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10:00 PM
@0celo7, glued together, does it just mean...wait, okay another question:
 
@heather There is hardly any intuition in a lot of pure math , unfortunately. I suggest, if you're interested, to get a topology text and start there since all it requires is basic set theory.
 
R squared means the set of all real coordinate pairs, then R cubed would mean the set of all real coordinate "triplets"?
@Obliv, what would be a good one?
I'd love to learn about it.
 
Bourbaki :^)
 
Bourbaki...
googling
 
@heather I haven't tried learning it yet because I don't have the time right now. But, NO JOKING, I want to start with bourbaki.
I do not suggest you do the same. @0celo7 is trolling
 
10:02 PM
okay
oh, don't use Bourbaki?
 
Flagging!
 
I'm rather confused
 
@heather it expects familiarity with mathematical reasoning. Something that you probably don't have yet.
 
Ah, yeah, probably shouldn't read that then
 
@heather You know, you could read these calc 1-2 notes
 
10:06 PM
I wouldn't start with topology
 
They go over basic set theory in the first few pages
 
@SirCumference, thanks! Should be rather useful =)
 
@heather you shouldn't try to learn topology anyway. focus on trig & calc. eventually you'll build the foundation (ironically) to learn modern math
 
@heather Thank @bl00, he showed me them
Said they were the best way to learn calc
 
@sirC you know, you could also read those notes.
 
10:07 PM
@Obliv I've been
 
how is it
 
@Obliv, oh, geesh. So rewind a tad: don't learn topology?
 
Reminds me why I love learning math. I've gotten to page 66
Very intuitive
 
@heather If you want to learn what @0celo7 is talking about in chat, i suggest you learn topology the right way (not frantically searching wiki pages like I do sometimes when I'm bored). But, I suggest you don't try to learn what he's talking about until you finish your primary math education first.
 
Okay. So. I learn trig and calc and algebra II and then I come back and learn topology.
Geesh.
 
10:08 PM
@heather On the contrary, I'd just look at the notes if I were you
 
Or abstract algebra. That's what I tried doing first. It's a matter of preference whether you learn topology/geometry or algebra
 
=) So many opinions
 
Everything 0celo spent the last 40 mins explaining could be summed up very nicely in the first few pages
@heather All right, I'll tell you now that you can learn calc and trig at the same time
 
abstract algebra? another thing? eesh.
@SirCumference, what is this revelation!? I can?
 
@heather Not sure if that's sarcasm, but yeah
Trig is certainly useful, especially in things like astronomy
Calc covers (generally) different things though
 
10:10 PM
Well, it wasn't quite sarcasm; I didn't know that, but I was also joking in how effusive I was in my response.
 
@heather you do not need to learn abstract algebra
certainly not before algebra 2
 
@0celo7 She said she's learning trig
 
@0celo7, well, I kind of assumed the second part
 
She probably is familiar with a good chunk of algebra 2
if not all of it
 
10:11 PM
@SirCumference, I'm going out of order. I dunno anything about conics, but I do know Algebra I and some of Algebra II; I'm doing Algebra II after trig.
 
@0celo7 Actually, I don't see why you can't learn abstract algebra before a basic algebra 2 course. (Not that I'm suggesting you do so) theoretically, it doesn't assume knowledge of algebra 2 because it's all built up axiomatically
 
conics are pretty useless honestly
 
@heather Don't confuse yourself. Learn algebra 2, it'll be useful for so many other things.
Then finish trig, which shouldn't take long
Then do calc
Then go off to whatever you'd like
 
Okay, so in the final consensus:
 
I suggest quantum calculus
 
10:12 PM
1. Algebra II
2. Trig
3. Calc
4. Topology/Abstract Algebra
 
4. Banach spaces
 
hmm
 
Ignore 0celo
 
@0celo7, what in the great wide universe is quantum calculus or banach spaces?
@SirCumference, ah, but that's no fun. =)
 
10:13 PM
Quantum calculus is something weird that I have no clue about
 
Right
 
@heather Anyways, trig is a short (but useful) subject
 
Banach spaces are something less weird that I have some clue about
 
It'll be the quickest to learn out of those
You shouldn't need to worry about basic set theory until you finish trig and algebra 2
 
