/sqt/ - stupid questions thread

in pseudo logic

∃x.xLeveryone

how can you express everyone using a quantifier? there's only two quantifiers and two places for it to go (before the existential or after)

[eqn]\exists x: \forall y: xLy[/eqn]
My guess

You can interpret this in two different ways. I assume you know the symbols for "for All" (upside-down A) and "there Exists" (backwards E), so I'll just use A and E because I can't be bothered to TeX it.

The first interpretation is that if you give me any person, you can find someone who loves him/her. In this case, you write it as Ay Ex: xLy. The second interpretation is that there exists a single person who literally loves everyone. In this case, you write it as Ex Ay: xLy. Quantifiers commute when they are the same type, but don't when they aren't.

that is correct. good job!

there exists a person x, such that for all people y, x loves that person y. now, can you explain why

[math]\forall y.\exists x.xLy[/math]

is incorrect? in other words, what is the english interpretation of this second statement?

It's weird, but I'm trying to figure out how bike gears work.

I know W=F*d and that's why the back gear hub works down to a smaller size for each setting to allow you to give more power and pedal harder.

But the front gear set by the pedals size up up allow more power to be put in the pedal. It seems contradictory. Why don't the front gears behave the same way the rear ones do in terms of sizing and power?

>what is the english interpretation of this second statement?
tfw no gf

I-it's o-ok...
I just remember the hopes and dreams I had in the first semester....

is this a correct statement of the twin primes conjecture? I feel like there it should be

[math]\forall q.\exists p.\forall x, y, z, w.(p > q \land (x, y, z, w > 1 \rightarrow (xy \not=p \land zw \not=p+2) ))[/math]

the additions being z and w

Ah, that clears up everything!
One more question about notation though:
Using notation where yPx means y is the parent of x, how exactly would I write "everyone loves their parents"?
Would it be ∀x: yPx: xLy

you want a conditional in there, that statement is malformed. you can only have a quantifier before a colon

how would you quantify over parents?

The one word I understood in that was colon
It's the place where dragon dildos go right?

a quantifier is a ∀ or ∃. what i'm saying is your statement doesn't make any sense at all, it's like a SyntaxError if you've done any programming

it's like if I said [math]5 + / 3 * = 1^+ [/math]

it's not that it's wrong, it's that the syntax itself is incorrect so it doesn't mean anything.

you're using yPx like a quantifier but that's not allowed. in fact "y" is not even defined in that statement. you need another way to introduce and "filter" y. have you learned about implications? the [math]x\rightarrow y[/math] operator, defined as

x | y | x->y
T | T | T
T | F | F
F | T | T
F | F | T

Just use the limit infimum. It's cleaner.

You use "implies" to declare this statement. It's a right arrow (p -> q) that's logically equivalent to (q or not p). So you have Ax Ay: yPx -> xLy.

So I'd do ∀x: yPx -> xLy ?

well, that was from a textbook. just trying to figure out if I understand it right or it's an error

Also, I have a question of my own (since I just gave answers to five.) HOW TF DO YOU USE LATEX HERE?! RAWR.

you can't use the variable y because you've never introduced it. you can only introduce variables in a quantifier. thus your statement is not well formed. is the correct answer.

\[math\] latex code here \[/math\], without the backquotes. if you have 4chanX there's a "tex" button you can press to preview

[math]x + y = z[/math]

The original statement was correct. The x and y are to show that p and p+2 are prime. The q is to show that there exists a q that there are infinitely many such p. You don't need z and w because if x and y multiply to one of them, then the entire expression fails due to the "and" operator.

You are my prince.

hmm, but if p and p+2 are both primes, then the consequent would still evaluate to false, right? since there's no way ab=ab+2 for fixed a, b

I just came here from a random link on the front page and I feel dumb now.

I go back to rest of Veeky Forums.

I should go through this a bit more slowly. You want to say that p and p+2 are prime. So that means you want there to be no way to write p or p+2 as a product of x and y for any x and y. That means for any x and y you pick, if x and y are both larger than 1, you want x times y to not equal p AND x times y to not equal p+2.

How the fuck do i use LaTeX?

maths.tcd.ie/~dwilkins/LaTeXPrimer/

ok, I think I understand now. Thanks.

where can i test this?

where can i test this

My mom got me Microsoft Band for my 28th birthday. Is it actually useful for exercising or should I tell my mom to return it?

download texstudio/texmac. if you want to use your own editor (ex vim), just download the texcore and an appropriate editor plugin.

