/sqt/: Stupid Questions Thread

Differentiate the hamiltonian with respecr to x and it immediately follows from the definition

What mathematics subjects should I look into (Khan Academy or something) if I'm interested in Computer Science to further High School knowledge?

Create a two dimensional array like this;

int A[3][1];

You can assign values to each "box" of your table with a double nested "for" loop that starts from i=0 and j=0 and ends at 3 and 1 respectively.

Linear algebra. Search up "khan academy in a stick", it contains a shitton more material that comes with a worse GUI than the site itself plus a lot of older videos. Unless I haven't found those videos in the real site yet.

*A[4][2];

How do we fourier transform this? I'm thinking either represent sine as exponents or use fourier sine transforms? Leaning on the former

Can someone explain why/how is run differential stat better predictor of future performance then win percentage?

And how could more than one of
x > y, x = y, x < z
be right at the same time?

Anyone know how to get a p value from whats given here?

use the definition...that is, integrate over [0, 2pi] instead of (-oo, oo)

an order is meant to be a generalization of the 'less than/greater than' signs you're used to for real numbers. It's saying that part of being an order means only one of those statements can be true, just like for the normal less than sign only one of those statements can be true.

Given some relation on a set, it's not obvious that only one of those should hold.

You're defining sensible requirements to any reasonable usage of those symbols.

How do I stop studying and create? I've been reading books for a decade and a half and never built anything that wasn't an exercise.

But that is impossible, that is property one of the definition.

What are you even asking?

I mean, you could create a relation defined on set S so that two or the three can be a true at the same time but then that would not be an order, it would just be a normal shitty relation that isn't even worth studying.

sketchtoy.com/67016183
How would you prove that DE=DC=CE ? D is placed randomly on the circle, between B and C

This is the graph of [math]y = x^{y}[/math] which does some extremely weird funky shit that I have no idea what it's doing.

It doesn't even look like a function since it loops back around over multiple x values, so I'm not even sure this is legal or how to properly evaluate it. I know that WolframAlpha said that finding a solution for it maxed out the computation time allotted to me.

My question is just how can I find the 'maximum' value furtherest to the right of the curve? It looks like it's around 1.44 something and I'm wondering if that's significant or not? I originally thought it might be root 2, but it's not.

I don't have a deep enough knowledge of complex analysis to explain in detail why it happens, but it seems to me that this is what's happening:

Wolfram alpha solves for y using something called the Lambert W-function; you end up with W(-logx) in the form. The W function is only defined on the reals for numbers >= -1/e. So the largest viable x is x=e^(1/e), which is about 1.44.

Thank you very much!

Help me Veeky Forums, for the life of me I can't figure this out and I feel like a moron. DIY job but math related.

I want to build an aquarium out of plate glass. The dimensions I'm looking at are

750 x 300 x 600

The source of plate glass I have is a single plate glass shower door of suitable quality. The door's dimensions are 1785 x 745.

There is also another piece of the same material with the dimensions of 710 x 780.

Assuming I make accurate cuts and don't waste material, will that quantity of plate glass suffice for the project?

Refer to the attached picture.

Just find the max of y = x^(1/x), which is the inverse function.

never worked with glass, but I'm guessing it's not as easy as cutting through paper. So my question is: once you start cutting, do you have to go through the whole length of the glass?
Or is it possible to cut a piece in the middle of the glass plate while the rest remains intact?

as long as you keep it on a level surface you can cut it without it falling apart.

My question was not about how to cut the glass. I'll use a fucking glass cutter. My question was whether the source material I have will suffice for the aquarium design. The total area of source material is more than enough, but it must be able to provide whole pieces of (in mm):

1x (750 x 30)
2x (750 x 60)
2x (30 x 60)

you can't.

can't your aquarium become 745*300*600?

I asked the question about how you cut glass because you can't use as much glass if you have to cut all the way through, as opposed to just cutting what you need without waste.

Thank you guys. I started self-studying Rudin and well, it's not much similar to high school maths.

As someone else said just take the inverse function and find it's derivative. At x=e the value of y is ~1.445.

okay.

so how does one work that out? is it the solution for surface area?

god, since turning my mind and energy to editing and writing I've become as numerically sharp as a bowling ball.

I was half heartedly sketching out the net on a poorly scaled door for about 20 minutes before I realissseeejejehhjdksmdmdddddddkdd

well basically the easiest part is realizing you will need both pieces of glass (the surface of the big glass part is not enough)

then start with the smallest glass and see what you can fit in.
either 750*600 once OR 750*300 twice, which is almost the same thing. You're not getting any more from that piece.
So let's say we get rid of one 750*600 using the small glass plate, because it's easier to fit two 750*300 if you have to separate them somehow.

