/sqt/ - Stupid Question Thread

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If we invent the singularity will it be awesome when the machine assists you when you research stuff? Granted that the singularity does result in a superintelligence it could solve the Millennium Prize Problems in hours. Imagine the computer showing the way and giving you tips while you research them yourself. It would be like a chess computer.

How are gas powered items like weed eaters tested before sent to the retailer? Do they actually put fuel in them ? If so what happens to it after?

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Is there a minimum yield for an atomic bomb?

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Which vitamin/nutrient deficiencies can be self-diagnosed?

>>8848543
why is topology the coolest field of math to study?
>>8848552
not every single lawn mower or weed eater is tested before being sent out. the design and prototypes are tested and once the design is finalized, the manufacturer uses standardized parts in each item to prevent some from breaking and other from not. its not perfect, but most gas powered machines dont break down quickly unless misused, and those that do are either returnable to the retailer or can be repaired/replaced by the manufacturer.
>>8848551
the singularity probably wont ever happen but it would be really cool and existentially scary if/when it does.

>>8848595
why do you think it wouldn't happen?

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>>8848543
Attempting to prove pic related, so all I need to do is prove reflexive relation. It is sufficient to say that for all x, there is some y such that y=x, so the condition that for all x, there exist (x,x) is clearly met, and it is therefore an equivalence relation?

>>8848635
>it is sufficient to say..
sorry, meant
>is it sufficient to say..

>>8848610
i have 2 reasons, one is a more grounded and realistic answer, and the other is more of a realistic conspiracy theory. a singularity would be impossible as of right now with computing power as we are not close to being able to develop AI or an independently thinking computer system. computer processing power is growing at a very fast rate, but that power is useless as of now without humans telling the computer what to do. after all, until we develop an AI thats capable of both thinking on its own and independently learning on its own, a computer is just a machine thats on the same level as a car. i also genuinely believe that the people pulling the strings behind the scenes in governments around the world (jews, Rothschilds, Soros, Illuminati, free masons, aliens, etc...) would be threatened by the idea of having computational power so advanced that humanity would effectively be able to automate every single job in the world, requiring either the abolishment of money altogether, or a standard allowance for people to get by on. i dont think any group in power wants to have their source of power taken away, and theyll suppress it if a singularity ever becomes an issue.

>>8848635
yes

>>8848663
are you lying?

>>8848689
no

>>8848595
Point set topology is awfully dry.

>>8848543
I've been reading and studying math daily for 3 months. I make sure I go through anywhere between 10% of a book to 50 pages of a book a day(which ever is greater). I now find myself dreaming in math and constantly counting things in my head. I get upset and feel old if I make a mistake. Am I actually learning or am I only deluding myself? I want to use my math to earn money either through the internet or by automating something like a food cart.

>>8848704
k thx

>>8848930
Well, can you go back to previous sections and solve problems? I would define that as having learned if so. I can't say how it necassarily relates to your goals though, perhaps a more CS orientated route may be more applicable than strictly math.

>>8848551
I feel like we're closer to solving all the millennium problems than we are to inventing a strong AI.

>>8848656
>automate every single job in the world, requiring either the abolishment of money altogether
this is why I can't wait for everyone to loose their jobs to automation

>>8848930
>I want to use my math to earn money
Stopped reading there.

>>8848543
Surface integrals of vector fields give you the flux of the vector field through the surface.

Surface integrals of f(x,y,z) = 1 give you the surface area of the bounded object you're integrating over.

What do surface integrals of z=f(x,y), a scalar function, give you? My book literally does not tell me what it quantity they calculate, and afaik neither does wikipedia. what the fuck

How can a process have a nonconstant mean?

>>8849083
If its distribution changed over time

>>8848930
>I make sure I go through anywhere between 10% of a book to 50 pages of a book a day(which ever is greater)
The fact that you can do this raises serious red flags about how much you're actually retaining. People studying full-time don't go through anything near 50 pages of material a day. Doing that in a week is a very solid pace.

What the other anon said is a good idea though. If you can solve problems you studied a month ago, you probably actually learned that material.

How is quantum mechanics a random process? couldn't it be that we just don't know what the outcome will be, or that it's simply hard to predict?

>>8849180
do you not understand what "random process" means?

>>8849220
not that guy but I always hate the term "random process" because people never understand it

but I also feel like "Stochastic process" doesn't sound good either

>>8849220
Well that's why I asked?

How would I show the exponential of a diagonal matrix converges?

>>8849259
"random process" does not imply an absence of ability to predict

https://en.wikipedia.org/wiki/Stochastic_process

>>8849263
idk but probably just show each diagonal entry converges

>>8848543
are they playing magic the gathering? I quit playing recently and I kind of miss it already...

>>8848543
why don't we just use a symbol for 1/0 instead of just saying it's undefined?

for example, if we defined 1/0 as z then couldn't we say that 5/0 = 5z?

>>8849349
https://en.wikipedia.org/wiki/Wheel_theory

>>8849349
We do. 1/0=infinity = north pole of Riemann Sphere

>>8849263
o wow i see it now; it was a stupid question

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Having trouble with a problem on ODEs

Uploaded the problem as a pdf, but here's the latex (Not sure if the formatting will get screwed up, but here goes nothing)
Given the following theorem for First order differential equations:

Given the following theorem for First order differential equations:

In an equation of the form
[math]
P(x,y)dx + Q(x,y) dy = 0[/math]

The solution is in the form:
[math]\\
\frac{1}{F} \frac{dF}{dx} = R
[\math]

where
[math]
R = \frac{1}{Q} * \big( \frac{\partial P}{\partial y} - \frac{\partial Q} {\partial x}\big)
[\math]

And the problem is:
[math]
\sin (x)\cos (y)dx + \cos (x)\sin (y) dy = 0
[\math]

So...
[math] R = \frac{1}{\cos x\sin y} \big( -\sin x\sin y + \sin x\sin y
\big)[/math]
which is zero,
\\Because [math]\frac{\partial P}{\partial y} = -\sin y \cos
x[/math] and [math]\frac{\partial P}{\partial y} = \frac{\partial Q}{\partial x} [/math]\\
\\Am I making a mistake?

PS: The solution at the back of the book is given as:
[math]y
y = arccos(c/\cos (x))
[\math]
\end{document}

>>8848586
Given how they work, I'd say yes. The smallest I could find on Google is 0.01 kt.

>>8848990
A surface integral of some vector field dotted with the unit normal vector is flux. A surface integral of some scalar function z on some surface is the sum of the values of z on that surface. For instance if z represents the mass density of some surface as its x,y coordinates change then the surface integral of z on the surface is the total mass on the surface.

>>8848966
>>8848689

>Is it sufficient to say that for all x, there is some y such that y=x, so the condition that for all x, there exist (x,x) is clearly met, and it is therefore an equivalence relation?

Obviously not. What you would have needed to say is that because
1) every element of A maps onto some other element of A, so for all x in A, R contains (x,y) for some y of A
2) R is symmetric, so (x,y) in R implies (y,x) in R
3) R is transitive, so (x,y) in R and (y,x) in R imply (x,x) in R

>>8848975
i agree, but the powers that be probably dont just yet which is why the singularity probably wont happen for a long time, if ever.

