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Twink
Twink
04:00
byeTed
anon
anon
$\forall x\in R\,\exists y\in R\,(x=y+y\vee x=y+y+1)$ is easily seen to be equivalent to $R/2R\cong\Bbb Z/2\Bbb Z\vee R/2R\cong\Bbb Z/\Bbb Z$. Now I wonder about $\forall x \exists y\exists z(x=y+y \vee(x=y+y+z\wedge\neg\exists w(z=w+w)))$.
cyberskull
cyberskull
@KevinDriscoll have you decided to move your question to M.O. yet?
Kevin Driscoll
Kevin Driscoll
@cyberskull A good question. I really should
cyberskull
cyberskull
go for it
 
1 hour later…
cyberskull
cyberskull
05:21
\o/ . /o\ . /o/ . /o\ . Y.M.C.A.
Jack M
Jack M
05:51
hey
cyberskull
cyberskull
hi
Jack M
Jack M
06:36
is it acceptable to post a question in here if after several days, it's only had a dozen views?
Tobias Kildetoft
Tobias Kildetoft
@JackM the receptions tends to vary. But not much is going on here anyway right now, so you won't be interrupting anything
Jack M
Jack M
@Tobias I might drop by when there's some more people in fact
although it's on field/galois theory if anyone is interested in that area?
or I might just wait for the bounty
Tobias Kildetoft
Tobias Kildetoft
@JackM depends on the level. If too high, I would not be able to help
Jack M
Jack M
2
Q: Proof of necessary condition for constructibility of a number

Jack MI'm reading a proof of the necessary condition for a real number to be constructible, and it seems to leave out a few details that I can't really fill in. This is what I understand so far. We have to prove that: If the point $(p, q)$ is constructible with straightedge and compass starting fr...

field-theory galois-theory geometric-construction
DragonLord
DragonLord
06:51
I'm hoping to get the HP Prime soon
www8.hp.com/us/en/products/calculators/…
Does anyone have experience with this calculator? (I'm taking a linear algebra course this semester and will take prob&stats next (and final) semester.)
amazon.com/dp/B00CMWCT26
Jack M
Jack M
@DragonLord why not just use a laptop?
DragonLord
DragonLord
Full-scale computing devices (PCs, tablets, smartphones) are not allowed during tests, but handheld calculators are. The touchscreen makes exploring math concepts much easier.
You can use the familiar panning and pinch-to-zoom gestures on graphs.
Jack M
Jack M
oh, for tests
Tobias Kildetoft
Tobias Kildetoft
they allow calculators that do algebraic manipulations but not computers?
DragonLord
DragonLord
I'm in college. The professor allows us to use any kind of handheld calculator, but expects us to show our work. I use my calculator during lectures to better understand concepts (though I often have my Nexus 7 out to read Wikipedia articles on Gaussian elimination et al. during class).
cyberskull
cyberskull
07:13
@robjohn have you ever noticed how large the amazon.com link^^ is compared to all the rest?
DragonLord
DragonLord
1
Q: Amazon logo shown for Amazon links in chat is pixelated

DragonLord the FieryWhen I post a link to an Amazon product page in chat, the Amazon logo is very fuzzy: Can someone increase the resolution of the Amazon logo?

bug chat logo
@cyberskull ^
cyberskull
cyberskull
@DragonLord Are you saying that someone has already increase the resolution of the Amazon logo?
28 mins ago, by DragonLord
www.amazon.com HP PRIME GRAPHING CALCULATOR
Hewlett-Packard Calculators

Prime Graphing Calculator Handheld calculating in a sleek slim brushed metal design that looks great and performs even better. Enjoy a feature-rich calculating experience with familiar HP keypad and a large 3.5-inch diagonal multi-touch display. Explore math concepts with Dynamic Geometry CAS Advanced Graphing and spreadsheet applications. Save time and keystrokes with RPN and programmable functions and see intermediate results while you work. Easily switch between symbolic graphical and numerical table views with dedicated buttons. Be productive longer with a lithium-ion rechargeable battery - when you need to charge up the convertible charger works with the USB connection on your PC or a standard AC wall plug.
Just look at the difference!
Mathematics
Mathematics is the abstract study of topics such as quantity (numbers), structure, space, There is a range of views among mathematicians and philosophers as to the exact scope and definition of mathematics. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proof. When mathematical structures are good models of real phenomena, then mathematical reasoning can provide insight or predictions about nature. Through the use of abstraction and logic, mathematics developed from counting, calculation, measu...