So now you're left with your big plate of 1785 x 745, and you have to cut:
one 750*600
two 750*300
two 600*300

the problem is with the 745: you can only fit 2*300 or one time 600 in that.

So if you start putting your 750*600, you will be left with a huge unuseable space of 750*145.

And the rest of the space is not enough to fit the two 750*300 and the two 600*300

What happens between these expressions?
How do I generally operate on the numerators and denumerators to get a common denominator?

Multiply the top of the first expression by the bottom of the second expression, and the bottom of the first expression by the top of the second expression.

What's happening is exactly this, then simplifying.

Fact: until just now, I thought SQT was like SQL.

What separates a formal system from a deduction system in that formal system?

Why is decidability an important property in systems like first-order logic which is semidecidable but in every case where it is not decidable the reason it is not is because the process is infinite. Is this something that is only important for computers?

Why would Veeky Forums make daily 300 posts threads about fucking database queries?

Multiply each term by the common denominator over the common denominator excluding the portion of the denominator that it already has. You're in effect multiplying the terms by one, but giving them a common denominator.

(x+2)/(x+4) is multiplied by (2x-1)/(2x-1).

(2x-1) * (x+2) = 2x^2+3x-2
(x+4) * -(x+3) = -x^2-x+12

(2x^2+3x-2)+(-x^2-x+12) = x^2+2x+10

So after multiplying the numerator of the first fraction by the denominator of the second fraction and multiplying the numerator of the second fraction by the denominator of the first fraction and then summing these products up to attain x^2+2x+12, why do we divide this by the product of the fractions' denominators?
This is something extremely simple but is somehow 0% intuitive. Should it be intuitive?

>x^2+2x+12
Meant x^2+2x+10

Think of it without the variables. If I wanted to add 1/2 + 3/5 I'd have to have a common denominator. Easiest way to do that is to multiple 1/2 by 5/5 and 3/5 by 2/2.

Then I just perform addition as I normally would.

bumperino

I have a congrulence of

86^65 mod 133

how do I simplify (get it in x^1 mod 133 form) that?

anyone know a good youtube video for explain the sequential criterion for continuity and limits?

brutish force

86^65 mod 133
86*((86^4)^4)^4 mod 133
86*(44^4)^4 mod 133
86*23^4 mod 133
109

am i stupid if i can't solve this

Should the Kroneckor delta (in the context of GR tensors) be written with its upper/lower indices disjoint from each other, like all other tensors with contra/covariant parts? i.e.
[eqn] \delta_{\mu}^{\ \ \nu} [/eqn]instead of how every author I've seen does it,
[eqn] \delta_{\mu}^{\nu} \, . [/eqn]
(Or perhaps it should be [math] \delta_{\ \ \mu}^{\nu} [/math] -- I've literally no idea since I've not seen it written like a "proper" tensor before.) I figure it doesn't really matter, because of the nature of the Kronecker, but I'd like to know what the proper mathematical notation is, for my autism. (All I have is access to physics books about this.) What about higher rank Kronecker deltas?

[math] \delta_{x, y} [/math]

If the author isn't going to use a popular method to represent it then he should specify what the unpopular method means. All that matters is that the reader understands that that symbol in that context is the Kroneckor delta. That doesn't mean that certain representations aren't more intuitive or elegant or whatever though. I dunno what the popular representations are in physics though.

The placement of the indices don't matter on the kronecker delta except for summation purposes. In terms of GR just think of it as the euclidean metric / identity matrix.

The Kronecker delta is symmetric in its indices, the order doesn't matter and thats why it is usually written as:
[math] \delta ^{\mu} _{\nu} [/math]

Alright, good enough for me, I guess I'll just deal with it.

Do you know how to decompose a tensor with respect to the bases for the tangent and cotangent spaces using the tensor product?
If you write out this decomposition it'll make a lot of sense.

I haven't studied math at any high degree, but I think it would be interesting to be able to understand (or to at least read) any mathematical formula. Is there a good website/video that generally covers what all symbols/rules for them are?

The problem is, every field of mathematics uses and reuses tons of different symbols.
Theres not really a set definition for each symbol because the context matters.

