/sqt/ Stupid Questions Thread

Struggling to make progress on (a) and (c), any tips.hints/tricks?

is it rude if I resend an email multiple times in a day if it's urgent? A professor simply won't answer my emails. He's being a total retard. What can I do? I need him to answer a question today or tomorrow, I don't have enough time.

Meet in person

shit you're right I guess the only way to do this is to meet in person, otherwise they don't give a shit about you

define why

is flat earth real?

Could it be possible that the universe isn’t actually expanding faster but just rotating around a point?
Could that explain the light shifting in phase?

Is this the new meme?

If you're asking "is the earth actually flat?" then the answer is no.

If you're asking, "do people really believe that the earth is flat?" the answer is yeah, there are probably a few. But a lot of the people who debate it online are just trolls and don't really believe in a flat earth.

a. alpha is just the image of x under the projection Z_3[x] -> Z_3[x] / (f)
b. Can be verified easily
c. Use the division algorithm

What would be an interpolation function F interpolating f such that
[math] \dfrac{dF}{dx}(k)=\dfrac{1}{2}f(i+1)-\dfrac{1}{2}f(i-1)[/math] ?

Am I getting close?

Given a list which may contain duplicates, such as {a,b,c,d,a,b}, how can I calculate the number of unique permutations that don't start with, say, a?

that's a second order aproximation for the first derivative [math]\frac{\partial f(x_i)}{\partial x}=\frac{f(x_i+h)-f(x_i-h)}{2h}+\mathcal{O}(h^2) [/math] (in your case h=1)
you can get that by differentiating the quadratic interpolation in [math] x_{i-1},x_i,x_{i+1} [/math]
don't ask me about the g though, I never did interpolation in this weird way with convolutions etc

Why is this class slogging by?

>Given a list which may contain duplicates, such as {a,b,c,d,a,b}, how can I calculate the number of unique permutations that don't start with, say, a?
Inclusion/exclusion principle

Set of words that doesn't start with a=All words - words that start with a=(5!/(2!*2!)-(4!/2!)

[math]9cos^2x+cosx-10[/math]

I am supposed to factor this expression. I am told to "Rewrite the middle term as the sum or difference of two linear factors."

which turns out to be [math]9cos^2x-9cosx+10cosx-10[/math]

What is the sum or difference of two linear factors formula or what does it look like?

I'm trying to find the variation of an anti-symmetric tensor [math] F^{ \mu \nu } [/math] under a Lorentz transformation. So far I've got:[eqn] \delta F^{ \mu \nu } = \delta \left ( \Lambda ^{ \mu } _{ \rho } \Lambda ^ { \nu } _ { \sigma } F^ { \rho \sigma } \right ) \\ \delta F^{ \mu \nu } = -\frac { i } { 2 } \omega _{ \alpha \beta }\left [ \left ( J ^{ \alpha \beta } \right )^{ \mu } _{ \rho } + \left ( J^{ \alpha \beta } \right ) ^{ \nu } _{ \sigma } \right ] \\ \delta F ^{ \mu \nu } = -\frac { i } { 2 } \omega _{ \alpha \beta } \left [ i \left ( \eta ^{ \alpha \mu } \delta ^{ \beta } _{ \rho }- \eta ^{ \beta \mu } \delta ^{ \alpha } _{ \rho } \right ) + i \left ( \eta ^{ \alpha \nu } \delta ^{ \beta } _{ \sigma } - \eta ^{ \beta \nu } \delta ^{ \alpha } _{ \sigma }\right ) \right ] F^{ \rho \sigma }[/eqn]From here I just do the contractions with F and the deltas, but this doesn't look right. Anyone got any feedback?

en.wikipedia.org/wiki/Rayleigh_scattering

>9cos2x+cosx−10
> I am supposed to factor this expression. I am told to "Rewrite the middle term as the sum or difference of two linear factors."
> which turns out to be [math]9cos^2x-9cosx+10cosx-10[/math]
> What is the sum or difference of two linear factors formula or what does it look like?
You were nearly there. Notice that
9cos^2x-9cosx=9 cos x (cos x -1)
and
10cosx-10= 10 (cos x-1)

Therefore
9cos^2 x+cos x−10= (9 cos x +10) (cos x -1)

Why don't we make rocket fuel from water?
Why is it not viable to take hydrogen and oxygen out of water and use it as
rocket fuel? Do we not have any efficient way to electrolysis in large scale?

