher that you're keen 😅 The further maths are good papers from a teaching and testing pov. And yeah, the space is one of those small design things you pick up on. I find questioning techniques and exam design really interesting
I'm very excited for university in a few years
because then I'll be around people who actually know what I'm talking about 
Great to hear! I hope you get some good lecturers when you go, it can make or break a topic I've found. Some calc course I took were a drag because of the person lecturing, other were fantastic! I did medical mathematics and financial calc with the same person and he was by far my favourite!
Hello
How's your part of the world going at the moment?
I'm hoping to go to cambridge
wait, you're not in college? so are you like a sophomore or something?
Ayyye! Same!
What does sophomore mean
Nice
year 11 uk
so yes
Oh nice, are you hoping to study math>
yes
I'm hoping you go to Cambridge too! That's great
@rapid folio I’m still pogging about the fact I got a 50 in methods last year
What part of the country you in?
Vic
Thought so, from the word "methods" 😅 I'm NSW
Idk why I assumed you were Vic too
they go through content very quickly
which i think I'll enjoy
for now just enjoy your days in school.
See, I'm a slower mathematician, university was a lot of walks and sessions in coffee stores because I had to take time to digest and understand stuff
Also, this
i am
because as soon you step foot on campus, time will go so quickly that you will forget everything in the world
like time flies
I can kind of agree with this
Yeah just a heads up. I know it sucks. I wished I knew earlier and took high school for granted. Instead of wanting to leave quickly.
Some of it moved in slow motion at the time but in hindsight it was all lightning fast lol
Idk
It is but then you wished you had done more things than just study.
When I think about high school it feels like it dragged on forever for me
you only remember the novel experiences
I do not really wish that lol
But
I do wish that I had done certain things differently
I mostly wish that id like
Not decided to do the job I decided to do
Cause I think that the networks and social ties I got out of it are all totally worthless now
That might not end up being true
Idk
what job
But it would have been nice to focus a little more on the math circles
Resident Advisor in the dorms
It was a lot of work, sometimes fun but I had one particularly awful year with a lot of really serious situations I had to respond to
I guess I gained a lot of skills from it but i'm also a very anxious person and it definitely worsened that
In a way which I think is a little irreparable
But probably not totally
I have some friends at cambridge so if you have any questions I can forward them
but it might be a bit early to have uni-related questions seeing as you're in y11
In college, I would avoid taking an interesting class because it was with a bad professor. I regret my time as a undergrad. I wished I took those interesting classes. Now I tell my friends and peers to take those interesting classes.
Idk, hard to learn from a bad professor. When you have an unbelievably inspiring teacher it is hard to go back.
Is different for everyone. But i understand your point
hiii
Nice PFP.
It just means you treasure your memories there
I wish I would feel the same
Although, I constantly feel like an outlier so I honestly doubt it
Good advice but you have to be aware it's not always easy. Life in school can be very difficult for people
I totally agree 🙂 it is different for everyone. I've been going to school for a while and have learned the teacher makes the experience. Many classes I've taken I could of just read the book and learned what was needed. Undergrad is about jumping through hoops to get you in the door of the more interesting stuff in the real world or grad classes.
My linear algebra prof just copied the script onto the board literally. 🤔My crpto prof barely looks at the script and explains the most complex constructions and the reason of every step in a first intuitiv and then formal approach.
Almost all of my profs just read out the notes on the screen, barely even writing
imagine having notes and not just winging every lecture
why write when you can experience
Imagine not simply skipping every lecture
you are only allowed to do this in your last year
also i cannot skip lectures that i have to teach 😭
Not with that attitude at least
just get your stunt double to do it
read #❓how-to-get-help
what
U ok bro?
Just git gud and you can 
just be better smh
Let me just find someone who is 195 cm tall for my stunt double.
,w 195cm in inches
6' a billion''
Yep.
My basement.
Is it fine to visualize basically everything in topology in R^2 in my head? I feel like that helps it stick, but at the same time like I should stop doing that and get used to it as an abstract, general subject. Which one would help more in the long run?
it worked fine for my metric spaces course, but it might be unhelpful as you study topology more
i'm interested to hear answers too
I think maybe the eventual goal is to gain intuition for when you can rely on R^2 and when you cant
Sometimes drawing a picture in R^2 or R^3 is good enough and sometimes it’s not
to me, it happens to be enough more often than not
And being able to look at a problem and recognize “if i just think about R^2 I shouldnt be missing anything important” or “i cant rely on R^2 here because something more subtle is happening”
with minor adjustments ig
Is important
well behaved metric spaces tend to work pretty ok, especially separable ones
res is right. general topology can get kinda fucked, like projective spaces, the sorgenfrey line/square, zariski thingies and so on
Alright, understood, thanks folks. I guess I'll stick with it until it's made clear at some point that R^2 just won't cut it
From you what you said, Fractal, it'll probably be pretty clear when that time comes
And got it Bananas, I'll try and start practicing that recognition of whether R^2 suffices, many thanks
what are the unusable help channels for
The ones in the hidden section?
yea
they're there so they don't fill up the available help channels category
uhh
gmod is so wise
shouldn’t they be available?
if not there would be like 20 of those channels up there
there are always a few available
wow
yes
why aren’t the hidden ones available
oof
cause it would clutter up space
why would they be available
you only need a few available
^^
I need at least 20 at once
YES.
i went thru precal and its basically just algebra 2
chmonkey
What
chmonkey
Quantum