It's basic enough that it doesn't matter when you learn it tbh @sirC
 
10:14 PM
@heather Then you can read the notes, which describe logic and basic set theory, followed by calc
@Obliv Yeah, but it won't play much use at those points
@heather The difficulty of learning calc depends on where you learn it from. Some teachers make it confusing as hell, others explain it in a really intuitive way
The notes I sent you are the best ones I know of
They should make it pretty easy
 
@SirCumference, yeah, trig is pretty short; I'm already more than 50% of the way through the Khan Academy course. Sounds good about the calc; that shouldn't be too bad.
So I guess, I have the question of what I should use to learn Algebra II/topology/abstract algebra
 
Algebra II before all
Oh crap
Didn't read that xD
 
By the way, I just wanted to say thanks to everyone for helping
 
Khan academy is all right, not the best, but pretty good in algebra 2
Np
 
Okay, Khan Academy for algebra II
 
10:21 PM
@heather It could also help to learn some precalc from Khan Academy. Despite its name, precalc is not actually useful for or related to calc, but it will enlighten you on some concepts you probably missed out on when learning trig and algebra 2
 
Oh, okay. That's good to know.
 
That plays a role depending on what field you want to go into, or just in general for doing math on your own
Useful in that regard
 
So should I use Khan Academy to do precalc as well?
 
Yeah, their precalc is pretty good
 
alright, sweet
 
10:22 PM
Just remember precalc paradoxically isn't related to calc. It's just useful math knowledge one should know before leaving high school or starting some higher mathematics.
As I said, calc can be easy and enjoyable, if you learn it from a good teacher
 
Wonder why they call it that, then (precalc, I mean)
Just call it "math wrap-up" or something
 
@sirC it's very useful for calc 2 actually. If you didn't take precalc calc 2 trigonometric integrals will be impossible to solve.
 
@Obliv Oh that's true
 
or at least be very unintuitive.
 
10:24 PM
then call it precalc2
=P
 
But precalc covers so many different abstract things, it's not really focused on calc or any subject in particular
 
I thought it just went over trig? I don't even remember lol
 
@Obliv Nah, some schools do that, most don't
Mine actually described ellipses, matrices, etc.
 
@Obliv, no I don't think so, the list of topics on khan academy covers trig and functions and conics and a veritable math stew.
 
Came in handy when I took astronomy
@heather Yep
 
10:25 PM
hmm...is adding complex numbers different than adding normal numbers? Or do you just add the normal parts and then add the complex parts.
 
how else would you add them?
 
@heather The latter
 
okay
 
@0celo7 No need to ask that, she's just making sure
 
@0celo7, I dunno, some magical way invented by people who decided to call the square root of -1 $i$ =P
 
10:26 PM
Oh god...
Don't say "the square root of -1"
Everyone in the chat will hunt you down
I made that mistake on my own
 
::loads rifle::
 
@heather Read from here down if you want the full idea, on what imaginary numbers are
 
alright, fixing, fixing
 
Square root of negative one works in 75% of math
You'll find problems with it that require a change in definition, which is explained by higher math
 
oh, wow. cool!
 
10:29 PM
@heather Take, for example, this
$-1 = i \cdot i = \sqrt{-1} \cdot \sqrt{-1} = \sqrt{(-1) \cdot (-1)} = \sqrt{1} = 1$
 
whoa...what...
 
If we define $i$ as the square root of -1, we've just proved -1 = 1
 
-1 = i*i, right
 
Another example is
 
and then that's the...right
 
10:30 PM
$\frac{1}{i} = \frac{\sqrt{1}}{\sqrt{-1}} = \sqrt{\frac{1}{-1}} = \sqrt{\frac{-1}{1}} = \sqrt{-1} = i$
 
and then oh, gosh, what happened?
 
@SirCumference whoa
 
If $1/i = i$, then $1 = i^2$
 
this is madness, what is happening?!
 
@heather But yeah, you won't find problems with your definition unless in certain cases
 
10:31 PM
@SirCumference, how do you fix the problems?
 
