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11:05 AM
Never mind. I got it now :)
 
11:47 AM
[Random]
Update notation to :O:
$\underbrace{[...]}_{n} := [...]_n$
Therefore:
Let _ be the empty list
The sequence goes as follows:
_
$[0]_0$
$[0,1,2,...,n]_n$
$[0,1,2,..._{\text{Huge}}$
$[0,1,2,...]_{\omega}$
For a foundation where ordinals are defined:
$[0,1,2,...,\alpha]_{\alpha+1}$
$[0,1,2,...]_{\lambda}$
where $\lambda$ is a limit ordinal and $\alpha$ is any ordinal
Continue:
$[0,1,2,...]_m$
In general $[0,1,2,...]$ is a countable unbounded list. The subscript gives a notion on its "size" in terms of how many steps is needed before an entry arbitrary large is reached. In other words, the subscript gives a measure on how many steps before it effectively becomes something similar to a proper class in set theory
 
12:25 PM
Of course not intended for anyone, but some guy needs to stop posting crackpot theories related to set theory in Mathematics chatroom.
2
 
I never said what I said is true. The above is more like a brainstorming process than an actual theory, thus it is not even wrong
Everybody in this chatroom knew what I wrote is legitimate and what is nonsensical rambles
otherwise why would I use a [random]
 
I never said my comment was intended to anyone. Also, I don't think anybody reads what someone writes. (Again not indended towards anyone)
 
Of course, whether all of the above "response" is visible to any of you and whether any of you care is not my concern. As long The Plan remains unhindered, those who choose does not have not have a choice
(To the whole chatroom) I "respond" because I know what I wrote is nonsense and you guys knew it, as long you know when I am sane and the flooding controls is intact, then it will be ok
 
Hello anyone know how can 1.052 x 12.504 x 0.53 = 6.7280 ? The result should be 6.9717 which is way higher. I've seen this same calculation in a lot of lectures and in the chemistry book but what the heck?
 
Anyway, as a cautionary measure, better to once again reiterate that anything that follows after [random] does not necessary have to make sense. This is because they only make sense after an interaction with the community
 
12:35 PM
Anyway, again not indended to anyone, this site is for generally discussing math, not crackpot theories and random thoughts which occurs to brain. Someone may open a new room for that. Of course, if getting people's attention is the actual motto, then opening a room and talking there would work ...
 
Traffic of a very narrow topic in a new room is too low to be of significance
but perhaps:
4 hours ago, by The Great Duck
stop wasting them away in chat threads nobody is gonna read
 
Can someone tell me please why it is 6.7280 is it a mistake? It's driving me insane :)
 
I should figure out how to make those stream of consciousness more coherent
@someone We need to know where the 3 numbers came from first. What quantities are they representing
 
@Secret So why don't try thought dumping in The Nineteenth byte ? A lot of people frequent that room, so I think it's a fantastic idea !
 
uh, do you think the stuff I am talking about is even remotely related to programming and coding puzzles?
 
12:39 PM
@Secret It is just an example given to show how to calculate the number of significant figures in multiplication e.g 6.7208 = 6.7 which takes the least number of significant figures (0.53)
 
not related to math too. That's the point
 
@Secret that's the exact snippet from the book i.imgur.com/HNrOre5.png
 
Yeah I think I agree with you: 1.052*12.504*0.53=6.97173024 which to 2 sig fig should be 7.0
 
It is probably a mistake but the exact numbers are mentioned way often even in practice questions and power point slides :) so weird
 
you might want to check with your instructor. I cannot think of any round up nor round down that can produce 6.7208
 
12:55 PM
The book is insanely inconsistent in the second example of multiplication they did not round but only count the significant figures, but in subtraction they did in one example and not in the other smh.
 
hmm $$ \int \int_D 1-6x^2y dA, \quad D=[0,2]\times [-1,1] $$
 
you want to convert that to a double integral?
 
yes thats right
i don't understand the notation
$$\int \int_{-1}^{1} \int_{0}^{2}1-6x^2ydxdy$$ ??
also $[0,2]$ denotes closed interval ?
is it $[x]\times[y]$ ?
$0\le x \le 2$ and $-1 \le y \le 1$ is this same ?
 
Yup, square commonly denote that edge of the interval is closed
So basically you are integrating this function over a rectangular region
 
@Tuki this explains it pretty well tutorial.math.lamar.edu/Classes/CalcIII/DoubleIntegrals.aspx see R=[a,b] x [c,d]
 
1:04 PM
yes this is exactly what i wanted thanks @someone
 
1:17 PM
Just like how reality cannot handle infinite entities, the point is the chat will be plunged into unusability, and this is more than enough for the adversories to achieve their goal.
3
Alex K Chen: Yeah fine, I will deal with the flooding problem more seriously, so as not to accidentally flood someone else's screen
(uh, accidentally caught balarka and co in the middle of my rambling. I need to time more carefully since the chemistry event means he and his group are to be avoided from getting involved in these rambles which sounds like anti-normie stuff)
point is, I ramble a lot less when the topology people are here now, thanks to them helping me to better grasps the subject so I can actually said something more sensible
I will soon figure out manifolds, and after that, GR will no longer be so unintuitive to me
 
hi
I have question
How would I prove the sequence i,-1,-i,1 where the nth term is given by i^n
Would I use proof by mathematical induction?
 