darn you got me
when proving G is a group do I just have to prove that
operation is associative
identity element exists and ea = ae = a for a in G
every a in G has an inverse a^-1 in G
(so just definition of group)
Yes
Or if you’re me you just think “are there inverses” and once I convince myself there are I move on
okay
how about this
here's context
ignore the words
i like talking and i am bad at this

so do I always have to show that the inverse is in the group too?
I feel like (zw)^n = 1 is implied since the definition of a bianry operation means the group is closed right?
but this is you showing the group is closed
closure is not defined by binary operation
yeah you gotta show for z != 1 that you have w such that wz=1
(wz)^n right?
No
n ranges in Z^+
OH an inverse lol
wait I'm confused
Wait what am I even talking about
so would I just add "assume z \neq 1"
I am being Hurb
in the inverse section
okok can we back up I think I'm getting confused
well it doesn't matter just trying to make it clear when it is nontrivial yeah
what am I missing from my proof?
well what's 1/i in the form x+iy
1/(0+1i)
nope
when you showed stuff with associativity earlier you only were using stuff that looked like x+iy
do I conjugate and divide
x,y are real numbers
well, truthfully the proof I have in mind this doesn't matter but still good to know how to do this stuff
main thing is you can't just say 1/i because we're sort of saying that its existence is in doubt, it's like saying the inverse of 0 is 1/0, I can't just write that symbol down and guarantee it exists
well the proof I have in mind is we know z^n=1 so we can write it as z^(n-1) * z = 1
Trying to see what we can do with that 
we know z^(n-1) is in our group cause (z^(n-1))^n = (z^n)^(n-1) = 1^(n-1) = 1
I think maybe I shouldn't have told you this so soon haha
I follow this
I feel like one thing I should mention
I said you only have to prove the group axioms
Inverse, unit, associative
Yes, but apparently I'm missing something there
But in this case we’re constructing the group as a subset of C
So you need to prove that it’s closed under the operation
Okay
Why don't D&F mention closure as a group axiom :(
So
It’s because it isn’t one
Let me explain
A group operation is a function G x G -> G
It tells you how to multiply two things
But here we have this intuitive notion of multiplication inside C
And we’re taking that to be the multiplication in the group we constructed
This gives a function G x G -> C
We know the output is a complex number
But does it live in G?
GOT IT
But the group doesn't have to be closed under the operation
No it has to
:zonkies:
Since it maps G x G -> G
That's what I originally thought
In this specific case
We don’t know that it maps into G
yet
You can prove it
But a priori all you know is the function goes G x G -> C
So it’s less of “does this set with this operation satisfy the group axioms”
Okay
You don’t even know that this is an operation on G
Since you aren’t sure if it maps into G
Does that make sense?
I think. We don't know that it maps into G (at least, not "yet") so we must show that it does map into G
Yeah
So I guess I'd take
So it’s not an issue of “is G a group with this operation”
Because you aren’t even at the point of being able to say it’s an operation on G
That’s why closure isn’t mentioned as an axiom