$i^2=-1$
 
Must people don't even realize the problem with the definition and never encounter it
@0celo7 Not even that, I think you gave a better definition before
 
there are PhD math books that write $\sqrt{-1}$
 
Wait nvm
It was Slereah
Jul 19 at 22:33, by Slereah
It's the algebraic closure of $\Bbb R$
That's the proper definition of $i$, which, as I said, requires higher math
 
it's the Clifford algebra of $\Bbb R$
 
10:32 PM
But you won't need to worry much about it until later
 
er...I think i'll just hold off on that, yeah. =)
Maybe I'll bug my math teacher with that problem tomorrow...=P
 
:P
Another really cool thing calc proves is $e^{\pi i} = -1$
Which won't make sense until you learn about Taylor series
Then you see beauty in that formula
 
oh, wait, isn't that euler's thing?
 
calculus does not prove that
 
I've heard of it.
 
10:34 PM
@0celo7 Taylor series does
 
you need a lot of nontrivial analysis
@SirCumference Proof that you can rearrange taylor series?
also you need complex taylor series
 
@0celo7 Actually, I learned it here
Knowing the Taylor series' of sine, cosine and $e^x$ is all that's needed
 
@SirCumference that's wrong
 
@0celo7 What seems wrong in it?
 
It's a cute trick, but the part where the two sums are separated is a bold claim
it needs justification
 
10:36 PM
It explains that
It even gives a second example, which I never read, about derivatives
I should actually look at that
 
@SirCumference where?
 
@0celo7 I think below the first explanation
 
quote?
 
> However, here's another way of understanding why $e^{ix} = \cos{x} + i\sin{x}$. It too involves some calculus, but I can describe the calculus involved more easily.
Read from there down
 
not that
@SirCumference this
 
10:38 PM
@0celo7 Oh, what do you mean "where the two sums are separated"?
 
later.
 
Wh-what?
I thought we were talking
You just paused the conversation...
 
@0celo7, have a good day, and thanks for all your help!
Oh, and you better see that eye doctor tomorrow. =)
 
@SirCumference I have to eat eventually
@heather I have a legit appointment and they can charge me for not showing up
 
@0celo7 With your profile pic I can only imagine catfood...
 
10:43 PM
Mice
The occasional rat
Bird
Dog
 
@0celo7 before you go can you let me know whether this is the right idea for maximizing a function $f(x,y)$ with a constraint $g(x,y) = k$
actually nvm just go I think I understand
yeah I just don't get why there's a scalar multiple in $\nabla f(x,y) = \lambda \nabla g(x,y)$
 
@SirCumference, algebra II is going pretty well so far. Imaginary numbers aren't that bad. =)
 
rob
@heather Most people find that mixing real numbers with imaginary numbers is complex
2
 
10:58 PM
@rob, well, it probably helps that I already know a bit about the complex plane and stuff.
 
rob
@heather Just so
 
@rob, I'm sorry, I don't know quite what that means, though I've heard the expression.
 
rob
After a while I suppose it all becomes rather plane
2
 
@heather Complex numbers are basically "imaginary number + real number"
 
plane? very punny =P
@SirCumference, indeed.
 
11:01 PM
If I asked you what "$3i + 1$" is equal to, you can't figure that out
You have to call $3i + 1$ a number in itself. We call those numbers complex numbers
 
Let's see, it'd be $\sqrt{-3}+1$, right?
Or then, approximately
oh, wait, no...
okay, I get what you mean now.
 
It'd be $\sqrt{-9}$, actually
 
rob
Explained puns are the worst puns
 
You take the square root of the number, and if the number is negative, you put an $i$
 
oh, yeah.
right. =)
 
11:03 PM
But interestingly, the cube root of $-9$ is completely real
Only even-numbered roots produce imaginary numbers.
 
@rob It's almost PUNishment ^^
 
rob
My last ten posts to this room have all been puns, trying to see if any would get a response out of you guys
... unfortunately no pun in ten did
3
 
@rob, well, you sort of got a response from me...
 
We can take $\sqrt[3]{-9}$ and get $-3$, because $-3 \times -3 \times -3 = -9$
 
Feeling PUNny?
 