Jack M
Jack M
it looks like the amazon link grabs the full product description, regardless of how long it is
cyberskull
cyberskull
07:30
yes, it does look that way
cyberskull
cyberskull
07:44
Connect wirelessly to a PC

Wireless connectivity and the HP Calculator Connectivity Kit allow you to connect to your PC.
DragonLord
DragonLord
08:14
@cyberskull: This functionality requires a separately-sold accessory. Otherwise, you can use a Micro USB cable (supplied) to connect the calculator to a PC.
 
2 hours later…
Chris's sis
Chris's sis
10:42
Greetings
Danny Cheuk
Danny Cheuk
11:08
Hey
Shahab
Shahab
11:34
hey
Jack M
Jack M
would anybody be able to explain something from field/galois theory to me?
Nick
Nick
11:58
@JackM: Maybe MathDoctorBob? youtube.com/watch?v=LUSWqVfWrM8
@JackM: There's also wikipedia en.wikipedia.org/wiki/…
Jack M
Jack M
@Nick it's a very specific question, but thanks anyway
I already have two textbooks and some class notes to work from :)
Nick
Nick
@JackM: don't worry someone will help you out in a sec (it won't be me. I can't comprehend much of it) You may need to wait but in the mean time, I hope you that you can try to crack open the nut on your own. It may seem hard at first.
but as a great mathematician (I forget who) once said:
A problem worthy of attack proves it's worth by fighting back.
Jack M
Jack M
12:15
@Nick seems it was piet hein, the guy who wrote all those little haiku thingies
Nick
Nick
@JackM: Or it could be Erdos. No one knows.
what'sup
what'sup
hi guys
can you tell me the new big questions Because i wasn't here .
Jack M
Jack M
"why" is still pretty popular
Tobias Kildetoft
Tobias Kildetoft
12:31
"why not" is gaining on it though
Jack M
Jack M
I'm not sure how long you've been gone though
those are both pretty old
Nick
Nick
Almost as old as the Answer to life, the Universe and Everything.
robjohn
robjohn
@DragonLord Heh... my gravatar seems to annoy MSO
Nick
Nick
12:47
@robjohn: You can't really blame him. it's a good design but it doesn't really reflect who you are, does it?
robjohn
robjohn
@Nick You don't see me as mean and square?
Nick
Nick
@robjohn: I see your gravatar to be mean and square. You seem more like a circle to me. ( Maybe you're hectogon, I really can't tell the difference) and as far as statistics is concerned, you're like a mean deviation about median.
Tobias Kildetoft
Tobias Kildetoft
►
it doesn't have a hectogon unfortunately. It only gets to dodecagon
robjohn
robjohn
@TobiasKildetoft Decimalists the world around will be disappointed.
Tobias Kildetoft
Tobias Kildetoft
@robjohn while it might have gone to hexadecagon, going all the way to hectogon seems like overkill
Nick
Nick
12:58
Yeah, going beyond dodecogon in 2D geometry is like studying the properties of elements beyond Ununonoctium in Chemistry. They all exist (sort of) but they're completely useless to learn about.
robjohn
robjohn
@Nick icosahedrons are dual to dodecahedrons and they are cool.
Tobias Kildetoft
Tobias Kildetoft
@robjohn but now we have gone up a dimension
robjohn
robjohn
@TobiasKildetoft Dang, I hate it when that happens...
Nick
Nick
@robjohn: 2D, my friend, with the exception of our humble noble circle.
You know what, Tesseracts are the coolest.
On the same note, I was wrong about chem. Unseptbium is sexy.
robjohn
robjohn
@Nick Never saw that centerfold.
Chris's sis
Chris's sis
13:13
Greetings noble minds!
@robjohn Have you seen the first member of my new limits class, that is $$ \lim_{n\to\infty} e^{(\displaystyle -n^{2012}+n^{2011}/2-n^{2010}/3+\cdots+n/2012)} (1+1/n)^{\large n^{2013}}$$ ?
Nick
Nick
@robjohn: You've never heard centerfold, either. youtube.com/watch?v=BqDjMZKf-wg
robjohn
robjohn
@Nick er, yes I have.
@Chris'ssis haven't seen that yet.
