/sqt/ - Stupid Question Thread: Linguistics Edition

I think its mostly infinite sums with some calculus, but I'm not sure

What are prereqs for Real Analysis? Trying to form a sort of math roadmap.

>Are some languages harder to lip read? If so which is hardest?

Any language that heavily features sounds not associated with the lips (e.g. tones, nasalization) would probably be really hard to lip read.

Let's say I wanted to get the percentiles of a data set A={1, 2, 3, 4, 5}. If I wanted to get the percentiles of B, the set containing n duplicates of each element in A, would I get the same results?

The same percentiles for B as for A, to clarify

Why do we allow scientists to create new strains of viruses and other dangerous diseases in labs? They may be safe but what if something horrible was made and accidentally or intentionally leaked? How are new diseases created in labs and how do they form naturally? Could a breakout of a deadly disease make humans go extinct in the modern world?

What is the abstract algebra classification for a polynomial with negative exponents?

for example

[math]\frac{(x+2)^4}{(x+3)^5}[/math]

I'm ready to be raped with abstract algebra words I don't understand

What you posted is called a rational expression.

en.wikipedia.org/wiki/Rational_function

>I'm ready to be raped with abstract algebra words I don't understand
I love it

Quantum Question Normalising Wave function

>pic related

How do i do part (a), studying for exams and i got stuck. I know Ill have to multiply the wavefunction by its complex conjugate and integrate over all space but what do i do with the integral he gave me in the question thats = D? Pretty confused, help would be appreciated

Wait i didnt even begin the question now that ive wrote down the first step its p obvious i need to substitute int psy^2 with D. oof think I might have it, sorry for wasting time lads

If you put a live wire or some other source of electricity into water that's flowing, does the charge get carried along in the same direction as the water? Or can it travel upstream?

Aigner - Combinatorial Theory

Not sure how authoritative it is, but it really tried to give a relatively general framework for combinatorics (that being said, combinatorics is pretty diverse and "horizontal" in nature so I don't think there'll ever be a definitive text)

The speed of electricity in salt water is just over 0.1c, from the PoV of the electricity, the water is stationary.

Thanks senpai. If you had some super hard water jet, would you be able to get the electricity to travel down stream, or is getting water to go at those speeds unfeasible?

Does this also mean you could put a wire in the spray from something like a hose or riot cannon and shock people from long distance?

>Electrified squirt guns when

>is getting water to go at those speeds unfeasible
Yes, getting a stream of water to 10% of the speed of light is pretty unfeasible, it wouldn't be a so much a stream of water as it would be an unstoppable destructive force. That would be 33k times faster than a water cutting jet, requiring over a billion times the energy.

>Does this also mean you could put a wire in the spray from something like a hose or riot cannon and shock people from long distance?

Water jet based electrostun devices have been a dream of police and military forces for a long time but it's actually very hard to create a solid stream of water that travels over long distances and, if it were possible, you'd have to have a complex control system because initially it would put a potential difference across the target of that between the stream and earth but, as soon as the target got wet enough for there to be a continuous wash of water from the jet impacting the target to the ground they'd only experience a voltage of the PD within the stream for that distance.

In short, you'd either have a stream that would kill them on contact and mildly shock them after stream-ground contact is made or a non-lethal incapacitating shock for a fraction of a second followed by something as effective as a non-Joker joy buzzer.

Oh shit, I'm a brainlet, I didn't realise by c you meant speed of light.

Ah well, time to rig up an electrified water gun and go around zapping people.

I'll check the obituaries about a week from now.

Or you could check the super hero list for cool people who have electric super powers

Link?

>inb4 Area 51 database

Finishing core classes and finally getting into my science classes.

Want to major in biochemistry or cellular biology and would like some books that I can read on the topic as well as books I can read about preparing for majoring in STEM.

I'm specifically not looking for text books, though

bump. I'm thinking about switching to some kind of engineering or applied mathematics and I'd also like to get a feel for what I'm getting myself into.

