#serious-discussion

1 messages · Page 492 of 1

quick bronze
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Gun for high grades

crystal stone
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Some do, some don't

quick bronze
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But the ones who do would irritate me as a prof

crystal stone
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So then it's on you as a professor to create incentives to learn over to nitpick for grades

quick bronze
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Also the amount of people who cheat

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Especially during covid is high

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And rampant

crystal stone
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They eventually get caught

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It's hard to cheat your way through a 9-5 job

quick bronze
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Like in HS that was everyone

crystal stone
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If you don't actually know what you're doing

quick bronze
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True

crystal stone
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People cheating always drives me up a wall

quick bronze
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Y

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Lol

crystal stone
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If you're graded on a curve, then you are hurting someone else's grade for your selfish unearned gain

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Although, most of that fault lies with the incentive brought on by the prof./education system

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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

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If they cheat their way through the system, then that can literally kill someone

quick bronze
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Yeah

pure sun
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grades are the worst thing to happen to education

crystal stone
pure sun
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no

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haha

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not on a large scale

crystal stone
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It's very difficult to do so, even when the grades are essentially meaningless

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I taught at Russian School of Math for 5th, 6th, and 7th grade - which is an after school program for ultra math nerd kids

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Our internal grading and recommendation system meant almost nothing in reality

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But the kids took it super seriously if they couldn't solve a quiz problem or something

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I kept trying to tell them that this doesn't matter, but they kept getting stressed over it

gentle bay
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Russia is soo cool at that stuff.

crystal stone
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Russian school of math is an american education company rooted in soviet union curriculum

gentle bay
#

So what was being taught for say 7th grade?

crystal stone
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Just algebra & word problems

gentle bay
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What level Algebra?

crystal stone
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7th grade

vivid halo
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it's been interesting

gentle bay
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Wait so how is it ultra math nerd?

pure sun
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im doing that right now

vivid halo
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how's that going?

pure sun
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in my precalculus classes

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I think it works really well

crystal stone
vivid halo
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yea that's the impression I get too

crystal stone
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Kids that don't enjoy it leave the program quickly

vivid halo
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I kinda want to work it into my classes

pure sun
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idk how to scale it up to like several hundred studenst though

gentle bay
pure sun
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which is what our calc classes are

vivid halo
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oh god

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yea that sounds not really possible lol

crystal stone
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How did you implement the mastery based stuff?

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Did you give an oral exam? More open ended questions?

pure sun
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no i think oral exams are great though

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thought about doing that as well but havent tried it yet, but mi ght do it next semester in my intro to proofs class

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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

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students pick and choose which questions to attempt each week based on what skills they've been practicing

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your goal is two checkmarks per objective

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(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)

gentle bay
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Buncho Bananas you are a professor?!!? stare.

pure sun
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maybe

gentle bay
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That's super cool cros.

fair mural
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more people here than you’d expect seem to be professors

gentle bay
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?

pure sun
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I mean

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it depends on what you mean by "professor"

vivid halo
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Buncho has tenure nozoomi

pure sun
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do you mean "someone who teaches collegiate math classes"? or "someone whose job title is Professor"?

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hahahaha

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no i do not

pure sun
pure sun
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yeah

gentle bay
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That's cool!

pure sun
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so there aren't that many people here of that level

gentle bay
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Oo.

pure sun
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but youre right that there are a handful

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of us

gentle bay
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Which books does the Uni use for proofs?

pure sun
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if you're like 15 years old and assume that discord is only used by high schoolers then it might be surprising lol

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but there are twenty-somethings on here as well :P

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you mean like intro to proofs?

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depends on the person teaching the class

gentle bay
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I see.

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I will soon start proofs so I was asking for proofs books yesterday here lol.

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So asked for your recommendations lol 😅.

pure sun
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i dont have any, sorry :/

gentle bay
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Okie.

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Hey Nami.

leaden torrent
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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"

gentle bay
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Wow.

fair mural
hearty gate
#

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 ...

vast surge
deep mango
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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.

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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.

neat lintel
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also Berkeley math tourney

deep mango
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Yeah I was involved with that a little, it was fun. Great group of people

honest veldt
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anyone got an example of a homomorphism that's not bijective?

surreal sapphire
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the zero morphism

deep mango
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sure. the map from Z to Z which is given by phi(n) = 3n is a homomorphism.

toxic schooner
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any non isomorphic homomorphism? catThin4K

honest veldt
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Thanks folks

deep mango
honest veldt
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I'll check both of these by hand, but why the sotrue?

deep mango
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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.