Chris's sis
Chris's sis
@robjohn It's called "super limits class". (I gave them a name)
Nick
Nick
@robjohn: Wow, you're that old, you fossil
user image
 
1 hour later…
John Wilson
John Wilson
14:47
hello
Jack M
Jack M
15:02
hi
Chris's sis
Chris's sis
@Nick @robjohn is one of the most brilliant persons I've ever met. Be sure his mind is far younger than many apparently young people. By the way, someone around 50 years old is pretty young.
Tessa Danger Bamkin
Tessa Danger Bamkin
15:35
hello
combinatorics help? math.stackexchange.com/questions/505981/… im completely stuck. until then im going to try and do some other questions.
Nick
Nick
@Chris'ssis: Aww, shucks, i didn't mean to offend him. 50 is the new 20. And yeah, he is super smart. But I still think he's more like a circle. (Why? cuz I like pi)
See. I'm never serious.
Chris's sis
Chris's sis
@Nick ok ;)
Nick
Nick
Ooh, I have a weird clock over here.
user image
What is 11 supposed to be?
Tessa Danger Bamkin
Tessa Danger Bamkin
I feel so hopeless at maths. art is much easier.
PGFTricks
PGFTricks
15:52
@Nick (1011) in binary.
anon
anon
16:05
@PGFTricks out of curiosity how does the strange 06 represent the binary string 1011?
Jack M
Jack M
also what is the $g$ in $\ceil{g}$
$\roof{g}$ ?
PGFTricks
PGFTricks
@anon 0B might be a number in hex.
anon
anon
is it normal for hex digits to be lowercase letters rather than uppercase?
seems like it's being roundabout for the sake of being roundabout then
that clock is rather silly
PGFTricks
PGFTricks
@anon Both are used.
anon
anon
I see
PGFTricks
PGFTricks
16:08
Without seeing the labels we already know the value.
cyberskull
cyberskull
true dat^
anon
anon
what lame starring
Chris's sis
Chris's sis
@Nick $11$ is related to the hexidecimal system, that is $0b$.
I need to rest half an hour ... (back later)
cyberskull
cyberskull
later
marcelolpjunior
marcelolpjunior
Help
$$\int \frac{x^2\;\;dx}{(x^2+4)^{\frac{3}{2}}}$$
Daniel Rust
Daniel Rust
16:18
►
PGFTricks
PGFTricks
I really need your contributions as mathematicians in my question:
2
Q: Is learning mathematics good to build personal character?

PGFTricksIn my experience, people who are well trained in mathematics will have strong toughness and confidence in solving their daily life activities or problems. Is learning mathematics good to build personal character?

personality
cyberskull
cyberskull
"it depends"
Shahab
Shahab
@PGFTricks: Do you want personal opinions?
PGFTricks
PGFTricks
@Shahab Yes. Any opinion is OK.
Shahab
Shahab
I do not believe mathematics helps in any way which is exclusive to mathematics
discipline of mind, perseverance and logical thinking faculty are strengthened by doing mathematics but all these can also be obtained through other ways
PGFTricks
PGFTricks
16:29
The question may be read as "What are the advantages of having strong math skill in our daily life?" Because I want to persuade kids who don't want to learn math.
Shahab
Shahab
I have posted a similar question on the math stackexchange site because I am also interested in knowing about this
Daniel Rust
Daniel Rust
@Shahab Just because maths isn't the only thing which teaches those qualities doesn't mean they don't contribute to answering @PGFTricks's question
Shahab
Shahab
@DanielRust: Yes, of course. I never said mathematics doesn't contribute to character building.
cyberskull
cyberskull
@PGFTricks Trying to persuade kids who don't want to learn math is a different question.
anon
anon
outside of personal finances (a major component of which is just self-discipline and responsibility not math IMO) and proving to institutions that you know and can handle stuff, school math isn't really necessary for people to know or use who do not do any technical work.
Shahab
Shahab
16:33
@DanielRust: If you carefully read what I said, I said that I do not believe that it helps in a way which is not possible to do otherwise
7
Q: Studies on lack of mathematical education

ShahabI am looking for studies which compare students who did not receive mathematical education beyond basic mthematics and those that learned maths upto introductory calculus, with the assumption that both groups recieved similar education in other subjects such as social sciences and natural science...

soft-question education
Sadly I haven't had any response to this question yet.