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Basically i started studying CS even though im a complete noob.
We doing Haskell now.
I have to write a funktion "berechneNote k b" that sums up two Floats k = "Klausurpunkte" and b = "Bonuspunkte" and gives out a Float. Let the german words not confuse you.
So far i managed to do all that since it's the basics i remember from playing with Haskell for 2 days a year ago.
However if the value of k > 100 it should give you an error message like "more than 100 is imposible" and if b > 20 a different error message. This i cannot do anymore since i just dont have an example for this eccact problem.
I just don't understand where to put "if k > 100" etc...

If possible give a solution with explenation on the syntax.

>>8848543
Why does he pose with the buttcrack?

>>8849421
F isn't really a solution to the differential equation. It's an "integrating factor" - a function which can be used as a scaling factor for the original differential equation so that it becomes exact: [math] \displaystyle \frac{ \partial FP }{ \partial y} = \frac{ \partial FQ }{ \partial x} [/math].

https://www.cliffsnotes.com/study-guides/differential-equations/first-order-equations/integrating-factors

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>>8848635
For all x there is a y such that xRy, but R is symmetric, so yRx. Use transitivity to conclude that xRx.

Just started an intro to probability book and I'm a little confused about notation and i want to make sure I have all of the terminology and concepts ironed out properly.

So if we have a sample space S, a random variable, say X:S->R (call the image X(S)), and a pdf, call it p, it makes sense that p:X(S) -> [0, 1] and when we want to talk about the probability X assumes a particular value we write p(x). Then my book starts using capital P(X = x) out of no where and doesn't really explain what P is. So what is the difference between p and P here?

>>8850046
I still don't really understand how to solve it though... Shouldn't the integrating factor be zero because R is zero?

>>8850605
At least in my stats class, lowercase probabilities were PDFs and Upper cases were CDFs (Cummulative Distribution Function)

ie: In a fair dice roll, f(3) = 1/6
F(3) = f(1) + f(2) + f(3) = 1/2

>>8850605
[eqn]p(x) = P(X = x) = P(X^{-1}(\{x\})) = P\left( \left\{ \omega \in S \middle| X(\omega) = x \right\} \right) [/eqn]

>>8850605
>pdf
Are you working with discrete random variables? If so then the terminology "probability mass function" for p is more accurate.
Most intro books won't be so pedantic, but when you get into continuous random variables (e.g., height or weight, which can take values to arbitrary decimal precision) the analogous "probability density function" -- which is usually then written as f(x) rather than p(x) -- can take values greater than 1. This doesn't violate the laws of probability, but I'll leave it to your book to explain why.

Otherwise, so long as your random variable X is discrete, P(X=x) is basically shorthand for p(x) and they have the same meaning. But when X is continuous you'll need to use something like [math]P(X\leq x) = \int_{t \leq x} p(t) \,\mathrm{d}t [/math] instead.

Sidenote: Even when X is discrete, you can choose to specify its distribution in this "cumulative" form instead, since you can convert between the two using [math]P(X\leq x) = \sum_{t \leq x}p(t)[/math] and [math]P(X=x) = P(X\leq x) - P(X < x)[/math], but when X is continuous the cumulative form is the only one you can use.

Is there an easy way to remove calcium from a solution I need to drink? Calcium ascorbate + broc powder + water and I dont want the calcium.

>>8848543
Does anyone have a reference for a calculus 3 practice set of problems that is just about functions from [math] \mathbb{R} [/math] to [math] \mathbb{R}^n [/math] with solutions but preferably full procedures at the back?

I have a test about these functions next week and I'd like to practice while being able to compare my procedure with the answers. I already exhausted Paul's Math Notes.

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h-hi
just got into series for the first time in calc 2
does pic related converge or diverge and help me solve it pls?
I know comparison test, lim comp test, integral test, root test and ratio test
idk anything about absolutely conv or div yet
I tried using comp test with 1/k (as a p series would be easy if it worked) but it was one of those cases that didnt conclude anything

>>8850865
[math] \sum_{n=1}^{\infty} \frac{2 + cosk}{k} = \sum_{n=1}^{\infty} \frac{2}{k}
+ \sum_{n=1}^{\infty} \frac{cosk}{k} = 2\sum_{n=1}^{\infty} \frac{1}{k}
+ \sum_{n=1}^{\infty} \frac{cosk}{k}[/math]

So this is a series that has all of its partial sums bigger than the equivalent partial sum for the harmonic series.

Now comparison test and you are done.

>>8850865
>>8850878

Wait no no. I am fucking retarded.

Notice that cosine of k always varies inside [1,-1]

So at best the numerator becomes 2 + 1 = 3
and at worst it becomes 2 - 1 = 1

So this sum's partial sums are always larger than or equal to the equivalent partial sum of the harmonic series.

Say I have the usual ring axioms, except the axiom about inverses only mentions the right inverse. Is it still possible to prove the cancellation law?

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Not /sci/ here
Where should be one's eye located to see a real image
https://www.youtube.com/watch?v=h6NqaDxi2KY

It's possible but it never says where one's eyes should be

>>8850878
>>8850886
if the harmonic series is bigger and we know it diverges doesnt that mean we cant use the comp test since the comp test says if the biggest converges so does the smallest and if the smallest diverges so does the biggest?

>>8850901
I proved the harmonic series is smaller than this series.

If the smallest diverges so does the biggest.

When finding the derivative using the definition of a derivative, is it ok if there is an "h" left over in the end?

>>8850934
no because h disappears when you take the limit

>>8850932
o-ok thanks senpai

>>8850938
The problem didn't have a limit though
It just asked to find the derivative

>>8850953
the definition of derivative is a limit

>>8850934
Yeah because the h vanishes.

If we have a random process X we know to be wide sense stationary, is |X| WSS as well?

I know the mean would still be constant but I'm not sure about the autocorrelation

>>8848552
Depends on the item and manufacturer. I know that at Scania here in the Netherlands, were the taktime is a few minutes (every few minutes a fully functional truck is made), they do test every single one. Probably not every little aspect but they sure as hell check is they drive because they are often driven to the customer after.

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Why is the answer u(t-1)e^(-t+1) - u(t-3)e^(-t+3)
and not u(t-1)[1 - e^(-t+1)] - u(t-3)[1- e^(-t+3)]?
If I use convolution, my bounds are from 1 to t and from 3 to t
When I plug in t in the integral I get e^0 which gives 1.

>>8851039
what did you get instead of y(t)=s(t-1)-s(t-3)?

>>8851039
Why are you doing an integral? You're given the step response and step inputs

>>8850953
Oh so the h = 0

>>8851058
I understand the answer is easy to come to just by looking at it but shouldn't I be able to use convolution to solve it too? I guess by step response they don't mean impulse response

>>8851069
No they obviously don't

Step response is the result of the convolution of u(t) and the impulse response

suppose [math]\mathcal{R}[/math] is an equivalence relation on a set X. then [math]\mathcal{R}[/math] is an equivalence relation on [math]X'\subseteq X[/math] right? or is there a counterexample

>>8848592
plz go see a real doctor and have your blood tested, it costs less than 100 dollar

>>8849923
it's only cropped like that

>>8850840
no. also you can't overdose on calcium.