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so both can happen.

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slim is mad that his answer to this question was just a rephrasing of the question and that i actually gave an answer

toxic schooner
honest veldt
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Just so I'm sure I've got this right, these maps preserve the structure of these groups under both addition and multiplication?

deep mango
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oh

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umm

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i was giving group homomorphisms

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if you want them to be ring homomorphisms

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uhhh

honest veldt
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No, no, I do want groups

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I meant like, as separate examples

deep mango
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ok then it's just preserving addition

surreal sapphire
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what if you have a bijective homomorphism that is not an isomorphism sotrue

toxic schooner
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but group mapping dont preserve both, no?

deep mango
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Z is not a group under multiplication

honest veldt
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Oh right right, I see

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Thank you

honest veldt
toxic schooner
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4/6

deep mango
toxic schooner
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not in Z

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Z? field? stare

honest veldt
deep mango
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that's because 3*n * 3*m does not equal 3*(mn)

surreal sapphire
deep mango
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trying to decipher if you sent this seriously or if you're baiting me into responding hmmCat

toxic schooner
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are u making stuff up

deep mango
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ok then i will react

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😌

errant furnace
toxic schooner
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i should do a lot of algebra soon stare

surreal sapphire
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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

toxic schooner
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I see

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what would be such a general setting?

surreal sapphire
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topological spaces as i mentioned

toxic schooner
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ah catThin4K

surreal sapphire
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in even more general settings (categories in which the underlying objects arent sets), it gets worse

toxic schooner
#

categories coming to haunt me again

errant furnace
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Grp

deep mango
flat harbor
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just pretend they dont exist youll be fine

deep mango
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Oh shit i got an email from courant tech support

surreal sapphire
deep mango
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Lets see if they'll change my website url to something not idiotic

toxic schooner
surreal sapphire
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yes i do the same

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its fine

errant furnace
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but you brought them up

toxic schooner
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i doubt if i can do that for long tho

errant furnace
deep mango
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Nope! Lol

surreal sapphire
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i just wanted to sound smart

deep mango
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Alright fuck me I guess

toxic schooner
surreal sapphire
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debatable

toxic schooner
tiny marten
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Who needs categories anyways

deep mango
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I'll just keep using my berkeley website for now until someone decides to have respect for me

toxic schooner
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homology?

surreal sapphire
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but like the topological spaces example is worth to keep in mind

toxic schooner
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i see, yeah i will try to keep it in mind

atomic hornet
deep mango
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Not gonna self dox that easy 😇

fair mural
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ryc i won’t dox you

bright hill
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You guys have like, secret identities on discord?

mortal igloo
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I'm secret

leaden torrent
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you say that as if its abnormal?

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has social media normalized posting your personal info publicly nowadays

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when i was a kid, we were always told to not share anything personal on the internet

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even saying my university here gives me weird vibes even if i know its fine

bright hill
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I was told that too

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But I was never told the reasoning behind it

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So ig I just shrugged it off as superstition

deep mango
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Well if everyone promises not to dox me, I guess I could just tell everyone.

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Isn't the recording of my talk enough??

toxic schooner
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i have doxxed myself quite a lot

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i shared my face here, so thats already a lot KEK

pale orchid
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shyshu of the golden doxx

ancient flame
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gdoxx

toxic schooner
honest veldt
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Is there a way to check for myself if this is a homomorphism? Or do I take this for granted

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Oh wait I cropped it out

pale orchid
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D_2n

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you are tempting me, strad

honest veldt
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Eddy don't do it

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I know it's unbearably tempting but you are strong

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Thank the lord this book uses the D_2n notation and not the other common one

toxic schooner
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what is the common one?

honest veldt
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It's exactly what eddy cannot resist

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D_n

toxic schooner
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Ooof

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lol

honest veldt
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Say for example I have an element rr (r^2), how do I know what this is mapped to in D_2k?

brave hollow
brave hollow
honest veldt
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Ohhh right right, I get it

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Merci beaucoup

steep mountain
icy forge
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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

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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

ancient flame
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im just skeptical about everything

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like I share as little as possible

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y'know

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bc I feel like if people have my info then they will come to my house and murder me irl

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which I know won't happen

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but if I keep that in the back of my mind then I won't post anything out of stupidity

deep mango
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yeah it's too late gmod i already doxed you to the whole server

fair mural
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someone’s already coming to your house to murder you

rotund steppe
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😳

icy forge
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Don't grief my MC house