PGFTricks
PGFTricks
@cyberskull No. It is relevant. The answers I got will support me to persuade the kids with good reasoning.
marcelolpjunior
marcelolpjunior
@PedroTamaroff
Boa tarde, espanhol sí?
sonicboom
sonicboom
In ring theroy...what are the units of Z_7 .... i.e. the integers modulo 7
I think it is all the elements of Z_7 itself - {0, 1, 2, 3, 4, 5, 6}
?
Daniel Rust
Daniel Rust
7 is prime so everything except 0 is a unit
Shahab
Shahab
@sonicboom: In any Z_n the units are the elements which are not zero divisors
cyberskull
cyberskull
16:37
@PGFTricks That is more of an educational psychology question, no?
marcelolpjunior
marcelolpjunior
@PedroTamaroff Pedro?
Daniel Rust
Daniel Rust
In general, in $\mathbb{Z}_n$, the set of units is the set $\{1\leq i\leq n-1\mid \gcd(i,n)=1\}$.
cyberskull
cyberskull
Hi @TedShifrin how are you?
sonicboom
sonicboom
Ty guys
Ted Shifrin
Ted Shifrin
hi @cyber ... just stopping by for a second on lunch break ... you making trouble?
cyberskull
cyberskull
16:42
@TedShifrin Who me? ;-)
};-)
PGFTricks
PGFTricks
@cyberskull I posted a new question: parenting.stackexchange.com/questions/8988/… for you! :-)
cyberskull
cyberskull
@PGFTricks Thanks honey! :D
PGFTricks
PGFTricks
@cyberskull :-)
Shahab
Shahab
@PGFTricks: Have you heard Lockhart's Lament
sorry, have your read Lockharts lament
PGFTricks
PGFTricks
@Shahab Not yet.
Shahab
Shahab
16:54
Maybe the best way to get kids interested in mathematics is to present maths in an appealing and beautiful way.
When they learn how fun it can be they will be drawn towards learning more...Lockhart's Lament is an essay on what is wrong with the way currently maths is taught to children and how it can be remedied.
Essentially, the point being the intrinsic beauty of the subject is ignored
in the current teaching methodology
worrydream.com/refs/Lockhart-MathematiciansLament.pdf
PGFTricks
PGFTricks
@Shahab Thanks for the link.
I am teaching algebra but the kids don't like variables, they like numbers. :-)
Shahab
Shahab
@PGFTricks: No problem
I was browsing today and saw a great game for solving linear equations in one variable
PGFTricks
PGFTricks
@Shahab What is that?
Shahab
Shahab
scratch.mit.edu/projects/2477436
Jack M
Jack M
to get back to the "personal character" thing
Shahab
Shahab
17:01
maybe your students will enjoy it.
Jack M
Jack M
that @PGFTricks was asking about
cyberskull
cyberskull
@Shahab thanks for sharing
Jack M
Jack M
I find that most kids (probably most adults) have this perspective on the world where there's "normal people" (them) and then "geniuses", and that certain things (math, science, good art) are only accessible to these mysterious "geniuses", and they shouldn't even try
realizing that that's false was a direct consequence of my learning mathematics
and I think that that's an important lesson for everybody
but again, that's not exclusive to math
Shahab
Shahab
@cyberskull: No problem...I got stuck on level 10 and didn't bother after that.
cyberskull
cyberskull
:D
Shahab
Shahab
17:07
:) it may be a resource for students learning linear equations
@JackM: yes, what you say is definitely not an exclusive realization of learning mathematics.
by learning mathematics (not of)
cyberskull
cyberskull
32 mins ago, by cyberskull
@PGFTricks That is more of an educational psychology question, no?
PGFTricks
PGFTricks
@cyberskull Yes. It includes that aspect.
cyberskull
cyberskull
@PGFTricks It is a very important aspect of learning.
@PGFTricks Here
Pedro Tamaroff
Pedro Tamaroff
17:28
@marcelolpjunior Hey.
Chris's sis
Chris's sis
@marcelolpjunior Wouldn't we like to consider $$\int \frac{x^2\;\;dx}{(x^2+4)^{\frac{3}{2}}}=\int \frac{x^2+4-4\;\;dx}{(x^2+4)^{\frac{3}{2}}}$$?
robjohn
robjohn
@JackM I am assuming $g=9.80665\,\text{m}/\text{s}^2$, that is the acceleration of gravity at the Earth's surface.