>>8851188
my blood's tested every 2 months when i donate blood so i know i have enough iron but i only know that once they prick my finger to test

are there really none that can be tested without 100 dollars? it's something i'd want to be able to check sort of regularly, i'm just a grad student who gets into shit diets sometimes so it'd be nice to be able to know what i'm missing

>>8851169
>suppose R is an equivalence relation on a set X. then R is an equivalence relation on X′⊆X right? or is there a counterexample
just think about it

>>8851204
stop donating blood. it's enough when you do once per five years and only 5 times in your life.
how shitty is your diet? i'm almost sure you dont miss anything.

How do I do GR?

I learn how to calculate things like covariant derivatives and play around with index notation and metrics but none of it means anything to me.

I have no idea what I am doing

>>8851206
i assumed it was true because the [math]\forall[/math] conditions are inherited by the subset. is that right?

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>>8851169
If [math]\mathcal{R}[/math] is an equivalence relation on a set [math]X[/math], then the sets [math][x]_\mathcal{R}=\{ y\in X\ |\ x\mathcal{R}y\}[/math] partition [math]X[/math]. Now, restricting to a set [math]X'\subset X[/math], one gets a partition of [math]X'[/math] with sets [math][x]_\mathcal{R}\cap X'[/math], defining an equivalence relation [math]\mathcal{R}'[/math] on [math]X'[/math] by [math]x\mathcal{R}'y \Leftrightarrow (x\mathcal{R}y)\land (x, y\in X')[/math].

>>8851214
>stop donating blood.
but it helps people, it's too easy to save lives to not do it

>how shitty is your diet?
sometimes i'll eat instant noodles exclusively for 2-3 days, and i usually eat vegetables once a month

>>8851219
yes
as >>8851221 said equivalence relations are in bijection with partitions, so deleting the representatives of each equivalence class that aren't in X' gives a partition of X', and so gives an equivalence relation on X'

>>8851223
>but it helps people, it's too easy to save lives to not do it
it hurts your own life if you overdo it. stop it for minimum three years if you did it more than twice in one year.
>instant noodles exclusively for 2-3 days, and i usually eat vegetables once a month
that's alright for a period of a year or even two

btw if your diet is so shitty, I hope they throw away your blood. i wouldnt want to receive your shitty blood if i were ill.

>>8851243
>it hurts your own life if you overdo it.
wouldn't they recommend a longer wait time between donations if so?

> stop it for minimum three years if you did it more than twice in one year.
i've been trying to do it 6 times per year for the past 4 years or so

>btw if your diet is so shitty, I hope they throw away your blood. i wouldnt want to receive your shitty blood if i were ill.
they tell you if they throw it away and they've never told me so I guess it must not be that bad

>>8851243
I've done it 5 times the past years, what's so bad about it?

>>8851261
past year*

>>8850840
Why would you remove calcium?

First, filter the powder out, coffee filters work fine just as any porous fibre.
Then precipitate calcium either as sulfate or carbonate (pick whichever is easier for you to get at food-grade purity):
a) sulfate route
Add a solution of MgSO4 (Epsom salt) or Na2SO4 (Glauber's salt), the difference is that with Epsom you're adding magnesium to your solution and with Glauber's it's sodium.
b) carbonate route
Add aqueous Na2CO3 to the drink. Na2CO3 can be prepared by heating NaHCO3 (baking soda) to 50-100 degrees Celsius until it stops producing CO2.

Filter out the calcium sulfate/carbonate. Finally add the broc powder again.
Check out the alternative names for these compounds.
Alternatively you could tinker with phosphates, stearates, or whatever.

>>8851294
dude no this will make mustard gas

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A question on MATH progression.

I've never had a formal treatment on algebra topics, should I get my feet wet on those before starting Spivaks? Or can I get to that when I am done?

IF I indeed need to understand everything related to Algebra, should I give Artin a try?

>>8851330
i'm assuming you mean spivak's calculus

i've never read it but i don't think you need any abstract algebra for any calc 1-2 material

>>8851344

Apparently Spivaks Calculus is more like a intro to analysis book, so people say.

Do I need Algebra for that, what do you think?

>>8851357
probably not

but it's worth learning algebra anyway

>>8851294
the broc powder is full with calcium, too

>>8849421
Recall that the differential of f(x,y) is

df = (df/dx)dx + (df/dy)dy

Now look at the ODE you were given. It matches this form. This means that there could be a function f whose differential is the given ODE and whose value df = 0.

If this is true, then P = df/dx, Q = df/dy.

We know that the mixed partial derivatives of a function equal eachother, so an easy way to check if f exists is to take the derivative of P wrt y and the derivative of Q wrt x and see if they equal eachother.

In your case, they both equal -sin(y)cos(x) and so we know f exists. We call this ODE exact.

Now the task is to find f. You use the clues available to you.

Take the integral of P wrt x:

f(x,y) = -cos(x)cos(y) + C

We know C cannot be a function of x, since it disappears upon differentiation wrt x, so this becomes

f(x,y) = -cos(x)cos(y) + h(y)

Now take df/dy and see how it compares with Q.

df/dy = -cos(x)sin(y) + h'(y) = cos(x)sin(y)

h'(y) = 2cos(x)sin(y)

Integrate

h(y) = -2cos(x)cos(y) + C

Now we know what f is.

f(x,y) = -cos(x)cos(y) - 2cos(x)cos(y) + C

= -3cos(x)cos(y) + C

Since the differential of f is 0, we can say that f = D, some constant, since the differential of a constant is always 0.

D = -3cos(x)cos(y) + C

Combining constants and solving for y gives

y = arccos(C/cos(x))

Note: The constant of integration in h is usually ignored, since it always combines later.

>>8851364
>>8851344

I have another question, friend, to you or anybody who has any idea.

I am studying elementary geometry and I also read some of the Geometry chapters in Langs Basic Math, or what he calls ''Transformations'' (Mapping, Isometries, Congruences, etc)

After I was done, I wanted to move to a book called ''Introduction to Geometry'' by Coxeter which is another book which deals with geometry through transformations or algebra.

I suppose a treatment of abstract algebra would be preferable than any other training in calc?

>>8849906
> Studying CS
> Actually using a good language
Im fucking envious
I also see u are german, would you mind telling me where u study?

>>8851369
Drink water instead.
Again, why do you want to get rid of calcium?

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Can anyone help me out with pic related please?

>>8849906
I sure hope they aren't having you start off in Haskell in your university. It's a fun language but you're going to do have to do a lot of relearning once you end up on a C-based language later.

main = do
k <- readLn
b <- readLn
k > 100 -> putStrLn "K is too big"
b > 20 -> putStrLn "B is too big"
do your other garbage here

I *think*. /dpt/ on /g/ is full of haskell lovers so you might have better luck there.

>>8849906
yourFunction :: Float -> Float -> Either String Float
yourFunction k b
| k>100 = Left "k more than 100 is impossible"
| b>20 = Left "b more than 20 is impossible"
| otherwise = Right (k+b)

Either is a method of linking two types together. Either String Float (you can use Either with other types, obviously) is either a Left with a String (e.g. Left "abc", Left "qwerty") or a Right with a Float (e.g. Right 4.0, Right pi).
Now for the syntax: the | deal is called guards. Guards work like if/else if chains: the function will check if k>100, if yes then it will return Left "k more than 100 is impossible". If not, the function will check if b>20, if yes it will return Left "b more than 20 is impossible". If not the function checks "otherwise". Haskell's otherwise is a condition which is always true (in fact it is equal to True). In this case the function must return Right (k+b). Notice where the = marks are.