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It's built with nether brick

mint patio
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This seems really useful

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Like a really nice way to describe a group

bronze pelican
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How do you prove this

honest veldt
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The book proves stuff about presentations at some point, I don't remember what exactly

bronze pelican
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Oh this is just a definition

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I was thinking this was saying any group that is finitely generated has its relations also being finitely generated

honest veldt
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Wait, how can you generate relations?

static loom
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I think that's a difficult problem in general

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I forget the technical phrasing for "how bad" it is lol

honest veldt
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Oh, I thought it mightve been something I missed in the book, definitely not then

static loom
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I guess you can get a presentation by starting with the cayley table and mucking around there and boiling down stuff idk

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I think this has something to do with the definition of solvable groups, I'm sure someone knows more than me here

bronze pelican
# honest veldt Wait, how can you generate relations?

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 .

honest veldt
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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

modern drift
#

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

bronze pelican
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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.

tiny marten
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free groups and words are cool

agile sundial
#

Nothing in life is free 😡

frigid lark
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🤔What about the cosplayers who walk in fairs with a sign that says free hugs.

fair mural
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of course that’s free

frigid lark
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No new avatar 😭

fair mural
#

nope i can’t find any

rapid folio
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Hey all

alpine kindle
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hi corra

rapid folio
# alpine kindle hi corra

Hope you're doing good, thought I'd hang out while I prepare some lessons for when teaching starts up again manYES I find lurking and doing some chatting here gets me motivated

alpine kindle
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oh

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nice

alpine kindle
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@rapid folio what are your lessons on

tender musk
#

Is Year 7 and Extension 2 the equivalent to a senior in high school

rapid folio
alpine kindle
rapid folio
alpine kindle
#

huh?

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what country

rapid folio
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Australia

tender musk
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So you teach 6th grade, 9th grade, and 12th grade?

alpine kindle
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ohhh

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nvm

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year 7 uk is 6th grade

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how is being a maths teacher

rapid folio
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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

alpine kindle
#

interesting

rapid folio
# alpine kindle how is being a maths teacher

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.

alpine kindle
#

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)

alpine kindle
rapid folio
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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.

alpine kindle
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the further maths a level papers are interesting

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they give you a lottt of space

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I'm currently in year 11

rapid folio
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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

rapid folio
# alpine kindle I'm currently in year 11

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

alpine kindle
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I'm very excited for university in a few years

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because then I'll be around people who actually know what I'm talking about opencry

sly thistle
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Sup nerds

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Nvm looks like this convo happened a while ago

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😢

rapid folio
# alpine kindle I'm very excited for university in a few years

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!

rapid folio
#

I just didn't respond because I was working 😅

sly thistle
#

Hello

rapid folio
sly thistle
#

Hmm

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In what respect?

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I’m Australian so

alpine kindle
plush venture
rapid folio
sly thistle
#

What does sophomore mean

sly thistle
plush venture
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second year studies

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in USA

plush venture
#

Oh nice, are you hoping to study math>

alpine kindle
#

yes

rapid folio
sly thistle
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@rapid folio I’m still pogging about the fact I got a 50 in methods last year

rapid folio
#

What part of the country you in?

sly thistle
#

Vic

rapid folio
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Thought so, from the word "methods" 😅 I'm NSW

sly thistle
#

Idk why I assumed you were Vic too

alpine kindle
plush venture
#

for now just enjoy your days in school.

rapid folio
#

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

rapid folio
alpine kindle
#

i am

plush venture
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because as soon you step foot on campus, time will go so quickly that you will forget everything in the world

alpine kindle
#

huh?

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wdym

plush venture
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like time flies

alpine kindle
#

no i know what you mean

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sorry

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just like

sly thistle
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Sorry that’s a bad pun

alpine kindle
#

I've never heard that before

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about university

deep mango
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I can kind of agree with this

plush venture
#

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.

deep mango
#

Some of it moved in slow motion at the time but in hindsight it was all lightning fast lol

sly thistle
#

I mean that’s how it is isn’t it?