>Are some languages harder to lip read?
Yes, any form of sign language is impossible to lip[ read.

Is there a biological explanation for why dicks become so sensitive to any contact after ejaculation?

So something I used to do a long time ago in middle school is think that any sequence of numbers with an unknown pattern could eventually be reduced to a sequence of ratios between the terms. Then if those ratios don't form a clear pattern, you could get the ratios of THOSE ratios, repeating until it was reduced to a clear pattern.

Obviously this doesn't (always) work, but I suspect that this is an actual thing and I want to know the name of it.

I have a question about the relationship between current flow and electron drift in an electric circuit.

I know that both phenomena occur, and that the electron drift occurs in the opposite direction of the current flow.

But my question is this: Does the amount of current flow EXACTLY determines the corresponding amount of electron drift? Or can there be some variation between the two?

In other words, does 1 C/s of current flow necessarily demand that exactly -1 C/s "worth" of electron drift is also occurring? (I use the word "worth" here to mean that I count each electron that drifts by the selected point as representing -e amount of charge.)

My physics textbook doesn't make this very clear....

I'm not understanding very well what has been done in the pic related.

I get the second parenthesis in the first member of the equation was multiplied by 1 (4/4 = 1) and then what? Does this trick has a name? Where could I find more about it?

The 4 in the numerator was distributed. Then both sides were multiplied by 4 ; canceling out the 4 in the denominator and changing 10 to 40.

First, simplify just the numerator (ignoring the denominator for now). Do this by multiplying the 4 into (15x^2+8x+1) to get (60x^2+32x+4) in the numerator.

Once you're done with that, notice that you still have a 4 remaining in the denominator.

So simply multiply both sides of the equation by 4 to "get rid" of that 4 in the denominator.

What have you done so far?

Forgive me for my dumbness in advance.

I understand the 4 in the numerator was distributed and that both sides was multiplied by 4 to cancel out the 4 in the denominator of the first member of the equation but I keep looking to this and thinking "there's something wrong".
Shouldn't I multiply both parenthesis each for 1 or 4/4? Is it even, lets say, "allowed" to be done only in the second parenthesis? I'm really confused about it, my basic math is completely rusty

Thank you

[math]\psi^2[/math] won't integrate to D, though, and that value of [math]\psi^2[/math] isn't important for this question..

Quick question about Fourier transforms. When I transform the equation [math]u_{t} = \frac{1}{4}u_{xx}[/math], that means I only take it respective to [math]x[/math] and treat the other variables constant right? That would give me [math]\hat{u_t} = -\frac{1}{4}k^2\hat{u}[/math]

It might help if you use variables to represent all the complicated stuff.

Your equation is basically this:

A(4B/4) = 10

.. where A and B are the two polynomials.

Right away, it's clear that the 4s cancel, giving you this:

AB = 10

However, your second equation has 40 on the right side, not 10. To mirror this, you need to multiply both sides of the equation by 4:

4AB = 40

The nice thing about multiplying 4 times A times B is that you can do them in any order.
Therefore, all of these equations are identical:

4AB = 40
4(AB) = 40
(4A)B = 40
A(4B) = 40

Well, as it turns out, the second equation in your pic chooses to leave A alone, and to multiply 4 by B, so your case is this one:

A(4B) = 40

Now, let's plug in the actual polynomials for A and B:

(60x^2+32x+1) ( 4 (15x^2+8x+1) ) = 40

Multiplying the second parentheses out, we get exactly the second equation in your pic.

Thank you

Ohhhh, now I got it! Wow, I'm so fucking stupid!

So if I have n parenthesis = x, being algebraic expressions what's within the parenthesis and x belonging to the integers higher than 1, I could multiply and divide only one of those parenthesis, distribute the number in the numerator to the respective parenthesis then multiply both members by the number that would cancel out the number in the denominator and I would keep the equality? Awesome!

Even though it was so obvious, I really appreciate the time you took to type this in order to help me understand what happened, thank you!