>Do we not have any efficient way to electrolysis in large scale?
That's certainly one problem.

user, do you know how factoring polynomials works? Bevause that's a binomial of 9u^2+u-10 with u=cos

Thanks for the reply. I'm really not entirely sure what you can go from [math]9cos2x+cosx−10[/math] to [math]9cos^2x-9cosx+10cosx-10[/math]

I don't know why you can plug in [math]9cosx+10[/math]

>binomial
Ignore that shit

I can factor regular stuff like [math]ax^2+bx+c[/math] but this is the first time I have ever factored trig. There's something pretty basic I'm missing. But I'm not sure what it is.

Literally substitute cos=u then factor and replace when you get it done

> (You)
>Thanks for the reply. I'm really not entirely sure what you can go from 9cos2x+cosx−10 to 9cos2x−9cosx+10cosx−10[/math]Idon′tknowwhyyoucanplugin[math]9cosx+10

cos x= 1*cos x = (10-9)*cos x

It's not so difficult, just do the following:
>Literally substitute cos=u then factor and replace when you get it done

It's just factorizing a second degree polynomial, just writing cos x instead of the usual independent variable.

in mathematica i can do for example
>a + b + c //. m_ + n_ :> {m, n}
>{a, {b, c}}

but what if i have a more complicated expression

how do i get from for example
>If[c, a, b] + x
to
>{c, a, b} + x

nvm i got it

>If[c, a, b] + x /. f_If :> {Delete[f, 0]}
>{c + x, a + x, b + x}

How do you solve math without a calculator

dayum you can even do this
>a + b + c /. m_ + n__ :> {m, n}
>{a, b, c}

There are a number of algorithms for many basic things. If you can't long divide in your head you're retarded, bro

That'll only work if c isn't a boolean, otherwise it will evaluate before Replace has a chance to get it. If you want to stop things from evaluating you have to do stuff like in pic related.

what's a "real function"? is it just shorthand for a real-valued function of a real variable

Yes

hi Veeky Forums
I majored in CS and did some math on the side (not enough to be a math minor). I decided to major in math and I'm starting from scratch, but I'm finding most first courses boring as I know most of the concepts already. However, I don't feel confident yet in my ability to completely forgo studying for those courses. Should I just pace up and study by myself the stuff that I don't know and start more advanced material, should I keep with the pace of the lectures (which is going rather slowly) or should I just start looking into more advanced stuff and learn what I'm missing of the introductory courses on the go?
I feel like I should invest time in the introductory courses, but I also feel I'm wasting time by going over stuff that I'm already comfortable with (sometimes it's hard to tell these two apart), so what should I do?

more of an /r/, does anyone use LabVIEW, and anyone have access to the core 1 class they offer? Its 500 dollars from their website, fuck that shit

wow, just found it on an towelhead site cheers

mediafire.com/folder/w69s7binv825r/LabVIEW_course

Set A = {"Hello"}
P(A) = 0.05

Set B = {"World"}
P(B) = 0.1

Obviously AUB = {"Hello", "World"}
but what would be the set of {"Hello world", "World Hello"}?

closest with standart operations would be {AxB,BxA} = {{(Hello,World)},{(World,Hello)}}
what kind of measure is P anyways?

It's called the set of permutations

Would it be correct to say that ML-based prediction algorithms are concerned not with the past and future, but only the present because of the law of large numbers?

P is the probability of the word occurring in a theoretical query.
So would it be 2^2?
|AUB| = 2
|Possible outcomes (word can occur)| = 2

Or am I missing something?

I want to build a vacuum chamber so that I can "plasma clean" the oxides off of pure indium and antimony and run some sputtering tests. I have access to some pretty reasonable Edwards vacuum pumps and vacuum lines. I don't know how to go about constructing a cheap vacuum chamber though.

How can I build a safe vacuum chamber? I'm not sure what design I should go for (cylinder capped on either end vs bell jar on a platform) or how thick the vacuum chamber walls should be.

Too hard for Veeky Forums?

I once asked what 7 squared was and got 0 replies if that puts Veeky Forums into context.

Why is social welfare a "high demand" major nowadays?

I'm having a hard time understanding the Quine-McCluskey algorithm for minimizing boolean functions.

There's a lot of money in nonprofits

How important are lectures for learning? I'm reading some uni math courses but can't go to the lectures. Will course books and internet resources be sufficient?

>In the modern world you need to have a degree to even get a look in
>Not everyone is smart enough to do study a real subject
>Therefore they have to """"study"""" what is effectively Opinion Studies.
That's the sad truth.

this. corporate douchebags think it looks good to donate to "progressive" causes

I'd love to help if I'd taken a course on QFT. Maybe in a couple of years.