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Everything in hindsight that is

deep mango
#

Idk

plush venture
#

It is but then you wished you had done more things than just study.

deep mango
#

When I think about high school it feels like it dragged on forever for me

alpine kindle
#

you only remember the novel experiences

deep mango
#

I do not really wish that lol

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But

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I do wish that I had done certain things differently

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I mostly wish that id like

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Not decided to do the job I decided to do

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Cause I think that the networks and social ties I got out of it are all totally worthless now

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That might not end up being true

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Idk

alpine kindle
#

what job

deep mango
#

But it would have been nice to focus a little more on the math circles

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Resident Advisor in the dorms

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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

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I guess I gained a lot of skills from it but i'm also a very anxious person and it definitely worsened that

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In a way which I think is a little irreparable

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But probably not totally

frozen merlin
#

but it might be a bit early to have uni-related questions seeing as you're in y11

plush venture
#

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.

autumn aspen
plush venture
spare kelp
#

hiii

gentle bay
#

Nice PFP.

bright hill
#

I wish I would feel the same

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Although, I constantly feel like an outlier so I honestly doubt it

icy forge
autumn aspen
# plush venture Is different for everyone. But i understand your point

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.

frigid lark
#

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.

devout nacelle
#

Almost all of my profs just read out the notes on the screen, barely even writing

surreal sapphire
#

imagine having notes and not just winging every lecture

flat harbor
#

why write when you can experience

devout nacelle
neat lintel
#

hello guys how can I apply for a role

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role that does nothing

fair mural
#

scroll up in there

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you’ll see a message you can react to to get it

surreal sapphire
#

also i cannot skip lectures that i have to teach 😭

sick burrow
#

Not with that attitude at least

alpine kindle
#

just get your stunt double to do it

toxic schooner
steep mountain
#

what

bright hill
#

U ok bro?

devout nacelle
alpine kindle
#

just be better smh

dire mulch
fair mural
#

,w 195cm in inches

fathom swallowBOT
fair mural
#

wow

#

that is tall

#

are you actually that tall

vagrant kestrel
#

6' a billion''

dire mulch
fair mural
#

my gosh

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have you ever hit your head on anything

dire mulch
#

My basement.

fair mural
#

rip

#

stereotypical tall person stuff

honest veldt
#

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?

frozen merlin
#

it worked fine for my metric spaces course, but it might be unhelpful as you study topology more

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i'm interested to hear answers too

pure sun
#

I think maybe the eventual goal is to gain intuition for when you can rely on R^2 and when you cant

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Sometimes drawing a picture in R^2 or R^3 is good enough and sometimes it’s not

last oxide
#

to me, it happens to be enough more often than not

pure sun
#

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”

last oxide
#

with minor adjustments ig

pure sun
#

Is important

last oxide
#

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

honest veldt
#

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

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From you what you said, Fractal, it'll probably be pretty clear when that time comes

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And got it Bananas, I'll try and start practicing that recognition of whether R^2 suffices, many thanks

frank orchid
#

what are the unusable help channels for

wild lantern
#

The ones in the hidden section?

frank orchid
#

yea

ancient flame
#

they're there so they don't fill up the available help channels category

frank orchid
#

uhh

deep mango
#

gmod is so wise

frank orchid
#

shouldn’t they be available?

ancient flame
#

if not there would be like 20 of those channels up there

#

there are always a few available

deep mango
#

wow

ancient flame
deep mango
#

ctrl a delete

#

you sniped me

frank orchid
#

why aren’t the hidden ones available

ancient flame
#

oof

deep mango
#

cause it would clutter up space

#

why would they be available

#

you only need a few available

ancient flame
#

^^

wild lantern
#

I need at least 20 at once

ancient flame
#

YES.

deep nebula
#

i went thru precal and its basically just algebra 2

jovial ember
#

20$/1 35$/2

#

19 dollar Fortnite card

#

Who wants it??

fair mural
#

chmonkey

jovial ember
#

What

fair mural
#

chmonkey

jovial ember
#

Quantum

fair mural
jovial ember
fair mural
#

darn you got me

mint patio
#

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)

jovial ember
#

Yes

#

Or if you’re me you just think “are there inverses” and once I convince myself there are I move on

mint patio
#

okay

#

how about this

#

here's context

#

ignore the words

#

i like talking and i am bad at this

mint patio
# mint patio

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?

brave hollow
#

but this is you showing the group is closed

#

closure is not defined by binary operation

static loom
#

yeah you gotta show for z != 1 that you have w such that wz=1

jovial ember
#

It’s cuz

#

n ranges in Z

#

Not in N

jovial ember
#

No

mint patio
#

n ranges in Z^+

jovial ember
#

wz

#

Oh okay well it actually doesn’t matter

#

teehee

mint patio
#

wait I'm confused

jovial ember
#

Wait what am I even talking about

mint patio
#

so would I just add "assume z \neq 1"

jovial ember
#

I am being Hurb

mint patio
#

in the inverse section

jovial ember
#

Well no

#

If z = 1

#

It is its own inverse

mint patio
#

okok can we back up I think I'm getting confused

static loom
#

well it doesn't matter just trying to make it clear when it is nontrivial yeah

mint patio
#

what am I missing from my proof?

static loom
#

let's look at it concretely

#

what's the inverse of i

mint patio
#

1/i? 🥴

#

(i)(1/i) = 1

#

(1/i)(i) = 1

static loom
#

well what's 1/i in the form x+iy

mint patio
#

1/(0+1i)

static loom
#

nope

mint patio
#

do you want me to conjugate?