1:35 PM
@IPAddress Just use that $i^{4n+k}=i^{4n}i^k=(i^4)^ni^k=1^ni^k=i^k$
How do I solve this homework-like question?

Let $V$ be a vector space with inner product $\langle \, ,\,\rangle$ over the field $\Bbb K$ ($\Bbb R$ or $\Bbb C$). Suppose that the linear operator $T:V\to V$ is NORMAL, (i.e. there exists $T^\ast$ adjoint operator of $T$ and $T\circ T^\ast=T^\ast\circ T$).

If $T(v)=\lambda v\neq 0$, $T(u)=\mu u\neq 0$ and $\lambda\neq \mu\in \Bbb K$, then prove that $\langle u,v\rangle =0$.
 
@AndersonFelipeViveiros thanks
 
@ip
* @IPAddress You're welcome
 
2:19 PM
so this notation $$ \int \int_D f(x,y) dA \quad D=[a,b]\times[c,d]=\int_{-1}^{1}(\int_{0}^{2}f(x,y)dy)dx $$ ??
hmm is false and i cannot remove this
@Shobhit you there ?
 
yes, but i dont have much time, exam tommorow @Tuki
 
ok
 
3:27 PM
Hi,
$a$ is an integer, such write in basis $b$ with only $\{0,1\}$ and the size is $n<b$.
Is it true that $a^2$ is a palindrom in basis $b$ ?
sorry a mistake
$a$ is an integer, such write in basis $b$ (is palindrom) with only $\{0,1\}$ and the size is $n<b$.
Is it true that $a^2$ is a palindrom in basis $b$ ?
 
why are bilinear maps represented as the tensor product of the dual space of vector spaces as opposed to just the tensor product of non dual vector spaces?
Isn't there an isomorphism between both? Is it just convention?
 
What guarantees strict inequality here: $$\frac1{(n+1)!}+\frac1{(n+2)!}+\frac1{(n+3)!}+\ldots < \frac 1{(n+1)!} \left(1+\frac 1{n+1}+\frac1{(n+1)^2}+\ldots\right)$$? I see why weak inequality should hold.
 
Put a space somewhere in there
 
Well, it looks good in main site!
 
LaTeX gets annoyed if it's too long without spaces, it puts a line break somewhere arbitrarily
 
3:42 PM
@AkivaWeinberger you mean chatjax
 
@Secret What's "The Plan"?
 
what latex editor you use ?
 
and in this case it seems to have put the line break between "\fra" and "c"
 
@AkivaWeinberger Thank you!
 
@Silent $\frac1{(n+2)!}= \frac1{(n+1)!}\frac1{n+2}<\frac1{(n+1)!}\frac1{n+1}$
and similarly for all later terms
 
3:45 PM
@AkivaWeinberger Yes, but that guarantees that $a_n<b_n$, but all we know from that is $\lim_\limits {n\to \infty} a_n\le \lim_\limits {n\to \infty} b_n$, right?
 
$\ {\left(\dfrac {1+i}{1-i}\right)}^m= 1$, find the least positive integral value of $m$.
Attempt:
 
@Silent Is $a_n$ the partial sum, or the term?
 
Partial sum. @AkivaWeinberger
 
$\implies e^{mi\dfrac{\pi}{2}}=1 \implies \sin (\dfrac{m\pi}{2})= -i $
 
What we know is that $a_{n+1}-a_n>b_{n+1}-b_n$, in that case
which is stronger
 
3:52 PM
Which is not possible, hence there's no solution.
 
In fact, it's equivalent to $a_{n+1}-b_{n+1}>a_n-b_n$, if we want to go down this route
 
But another method (rationalisation and checking) yields he right answer i.e. m =4.
 
and thus by induction $a_n-b_n>a_1-b_1$ by induction, and we know $a_1-b_1>0$
 
Why is my 1st method incorect?
 
And so $\lim a_n-\lim b_n\ge a_1-b_1>0$ and so $\lim a_n-\lim b_n>0$
but that's all ugly
so let's do that again but with the terms
If $A_n>B_n$, then $\sum A_n>\sum B_n$
 
3:55 PM
I think i got that!
You will have to use too much effort!
@AkivaWeinberger
 
and that's just 'cause $A_n-B_n>0$, and so $\sum(A_n-B_n)>0$ (since adding positive stuff can only get you positive stuff)
and so $\sum A_n>\sum B_n$.
But yeah, from the first perspective, the gap between the partial sums increases, so it can never go down to zero
 
you are persistent!
 
@Abcd Don't you want $\sin(m\pi/2)=0$?
And $\cos(m\pi/2)=1$
 
@AkivaWeinberger well, no.
its 0.
 