If you really want to, you can make it an explicit if/then/else chain:
yourFunction k b = if k>100 then Left "k more than 100 is impossible" else if b>20 then Left "b more than 20 is impossible" else Right (k+b)
but it's more cluttered.

Enjoy reading up on http://learnyouahaskell.com/syntax-in-functions#guards-guards, hoogle and wikis.

>>8851723
I meant to have double spaces before each |.

>>8851294
Thanks. I wanted to remove calcium because it further exacerbates my digestive problems.

>>8851204
why dont you just monitor the nutrition in your diet and estimate from that your potential deficiencies?

>>8851764
there's tons of factors that affect intake of vitamins/nutrients (i.e. orange juice helps you absorb iron, but caffeine and chocolate do the opposite), i don't know all the different interactions

i guess it's not practical to expect to be able to really monitor these things without drawing blood

Is there any math branch similar to black magic (aka weird symbols, graphs and completely abstract stuff that just werks)?

What is the point of The Belmont Report? It literally added nothing to the IRBs, so why was it created at all?

>>8851881
> Is there any math branch similar to black magic (aka weird symbols, graphs and completely abstract stuff that just werks)?
inter-universal teichmuller theory

What are good scientific hobbies to get into? Is programming any fun? I've been spending too much time on /pol/ and want something else to occupy my time.

>>8851927
>What are good scientific hobbies to get into?
working through textbooks
reading papers

>>8851949
Literally, neither of those things are interesting. I want to do things myself, not just read about it.

>>8851958
you'll get ideas for things to do from papers
you get the background to do these things from textbooks

>>8851927
Programming is a surprisingly fun, interesting and useful hobby. Pick up some basic python, then do this Haskell course:
http://www.seas.upenn.edu/~cis194/spring13/lectures.html

(If you're going to program as a hobby you might as well use the languages that aren't butt-ugly)

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you\re playing a gambling game that has only a 42.22% chance to win.

you have $100000. and start with a $392 bet
- you bet 0.392% of what you have after a win and every win after that
- you bet 2 x 0.392% after a loss, then double that bet for every loss that immediately follows a previous loss (basically you're trying to earn back your loss after every loss)

1. whats the probability of you walking out with a profit after 40 games?
2. approximately how many games would it take for you to go broke with a 99% probability?

How do I prove that [math]J = (\vec{J}, c \rho) [/math] is a four-vector?

[math]\vec{J}[/math] is the current density, [math]\rho[/math] is the charge density, and [math]c[/math] is the speed of light.

>>8850850
Shamelessly bumping my question.
Come on, there has to be something.

I tried looking for books but all I find are books with, at best, the answer at the back and that is useless for me.

can I learn calculus using Spivak's book even if I had a poor high school education? If not, what would be a good book to learn calculus and to use as a kind of a prerequisite to Spivak's?

ty

>>8852403
>can I learn calculus using Spivak's book even if I had a poor high school education?
only you can answer this

try opening spivak and see how far you can get, and how many exercises you can do

>>8852403
Try it, if you're having a bad time watch the Khan Academy's Calculus sequence, and use Stewart for practice.

>>8852424
>>8852424
I did and I was just starting chapter 5 as I was typing that post; it is very well written and the theory is great but I'm having trouble with some of the problems

actually I'm looking for a good calculus book, maybe even a precalc book, to learn by my own because I don't think I'm able to do Spivak's with my not-so-solid background in HS math, to be frank with you

Apostol's calc books and Velleman's how to prove it would be the recommended books for me to start?

ty

>>8852449
I was thinking of Apostol but I'll take a look on Stewart

ty

Need some medical help please.

So, I got surgery to repair a fully ruptured achilles tendon a few weeks ago. Had a cast on for 10 days, then was put into a ankle brace.

Yesterday I accidentally stepped on the foot in the wrong way and really stretched the tendon passed its limit, and I was bleeding quite a bit through my open wound. However, I know that the tendon is still attached.

Is there anything that could have gone wrong that I should see a doctor for? Or do you think I just need rest and wait for it to heal? A tendon cannot grow in the wrong way, can it?

I fucked up /sci/.

I've got 5 hours to finish a research paper I haven't started. The dataset is for 2012 US Presidential Campaign Contributions, I just need to come up with a solid hypothesis that my professor says needs to be of "relative complexity"

Right now all I can think of is "The republican party, on average, receives more money than it's competition during the election season."

Does anyone have any ideas for what I should do for my hypothesis because the one I've got so far is shit.

>>8852751
Look into the way industries hedge their bets and donate to both sides e.g. casinos.

What industries donate a lot? Is it industries that are much affected by government regulation?

Contrast rhetoric with donations received and votes taken.

>>8852751
get working son, nothing like the last minute, is there a re-submit option?

>>8852745
How did you rupture out of curiosity? I would at least call the doc.

>>8852787
Thanks for the input, decided to go simple and make the claim that the republican party gets most of their contributions from the souther states (as defined by the US census)

>>8852823
Due at 1pm EST, and nope, all nighter tonight.

>>8848543

if conformal maps are used to "transform" complicated boundaries into simple ones (rectangles) would another problem be the region having a hole that still doesnt look nice after the initial boundary becomes nice and thus the problem is finding a function that makes both the boundary and holes of the region nice? is that a type of problem or is this never a concern?

>>8852104
One way to do it is to break the charge density into the sum of every charged particle
[math]\rho (\vec{x},t)=\sum_i q_i \delta^{(3)] (\vec{x}-\vec{x}_i (t) )[/math]
where x_i are the position of each charge, and
[math]\vec{J}=\sum_i \vec{v}_i q_i \delta^{(3)] (\vec{x}-\vec{x}_i (t) )[/math]
And see that this quantity transform as as 4-vector.

Energy warps spacetime.
So if you have a spring, how is the energy (and warping) distributed? Uniformly across the spring? Only at the end?

Furthermore, what about Gravitational potential. If you are on a platform, where is your GP located? Inside you? Where you are going to land?

And GP and KE are all contingent on the reference frame. So different observers would see different amounts and locations of spacetime warping? I thought gravity was invariant.

Could I realistically land a job with an associate's/certificate in computer science from my local community college? I'm thinking of going to school for it but wondering if it's useless and if I should aim for a bachelors instead

Best way to start learning basic theory of general relativity?

>>8852971
Landau, Classical Theory of Fields

How would I go about citing this in the IEEE format?

https://www2.census.gov/geo/pdfs/maps-data/maps/reference/us_regdiv.pdf

>>8848543

If I travelled in a straight line up from my current position, with a velocity enough to keep my trajectory close enough to travelling as straight as I could possibly go, would I eventually find a planet that is in the exact same position that my initial starting point was?

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Okay, what test do I use to check whether eye colour is inherited?

>t.guy who should've paid attention in stats class

according to one patent of 1899 if you take aluminum stearate, aluminum resinate and aluminum oleate and mix it in some benzol you will get a tranparent plastic.in the patent it is stated that it can be used as a replacement for celluoid. what is this called? is it made today? why didnt it replace celluloid?