#

that's not x+iy though

static loom
#

when you showed stuff with associativity earlier you only were using stuff that looked like x+iy

mint patio
#

do I conjugate and divide

static loom
#

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

mint patio
#

huh

#

okay

#

how would I prove it exists then?

static loom
#

well the proof I have in mind is we know z^n=1 so we can write it as z^(n-1) * z = 1

mint patio
#

Trying to see what we can do with that thonkSpin

static loom
#

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

jovial ember
#

I feel like one thing I should mention

#

I said you only have to prove the group axioms

#

Inverse, unit, associative

mint patio
#

Yes, but apparently I'm missing something there

jovial ember
#

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

mint patio
#

Okay

jovial ember
#

Idk if this was mentioned earlier

#

But imo this is the hardest part

mint patio
#

Why don't D&F mention closure as a group axiom :(

jovial ember
#

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?

mint patio
#

GOT IT

jovial ember
#

So it’s not an axiom of a group because

#

An operation has to be closed

mint patio
#

But the group doesn't have to be closed under the operation

jovial ember
#

No it has to

mint patio
#

:zonkies:

jovial ember
#

Since it maps G x G -> G

mint patio
#

That's what I originally thought

jovial ember
#

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”

mint patio
#

Okay

jovial ember
#

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?

mint patio
#

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

jovial ember
#

Yeah

mint patio
#

So I guess I'd take

jovial ember
#

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

jovial ember
#

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

mint patio
jovial ember
#

I think so?

mint patio
#

And then after that we know it maps G x G -> G and so it's closed under the operation

jovial ember
#

You’ve shown inverses exist

#

You’ve shown it has an identity

mint patio
#

I need to show that inverse^n = 1

#

and that zw = 1 (this isn't true is it?????)

jovial ember
#

(I mean you have to know this to even do inverses lol)

#

Right

#

And you know it’s associative

jovial ember
#

w = z^n-1

mint patio
#

wait

jovial ember
#

You assumed z^n = 1

mint patio
#

zw
= z(z^(n-1))
= z^n
= 1

#

oh

jovial ember
#

Swag

mint patio
#

but how can you just say w = z^(n-1)

jovial ember
#

Cuz why not

#

It’s an element

#

And you can show it lives in G

wicked ore
#

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?

mint patio
mint patio
#

oh

#

yes

wicked ore
mint patio
#

fuck

#

I don't like that

#

LMAO

#

okay

#

well I like the proof

static loom
#

lol

mint patio
#

don't like that I have to do that

#

So I guess

wicked ore
#

Wait what are we proving

jovial ember
#

Oh I guess it does follow from G being closed under the operation

#

Group of roots of unity forms a multiplicative group

wicked ore
#

Do we know that multiplication is closed on G

jovial ember
#

Feather still has to prove this

wicked ore
#

How does one normally prove closure

cold needle
#

directly ?

mint patio
#
  1. Show associativity, existence of identity, and existence of an inverse
  2. 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?

wicked ore
#

That was stupid

cold needle
#

which parts did u do

mint patio
#

1

cold needle
#

cool

wicked ore
#

What’s the associativity proof

mint patio
#

Oh I just FOIL'd it

wicked ore
#

Oh

cold needle
#

foil

jovial ember
#

Honestly I would’ve just said multiplication in C is associative

cold needle
jovial ember
#

Which we know from our complex analysis class

mint patio
#

that we haven't taken yet

jovial ember
#

They don’t know that

mint patio
#

LOL

wicked ore
#

Oh that’s right

jovial ember
#

I mean if you weren’t sure why yourself

wicked ore
#

Not that complicated ok

jovial ember
#

Then it’s good to go through it

cold needle
#

why foil tho you have exponential form and exponent rules n all

mint patio
#

right

cold needle
#

add the args multiply the magnitudes

mint patio
#

I forgot

#

metal

#

that's it

#

i forgor 💀

cold needle
#

thats fine

mint patio
#

are u happy now do u feel superior metal ?