This is a graph of elevator motion. Why isn't it symmetrical? Why doesn't the elevator go down in the reverse way it goes up?

It think you appreciate the gravity of the situation.

Isn't it mechanical action that lowers the lift?

Yes

Idk lol I guess it gives a more uniform G force.

Propositional Logic, Predicate Logic, then Set Theory.

Propositional Logic will get you get you thinking about how to parse statements so they can only be evaluated as true or false. Predicate Logic inherits all of the connectives and techniques of Propositional Logic, but gives you the symbols [math]\forall[/math] and [math]\exists[/math] so you can represent quantifiers "all" and "some" symbolically. Set Theory inherits all of Predicate Logic, but adds [math]\in[/math] so you can represent the verb "is" symbolically.

Real Analysis deals less with functions but with the semantics of functions by means of predicates, so rather than calculating a limit and then saying, "Yep, there's a limit," you look at the definition of a limit and see what can and cannot be follow from it according to the rules of logic.

It can seem daunting, especially if you look at the reputation Baby Rudin has on Veeky Forums, but once you learn the techniques of logic you'll realize it's not that difficult and in some ways easier (and IMO a little more shallow) than actually doing calculations.

You're going to want to read up on predicate logic and set theory. Get comfortable with quantifiers and their proofs. I've was going to write a whole thing where I gave an overview of why you should start with propositional logic then transition into predicate logic and then set theory, but I forgot about domains and understated the importance of set theory, which are both important and these lecture notes are better than what I could write out anyway.

cs.utexas.edu/~schrum2/cs301k/lec/topic04-predicateLogic.pdf

I'm sure if you're interested in real analysis you're probably already familiar with propositional logic so that was another reason I omitted it. There's plenty of info out there with all the definitions you need. If you use this search format in google: "[insert subject] .pdf site:.edu" you can find lecture notes on almost any subject.

Good luck.

What do engineers really do? Make stuff in CAD all day?

I sit in MATLAB all day fixing shitty code, that I could have probably rewritten better and cleaner in C.

Does [math]a+a\bigg(\sum\limits_{n=1}^{\infty}(b-ab)^n\bigg)[/math] simplify to [math]\dfrac{a}{b-ab}[/math]?

I was just trying to solve some dice probabilities and ended up learning about infinite series(and LaTeX just to make this post), but then I realized I didn't need to use an infinite series.

Mohawk has no labial consonants other than "w". So I imagine it would be hard to lip read.

How the fuck do you sing in Chinese?
I mean, the tone of the syllable carries some of the meaning of the syllable, right? So does the tune have to fit exactly what the words are? But the words are random wrt tones, and Chinese music doesn't sound random.

very clearly NOT a fucking koala you mongoloid

>wolframalpha.com/input/?i=a+a sum(n=1 to infinity) (b-ab)^n
Nah. Also, it's just a geometric series, you should be able to find its closed form.
Also, use "\left(" and "\right)", usually better than "\bigg"

Thank you user

I realized where I fucked up some time after posting, but I didn't work out the solution. How does wolfram decide how to format its outputs? Because I'm pretty sure [math](a-1)b+1[/math] isn't a correct way to write that.

My next question is, is this particular formula used for anything outside of this obscure dice game?

Would you solve this using a similar thing to the method usually shown to show that the naturals are as numerous as the integers?

I don't even get the question, isn't that already in the definition of even?

Oh shit, I didn't even see the even part. I guess it is.
So for the 'infinite' part could we just add any number of +1-1s?

Not a troll

Legitimately; how does one solve this question?

How does Google Translate work, step by step.

What tech and methods are employed?

Are there series that converge when their variable is set to 1, but diverge if the variable is set to even an infinitesimal amount above 1? In other words, series that can achieve a state of being "on the verge of infinity".

How do I write cheat sheets in [math]\LaTeX[/math]?

Calculus II

You can spend too much effort trying to synchronize tone and melody, or you can disregard tone altogether as it will still be understood to a certain extent given its context.