In regular expressions does:
[math]ab*+ab[/math]
mean a(b* + a)b or a(b* + ab)?

>>8853131
a(b*+b)

How do I prove something via inductive reasoning?

>>8853186
>How do I prove something via inductive reasoning?
1. Prove for n=1.
2. Prove it for n+1 assuming that it is true for n.
3. ??????
4. Profit.

>>8853077
>if stuck half-way into a question, show your work so far

Here is me trying to work it out manually:

[code]void chi ()
{
num observed[] = {2524, 1060, 528, 896};
num expected[] = {2184.18, 1339.82, 867.82, 556.18};
num output = 0;

for (int counter = 0; counter < 4; counter++)
output += sq(observed[counter]-expected[counter])/expected[counter];

std::cout << output; // Output is 452
}[/code]

Which seems way too high, but Rstudio gives me:

[code]> observed

Parent_Light Parent_Dark
Child_Light 2524 1060
Child_Dark 528 896

> chisq.test(observed)

Pearson's Chi-squared test with Yates' continuity
correction

data: observed
X-squared = 474.66, df = 1, p-value < 2.2e-16[/code]

Which also seems extremely high, but also fairly substantially different from my C++ answer. Also that is one absurdly small p-value. Am I on the right track?

So guys, I have a trivial problem for you and the solution isn't what I'm asking for.

Imagine doing a simple geometry test:
A. Prove that a given plane E is equal to a family of lines g.
B. "Check if any g intersects with the x3-Axis and if so state the point in which they intersect."

Now imagine you solved A and E is equal to g. Checking whether g intersects with the x3-Axis is more complicated than checking whether E is BUT does B imply that one has to state which of the lines in g intersect with x3?

>>8853197
How do I solve #2 though?

>>8853451
>How do I solve #2 though?
That depends on the problem. For example, to proof that 1+2+...+n=n(n+1)/2.

1st step: 1=1*(1+1)/2=1.
2nd step: 1+2+....+n+(n+1)=(n(n+1)/2)+(n+1)=(n^2+n)/2+(2n+2)/2=(n^2+3n+2)/2=(n+1)(n+2)/2.

Q.E.D.

4chan has devolved into an endless cavalcade of fallacies, lies and memes.

Knowing this, is there any reason whatsoever to get into an argument ever?

>>8848543
X is a compact set.
f:X to X is an isometry.
Prove that f is onto.

>>8853499
if connected then obvious because continuous
otherwise, no. consider a row of spheres and f sending each sphere to the next with the identity

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How do you know if a certain area is polluted with ionizing radiation?
And what steps needed to take to protect one self from it?

>>8853477
>>8853477
>4chan has devolved into an endless cavalcade of fallacies, lies and memes.
this your first day on 4chan?

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Can I change the maximum speed of light?

I've been working on a Physics project that was split into two seperate, but related, experiments (call them A and B)
In a lab report would it be better to structure it as:

Method for A
Results of A
Conclusion of A
Method of B
Results of B
Conclusion of B

or

Method of A
Method of B
Results of A
Results of B
Conclusion of A
Conclusion of B

Now I'm writing it out maybe the first way would be better but keep both conclusions until the end?

>>8853603
You'd use a Geiger counter which detects the amount of radiation in the air.
The type of protection you need depends on the type of radiation. Alpha radiation is Helium nuclei which are pretty big so can't even pass through paper. Beta radiation is electrons which are more dangerous since they can penetrate your skin. Gamma radiation is even more penetrating.
There's not too much you can do to protect yourself fully from radiation in the air, unless you surround yourself with lead or something. Hazmat suits are normally worn but the main purpose of that is to stop contamination and prevent you breathing in anything dangerous.

Hey guys, I recently started a course in statistics and probability and there's one concept I can't really grasp.

Imagine you have an urn containing r red balls and b blue balls. You want to calculate the probability of getting k blue balls after taking n balls out of the urn.

The total amount of outcomes are [math]{(b+r)}\choose{k}[/math] - so far so good.

But calculating the successful outcomes is where I don't get it. My book says according to the multiplication principle we do [math]{b}\choose{k}[/math] * [math]{r}\choose{n-k }[/math]. Why? Doesn't make any sense to me. How can we first calculate only for the blue balls, when they're mixed together with the red ones. And why doesn't the order matter?

>>8853656
>Geiger counter
https://www.youtube.com/watch?v=rNe1UBfJvoo
Is this legit?
I'm asking because my boss, wants me to go to an area with a lot of new cases diagnosed with cancer.

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>>8852971

>>8853677
picking n balls is picking k blue balls and n-k red balls

>>8851215
open a book

>>8853677
heh, blue balls

why are they hiding flat earth

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what am I doing wrong /sci/?

as far as diagonalization goes the order of the eigenvalues in D shouldn't matter as long as the corresponding eigenvectors in P are in the same order and you should be able to multiply the eigenvectors in P after the Gram-Schmidt process by any non-zero constant and they remain valid, right?

What is consciousness?

>>8853708
looks a bit questionable, but there's a lot of people saying it worked for them so maybe it does genuinely work. although that might be best for detecting radiation coming from objects held close to it rather than in an area.
If a real geiger counter is too expensive, you might be able to rent one from somewhere online, or maybe from a university. Firefighters might have one too so maybe you could call them to check it out if it's really important.

>>8853811
the question says P should be orthogonal

>>8853677
Let first [math]X[/math] be the variable equal to "the number of blues balls in the urn after n balls were picked out".

The value of X go between 0 (if all the blue balls were taken out) and b (if none were taken out)
[math]X(\Omega) = {0;1;...;b}[/math]

For k between 0 and b,
[math]P(X=k) = \frac{\binom{b}{b-k} \binom{r}{n-(b-k)}}{\binom{r+b}{n}}[/math]

The reasoning goes like this. If there is k blue balls left, it means that b-k blues balls have been picked and n-(b-k) red balls have been picked (because overall, n balls were picked). We divide this value by the total number of outcomes.


Using the "total probability formula" for the "complete event system" [math](X=k), k \in {0; ... ; b}[/math] (I'm not an english speaker, maybe you don't now tkhis theorem by this name), and calling [math]B[/math] the event "picking blue".

[math]P(B)=\sum_{k=0}^{b} P(X=k) P_{[X=k]}(B) = \sum_{k=0}^{b} \frac{\binom{b}{b-k} \binom{r}{n-(b-k)}}{\binom{r+b}{n}} \frac{k}{r+b-n}[/math]

Which is not so bad after all. I may be wrong (I'm a student just like you), and maybe some case distinction is needed (if n is too big...).

theoretical physics is generally regarded as the hardest degree but is it the most beneficial? I'd only study it over another course for the benefits and I'm not interested in the field of tp itself.

What course would best fit someone who's favourite subjects at high school were maths and applied maths? What maths based degree is objectively the most useful?

>>8853880
uhhh why not applied maths if you like math but are paranoid about not being useful

>>8853880

Discrete math imo

>>8853656
>Now I'm writing it out maybe the first way would be better but keep both conclusion until the end

Yes, I'd do A A, B B, A B

>>8848543
In my chem class, the professor just pulled E = E° - (0.0592V/n)log(Q) out of nowhere. Previously we were working with E° = (-RT/nf)ln(Q) so I assume they're related, but I can't find the relation.
Is 0.0592 derived from something or is it just a magic number that I need to memorize?