PGFTricks
PGFTricks
17:44
@cyberskull Thanks.
cyberskull
cyberskull
np
Kevin Driscoll
Kevin Driscoll
@robjohn That's the most accurate quote of $g$ that I've ever seen
cyberskull
cyberskull
@KevinDriscoll not even Physicists quote it that accurately?
Kevin Driscoll
Kevin Driscoll
HA! $g$ rarely comes up in research-level problems because the only people who do gravity are working on General Relativity or String Theory, and so they go WAY beyond needing $g$
and so most often it's just an intro physics thing and they use $10$ or $9.8$ or $9.81$ if theyre fancy
@cyberskull
the universal gravitational constant, $G$, however I have seen quoted to many more decimal places
cyberskull
cyberskull
@KevinDriscoll just don't ask him to quote $\pi$ ;-D
Kevin Driscoll
Kevin Driscoll
17:53
No thanks @cyberskull, don't wanna be reading it all day
cyberskull
cyberskull
Indeed.
robjohn
robjohn
@KevinDriscoll That's the value I've seen since I was a wee child. It is just a couple of digits more than $32.16\,\text{ft}/\text{s}^2$
Kevin Driscoll
Kevin Driscoll
@robjohn Clearly society is declining, I've never seen something more precise than $32$
cyberskull
cyberskull
we were taught to remember the speed of light to nine digits
Kevin Driscoll
Kevin Driscoll
18:08
@cyberskull I'm a theorist $c = \hbar = 1$.
cyberskull
cyberskull
Yes, for correctly chosen units.
:-)
robjohn
robjohn
18:49
@cyberskull $299792.458\,\text{km}/\text{s}$ exactly
They define the meter that way :-)
after defining the second by cesium-133
Kevin Driscoll
Kevin Driscoll
@robjohn Indeed
robjohn
robjohn
@Chris'ssis You impugn my simplicity...
Chris's sis
Chris's sis
@robjohn my former work colleagues used to call me "genius" and I was proud of it. There is no worry about it.
@robjohn you should be proud and that's all. :-)
robjohn
robjohn
@Chris'ssis :-)
Chris's sis
Chris's sis
@robjohn How does it seem to you that limit I showed you above as difficulty level?
robjohn
robjohn
19:05
@Chris'ssis I haven't had a chance to work on it. Let me work on it.
Chris's sis
Chris's sis
@robjohn Oh, I see. OK.
robjohn
robjohn
It's pretty straightforward:
$$
\begin{align}
&\lim_{n\to\infty} e^{(\displaystyle -n^{2012}+n^{2011}/2-n^{2010}/3+\cdots+n/2012)} (1+1/n)^{\large n^{2013}}\\
&=\lim_{n\to\infty}e^{-n^{2013}\log(1+1/n)+1/2013-1/(2014n)+\dots}e^{n^{2013}\log(1+1/n)}\\
&=e^{1/2013}
\end{align}
$$
Chris's sis
Chris's sis
@robjohn I see.
robjohn
robjohn
@Chris'ssis It's nice, but if someone is familiar with series, it might not be that challenging.
Chris's sis
Chris's sis
@robjohn true
cyberskull
cyberskull
19:39
@KevinDriscoll Once you have defined the meter using the speed of light, you don't need to use cesium-133 to define the second, right?
Kevin Driscoll
Kevin Driscoll
@cyberskull No you still do
because the meter is defined as the distance light travels in vacuum in a certain amount of time
cyberskull
cyberskull
@KevinDriscoll elaborate please
Charlie
Charlie
Isn't it cool?!
cyberskull
cyberskull
what is cool?
Charlie
Charlie
What Kevin was explaining
It's.fascinating
cyberskull
cyberskull
19:51
yes
but he stopped at the good part :(
Pedro Tamaroff
Pedro Tamaroff
@robjohn Answering a la rob
robjohn
robjohn
@PedroTamaroff with graph?
Charlie
Charlie
@cyberskull :?