Diarrhea and lactose intolerance

So I eat, get sick real soon and get the shits.
What am I shitting out?
Why is this the response for a food I can't absorb?
Why doesn't it come out as a nice dry shit at the end of the tunnel?
And now for the real question
Can I eat as much ice cream as I want without absorbing the fat?

How do I enter (1+.04/12)A_(n-1) + 50 into a ti 83 calculator? Doing sequences and this shit is driving me mad.

Why does every person look weird to me?

Is this the result of years and years of drugs and isolation?

It's mostly white people -- I'm white -- but everyone looks weird to me and causes a very uneasy feeling.

Fugg everyone is in the uncanny valley?
How do you look in the mirror?
Closest thing I know is face blindness or Prosopagnosia.
Yeah it sounds like you damaged your brain. Try asking a psychologist or keep googling to find out more

probably comes down to how much you like yourself

It's honestly probably a combination of neurological damage and self-image like you've said, and if I would point to any direct thing it would be the latter.

And how do I look in the mirror?

I honestly try to avoid it, it's not that bad usually but it made me stop smoking because 90% of the recent occurrences have ended in me freaking out.

Neat. Can you describe the weirdness more?
And how do you feel when you see these faces?

if the human came from the monkeys, why there are still some monkeys ?

>W = F*d
>Winput = dE/dt
This is a simplified expression of the first law of thermodynamics. E is energy, and t is time. Put in more energy in less time, and you're putting more power in. That's what's at play here, but I think it can be explained more intuitively.

Imagine a large front gear turning a large back gear. Turning the front gear turns the back gear by roughly the same amount. You turn the pedal once, you turn the back wheel once.

For a small front gear and a large back gear, you need to turn the pedal a couple of times if you want to turn the back gear just once. The energy output is still the back wheel, so you still need the same amount of energy to turn it around one time. It's just that this time, you're spreading the energy between, say, two turns of the pedal instead of just one.

For a large front gear with a small back gear, you get the opposite effect. A small turn in the front gear will mean a much larger radial turn by the back gear. In this situation, you need only one turn of the pedal to turn the back wheel twice. That means that for every time you turn the pedal all the way around, you need to output twice the energy compared to the situation where the gears were the same size. Naturally, this makes it harder to turn the pedal and forces you to put in more energy with each turn, allowing you to put in more power with less turn speed.

I'm learning logic right now. The P and Q stuff

does this have a practical application?

literally it applies to any thought you will ever have in your entire life

every field from math to cs to english to economics to art history to archeology to deciding what to eat for dinner to buying a dog to getting up to get something out of the fridge involves logic.

It does have unabsorbed nutrients in it, but your body's immune response is what mixes it with that goo. When your body is protecting itself from what it perceives as a foreign toxin, it often produces mucous to suspend the pathogen in, which is what happens to the dairy product in your body. This also suspends electrolytic secretions from your pancreas, and your body can't reduce it once it gets to your intestines since that would mean absorbing the dairy. The mixture of unabsorbed nutrients, mucous, and electrolyte secretion are ultimately what make the stool very soft.

In two words, it's ass snot. Whether or not your body is absorbing much of the fat depends on your particular case. If you want to gorge on ice cream while sitting on the pot for all of eternity, that's your choice, but I wouldn't recommend it, since your body will likely dehydrate from adding so many of its own fluids to your stool.

not true, it involves intuition

what if i don't want to?

>should I touch this stove?
>well, if I touch the stove -> I get burned
>I do not want to get burned
>modus tollens
>I do not touch the stove

sure the brain does this for you automatically but it's all just logic

Can I deduce that I should absolutely learn the stuff with the Q and P?

No. Turns out your brain is pretty good at this kind of stuff already. English majors usually never take logic but they definitely apply it to all their papers, for example.

But studying it in a formal context will help solidify concepts, and it will show you some things you may have not considered. You will definitely find your arguments and thought process clearer and better organized, even if you don't explicitly convert the situation or debate at hand to symbols. Basic propositional logic, and first-order logic is good for everyone to have.

Faces were generally just labels before and something I never really thought about much. Looking at people now I can't help but to dissect their entire visage and eventually being then almost instantly the realization of how disgusting and weird humans are and how we look hits me. Feelings similar to the uncanny valley, disassociation, nausea, paranoia -- like I've momentarily broke the fourth wall -- until I remind myself that thinking about it is pointless and keep doing whatever.

Aight, let's say I'm in an underwater base like three miles deep, just anywhere where the pressure would kill me. Let's say the hull is breached in whatever room I'm in and somehow I survive the water rushing in, would I be fine in the room, or would the pressure translate into the room? If the former, would sticking my arm or something out of the hole be lethal?