Because you’re already at the point you have a function G x G -> G
It doesn’t even make sense for it to not be closed under the operation
So once we show that it is an operation on G then we're all good?
I think so?
And then after that we know it maps G x G -> G and so it's closed under the operation
(I mean you have to know this to even do inverses lol)
Right
And you know it’s associative
wait
You assumed z^n = 1
Swag
but how can you just say w = z^(n-1)
How do you know z^n-1 is in G
Oh it’s closed under multiplication
z is an element, so z multiplied by itself n-1 times is an element
Right?
that's what we're trying to prove though isn't it???
this was my proof earlier
Oh that’s lit
lol
Wait what are we proving
Oh I guess it does follow from G being closed under the operation
Group of roots of unity forms a multiplicative group
Do we know that multiplication is closed on G
Feather still has to prove this
How does one normally prove closure
directly ?
- Show associativity, existence of identity, and existence of an inverse
- Prove that the operation maps to G (and hence G is closed under it) by showing that any product under the operation is in G
is that right?
That was stupid
which parts did u do
1
cool
What’s the associativity proof
Oh
foil
Honestly I would’ve just said multiplication in C is associative

Which we know from our complex analysis class
They don’t know that
Oh that’s right
I mean if you weren’t sure why yourself
Not that complicated ok
Then it’s good to go through it
why foil tho you have exponential form and exponent rules n all
right
add the args multiply the magnitudes
thats fine
are u happy now do u feel superior metal ?
Is this p[art right
- Prove that the operation maps to G (and hence G is closed under it) by showing that any product under the operation is in G
Or is there more I have to do to show closure
nah
No that’s it
just product two roots and thats all
poggers
Just show if you have z,w in G then so is zw
and we do that by saying let w = z^(n-1)
but then we have to show that such w is even in G
which it is since w^n = (z^n)^(n-1) = 1^(n-1) = 1 (thanks mero)
and we're all set
okay
that's not bad
good thinking
This is for closure? Or
yes
No
no.
That’s showing inverses exist
Ok ok
wat
That doesn’t show it’s closed under multiplication
This was just showing z has an inverse
You have to let z,w be arbitrary to show it’s closed under multiplication
So z^n = 1 and w^m = 1
Show (zw)^k = 1 for some k
Ohhhh
Hey abs!
Yo
Wassup?
uhhh
Not much
What you studying these days?
Wow lol
.
Let k = nm? lol
Yah
oh
Why does that work tho
wait can you actually do that
Yes lol
why not
Oh I’m stupid
oh
Yeah I though k was some fixed unknown quantity
Oh and University started or still 12th grade going on lol?
You can sorta choose what k you want
There's plenty of k just choose one 4head
Yeah
"I just happen to know..."
Cool.
Man proving that sets and operations form groups feels like
what if k is prime?
Im crawling at the rock bottom of concrete math
And algebraic tricks are the only way to climb up
(z^n)^m * (w^m)^n
1^m * 1^n = 1 * 1 = 1
ya


cute

I'm confused why I have to prove that an inverse element exists
but I can just "say" an identity element exists? that it's 1?
?
no?
thats not obvious
Wel you have to prove it
wait
But like
Inverse and identity are part of the axioms
what do you mean feather
So 1 is the identity
for example, in R, or Q even, there is no inverse for 0
You technically have to prove that 1 is the identity
under multiplication
like I don't see why this doesn't work?

.
But it’s hard to see that z^-1 is in G
And again, you technically either
1:
Need to know that’s the inverse in C
need to do a bit of multiplication to see it clearer
whereas it's obvious that 1 is in G
right cus 1+0i
yeah
and its fixed
Oh okay
to me it is obvious that inverse is in G 
Lol
you still need to know how to show 1/(a+bi) in the form x+iy from earlier when you had trouble
Well, sort of
What is 1/(a + bi)? I’ve not done much complex numbers
I mean a lot of this honestly
Depends on how much of C you are allowed to assume you know
im going to stop breathing now
lol
(x - iy)/(x^2 + y^2)
u can multiply and divide by (a-bi) to get a a+bi form for the inverse
Isn’t 1/(a+bi) just shorthand for (a+bi)^-1? Then it’s circular
But if you know that or not depends on how much you know about C
this
See my point above
Oh
I think I need to prove more abstract or unfamiliar sets are groups to really understand
because right now I'm still kinda 4heading some of this
Did you do linear algebra?
and wait chmonkey you said I need to technically show 1 is an element
yes dootdooter
slightly different perspective on what chmonkey already showed $z\bar z=|z|^2$ then $\frac{\bar z}{|z|^2} = \frac{1}{z}$ and since $|z|$ is real you're fine
Merosity
This you mean?
right but is 1 a root of unity
how can unity be a root of itself 
Vector spaces are examples of groups when you consider their addition op.
Idk if you proved things were vector spaces or not?
nope
Ah dang :/
we did approximately zero (plus or minus zero) proofs in my LA class
because it was a lame engineering class