Pedro Tamaroff
Pedro Tamaroff
@robjohn And colours! Don't forget colours!
cyberskull
cyberskull
yay, don't forget colours
Charlie
Charlie
19:57
The true colours
Kevin Driscoll
Kevin Driscoll
@cyberskull Sorry. So the official definition is "Since 1983, it has been defined as "the length of the path travelled by light in vacuum during a time interval of $\frac{1}{299,792,458}$of a second"
cyberskull
cyberskull
@KevinDriscoll OK
Kevin Driscoll
Kevin Driscoll
so if you don't have a definition of a second, the definition of the metre is useless
I think what you're suggesting is that you define the meter and then define the speed of light
then, ya you don't need to define the second
you take the metre and $c$ as fundamental
cyberskull
cyberskull
exactly
Charlie
Charlie
Nevermind, skull
Kevin Driscoll
Kevin Driscoll
20:01
I think that isn't done because the exactly value of $c$ isn't all that fundamental
and so people would rather define an arbitrary unit and let $c$ float, rather than define $c$ but its also a fair bit historical accident
Daniel Rust
Daniel Rust
evening
Kevin Driscoll
Kevin Driscoll
Howdy @DanielRust
Twink
Twink
la da di da di, we like to party, dancing with Miley (8)
Charlie
Charlie
@DanielRust evening
@Twink Cyrus one?
Twink
Twink
yep
hi pal
Charlie
Charlie
20:12
:)
Twink
Twink
do you like Miley @Charlie ?
Charlie
Charlie
@Twink yes, since Hanna Montana
Twink
Twink
:D
so you like twerking?
Charlie
Charlie
Not necessarily
Twink
Twink
do you like Selena Gomez?
Charlie
Charlie
20:17
Don't like, but don't dislike, indifferent
Twink
Twink
I think her music is really cool
what about Taylor?
Charlie
Charlie
Nope
They make teenagers music
Twink
Twink
yes but it's cool music
it's for everyone not for teenagers only
Charlie
Charlie
I'm not very fond of
Twink
Twink
so which singers do you like?
Charlie
Charlie
20:22
I'm not aware of 2013's pop songs.
Twink
Twink
1 min ago, by Twink
so which singers do you like?
what kind of music?
Charlie
Charlie
@Twink hmmm.... I like Idan Raichel, I liked whitney, I like Celine Dion, and flogging Molly, metallica, infected mushroom, paddy and the rats, mosh ben ari, michael jackson, etc
Queen a lot
Chopin, Tchaikovsky, Vivaldi,
Twink
Twink
cool
Charlie
Charlie
My fav composers
Twink
Twink
I love Britney Spears and Selena Gomez
Vivian
Vivian
20:34
Is anyone know how to generate a random matrix with RIP condition?
Charlie
Charlie
@Twink never liked britney
Chris's sis
Chris's sis
20:49
I'll go to sleep with this question in my mind: Compute

$$\lim_{n\to\infty}\left(\frac{a_n}{n^2+a_n}+\frac{a_n}{n^2+2a_n}+\cdots+\frac{a_n}{n^2+na_n}\right)$$
where $a_{n+1}=\sqrt{1+na_n}, \space a_1\in(0,1)$
cyberskull
cyberskull
sweet dreams
Chris's sis
Chris's sis
@cyberskull thanks the great one! :D
cyberskull
cyberskull
:D
Charlie
Charlie
Hi @chris
Daniel Rust
Daniel Rust
21:24
Dunno why I bother spending 20 minutes answering a question written by a new user. There's such a small possibility it'll be acknowledged.
cyberskull
cyberskull
@DanielRust link please
Daniel Rust
Daniel Rust
@cyberskull haha nah i don't wanna beg for votes :P
just wanna blow off some steam
cyberskull
cyberskull
Ok np
Daniel Rust
Daniel Rust
But yeah, it's frustrating not getting any feedback from the OP.
Yisela
Yisela
hi guys! would this be a good fit for your site? graphicdesign.stackexchange.com/questions/21514/…
Daniel Rust
Daniel Rust
21:32
@Yisela It seems like an interesting problem. I'd say it's a maths question (maybe with some overlap with game dev).
Yisela
Yisela
there's a possible answer in GD posted as a comment, but I'm not sure what to do with the question. Community seems to think it's off-topic, and it's even been dowvoted.
Kevin Driscoll
Kevin Driscoll
I agree with @DanielRust that if you make the pattern requirements clear then it would be on topic here @Yisela
@Yisela I found your explanation a little confusing, so maybe elaborate more on what you're looking for
Ted Shifrin
Ted Shifrin
@Daniel: Do you feel more acknowledged by us old fogies? :D
Yisela
Yisela
well, it's definitely overlapping with other sites (yours and game dev, as you mentioned)
Daniel Rust
Daniel Rust
@Yisela The answer given in the comments doesn't quite satisfy the OP's second condition.