The pressure would eventually translate into the room if the hole isn't plugged. Try plugging it with your arm, and it'll feel the pressure outside.

High pressure is basically just it being pressed down on from all directions, which would be uncomfortable to say the least. If it's just your arm out there, you'll likely have the contents of your arm flow inward toward your body. This translates to some extreme blood and fluid pressure building up inside of you. Not healthy.

Writer nerd here, working on a small scale sci-fi story that I'd like to be backed up by some real science. Chemistry challenge here I suppose.
The basic premise of my question is one of my characters can set the air on fire by creating a spark with their fingers, basically by controlling some property of the air like an element or molecule present in it. Given those parameters, what element/molecule should they be able to control in order to create, say, a path of gas/air that will burn for some short time(seconds is really all I need)? Or is this not feasible?

How much energy is focused into the beam of a Casaba-Howitzer, and what is the theoretical limit of the energy that can be focused into a beam?

Why don't you do something like a tesla coil?

>English majors usually never take logic but they definitely apply it to all their papers
Actually, you'd be surprised by the number of lit and phil students who don't understand what an implication is

Oxygen is highly flammable, yet there's only about 20% of it in our air (check that number, I just gave what I roughly remember from HS). If your character could separate the oxygen from the rest of the molecules in the air, it should work.

Good trips. I was holding off on oxygen because I didn't believe it could catch on fire itself(from what I recently read fire is a triangle that needs three things- heat, fuel, and oxygen. So logically oxygen couldn't be its fuel). And if the character could control oxygen you'd get those nitpickers like "hey if they can do that why don't they just suffocate their enemies", plot hole spotters. And yeah, you're 20% number is correct.
The best answer I've found is perhaps if they control hydrogen, by separating it from the air and the environment around them, it could serve what I'm trying to achieve. Although I'm not sure if there's enough hydrogen present in atmospheric molecules that'd justify the use.

What's a good site for space-related news and other science stuff that's up to date and doesn't have a paywall?

I used to have the same problem, also from hallucinogens and years of isolation.

The problem went away from simple conditioning. I occupied my mind with things that were much more important. Think: putting yourself in life or death situations which force you to focus only on what you are doing. If you're going 120 mph in the middle of the night on a freeway you're going to focus on not hitting a deer, not people's faces. Same with any other extreme sport or activity that requires all of your attention like puzzles or fighting or free-soloing.

A neat side-effect is that by putting myself in situations that ultimately led to me focusing more in general, my life became more exciting and I actually overcame the depression I was experiencing as well. Didn't need medication or therapy anymore. Just did exciting shit all the time. Who woulda thought the solution was as simple as "do exciting shit all the time".

If you're going to win a war, you need to kill your enemy. If you're going to kill your enemy, you need to be accurate. If you're going to be accurate, you need to calculate trajectories of your bullets and vessels. If you're going to calculate trajectories of bullets, vessels or bodies of any kind, you need tables of functions faster than your enemies can get them. If you're going to produce ballistics tables of functions faster than your enemies can get them, you need CPUs. If you're going to make CPUs, you need Propositional Logic.

I'm not trolling. I seriously want to know what is going on here.

I'm starting my physics degree after this summer, some books that I should read to be prepared?

en.wikipedia.org/wiki/Removable_singularity

How's your math?

Both are right and wrong.
[eqn] \frac{x^2+1}{x-1} = (x+1) ; x \neq 1[/eqn]

You just restrict the domain to include all real numbers except 1. I don't get the (x+1) = 2 part though.

I guess that ok, but I'm a little bit rusty in derivatives and integrals.

>I don't get the (x+1) = 2 part though
When x=1, (x+1)=2

Oh yeah, literally plug and chug. Dafuq is wrong with me. John is a as dumb as me for plugging it in, even after he claimed it to be undefined.

SciShow
It's kind of like Fox News for science. A lot of shit and it's broken down for the simple minded, but it's news science and on YouTube nonetheless.

Do yourself a favor review all of your high school math again. Review to the point where what seemed advanced when you first learned it now feels easy. You should be able to, for example, derive the quadratic formula quickly. Once you are done reviewing, figure out what textbooks your classes will be using for your calculus classes and start working through the problems on your own.

You will be that much farther ahead of everyone who did not do this and spent their summer masturbating and playing video games.

If you need supplementary material on any topic use "[topic] .pdf site:.edu" to find lecture notes in google. The site:.edu filters out .coms which will usually give you ads for free books and the .pdf will just give you .pdfs since that's what most people publish their lecture notes in (or .ps).