rip
This feels a little sketchy, I don’t know. If I was inventing complex numbers, wouldn’t I have to invent what it means to divide them? I can’t just use variables like z and then say 1/z as if it’s just a real number.
Well, you have the right idea as far as proving lots of things are/aren't groups for practice.
OKAY so let me get all this homophobic shit down
To show a set is a group under some operation
sure, if you want you could write it as $z \bar z = |z|^2$ then since $|z|$ is real divide it through to get $$z \frac{\bar z}{|z|^2} = 1$$ keep in mind this is all after you've already shown multiplication of numbers of the form x+iy is associative and commutative and stuff
Merosity
Ok I see
we need to show
- Associativity of the operation
(Just take three arbitrary elements a, b, c in the set and show (ab)c = a(bc)) - Existence of an identity e
(First verify that whatever you declare as the identity is even IN the set, then show that ea = ae = a)
3, Existence of an inverse
(Have to take two arbitrary elements in the set and show that one is an inverse of the other, and also we need to show that the inverse is in the set too) - Show that the operation maps into the set (which means the set is closed under the operation).
To do this we just show a product of two arbitrary elements is in the group
So the 1/z thing is just applying “real number logic” to complex numbers, more as a notational choice sorta thing?
Another way to look at 3 is that you need to pick an arbitraty elt from the set then find its inverse in the set.
So is my list complete or am I missing anything?
I always thought a/b is notational shortcut for a * b^-1
it is yeah
The list looks right but I could be forgetting group axioms lmao.
Oh so then that complex number thing you showed me is like
How to find an explicit a+bi form
For inverses
yeah, like it's just a way of putting them in a form so that you can prove axioms and is convenient or whatever
I think proving closure should come first, because logically the others can’t follow without that, and sometimes proving the others is easier with closure
Yeah
Like I was saying before, to even get to asking “is G a group” you need to know you have an operation
So closure should be first
Yes