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How to get from step 3 to step 4?

How do I determine variance from measurement accuracy?

Specific: I have an optical telescope with a 1 arcsec / pixel CCD. I want to measure the right ascension of an object that's only .5 arcsec across. If a pixel lights up that says the object is at, for instance, 100 arcsec, what's the variance on that measurement?

>>8854264
it says how on the right...

>>8854264
Oh shit, is it as simple as [math]sqrt((e^{2t}+1)^2)=e^{2t}+1[/math] and simplifying from there? For some reason I was thinking a set of terms squared then square rooted doesn't equal the set of terms, but they just cancel don't they?

>>8854277
>Oh shit, is it as simple as [math]sqrt((e^{2t}+1)^2)=e^{2t}+1[/math] and simplifying from there?
yes

>For some reason I was thinking a set of terms squared then square rooted doesn't equal the set of terms, but they just cancel don't they?
yes sqrt(a)^2=a but sqrt(a^2)=|a|

>>8854272
Yeah I know I wsa questioning how to remove the radical, but I think I got it: the radical just cancels since the terms within it are all being squared right? so you can safely remove the power of 2 and the radical at once?

>>8854285
>>8854280
ty, forgot about the absolute value portion

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Could I arrive at the answer of 1.8581 without actually integrating? The question says to use a calculator to approximate the integral, but I don't know if I have to integrate first..

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>>8854388
>his calculator cant integrate

>>8854093
It's a number that takes into account the ln > log conversion and some other constant, like R and probably even T = 298K. Not sure if I'm missing something, it's been a while. Memorizing it it's definitely easier, I was used to use 0.05916, but it's basically the same.

>>8854264
One thing i didn't get is where the +2 went in the solution, when you go from step 3 to step 4.
Can you simply ignore it ? I don't see any way of cancelling it, except maybe using eulers identity...

>>8854420
look to the right of step 3

Any GNU/Linux users here? What programs do you use for math? Specifically, I'm looking for something that computes definite integrals and something that I can plot vector functions and such on.

>>8854454
I mostly just use wolfram
the premium account is really worth it imo

>>8854429
Yeah, i read it in the wrong direction. Thx.

Why is it that when I see unsettling shit like closeup pictures of parasites or Man After Man drawings, I want to take off my socks?

>>8854402
Ah, that makes sense. 0.0591407 is what I got when I used R=8.3145, T=298K, f=96485, and multiplied the whole thing by 2.303. Slightly different number, but close enough that my brain can accept that it's not completely arbitrary.
Thanks, I'm a programmer so I often feel very out of my depth when dealing with Chemistry.

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so to solve this it's just 1/6 * 1/6 * 1/6 ?

or am I retarded

>>8854667
you're retarded

>>8854700
pls explain ;_;

>>8854700
oh no wait i read it wrong it's just 1 / 6^5

right

>>8854718
(1/6)^5

>>8854725
well i mean that's the same thing isn't it

>>8854727
The results are the same in this specific case, but it's still important to be correct. (x/y)^z is very different from x/(y^z)

>>8854743
well I mean yeah but 1 to any power is one so it works out when I'm doing it in this case I guess

Alpha Centauri is the closest star system to us, but are we the closest star system to Alpha Centauri?

>>8849906
>| k>100 = Left "k more than 100 is impossible"
>| b>20 = Left "b more than 20 is impossible"
>| otherwise = Right (k+b)
>>8851678
>>8851723

berencheNote:: Float -> Float -> Float
berencheNote k b | k>100 = error "k more than 100 is impossible"
| b>20 = error "b more than 20 is impossible"
| otherwise = k + b

>>8854763
Why the fuck do you care?

>>8854927
>hurr what kind of retard has intellectual curiosity

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how do i solve this

>>8854980
>do my homework for me
Jesus dude, did you even try? This is not what these threads are for.

>>8854992
I don't care about the answer I just don't know how to solve the problem or even start solving it

>>8854995
>I don't know how to start
That's a load of shit. You can't come up with a single coherent thought about this?

>>8855001
idk, on a 3 sided the prism I have no idea how to find out what the chance of getting the same color each time is

I know the chance of getting red both times would be 2/3 * 2/3 and for blue it would be 1/3 * 1/3 but I have no idea for "same color".

Same thing with the balls

Would knowing how to write math proofs help me in science?

>>8855189
Not directly, but it will help to build the ability to reason through things and build statements that you can know to be true because of logic without necessarily needing to test every step.
Plus more maths never hurts.

>>8855371
I'm contemplating whether I should do /sci/ proud and teach myself hardcore math even though my major (environmental science) is not very math heavy. I'm hoping once I'm done, it'll actually help somewhat.
Good idea?

>>8855383
at least learn something somewhat related

i'd assume differential equations show up in the harder parts of environmental science

>>8848543
Can intelligent people live a life that isn't utilitarian it seems normies are more orderly the intelligent people is this possible?

Also why are intelligent individuals seen as weird?

>>8855388
yeah they do

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Does /sci/ into MOOCs?

https://www.edx.org/course/teaching-social-justice-through-teachforamericax-sjsm-tfax

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>>8855509
Maybe some higher math?

https://www.coursera.org/learn/theorie-des-distributions/

I signed up for a geometry course as a non-math major to try and imporve my math skills and I'm cleary too fucking stupid for this.

Can someone help me with what should be a simple problem?

I have two great circles on S2 with C1 having equation x+y+z = 0 and C2 having equation y = 0

They clearly interersect at (1,0,-1) and my solutions say the acute angle between them is arccos(sqrt(3)/3) but I have no idea how this angle was determined. I've spent hours trying to figure this out. It should'nt be hard but I can't wrap my head around this spherical stuff.

I took this class as an elective in my final semester and now I might fail it and have to stay an extra semester.

>>8855012
you go through each possibility

ie:
2/3 you red first roll and 2/3 times you get red second roll. So of the 2/3 times you get red you get the same color 2/3 (of your inital 2/3 of getting red) = 4/9

Doing the same with blue is 1/3 you roll blue with the same colour being 1/3 (for your 1/3 chance of getting blue) or 1/9

Add them both together = 5/9 times

This simplifies the total possibilities where R1 = red side 1 and R2 = red side 2.

R1R1
R1R2
R1B
R2R1
R2R2
R2B
BR1
BR2
BB

You can see from all the combinations (9 total) 5 result in either RR or BB

Why do we dream?

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How do I do this- I'm dumb

>>8856191
we dont know for sure, but there are a couple of hypotheses.

>your brain conducts maintenance and growth processes at night and fires signals during this. your concious mind tries to make sense of the random noise since thats what its designed to do and thats a dream

>at night our brains evolved a way to make use of this otherwise wasted time to run a training program of sorts which is a dream hence why they often have to do with events from the day before

>your brain sorts out its memories and new information at night and you are experiencing this as dream, again answering why they often involve events that happened before

are examples i can recall off the top of my head. there are tons of studies running on this so expect new discoveries on sleep and dreams any day now (tm).

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>>8853065

Don't you love it when you stump the normies with a absolutely straight forward question in an AMA /sci thread.

TFW not one fucking aspie could offer an actual answer to a basic trig/geometry question.