If I have a differential equation

[math]u'' - e^{t}u'-e^{t}u=1[/math]

For which I want to find a general solution, I can start by solving the homogenous equation - in order to do this, I can use the characteristic polynomial or equivalently translate the homogenous equation to a two dimensional system which gives a 2x2 matrix of which I would need to find the eigenvalues. This would give me two eigenvalues as functions of t,

[math]\lambda_{1,2}(t)[/math]

And I can use these to determine the eigenvectors, combining these to construct the fundamental matrix. From there on its easy sailing. My question is, the eigenvalues of a matrix equation with variable coefficients look nasty. Is there a way to find a prettier solution?

Is there some convenient place i can download solution manuals for textbooks without paying?

Its the same kind of problem as those "fence in the cows" ones from the SAT or whatever. Just come up with an equation which describes the relationship of all the parts, then reduce and minimize.

Libgen

Can anybody give me a microscopic explanation on how lenses converge and diverge light?

Does cyclic homology require a unitary ring, or can it be a commutative non-unitary one?

is the inverse of a function always bijective?

Google "LaTeX cheat sheet templates"
and start learning more about your favorite markup language.

No, consider a function that maps 1 to 0, 2 to 0. Is the inverse bijective? In fact, what is the inverse?

obviously he was assuming an inverse exists brainlet, he's not asking about non-existent functions

Check retraction and section, the one-sided inverses

you really think of one-sided inverses when someone says inverses?

he said 'the inverse' so it's presumably unique, unlike retractions or sections

best way to approach it is through algebra. Fourier analysis is just projecting function onto bases of some periodic functions.

You need to understand some bits of integration.

>brainlet
Are you taking your frustrations out on me? Go do that somewhere else.

what frustrations?

No, I don't think of those. Nevertheless, there is a reason for the notion of mutual inverses. If the one posting the function used 1 or 2 instead of 0, he'd have a retraction

>is the inverse of a function always bijective?
>no, because look at this irrelevant example which isn't a non-bijective inverse of a function

what's the biggest reason why your surroundings sound so much louder than usual sometimes? the weather seems to be windy when/before it occurs. the most common explanations are retarded and/or don't apply to my circumstances.

can't it just be the air pressure? you know how water travels better in water, through the ground, or why not the classical example of train tracks, where you can put your ear against the rail to hear a train coming from a mile away. higher air pressure = higher air density = sound travels better through the air = surroundings sound louder?

>you know how water travels better in water
*you know how sound travels better in water

What's wrong with his head

en.wikipedia.org/wiki/Cutis_verticis_gyrata

eww he should let his hair grow a bit to cover that shit up

must be really painful if he gets ingrown hairs from that though

Thanks, I didn't think of that. I assumed googling LaTeX cheat sheet would just throw a bunch of LaTeX commands compilations.
Guess I should trust my favourite browser more.

I could also break my question up in smaller pieces: what I actually wanted to know was
>how to make colourful boxes and put text in them like you do in many cheat sheets
>how to avoid shit like on pdf related: equations being misaligned and going half way through the margin, the whole thing taking much more space than it should, ridiculously big spaces between the math and the text
>some nice font to chose, that would also cover my language's special snowflake letters (and perhaps other languages too, for names'n'shit)

>Corrupted file or unsupported file type.
wtf fourchan?
docdro.id/oTc7l1X

Since I'm posting my pdf anyways, could someone check for any typesetting mistakes I made (I know there's plenty but I may not be aware of all of them) and how I can fix them? Thanks.

If I use the interpolation function in MATLAB on a data set. How do I find the error of the results?

what is the bigger picture concerning arc sine, arc cosine, and arc tangent?

how do you calculate the trajectory of a projectile while taking into account the air resistance? assuming you have measured/estimated the drag coefficient and mass

I'm probably just retarded, but is there a specific term for the type of value that gets assigned to divergent series? Because it's equal in a sense, but it's not really a sum.