Yisela
Yisela
21:37
@DanielRust true
Daniel Rust
Daniel Rust
I think it'd definitely get an answer over here anyway.
@TedShifrin of course I do! :D
Yisela
Yisela
I'll suggest it gets migrated or migrate it myself, since I have your blessing :)
Kevin Driscoll
Kevin Driscoll
@Yisela OH! Sorry for assuming you were the asker. My b.
Yisela
Yisela
too complex to be a question of mine!
Ted Shifrin
Ted Shifrin
Heya @Kevin
Kevin Driscoll
Kevin Driscoll
21:41
@TedShifrin Good evening! What are you up to today? More Lie groups?
Daniel Rust
Daniel Rust
Actually I think I have an answer for it as well
user image
Charlie
Charlie
Hi @ted I managed to get that subject
Ted Shifrin
Ted Shifrin
Taking the night off, @Kevin :) solved that problem, finally, stupid me!
Kevin Driscoll
Kevin Driscoll
@DanielRust is that a Penrose tiling?
Daniel Rust
Daniel Rust
@KevinDriscoll Yeah (my specialty :D )
Kevin Driscoll
Kevin Driscoll
21:42
@DanielRust Ah! Okay, I had no idea
Ted Shifrin
Ted Shifrin
Hi @Charlie. What subject?
Daniel Rust
Daniel Rust
@KevinDriscoll Well, aperiodic tilings in general.
Yisela
Yisela
It'll probably need some tags: math.stackexchange.com/questions/506288/…
Ted Shifrin
Ted Shifrin
@Daniel's next career is interior decorating :)
Link
Link
Hey, I have this Vector: $A = -1i + 9j$
however
Daniel Rust
Daniel Rust
21:44
@TedShifrin Living the dream when that happens.
Kevin Driscoll
Kevin Driscoll
@TedShifrin Glad you figured it out. I'm still plugging away at mellin transforms and integral equations
Link
Link
I find the angle of the vector and get -83 degrees
Ted Shifrin
Ted Shifrin
Angle with what? @Link
Charlie
Charlie
@TedShifrin the algorthm thingy
Link
Link
what line is this angle from?
I don't know, thats the problem
Ted Shifrin
Ted Shifrin
21:45
Oh, great @Charlie!
Kevin Driscoll
Kevin Driscoll
@DanielRust I cant remember......are aperiodic tilings always related to quasi-crystals?
Link
Link
logic tells me it should be from the x axis
Kevin Driscoll
Kevin Driscoll
@link how did you find that angle?
Link
Link
just arctan(9/-1)
Charlie
Charlie
@TedShifrin :D
Kevin Driscoll
Kevin Driscoll
21:46
@Link Then its the x-axis
@Link Just draw the triangle formed by your vector that has legs equal to the 2 components
Pedro Tamaroff
Pedro Tamaroff
@TedShifrin ERMAGHERD.
Daniel Rust
Daniel Rust
@KevinDriscoll Only if they have pure point diffraction pattern (if and only if the $\mathbb{R}^d$ action on the tiling space has pure discrete spectrum).
Kevin Driscoll
Kevin Driscoll
and you can see how the trig works out
Ted Shifrin
Ted Shifrin
Careful, arctan will not necessarily put you in the right quadrant.
Link
Link
I did, but I expect it to be from the +x axis, not from the -x axis
Charlie
Charlie
21:47
@PedroTamaroff what happened?
Kevin Driscoll
Kevin Driscoll
Well you have to be careful with arctan
because the quadrant is ambiguous
Ted Shifrin
Ted Shifrin
@Pedro, er what?
Kevin Driscoll
Kevin Driscoll
Oh, @TedShifrin beat me to it
Charlie
Charlie
@TedShifrin Oh my God it means
Link
Link
How can I tell what quadrant it's from?
Kevin Driscoll
Kevin Driscoll
21:47
@DanielRust Ah I see! So the tilings are more general
Ted Shifrin
Ted Shifrin
In what language? :)
Link
Link
hmmm?
Ted Shifrin
Ted Shifrin
Draw a picture, @Link.
Kevin Driscoll
Kevin Driscoll
@Link It should be clear from yuor drawing of the triangle exactly which angle you're getting
Daniel Rust
Daniel Rust
@KevinDriscoll Yes, although we tend to only like the quasicrystals because we can actually meaningfully study them :P .