Go fuck your forever alone fleshlights you sad, sad, units. /sci is /b, a place filled with immeasurable twits who call themselves human.

Also

/thread

inb4 I have the answer to an easy question.

I'm working on a video game and elemental weakness is stored as a composite of the following numbers:

0x80 - Fire
0x40 - Lightning
0x20 - Ice
0x10 - Wind
0x08 - Earth
0x04 - Water
0x02 - Holy
0x01 - Dark

You can only have one of each number but it could have all, or none of them. So the range of potential results are 0 ~ 165.

I'm trying to find a way to work out which elements were used just from the composite. So far I have this:

is last digit odd, 1 present
last digit 4, 4 present
last digit 8, 8 present
last digit 2, 2 present
last digit 6, 2+4 present
second digit odd, 10, 8 and 2 CANNOT be used together. Either 10. or 8+2.
Second digit 60, 40 present
>85 - 80 present
Second digit 40, 40.
second digit 20, 20.

My biggest issue is that when 8+2 are together it ruins any reasonable check I'd make for 10. Is there a more elegant system than a series of logic checks? and if not then is this even possible?

Thanks.

Can someone draw a circle over cape canaveral that would represent the slice of sky 6km above ground as seen by a person lying at ground level?

Does infinite density exist or is it just a meme?

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>>8856687
maybe i've just misunderstood something but is this not just using the bitwise AND operator?

for instance
assuming 10000000 is fire and 01000000 is lightning
flaming lightning would be 11000000
to check that lightning is present, you would just see if the bitwise AND is equal to lightning

11000000 & 01000000 = 01000000

this also works for composite elements

ice lightning = 01100000
to check if flaming lightning has ice lightning, do the AND

11000000 & 01100000 = 01000000

because this is equal to ice lightning, it does not contain ice lightning, but it IS nonzero (it represents the elements shared by the two composite elements), so this is why you have to check for equality rather than just a nonzero number when checking composite elements

Is there a better method/shortcut for evaluating integrals of the form

[eqn]\int_{a}^{b}xe^{cx}dx[/eqn]

They arise very often in probability but doing them by parts is tedious and long.

>>8856772
should be x^n here, not just x

I'm wondering if I've picked the correct subject upon discovering something about myself in college. We had 15 assignments during the course of this year, 3 for each subject - maths, physics and chemistry.

I've always hated maths, loved physics and loved chemistry, so I applied for Astrophysics in Uni, but as I've actually started doing this I've found I actually loath chemistry because to me its boring as fuck.

When I started the course and did my first three assignments, I got a Distinction in Physics, Distinction in Chemistry and a mere Pass in Math. But since then, all of my assignments I've gotten a Distinction in Maths and thoroughly enjoyed it, while for chemistry my grades have bombed.

Did I make the right choice? I hope so because I can't change subjects now but I hope there's lots of maths involved in Astrophysics (never thought I'd say that) and less chemistry.

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>>8856777
I think integration by parts is the only way of doing it. However when I do integration by parts I find it helpful to do all my work in a table, like pic related. It is a nice shortcut especially when n is large, and you need to do it multiple times.

>first intro to stats test
>get a 65%
>class average is a 70%
>no curve

How fucked am I?

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WHAT THE FUCK?!

>>8856841
try again in english this time brainlet

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>>8848543
Why is science so depressing? I dont have a profession with it, but I love it as an amateur a lot and also understand most of the concepts, read the raw research myself from time to time.

But going through life, and knowing a little bit about many of the theories, and how reliable they are. And how they potentially can fit in your own life...fug its hard. Walking through life trying to theory craft, calculating chances, living entirely in the metaphysical. It is as if my senses are dulled and my soul has almost vanished.

Its great to avoid strife in life, and to avoid work conflict if you can live in the metaphysical of what the other person may think and may have done. But its not so great for your own self as it removes you from your more basic self.

For the rectangle with vertexes (1,0), (0,1), (2,3), (3,2), how do I set the intervals for x and y in order to solve a double integral?

>>8856848

I wrote it specifically with big fucking letters in paint for retards like you. kys

>>8856868
no you didn't brainlet, still looks like little slavshit letters to me

>>8856841
did you pick 1 root and the answer is 2 roots or did you pick 2 roots and the answer is 1 root?

>>8856871

It says ROOTS you fucking moron.

>>8856878

RED = WRONG, so that's what I picked, even though CLEARLY it's fucking right - unless wolfram alpha is mistaken as well.

>>8856900
>RED = WRONG, so that's what I picked, even though CLEARLY it's fucking right - unless wolfram alpha is mistaken as well.
it's not right, draw a picture and you'll see

>>8856900
if you're so convinced there's two roots why not list them so we can tell you which one is wrong?

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>>8856951
>>8856966

>>8856769
You're quite right. I assumed that 8+2 (holy+earth)on a binary level would be identical to 10 (wind). So AND would incorrectly flag it, that'd be correct if 8+2 was equal to 10 in hex, it's actually equal to 'a'.

I was overlooking something basic, a product of staring at a screen too long. Thanks a lot for the help.

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>>8856981
your picture is wrong

>>8856981
brainlet

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Guys, can you please help.
Is this correct?
It's in the context of a Taylor series.
T-t-thanks.

>>8857017
Yes

if science is great then how come no one figured out how to win the lotto?

>>8857032
http://www.dailymail.co.uk/news/article-2023514/Joan-R-Ginther-won-lottery-4-times-Stanford-University-statistics-PhD.html

>>8857032
>no one figured out how to win the lotto?
Because there is no winning strategy.

>>8857032
We have figured it out, but our Jewish overlords prevent us from revealing it to the masses.

>>8857023
I got it right? F-f-fuck.
Thanks friend.

>>8848543
I don't think this deserves its own thread, so I guess it goes here.

I won't dive too much into the details but something I'm writing takes place in a fantasy setting that has, among other things, magitek computers, which I'm designing based on old analog/mechanical computers like the antikytherean device, the Millionaire Machine, Michaelson's harmonic analyzer.

The question I have is how might I design a whiffletree with exactly twelve possible outputs, with a unique input for each? Since it's magitek/alternate reality stuff the input doesn't necessarily have to be purely binary. I'd like it if it was, but I think that might be mathematically impossible.

I rigged up something that might work (picture in next post) but since I'm sorta eyeballing it I'm not sure if it works out right.

I realize this is well beyond what is actually necessary or even useful to the setting. At this point it's mostly just a problem I'd like to figure out.

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>>8857088

>>8851554
>german function/parameter names
No need to be envious

>>8854454
I think python and R can do that

do i get banned for posting homework here?

Are memes a spook or are spooks a meme?

>>8856687
0x02+0x08 is not 0x10
0x10 = 16

Similarly, 0x20, 0x40, and 0x80 are not what you think they are

Sounds like you copied the code but don't understand it, look up hexadecimal numbers

>>8857116
Only if you tell no one that it is homework.

>>8857116
We won't do your homework for you, but most anons are willing to help clear up a point of confusion or two.

>>8857132
>>8857144
i just posted in /wsr/: 12=4524x+3564y, x and y must be integers. how do i solve this?

i think it's little work for someone who's good at maths, but unfortunately i am not.

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How do I show the first part? Shouldn't it be [math] I_A\circ B=B\restriction A[\math]?