So like
I’ve learned all these basic definitions and theorems and whatnot for abstract algebra
But it seems like it’s all in a void
Who invented these things? Why? What problems were they working on?
I hear the history is kind of messy
And the clean, simple definitions today were developed indendently of their original problem-context
quintics are solvable in terms of radicals bro
This is a bit afterwards, but people had long realized number theory was related to things other than just Z
The clean formulations are rather recent iirc
The Gaussian integers
x^5 = 1
C
x = 1^(1/5)
Various number fields
I mean
Maybe Noether was the one who formalised a lot of this?
You can deal with these algebraically
In 1800s did they even have the kind of rigor we have now
Not really?
no lol
So now it sounds ridiculous to talk about groups without the concept of a set, logic, all that foundational stuff
Yeah, I mean you can find a book by like uhhh
Hall?
No
It is linked in a reference on Wikipedia
It’s like from 1896?
The terminology is ass
Because they viewed these things in different ways
Oh I think it’s by Burnside
Breakthrough in logical rigor occur
Seems like the philosophy of math was completely overturned
Okay so like
A lot of assumptions were made
Because people were operating ok vibes
So defekind Cauchy, etc formalized things I think
Limits weren’t like formally defined yet
Yeah Gauss and Euler would have laughed at something like Rolle’s theorem
A lot of people assumed that continuous things were differentiator
So things like the Weierstrass function
Ah
There’s this quote from Bertrand Russell
People started constructing these to say “hey guys, these assumptions aren’t true”
I think it captures it kinda well with the Weierstrass function type stuff
So I think people started poring over the details to put things on more rigorous footing
There’s in algebraic geometry also around the turn of the century and into the start of the 20th
Ah
The Italian school of algebraic geometry had sort of abandoned rigor to operate just on vibes
And this led to a lot of false things being “proved”
Which brought some people like Weil I think to try to seek to make a rigorous foundation
Logic sometimes makes monsters. For half a century we have seen a mass of bizarre functions which appear to be forced to resemble as little as possible honest functions which serve some purpose. More of continuity, or less of continuity, more derivatives, and so forth. Indeed, from the point of view of logic, these strange functions are the most general; on the other hand those which one meets without searching for them, and which follow simple laws appear as a particular case which does not amount to more than a small corner.
In former times when one invented a new function it was for a practical purpose; today one invents them purposely to show up defects in the reasoning of our fathers and one will deduce from them only that.
If logic were the sole guide of the teacher, it would be necessary to begin with the most general functions, that is to say with the most bizarre. It is the beginner that would have to be set grappling with this teratologic museum.
Henri Poincare, 1899
And then Grothendieck said fuck you to them all and invented schemes which put all those other guys stuff into the trash
What? Really?
Yeah
I mean some of the stuff they “proved” we managed to reprove ages later
Schemes are so weird
But there’s also just false things
Like people made counterexample a and I think some of the ppl of the school were like
So things got messy
Also in the past math was a lot more tied to physics and chemistry and stuff
Bro what
A lot of the mathematicians also did other sciences
Yeah I was thinking math was in the natural sciences right
And they used physical intuition, or some things about the laws of certain physical phenomena to justify things
Yeah
I forget the specific one, but there’s a kind famous example, maybe by Riemann?
Idk
Which is kinda like this quote
A practical purpose
And even if it was not practical, they used practical intuition
I guess a lot of it was just that people began to question things and then they made counterexamples
So people went back to iron out the foundations
I’m sure there’s a lot more to this, and math history is a studied field
for a long time math and physics were deeply associated
So I’m sure books have been written on them
Ah
tons of famous historic mathematicians were also engineers or physicists
And the obsession with axiomatic stuff in the 20th century
super common
for a long time people used way less than rigorous assumptions about algebraic manipulations and stuff
Fluxions
and mathematics didnt get away from stuff like that till cauchy's era (often specifically because of cauchy) and then later with formal logic
formal logic sorta helps cause an explosion of math theory that differentiates pure math way more from sciences
there was an assumption called the universality of algebra or something
and it was this pretty much not rigorous at all assumption that allowed them to extend some operations like arithmetic to infinite sums
people like euler used it iirc
i mean effectively many times these assumptions did work but it falls apart at interesting stuff
formal logic was so powerful in mathematics that a bunch of people really did think it could be used to "finish" large swathes of mathematical and philosophical inquest
and it's why the philosophy adjacent to mathematics in the first half of the twentieth century appears to be disrupted and upturned with some results from later in that half
it wasn't really clear how far you could go with logic but it appeared to be really far, advents in logic made massive improvements to a ton of fields of math and the humanities
but some of the more ambitious ideas sorta gave way to reality
What’s an example of this?
well the really famous one is bertrand russell's logicism
Isn’t that a philosophy?
I’ve heard of it
But I don’t really get what it is
“All of math reduces to logic”, or something like that
it's been a long time since i took the class where we discussed this but bertrand russell hoped that logic could be used to answer a broad class of arithmetic questions
that is not true by the incompleteness theorems
since the incompleteness theorems are about a logical system that can express a certain level of arithmetic theory
Didn't this concern Hilbert's program as well
probably, i remember some stuff was all entangled
logic was very prominent back then and iirc some of hilbert's program is just problems in logic
Right, I believe Hilbert also held the opinion that all math could be formalised inside some sequent calculi so as to reduce all of math to mechanical symbol pushing
But Gödel blew it up with his theorems
yeah people had tons of big brain ideas on it
von neumann was also working on completeness
goedel's work was a really big deal and people really saw it as a work of genius immediately
its parallel with the halting problem is really beautiful too
the philosophy of math and math diverge a lot by like the 60s
a lot of philosophers still are trained in math (usually logic) by then but it's not like people betting their philosophical ideas in provable/disprovable notions as much lol

Pretty cool that you know all that stuff
It’s interesting how logic was such a big deal back then
I don’t think it’s nearly as large now
I think its more so an increasing segmentation of math from philosophy, the philosophers of math and logicians still exist
This is kind of a general phenomenon though
Does anyone here have mojang account>
You just blew my mind 🤯
wait the number 'n' in base n is represented as "10"?
damn
that's awesome

yep lol its interesting
what determines how many help channels are available?
need
What do you need ryc
there's basically always 5 available
unless they're ALL occupied
here i'll find it gamma
I see

also keep in mind that the menu is heavily contingent on me getting full
if we can also avoid that, then i would stack it with a lot more food
No that's a very respectable perfect day
most notably not included (which i mention later): seared scallops and connecticut style lobster rolls
My opinion of you has grown slightly
oh that's cool
FLAME
it doesnt like
visually look bad
but its very inconsistent and technical
like heres the definition of the exterior derivative in terms of differential forms
Is ring theory knowledge worth to learn algebraic geometry?
yes
you need it, yes