Kevin Driscoll
Kevin Driscoll
21:48
the one from the +x or -x-axis
Pedro Tamaroff
Pedro Tamaroff
@Charlie Today at the tennis class I told the 7 younglins to pick up 4 balls each, and told em if someone could tell how many they picked up total. One came to me and told me "28!" and I was like "Wow! How did you know?" "I am a mathematician". Cuteness overload. @TedShifrin
Charlie
Charlie
@TedShifrin this one
Ted Shifrin
Ted Shifrin
hands the baton to Kevin and shuts up
Link
Link
Hmm, okay then
Charlie
Charlie
@PedroTamaroff :3
@PedroTamaroff your heart melted
<3
Kevin Driscoll
Kevin Driscoll
21:49
@TedShifrin Salute Don't worry. This math I can do!
Link
Link
Got it... that makes so much more sense
Ted Shifrin
Ted Shifrin
@Pedro: Did you say, me too?
Pedro Tamaroff
Pedro Tamaroff
@TedShifrin Heh, no. But I have told him before.
"Mathematician to be." =D
Daniel Rust
Daniel Rust
"Everyone stand back! I'm about to do...... mathematics!"
Kevin Driscoll
Kevin Driscoll
@Link My advice with this vectors stuff is to always draw a picture. If you try and memorize a bunch of formulas about arctan this and sine that you'll get confused. Just draw a picture with a right triangle and its easy to figure everything out.
Ted Shifrin
Ted Shifrin
21:50
Ah :) your protegé
Pedro Tamaroff
Pedro Tamaroff
@TedShifrin I mean myself!
Charlie
Charlie
@PedroTamaroff you wannabe a mathematician, huh, kid?
Kevin Driscoll
Kevin Driscoll
@DanielRust Do you consider quasicrystals that live in non-euclidian spaces as well?
Pedro Tamaroff
Pedro Tamaroff
@DanielRust Do you know about crystallographic groups?
Ted Shifrin
Ted Shifrin
No, no, I meant he is because of what you said he said ... You said he said.
Pedro Tamaroff
Pedro Tamaroff
21:52
@TedShifrin LAWL.
Charlie
Charlie
i wanna steal a book from my uni library
no on will miss it
Pedro Tamaroff
Pedro Tamaroff
@TedShifrin What do you think of my approach here?
Ted Shifrin
Ted Shifrin
That's frowned upon @Charlie :)
robjohn
robjohn
@Chris'ssis Ah, something to work on.
Charlie
Charlie
@TedShifrin :D
Daniel Rust
Daniel Rust
21:55
@KevinDriscoll I've thought about them a little (hyperbolic space modtly) but they are far too complicated. There's also a bit of ambiguity about which symmetry group on your space you want to consider. There's not much we can say about them - although some authors (Goodman-Strauss) have done some work in the area.
Charlie
Charlie
@TedShifrin I love that book.. i sleep with that book
Daniel Rust
Daniel Rust
@PedroTamaroff Yeah they're some of the best groups :D. Have you ever seen the proof that there are 17 wallpaper groups?
Pedro Tamaroff
Pedro Tamaroff
@DanielRust No clue what those are. No idea about CG groups either, I just read it in the last section of BAI and though "Damn, that's a kick ass name."
Ted Shifrin
Ted Shifrin
Burn's book is good for an accessible discussion of wallpaper groups.
Kevin Driscoll
Kevin Driscoll
@DanielRust Ah okay. I'm just glad to know its an active area of research. I need to learn a lot more about group theory and symmetries if I want to be a proper physicist, but it'll probably take me the next 10 years
Daniel Rust
Daniel Rust
21:57
@Ted what would you say the preliminaries are, just basic group theory/geometry?
Ted Shifrin
Ted Shifrin
@Pedro: I might have asked if the OP knew about changing order of $\int$.
Pedro Tamaroff
Pedro Tamaroff
@TedShifrin That did cross my mind.
Daniel Rust
Daniel Rust
@KevinDriscoll Quasicrystals won the nobel prize only a few years ago.... it's still a very active area of research :P.
Ted Shifrin
Ted Shifrin
He does all the group theory. It's a problem-oriented book. Very nice.
Pedro Tamaroff
Pedro Tamaroff
@TedShifrin Oh.
Daniel Rust
Daniel Rust
21:59
@TedShifrin Ah that sounds nice.
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