>>8857149
What type of problem is this? It looks like a linear equation, can be arranged to one.

>>8857149
https://en.wikipedia.org/wiki/Extended_Euclidean_algorithm

You've done this in class

>>8857122
memes aren't a spook but spooks are a meme

>>8857170
why are you composing a set with a function?

>>8857178
Because I can, B just has to contain ordered pairs, and if it doesn't, no biggie, you just get the empty set

>>8857174
>wikipedia for math problems
my brain hurts. i mean that's how i got the 12 as the greatest common divisor of 4524 and 3564, but i can't get my head around how to reverse it and still have 12 left over.

>>8856098
pls respond

>>8857189
then i guess for any a in A you have (B circ I_A) (a) = B(I_A(a))=B(a) and B|A(a)=B(a)?

>>8857190
I bet you used the euclidian algorithm instead of the EXTENDED euclidian algorithm, because the extended algorithm gives you the solution directly (see s_i and t_i on wikipedia)

>>8857212
I've done maths up to differential equations so far, but I haven't come across a "euclidean algorithm" so far. The fuck.

>>8856098
>>8857196
The angle between the circles is just the angle between the normals to the planes. Try drawing a figure in case you don't get it.

>>8857207
Ah I see, I was doing the composition backwards

>>8857223
It's used to calculate the greatest common divisor of natural numbers (which means it can be used to check whether two numbers are relatively prime)

I hope you're not studying CS or math

>>8857229
Jesus christ, thanks, man. I still cannot for the life of me visualize it but I see now where the answer comes from.

>>8857250
guy you're responding to there wasn't me. and even i'm not primarily studying math, just taking some classes. thanks for the help

>>8857223
Yes, because all of the mathematics that has ever been thought about is contained within a four course sequence almost all college students take.

Can someone help me understand how the pumping lemma works?

For CFG S -> 0S1 to FSA.
So an FSA has a fixed number of states, and if the input word that the CFG can derive (e.g. 10 0s and 1s) is larger than the amount of states then that proves the FSA cannot accept it.

Is that right or is that not how it works?

How to go from

[math] \sqrt{2+e^{2t}+e^{-2t}} [/math] to [math]e^-t \sqrt{e^{4t} + 2e^{2t} + 1}[/math]

?

>>8857901
[math]\sqrt{a*b}=\sqrt{a}\sqrt{b}[/math]
In your case a=e^-2t

>>8857901
You are just pulling out e^-2t from the rest:
[math] \sqrt{ 2+e^{2t} +e^{-2t} } = \sqrt{e^{-2t} (2e^{2t} +e^{4t}+1) } [/math]
Hope this helps

>>8857901
In the second expression, it was supposed to be "to [math]e^{-t}..[/math]

And in a general sense, what is this called (I know it's factoring, but more specifically)? I would like to practice this a lot, I'm running into many problems like this while finding the magnitude of a velocity vector.

>>8857918
>>8857920
thanks guys

>>8851039

You're not thinking in proper logic. The system is LTI and that should give you a clue as to how the result should look like.

Meaning:

Your system is multiplied by e^(-t) over every part of your function x(t). This is linearity.

The input of your function wasn't moved along the t axis (wasn't displaced) by the response s(t). This means time invariant.

With those two in mind the example is properly written.

>If I use convolution, my bounds are from 1 to t and from 3 to t

I might be wrong but I think the bounds are from 1 to 3 and from 3 to t. You should get two integrals. If you're thinking of doing convolution.

>>8851069

Step response: u(t)
Impulse response: delta(t)

What does a graph of "f(x,y)=x mod y" look like?

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>>8857974
Roughly like this.

>>8857991
Yeah, that's what I expected

>>8857974
hope you like windmills

>>8857991
So that's how you use the modular function in wolfram.

>>8858030
You can get the same result by just entering "x mod y"

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>>8858044
...Are you sure?

What the fuck is the Precautionary Principle and where can I see the original text? Trying to rectify difference in its application to GMO food between two different papers.

>>8857991
What is going on with the area in the middle?

>>8858144
Some values break through the Matrix, so our robot overlords automatically filter those out of our mathematics.

best 3d plotting software for gnu/linux?

>>8858410
octave, gnuplot, sicpy, sagemath.. which one is worth investing the time to learn into?

>>8858437
>>8858410
pls

>>8857991
that's bretty cool

>>8851450
>Recall that the differential of f(x,y) is
>df = (df/dx)dx + (df/dy)dy
Shouldn't that be df = f_x dx + f_y dy where f_n is the partial derivative?

>>8858410
>>8858437
>>8858447
Depends, what's the application? Just graphing a few equations, doing stats/correlation studies, or something more abstract?

Wolfram alpha/octave if the first one, sicpy (or numpy or anything like that) for the second one, and octave for the third one.

>>8858733
right now, graphing parametric equations of more than one variable. Octave has been handling it ok now that i've invested the hour into learning the basics.

the way you phrased it has me inclined to think you believe that wolfram > sicpy > octave, how true would you say that is?

>>8858740
Wolfram alpha is good for just screwing around, since it's easy and takes no time to learn since it accepts almost any query. If it can't handle some specific query, there's nothing you can do since it's a website and not a programming language.

I don't know what sicpy is; I've only used numpy and it's worked fine for me. I wouldn't use it for graphing parametric functions because of how inconvenient it is to edit the source code and run it.

Octave is what you should use for this, and if you get used to it, you'll have no real need for the others.

In case you didn't pick it up this time, I basically just said octave > wolfram > numpy (for this one application, it'd be octave > numpy > wolfram if you're dealing with large amounts of data inputs)

>>8858759
>octave > wolfram > numpy

that's what I meant initally, thanks anon, glad I made the right choice.

>>8857417
It's been a while since i had to use the pumping lemma. CFG means Context Free Grammar? And FSA means finite state automata (for regular languages)?

I don't think your explanation is correct.
As an example: consider the CFG S->aS, S->a, so it has all words with an arbitrary amount of a's. You can derive an immensely long word from this (e.g. 1000 a's), but you can construct an FSA that only has 2 states to accept the language: (1,a,2), (2,a,2) (that means, you have two states, the first leads into the second by reading a, then the second leads onto itself by reading a).

You generally prove that a language is regular by constructing an FSA that can accept it. It has a fixed size, but if you construct it intelligently it shouldn't matter. The problem with S -> 0S1 is, that the FSA needs to "remember" how many 0s you read, and then read the exact same amount of 1s. But an FSA cannot "remember" because it has no memory. You will later see that there will be so called pushdown automatas which have a small memory where you can save letters.

I don't remember the mathematical aspects of the pumping lemma. I recommend looking that up somewhere else. For that easy example, there are tons of solutions, even on wikipedia:
https://en.wikipedia.org/wiki/Pumping_lemma_for_regular_languages#Use_of_the_lemma

Is this statement true or false?
∃ x >0 : x<p/q ∀p,q ϵ N

>>8858794
false since Q is dense in R (i.e. between any two real numbers there's a rational number)

>>8858809
But isn't R\Q also dense?

>>8858809
>>8858812
Never mind, I get it now. Thanks.

New thread:
>>8858725

alright sci whats the easiest, most effecient and reliable method for basic trinomial factorization? (into two binomials that is)