You could try en.wikipedia.org/wiki/List_of_mathematical_symbols for a big list of mathematical symbols and their uses.
In the end, if you're reading some algebraic geometry paper, in order to understand anything, you're most likely going to need to know algebraic geometry or have someone translate for you.

and even if you have a translator converting the expressions to english, you're not going to know what anything means.

en.wikipedia.org/wiki/Lattice_(order)
Why are lattices defined via sup and not max?
For finite sets isn't max=sup?

sup(a,b) doesn't need to be either of a or b. a lattice doesn't need to be totally ordered

why do i get really annoyed when i see ppl posting plebtier shit on this board
>has no degree
>wants to browbeat ppl on their math knowledge

I want to ace 1st year ECE at UofT
What do?

Programming is not a problem since I've been doing that for 8 yrs. Studying some Integral Calculus rn as that's not included in the HS curriculum in Canada

I was supposed to prove the first line

Did I do something wrong?

Ah shit, nvm I found it

Could someone explain case 4? Why the negative was added for -(a+b)

a

better proof:
|.| is a norm so the triangular inequality holds.

It's a bit of common sense and already understood crap

But this book is introducing it in a way I'm not used to, proofs and all, and it's really fucking with my brain

How to get from this:

[math]
\frac{(-1)^{k+1}}{3} +
\frac{2(-1)^k}{3} +
\frac{2^{k+1}}{3}
[/math]

To this:

[math]
\frac{(-1)^{k+2}}{3} +
\frac{2^{k+1}}{3}
[/math]

-1 to the power of anything is either 1 or -1 so long as the denominator of what you're raising to is odd. This means that either k or (k+1) will have an even numerator. If (-1)^(k+1) = -1 then 2(-1)^k = 2, likewise if (-1)^(k+1) = 1 then 2(-1)^k = -2. Really raising (-1)^(k+2) is redundant because (-1)^k works the same.

Take (-1)^2 out of first two fractions, do the math inside brackets and multiply.

could you elaborate?
i don't understand where this (-1)^2 is

Sorry, not (-1)^2, but (-1)^k

How do i proof that if lim(a(n)) = a, then lim(nth-root(a(n))) = nth-root(a) ?

lim(a(n)) = a => lim(nth-root(a(n))) = nth-root(a)

still have no idea, can you draw up steps?

drink some 90 proof

[eqn] \lim_n a_n = a \Rightarrow \lim_n \sqrt[n]{a_n} = \sqrt[n]{a} [/eqn]

Sorry, this is what i actually want to proof.
[math]\lim_n a_n = a \Rightarrow \lim_n \sqrt[m]{a_n} = \sqrt[m]{a}[/math]

The root function is continuous.

Anyone?

I just finished a semester of college precal and am taking calculus next semester.

So I decided to download Spivak's calculus (third edition) and am seriously at a loss for some of these questions

How the hell do I even do pic related?
Am I screwed?

if you're struggling with basic quadratics in the first chapter you need to put Spivak down and go get a high-school algebra text

You're just wasting your own time trying to learn from Spivak at this point.

a) Come on, man
b) Do as the hint says
c) Factor y^2 in the expression and use b)
d) Factor y^2, see what you can do with that
e) Complete the square

I'm merely confused about exactly what it's asking

Perhaps if you could work a quickly I'd understand

I've dealt plenty with quadratic equations and other math, I just never took the time to actually understand the proofs and whatever so it's like rebuilding a foundation for an already built tower

You just need to do some algebraic manipulations of the equation.

What it's asking is extremely basic 10th grade algebra. If that confuses you you're way too inexperienced to be doing calculus at all, let alone rigorous calculus.

Read (or skim) Gelfand's algebra.

I don't understand Quantum Mechanics

None of this shit make sense

Spivak is actually proving that. You can't just claim something is a norm without showing it, especially in an intro calc book, and think that counts for anything.

I don't really know what my question is, but I don't see how a meteorite half a mile long can wipe out all major life on earth. I mean if you zoomed out on earth, half a mile isn't even a pixel, and this shit is going to kill everything? Not saying it's wrong but I just can't fathom that reaction.

Just installed MiKTeX and using the TeXworks editor. Am I meant to type up the info in a word processor and then just copy an paste it into TeXworks in the appropriate template or should I be doing it purely in the editor?

20% for rain on Saturday, and 30% on Sunday. What's the probability for rain in weekend?

texworks is bad.
use techniccenter or litterally anything else.

> Am I meant to type up the info in a word processor and then just copy an paste it into TeXworks in the appropriate template or should I be doing it purely in the editor?
No. Find a template, run the compiler on it and see what it outputs.
Then edit it.

>Show that any stress-energy tensor derived from a field Lagrangian will satisfy the conservation law.

pls help senpai

>taking it literally
ffs