$\cos(4\pi/2)=1$
You said $e^{mi\frac\pi2}=1$, right?
 
3:59 PM
But $\cos3\pi/2 = 0$
 
$e^{mi\frac\pi2}=\cos(m\frac\pi2)+i\sin(m\frac\pi2)$
and you want that to equal $1$
 
@AkivaWeinberger Yeah.
And I took cos mpi/2 = 0
 
Why?
If $\cos(m\frac\pi2)+i\sin(m\frac\pi2)=1$, then
 
Okay, so we have to consider two cases.
m is odd and m is even.
 
looking at the real parts, we want $\cos(m\frac\pi2)=1$
and looking at the imaginary parts, we want $\sin(m\frac\pi2)=0$
 
4:02 PM
Ah! Simple!
Thanks.
 
That's not the way I'd do that, anyway
 
how'd you do it?
 
From $e^{mi\frac\pi2}=1$
We know that $e^{ix}=1$ when $x$ is a multiple of $2\pi$.
So $m\frac\pi2$ is a multiple of $2\pi$.
And that first happens when $m=4$.
Alternatively, of course, you can write $\frac{1+i}{1-i}=i$ through rationalization (or through the geometry of the complex plane)
(double-checking by seeing that $(1-i)i=1+i$)
 
@AkivaWeinberger hmm, i mentioned that above.
 
@Semiclassical Did you have a way to access Soviet Math Dokl translations? I can't find it in the transcript or my downloads anywhere but I need to access that paper we once talked about.
 
4:06 PM
Sure
 
if i have $\int \int_{D} xy^2dA$ and is bounded with $x=y^2,y=x^2$
 
If you do it through $e^{mi\frac\pi2}$, you can see from that that $m\frac\pi2$ needs to be a multiple of $2\pi$, which is how I'd do it.
 
How do i define more definite bounds ?
 
Draw it
 
yes i'm on it
 
4:09 PM
$y=x^2$ and $x=y^2$ both contain the points $(0,0)$ and $(1,1)$
 
now these two defines area
which bounds the $xy^2$
 
@Tuki Something like that
 
@AkivaWeinberger that looks suspicious
 
So $x$ goes from what value from what value? (Not involving $y$)
 
so i want to find out $\begin{cases} y^2-x=0 \\ y-x^2=0 \end{cases}$ ?
 
4:13 PM
We already know that that's solve at $(0,0)$ and $(1,1)$
 
true
 
From the picture, what range does $x$ go over?
Not involving $y$
 
goes from 0 to 1 ?
and y goes from 0 to 1
if you mean these to dots that are points where these lines intersect ?
 
Yeah, $x$ goes from $0$ to $1$
I'm thinking of having $x$ as the outer limit and $y$ as the inner limit
so the range for $y$ can involve $x$
$\int_0^1\int_?^?(xy^2)dy~dx$
The inner limits can involve $x$
(If I had the limits the other way around, then it would be the reverse- $y$'s range wouldn't involve $x$ and $x$'s range would involve $y$)
 
y goes from 0 to 1 also ?
but then this would be bounded by rectangle ?
 
4:20 PM
@Tuki Here's a picture of what we're doing.
The inner integral finds the area of one of those tiny rectangles (something times $dx$).
The outer integral adds up the areas of all those tiny rectangles, integrating from $x=0$ to $x=1$.
Note that the inner integral only finds the area of one of those tiny rectangles, for any particular $x$.
Let's say, as an example, that $x=\frac14$. That corresponds to one of the tiny rectangles towards the left.
What would be the height of that tiny rectangle?
(The picture I drew loaded, right?)
 
$y=x^2$
so $(\frac{1}{4})^2$
$=1/16$ ?
 
This picture is getting complicated
1/16 is the distance from the bottom of the rectangle to the x-axis
 
i think i see where this is going
 
The top of the rectangle touches the curve $x=y^2$
 
$$ \int_{0}^{1}(\int_{0}^{\sqrt{x}}xy^2dy)dx $$ ??
 
4:31 PM
Not quite. You didn't use the $x=y^2$ curve
 
but now it leaves variable
 
Hint: $x=y^2$ is the same curve as $y=\sqrt x$
 
yes makes sense
but integrals are basically Riemann sums when $dx\rightarrow 0$ ?
 
the rectangle x values approaches zero
 
4:34 PM
The bottom of the red rectangle I drew is $x^2$ from the $x$-axis. The top of the rectangle is how far from the $x$-axis?
Remember that it touches the $x=y^2$ curve, aka the $y=\sqrt x$ curve
 
@MatheinBoulomenos How did it go with your exam ?
 
4:51 PM
$\int_{0}^{1}\int_{y}^{1}e^{-2x^2}dxdy$
like in normal distribution
 
$$\int_0^1\int_{x^2}^{\sqrt x}xy^2~\mathrm dy~\mathrm dx$$
@Tuki
is the answer
 

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