Depends on the quality of the material and the extra effort you're willing to put in. Not impossible, but pretty labour intensive.

I'm not really good at math. Not a total brainlet but not "skilled" so to speak. Is it doomed to fail

in probability, what operations would require all events in the sample space to have equal probability?

Chi squared tests for equal distribution

Nothing else though?
Events wouldn't need to be of the same probability for addition/multiplication?

Not that I can think of. Granted I'm no expert

Do I need to get a Phd to get involved in cutting edge medical research? Or is there a faster way?

Just make significant contributions and some institute will give you an honorary PhD. Good luck finding some place that will hire you

how

pay a shit ton of money

Good question.

Even if he did rape a bunch of women, Dr. Cosby's contributions to world were vast

Any chemfags that can help me out here? Please tell me this looks familiar to you:

Log Ps = 4.81(1 - Tb/T)
Where Ps is the pressure of a vapor
Tb is the boiling point of the compound(that got turned into the aforementioned vapor)
T is the temperature at which we want to know the pressure of the vapor

With that I'm supposed to get Ps, but I have no idea if it's in atm, Pa, psi, mmHg, or if the temperatures are in celsius, kelvin, fahrenheit or fucking rankine. I've been looking everywhere but can't find this particular formula, and I should have asked the teacher sooner but you know how it is 'you had x amount of time to ask but now it's too late'.

It's the August equation.

Thanks man that one makes the most sense... though I don't see that 4.81 in any chart. And the boiling temperature is in the denominator. Fuck man this is all wrong, I can't get a reasonable result... Could it be another equation? Or should I just roll with it?

Is there any meaningful use for upper and lower bounds of a set that isn't just defining the supremum and infimum?

Let x = Sum of (10^-p) where p is a prime such that p and p + 2 are both prime.

Then x > 0.0010 and x < 0.0011 but to find the exact value of x would require solving the twin prime conjecture.

how the heck do I prove if [math]0\leq x \leq \epsilon[/math] for every [math]\epsilon >0[/math] then [math]x=0[/math]? Seems like a contradiction would work but I'm not sure what do to after I suppose [math]x\neq 0[/math].

you have a severe case of brainletism.

assume x is not zero, therefore by our assumption x>=0 we have x>0

set eps=x/2 and you have your contradiction

t-thanks
i'm trying to get better user, this takes time.

Prove to me that if x=1+yz
That y=x-z

trivial

well come on then boy do it

let [math]\Sigma[/math] be the set which contains the answer.
qed

FUCK YOU

Draw stuff user.
From the drawing your intuition should tell x=0.
Explain your intuition to a friend.
The proof will hopefully comes out of your mouth without you even realizing it.

How can numbers exist? If I have an infinite amount of numbers, how does it makes sense for any given one to exist? How can a number have a finite amount of digits? How can a given number be picked from an infinite amount of numbers, leaving infinite behind?

I've always thought of joint probability of independent events as a proportion. For the first O you have a 46 percent chance now treat the 46 percent as the whole prob space and then take 46 percent of that giving .46*.46=.2116

Are eyebrows genetic? If i have eyebrows that grow into a unibrow, does that mean i have middle eastern genetics?

>How can a number have a finite amount of digits?
you can write 0 as 0.000... just that the trailing zeroes after the decimal point are redundant (except if you're using them to specify how accurate a measurement is for example) since you know what 0 means

Do doors lose more heat if they are open further or not?
Because wouldn't a door that's only slightly open have a bigger difference in pressure so more air would leave?

Any good youtube channels for learning math progressively from basics to something more advanced, i hated and ignored math when i was younger and now want to learn.

>Any good youtube channels for learning math progressively from basics to something more advanced, i hated and ignored math when i was younger and now want to learn.
youtube.com/user/njwildberger

What's a proof that [math]\binom{n}{2}+\binom{n}{3}+...+\binom{n}{n}=n^2-n-1[/math]
As a related question, how do I search for [math]\binom{n}{m}[/math] on google?

what does this mean? Take example of dice rolling please.

pic related

>What's a proof that (n2)+(n3)+...+(nn)=n2−n−1
try induction

Search for C(n,m).

Anyway C(n,2)+...= C(n,0)+C(n,1)+C(n,2)+... -C(n,1)-C(n,0)= 2^n -n-1

So you wrote that wrong.