11:05 PM
@SirCumference, don't you mean of 27?
 
@heather Yep, I'm stupid
 
not stupid
 
Yes
 
rob
@SirCumference careless != stupid
 
Maybe
 
11:06 PM
I've made much, much, much, much $\times \infty$ more mistakes. And what rob said.
 
@rob You know, math puns can be enjoyable. You just gotta look at them from the right angle.
 
=)
 
Right angle.
...right angle...
 
rob
@SirCumference That's the normal way to do it
 
@rob ARGH
 
11:06 PM
@rob, $\sqrt{-1} \, \, \, 8^3 \, \sum \, \pi$ and it was delicious.
$!$: an attempt to make math more exciting
 
@heather Get real. ($i$)
 
=)
 
And be rational. ($\pi$)
 
Yes
 
Or, let me think, I saw a good one the other day...
 
11:08 PM
Yeah?
 
This is what sets me off.
 
there is a fine line between the numerator and the denominator...
 
Oh god
 
Yes
 
whenever you start graphing functions I get worried...
because you are plotting something.
 
11:09 PM
Yeah
 
I can't remember the difference between the numerator and denominator, I always get it mixed
 
math puns are the first sine of madness.
 
Eh...?
 
...sine...
 
I'm going off on a tangent, I knkow.
 
11:10 PM
Yep
 
Indeed
 
@BernardMeurer We're making math puns. They're integral parts of our life.
 
rob
My friend with poor credit is trying to rent an apartment. She's asked me to cosine the lease, but I'm going back and forth about it
Eventually I suppose I'll come around.
 
........
 
Yeah?
 
11:11 PM
to the guy who invented zero: thanks for nothing!
 
@rob Secant afford it?
(she can't)
 
@SirCumference BOOOO
@SirCumference STOP
 
the romans didn't find algebra very exciting
because X was always 10
 
@Obliv Nay, the best puns are the worst puns.
 
Nothing's that absence of something, Yet it must be true that there's nothing.
Therefore something always exists.
 
11:12 PM
a farmer with a field of cows counted 96 of them, but when he rounded them up he had 100
 
Yeah for real
 
there are only 10 types of people in the world: those who understand binary and those who don't
 
rob
@heather Sure it wasn't shepherd? Sounds like fuzzy math
 
@rob when maximizing a curve $f(x,y)$ by a constraint $g(x,y)=k$ they must both lie on the same tangent plane, right? Doesn't that mean either can be a scalar multiple of the other? So in a sense $\lambda \nabla f(x,y) = \nabla g(x,y) \equiv \nabla f(x,y) = \lambda \nabla g(x,y)$?
 
this conversation needs to be immortalized
 
11:14 PM
Yes
 
for a different value of $\lambda$ tho
 
rob
@Obliv You're going to make me turn on MathJax to get your joke
 
You mean, MathJokes?
I'm being serious, though. lol
 
@rob Uh, you don't just use ChatJax++?
 
Yeah
 
11:16 PM
Saves you from that problem
 
From the knowledge of function came the error, that was the first problem.
 
rob
@SirCumference I hadn't done so yet ... and after the spate of \renewcommand{\foo}{I'm a doofus} that went on in the sidebar the other day I think I'll refrain.
 
@rob Uh, what?
 
Thanks
 
rob
@SirCumference Never mind.
 
11:18 PM
@rob Explain pls
Why, what happens if I do $\renewcommand{\foo}{I'm a doofus}$?
eh wtf?
$\foo$
No idea what I'm supposed to be seeing
 
Yes
 
$\sum$ people like math puns
$\sum$ people don't
 
rob
@SirCumference chat.stackexchange.com/transcript/message/32954366#32954366 and preceding conversation.
@Obliv You asked me a real question.
 
@rob Er, I don't follow...
 
rob
...which I don't immediately understand.
 