For example, try "precalculus .pdf site:.edu" and see what kind of results you get.

You can use this for pretty much any topic. Often when you find a good .pdf written in a style you like, you can find the complete list of .pdfs also written by that person (not always) by going back a couple directories in the address.

For example, to find lecture notes on propositional logic I simply entered into google "propositional logic .pdf site:.edu"

google.com/search?q=propositional logic .pdf site:.edu

which led to me to the following link:

cs.cmu.edu/~emc/15414-f12/lecture/propositional_logic.pdf

which I then went back a directory to find the following index:

cs.cmu.edu/~emc/15414-f12/lecture/

which had more lecture notes, such as:

cs.cmu.edu/~emc/15414-f12/lecture/prop_logic.pdf

and

cs.cmu.edu/~emc/15414-f12/lecture/smc_sat.pdf

The faculty page is almost always attached to these links (/~emc) so if you like their writing you can find their publications and articles that way by going to their page. Same goes for finding other faculty in the department.

John is claiming that the left term can not be equal to the right term because they get different values for when you plug in x=1.
Fred is claiming they are equal cos he can use algebra to simplify the left term into the right term.
Sorry, I didn't make it very clear.
Also,
>dumb
hey man, you're smarter than me.

>The most efficient way of calculating the inverse of a square matrix is to use
elementary row operations

IS IT THOUGH

Why do the majority of people that proclaim to be smart, but in actuality of blog/magazine readers:
- Not understand the Gettier Problem
- Use fallacies
- Say they love science but completely reject empiricism and instead cling to doxa

?

Why is the weather news so shitty? It's literally thunderstorming outside but all the weather reports say it's partly cloudy, sunny, and with 0% chance of precipitation.

why did he sum ε at the end getting 2ε?

(Ref: en.wikipedia.org/wiki/Structural_rule)

In the exchange rule we can assume WLOG that [math]\Gama_2[/math] is the empty context, since any transposition can be expressed as a composition of adjacent transpositions.

Is it possible to assume that [math]\Gamma_3[/math] is empty as well, using some sort of cut-elimination-like argument?

I can tell you from my experience taking CC classes back in high school that most STEM faculty did not have PhDs, while most English faculty did. Funny enough, the "CS" department consisted of one guy whose entire experience with the field was maintaining computers in the air force. These places tend not to get a lot of STEM faculty, especially in something like engineering, so it should be very doable with just a Master's degree and some teaching experience (say, TAing; you could even try to get your own course in grad school).

Install TexLive, read the first page of the wikibook, and then write until you don't know how to do something. Google it, because someone else had the same question at some point, and then go back to writing until you can't do something. LaTeX is not hard.

>Fixing LaTeX
That [math]\Gama_2[/math] should be [math]\Gamma_2[/math] obviously.

Also, I suppose we can assume [math]\Gamma_3[/math] is empty but not [math]\Gamma_2[/math], which corresponds to the expression of a transposition [math](a_1a_2\cdots a_n)[/math] as [math](a_1a_2)(a_1a_3)\cdots (a_1a_n)[/math] instead of [math](a_1a_2)(a_2a_3) \cdots (a_{n-1}a_n)[/math].

Is the world ending 29th July?

youtube.com/watch?v=Wpk-026RmVs
So this girl makes toothpaste with baking soda + coconut oil, chemically how does that work, exactly?

Did our prehistoric ancestors wipe/wash their asses with anything? Or did they just have perpetually itchy assholes?

I seriously wonder about this every time my asshole itches.

How much of the sky would Jupiter take up if I was standing on the surface of Europa?

I cannot find these two eBooks anywhere. Can someone help me out, please?

> A Primer of Abstract Mathematics by Ash
> The Mental Calculator's Handbook by Fountain and Koningsveld

Need more context - I guess this is supposed to show that lim (a_n + b_n) = (lim a_n) + (lim b_n)?

This works. I tend to think they can't both be empty, but that would be really hard to prove; you'd have to exhibit a model of whatever logic it is.

how do magnets physically interact with each other?

I understand that photons carry the force, but how/why?

Everybody has someone who loves them
it's different from the first cause here x can be multiple persons

The baking soda doesn't dissolve in the oil but stays suspended. This it rubs abrasive grains of baking soda against your teeth thus removing plaques. Baking soda also helps neutralize odors

I'm not entirely sure what this question is asking.
For the first I guess it's (p^q) v r but I haven't a clue about the other two.

en.spaceengine.org/
Have fun!

Where dinosaurs just dumb big birds?

What is the best book for math to start from scratch?