cold needle
#

u still proved it

#

i never feel superior

#

there is always a bigger fish

mint patio
#

Is this p[art right

#
  1. 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

cold needle
#

nah

jovial ember
#

No that’s it

cold needle
#

just product two roots and thats all

mint patio
#

poggers

jovial ember
#

Just show if you have z,w in G then so is zw

mint patio
#

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

mint patio
#

yes

jovial ember
#

No

mint patio
#

no.

jovial ember
#

That’s showing inverses exist

wicked ore
#

Ok ok

mint patio
jovial ember
#

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

wicked ore
#

Ohhhh

gentle bay
#

Hey abs!

wicked ore
#

Yo

gentle bay
#

Wassup?

mint patio
wicked ore
#

Not much

gentle bay
#

What you studying these days?

wicked ore
#

Trying to prove closure

#

Lol

gentle bay
#

Wow lol eeveeKawaii.

mint patio
#

Let k = nm? lol

jovial ember
#

Yah

mint patio
#

oh

jovial ember
#

Why does that work tho

wicked ore
#

wait can you actually do that

jovial ember
#

Yes lol

cold needle
#

why not

wicked ore
#

Oh I’m stupid

mint patio
wicked ore
#

Yeah I though k was some fixed unknown quantity

gentle bay
wicked ore
#

You can sorta choose what k you want

brave hollow
#

There's plenty of k just choose one 4head

jovial ember
#

Yeah

brave hollow
#

"I just happen to know..."

gentle bay
wicked ore
#

Man proving that sets and operations form groups feels like

mint patio
#

what if k is prime?

wicked ore
#

Im crawling at the rock bottom of concrete math

jovial ember
#

k won’t be prime

#

I mean unless m or n is 1

#

But prime doesn’t mean anything

wicked ore
#

And algebraic tricks are the only way to climb up

jovial ember
#

Just compute (zw)^mn

#

First break it apart

#

z^mn • w^mn

#

Now what?

mint patio
#

(z^n)^m * (w^m)^n

jovial ember
#

The exponent rules you know from like, algebra still@hold

#

Yeah

#

And that becomes?

mint patio
#

1^m * 1^n = 1 * 1 = 1

cold needle
#

ya

brave hollow
jovial ember
neat lintel
#

cute

toxic schooner
mint patio
#

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?

cold needle
#

?

jovial ember
#

Wel you have to prove it

cold needle
#

wait

jovial ember
#

But like

wicked ore
#

Inverse and identity are part of the axioms

jovial ember
#

Take any z

#

z•1 = z

cold needle
#

what do you mean feather

jovial ember
#

So 1 is the identity

toxic schooner
#

for example, in R, or Q even, there is no inverse for 0

jovial ember
#

You technically have to prove that 1 is the identity

toxic schooner
#

under multiplication

mint patio
#

like I don't see why this doesn't work?

jovial ember
#

We just omitted mentioning it

#

Oh this technically works

toxic schooner
mint patio
#

.

jovial ember
#

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

cold needle
#

need to do a bit of multiplication to see it clearer

mint patio
#

whereas it's obvious that 1 is in G

jovial ember
#

Or 2: manually compute what happens when you multiply z and z^-1

#

I mean yeah

cold needle
#

right cus 1+0i

jovial ember
#

1^n = 1 for any n

#

Lol

mint patio
#

yeah

cold needle
#

and its fixed

mint patio
#

that wasn't sarcasm

#

LMAO

jovial ember
#

Oh okay

brave hollow
#

to me it is obvious that inverse is in G smugsmug

jovial ember
#

Lol

static loom
jovial ember
#

Well, sort of

wicked ore
#

What is 1/(a + bi)? I’ve not done much complex numbers

jovial ember
#

I mean a lot of this honestly

static loom
#

I mean independent of everything

#

just need to know how to do that

mint patio
#

why can't you just conjugate it and then divide real parts

#

wait

jovial ember
#

Depends on how much of C you are allowed to assume you know

mint patio
#

kidding

#

i lied i lied

#

stop

#

i wasnt thinking

jovial ember
#

No that is kind of why it is

#

What*

#

Inverse is

mint patio
#

im going to stop breathing now

static loom
#

lol

jovial ember
#

(x - iy)/(x^2 + y^2)

toxic schooner
wicked ore
#

Isn’t 1/(a+bi) just shorthand for (a+bi)^-1? Then it’s circular

jovial ember
#

But if you know that or not depends on how much you know about C

toxic schooner
jovial ember
wicked ore
#

Oh

mint patio
#

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

wild lantern
#

Did you do linear algebra?

mint patio
#

and wait chmonkey you said I need to technically show 1 is an element
yes dootdooter

static loom
#

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

fathom swallowBOT
#

Merosity

wicked ore
mint patio
#

what's wrong with this chmonkey

#

isn't that proving it's the identity

cold needle
#

right but is 1 a root of unity

mint patio
#

oh

#

that is

#

I have to

#

man

#

but that's like...