11:20 PM
thanks
 
@rob it wasn't a real question though. I was just wrapping my head around the two functions having to lie on the same tangent plane. only way those two would be equivalent would be $\lambda_2 = \frac{1}{\lambda_1}$
 
maybe
 
rob
@Obliv So you're looking for maxima on some surface f(x,y)?
where some other function g(x,y) must have a particular constant value?
I don't recognize the "tangent plane" in this context.
 
thanks
Is you helping Rob?
 
if you have the equation of a circle, say $(x-13.4)^2 + (y+2.6)^2 = 100$, how do you find the center point and radius without graphing?
I have a vague notion that the radius is the square root of the constant on the right, but I'm probably wrong.
 
11:27 PM
maybe
 
rob
@Obliv I think I've parsed your statement, but I don't understand it straightaway. Why would your function to maximize and its constraint need to share a tangent plane?
 
@rob g(x,y) doesn't have to constant actually
 
rob
@Obliv Oh. I thought you said that the constraint was g(x,y) = k
 
Actually, not really sure @rob I was trying to figure that out but I can't logically conclude that they must.
yeah I should have specified that k isn't a constant
 
A constants simply a chosen container size, therefore either.
 
11:31 PM
in that case they lie on the same tangent plane
 
Yes
 
rob
@Obliv Ah, now I see.
 
You is very helpful, thanks for helping Rob.
 
rob
So if g(x,y) is a 2d surface, g(x,y)=k (for some particular constant k) is a contour line, like you'd find on a topographical map.
Your image shows one contour for g, and a handful of contours for f.
 
@rob yes
 
11:36 PM
Yeah!
 
and we want the largest value contour line in which f and g intersect each other.
 
ok
 
rob
And you observe that a line tangent to g(x,y) = k is also tangent to f(x,y) = k' where k' is the largest value of f(x,y) on the g() contour.
@Obliv Yes, this.
But that's not a tangent plane, is it?
 
Wait, a line tangent to g(x,y) = k is tangent to f(x,y) = k'? I don't see that immediately.
 
Hi, everybody.
 
11:39 PM
Hey @daniel
 
Yeah!
 
@rob Oh cool! Are we learning about Lagrange multipliers?
 
rob
I mean, suppose that g(x,y) has some maximum at the origin in your figure
and f(x,y) has its maximum, apparently, in the upper right of your figure.
 
@daniel yeah I am trying to justify why two functions would have the same gradient (by some scalar factor) at a maximum b/t the two
 
rob
The tangent plane to g(x,y) at the intersection you marked comes out of the plane of the screen to the lower left
 
11:41 PM
@DanielSank, hello!
 
rob
but the tangent plane to f(x,y) comes out of the plane of the screen to the upper right
Or do I misunderstand what you mean by tangent plane?
 
@Obliv Oh, yeah, rob's picture proves it.
@heather Yo.
 
rob
@DanielSank It's Obliv's picture ... I'm not convinced of the proof.
 
@daniel I'm just thinking of a case where $g(x,y) = k$ crosses $f(x,y) = c$ for some $c$ then doesn't cross f(x,y) = c again afterwards
 
rob
The gradients, on the other hand ... in your example the gradients are parallel. Is that what you mean?
 
11:44 PM
@rob What's wrong with the proof?
The picture's a pretty good proof.
 
like, imagine if g(x,y) = k passed the point marked on the picture then never touched f(x,y) = 11 or f(x,y) = 9 again. Would they still share a tangent plane at f(x,y) = 10?
 
@Obliv Why do you care if there are multiple solutions?
 
rob
@Obliv Can you define "tangent plane"?
 
Sure, there can be multiple solutions. So what?
 
@rob do you have mathjax turned on?
 
rob
11:45 PM
@Obliv I'll manage ... TeX away
 
@rob $\nabla f \cdot g = 0$ would define the tangent plane b/t f,g
 
rob
Precedence question: gradient of the product of f and g? Or gradient of f, multiplied by g?
 
latter @rob
@daniel Hmm, I for some reason thought that the solution would only be at the red lines in that picture lol..
what if g(x,y) intersects the maximum of f(x,y)? would the lagrange multipliers method still work? @daniel
 
rob
Got to check out. Stay real, folks (except @heather: stay complex)
 
Cya @rob
 
11:52 PM
@rob, see ya...don't worry, it's not imaginary (okay, that was bad, but oh well)
 

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