#

😭

cold needle
#

Obvious?

static loom
#

how can unity be a root of itself stareFlushed

mint patio
#

you know

#

that I know

#

I can't say that

#

LMFAO

wild lantern
#

Vector spaces are examples of groups when you consider their addition op.

#

Idk if you proved things were vector spaces or not?

mint patio
#

nope

wild lantern
#

Ah dang :/

mint patio
#

we did approximately zero (plus or minus zero) proofs in my LA class

#

because it was a lame engineering class

cold needle
#

rip

wicked ore
wild lantern
#

Well, you have the right idea as far as proving lots of things are/aren't groups for practice.

mint patio
#

OKAY so let me get all this homophobic shit down

#

To show a set is a group under some operation

smoky tangle
#

Hey

#

This is me aman

static loom
fathom swallowBOT
#

Merosity

wicked ore
#

Ok I see

mint patio
#

we need to show

  1. Associativity of the operation
    (Just take three arbitrary elements a, b, c in the set and show (ab)c = a(bc))
  2. 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)
  3. 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
wicked ore
#

So the 1/z thing is just applying “real number logic” to complex numbers, more as a notational choice sorta thing?

static loom
#

yeah sorta

#

if it's a commutative group, fractions are well defined

wild lantern
#

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.

mint patio
#

So is my list complete or am I missing anything?

wicked ore
#

I always thought a/b is notational shortcut for a * b^-1

static loom
#

it is yeah

wild lantern
#

The list looks right but I could be forgetting group axioms lmao.

wicked ore
#

How to find an explicit a+bi form

#

For inverses

static loom
#

yeah, like it's just a way of putting them in a form so that you can prove axioms and is convenient or whatever

wicked ore
jovial ember
#

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

mint patio
#

oKAY

#

so put 4 at the top of the list

#

and NOW we're gucci

wicked ore
#

Yes

mint patio
jovial ember
wicked ore
#

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?

jovial ember
#

Arguably Galois was doing stuff to prove Abel-Ruffini

#

I think

wicked ore
#

I hear the history is kind of messy

jovial ember
#

Insolvabilitu of the quintic

#

These show up quite naturally in various fields

wicked ore
#

And the clean, simple definitions today were developed indendently of their original problem-context

mint patio
#

quintics are solvable in terms of radicals bro

jovial ember
#

This is a bit afterwards, but people had long realized number theory was related to things other than just Z

devout nacelle
#

The clean formulations are rather recent iirc

jovial ember
#

The Gaussian integers

mint patio
#

x^5 = 1

jovial ember
#

C

mint patio
#

x = 1^(1/5)

jovial ember
#

Various number fields

wicked ore
#

I mean

jovial ember
#

Things like Z[sqrt(n)]

#

Etc etc

devout nacelle
#

Maybe Noether was the one who formalised a lot of this?

jovial ember
#

You can deal with these algebraically

wicked ore
#

In 1800s did they even have the kind of rigor we have now

jovial ember
#

Not really?

mint patio
#

no lol

jovial ember
#

Set theory wasn’t even founded

#

But the work done is still largely good

wicked ore
#

So now it sounds ridiculous to talk about groups without the concept of a set, logic, all that foundational stuff

jovial ember
#

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

wicked ore
#

Jeez

#

Why did the like

jovial ember
#

Oh I think it’s by Burnside

wicked ore
#

Breakthrough in logical rigor occur

jovial ember
#

Uhhh

#

Idk, I think… Cauchy among others

#

Cantor

wicked ore
#

Seems like the philosophy of math was completely overturned

jovial ember
#

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

wicked ore
#

Yeah Gauss and Euler would have laughed at something like Rolle’s theorem

jovial ember
#

A lot of people assumed that continuous things were differentiator

#

So things like the Weierstrass function

wicked ore
#

Ah

jovial ember
#

The like fractal saw one

#

Continuous everywhere nowhere differentiator

wicked ore
#

There’s this quote from Bertrand Russell

jovial ember
#

People started constructing these to say “hey guys, these assumptions aren’t true”

wicked ore
#

I think it captures it kinda well with the Weierstrass function type stuff

jovial ember
#

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

wicked ore
#

Ah

jovial ember
#

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

wicked ore
#

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

jovial ember
#

And then Grothendieck said fuck you to them all and invented schemes which put all those other guys stuff into the trash

jovial ember
#

Yeah

wicked ore
#

Wait grothendieck invented schemes

#

Jeez

jovial ember
#

I mean some of the stuff they “proved” we managed to reprove ages later

wicked ore
#

Schemes are so weird

jovial ember
#

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

wicked ore
#

Bro what

jovial ember
#

A lot of the mathematicians also did other sciences

wicked ore
#

Yeah I was thinking math was in the natural sciences right

jovial ember
#

And they used physical intuition, or some things about the laws of certain physical phenomena to justify things

wicked ore
#

Yeah

jovial ember
#

I forget the specific one, but there’s a kind famous example, maybe by Riemann?

#

Idk

wicked ore
#

A practical purpose

#

And even if it was not practical, they used practical intuition

jovial ember
#

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

tiny marten
#

for a long time math and physics were deeply associated

jovial ember
#

So I’m sure books have been written on them

wicked ore
#

Ah

tiny marten
#

tons of famous historic mathematicians were also engineers or physicists

wicked ore
#

And the obsession with axiomatic stuff in the 20th century

tiny marten
#

super common

#

for a long time people used way less than rigorous assumptions about algebraic manipulations and stuff

jovial ember
#

Fluxions

tiny marten
#

and mathematics didnt get away from stuff like that till cauchy's era (often specifically because of cauchy) and then later with formal logic

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formal logic sorta helps cause an explosion of math theory that differentiates pure math way more from sciences

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there was an assumption called the universality of algebra or something

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and it was this pretty much not rigorous at all assumption that allowed them to extend some operations like arithmetic to infinite sums

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people like euler used it iirc

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i mean effectively many times these assumptions did work but it falls apart at interesting stuff

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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

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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

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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

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but some of the more ambitious ideas sorta gave way to reality

tiny marten
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well the really famous one is bertrand russell's logicism

wicked ore
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Isn’t that a philosophy?

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I’ve heard of it

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But I don’t really get what it is

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“All of math reduces to logic”, or something like that

tiny marten
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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

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that is not true by the incompleteness theorems

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since the incompleteness theorems are about a logical system that can express a certain level of arithmetic theory

devout nacelle
tiny marten
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probably, i remember some stuff was all entangled

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logic was very prominent back then and iirc some of hilbert's program is just problems in logic

devout nacelle
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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

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But Gödel blew it up with his theorems

tiny marten
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yeah people had tons of big brain ideas on it

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von neumann was also working on completeness

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goedel's work was a really big deal and people really saw it as a work of genius immediately

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its parallel with the halting problem is really beautiful too

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the philosophy of math and math diverge a lot by like the 60s

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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

devout nacelle
wicked ore
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Pretty cool that you know all that stuff

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It’s interesting how logic was such a big deal back then

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I don’t think it’s nearly as large now

blazing pawn
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I think its more so an increasing segmentation of math from philosophy, the philosophers of math and logicians still exist

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This is kind of a general phenomenon though

vague lion
random solstice
#

Does anyone here have mojang account>

timid bluff
quasi torrent
# vague lion

wait the number 'n' in base n is represented as "10"?

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damn

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that's awesome

toxic schooner
tender grotto
haughty bear
#

what determines how many help channels are available?

deep mango
#

need

sick burrow
#

What do you need ryc

deep mango
#

there's basically always 5 available

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unless they're ALL occupied

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here i'll find it gamma

sick burrow
#

I see

deep mango
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also keep in mind that the menu is heavily contingent on me getting full

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if we can also avoid that, then i would stack it with a lot more food

sick burrow
#

No that's a very respectable perfect day

deep mango
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most notably not included (which i mention later): seared scallops and connecticut style lobster rolls

sick burrow
#

My opinion of you has grown slightly

haughty bear
#

oh that's cool

fathom swallowBOT
mint patio
#

what makes DG notation so cursed

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why does everyone hate it

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anyone have pics

leaden torrent
#

it doesnt like

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visually look bad

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but its very inconsistent and technical

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like heres the definition of the exterior derivative in terms of differential forms

livid yacht
#

Is ring theory knowledge worth to learn algebraic geometry?

opaque patrol
#

yes

leaden torrent
#

you need it, yes