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Archived threads in /sci/ - Science & Math - 62. page
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File: javnice2.jpg (38 KB, 396x594) Image search: [iqdb] [SauceNao] [Google]
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This is too much for the /wsr/ plebes; could u guys help me figure out the fourier transform of the following function:

g(x)=(cos(alpha*x))^2

any book recommendations for someone with non-formal knowledge of integral calculus?
7 replies and 1 images submitted. Click here to view.
>>
cos^2(a*x)=(cos(2*a*x)+1)/2
=1/2+(1/2)*cos(2*a*x)
IOW, G(f)=1/2 if f=0 or f=a/pi and 0 otherwise.
>>
>>8480134
>non-formal knowledge of integral calculus.

Anon, there's no easy way to say this, other than you should sit down and read about integral calculus.

http://freebookcentre.net/Mathematics/Fourier-Analysis-Books.html

Here's a good list of free books on fourier analysis.
>>
>>8480134
You need to know integral calculus to use the Fourier transform in a naive way, but to understand Fourier theory you will need at least linear algebra and analysis.

To find the transform of that function, and to "figure out" the Fourier transform simply apply the formula (note that there are several equivalent ways of taking the transform).

$\mathcal{F}(f)_{k} = \frac{1}{2\pi}\int_{-\pi}^{\pi}f(x)e^{-ikx}dx$

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Hi /sci/
I learned in optics that group and phase velocities can be above the speed of light in vacuum.
I understand the argumentation stating that no information can be transferred via those only, but it conflicts with my understanding of special relativity.
If I were observing a point on a wave which moves with the phase velocity, how would it look like to me? I would say the γ factor would be imaginary, which gets me confused
Where is my mistake?
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>>8480094
I have no idea but at least I can tell you that I'm kind of sure that 4chan is not the perfect site for such a question.

Very cute cat though.
>>
>>8480094
https://en.wikipedia.org/wiki/Faster-than-light#Phase_velocities_above_c
https://en.wikipedia.org/wiki/Faster-than-light#Group_velocities_above_c
>>
>>8480156
Well I thought /sci/ WAS the right place

What precisely is an angle??

The problem is that defining an angle correctly requires calculus. This is a point implicit in Archimedes’ derivation of the length of the circumference of a circle, using an infinite sequence of successively refined approximations with regular polygons. It is also supported by the fact that The Elements [Euclid] does not try to measure angles, with the exception of right angles and some related special cases. Further evidence can be found in the universal reluctance of traditional texts to spell out a clear definition of this supposedly...
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>A relative measure of the degree of rotation from one line segment to another
>>
You run into the same road blocks as you would defining any "basic" object and you usually rely on some axiom of measure. This is not exactly some big deal
>>
>>8479968
It's why real geometers use turn, spread, cross, and twist.

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If topology is real why can't I turn my cat into a dog?! How does topology address the conscience state of mind? Is math on it's last legs here?
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>>8479952
Is topology the new quantum mechanics?
Topological consciousness when?
>>
Topology refers to human over thinking
>>
>>8479952
>Topology
>Topos = surface
>Logos = understanding/ conciousness

Are you implying that surfaces dont exist? Or that we cant try to understand them?

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is it possible for human to achieve immortality ?

How science can make us immortal?
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>>8479931
Find a way to isolate and store conciousness, if that's even possible.
>>
until scientist find a way to stop cells from decompose
>>
Nanobots that repair telomeres

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Hello /sci/

I have a quick question for you.

Imagine that someone would have green skin (actual green - like orcs in the fantasy books), but red blood. How it would mesh in places rich in blood, such as rosy cheeks or nose?

Am i overthinking it and it's just a mix of red and green just like you would get in the photoshop?
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light (photons) is additive because of how our eyes/brains process it (eg RGB pixels from a monitor can make many colors)

red light coming from deeper in skin, green light coming from top layer of skin, so you'd see yellow

but if you mix actual physical pigments (bulk phase), what happens is their absorbance regions overlap until there is no wavelengths of visibile light that they transmit. so basically there are an "infinite" amount of molecules all absorbing different EM bands, and there is no photons that make it to your eyes, so you see black.

when...
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>>8479762
here's an example of black ink spread out using TLC
>>
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>>8479780
So - if i understand it correctly - light would "come back" yellow, but because it has to travel "through" layer of molecules it would come back as slightly darker (depending on amount of light i'm shining)?

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I believe I have a proof shows its impossible to score 0 in the Mondrian art puzzle.
For those who don't know what that is the rules are as follows
>start with a square of side N
>split the square into rectangles
>no two squares can have the same side lengths (if you have 3x2 you can't have another 3x2 or a 2x3)
>your score is the largest rectangle's area minus the smallest rectangle's area (lowest score wins)

Therefore...
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(Cont)
Thus by skewing an aperture cut you can always make the core a square. And solving for other rectangles of the aperture cut you'll find the only possible side lengths that result in a shared area are phi (1.618) and 1/phi. Further solving for the side lengths of a mutation requires at least one to have a length of 0 or for one to have a different area which is not permissible. It is impossible to split a rectangle without a bisection or a core and thus the only methods for splitting a rectangle result in
1 a shared side length
2 an irrational side length
3...
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I suppose for clarity I should mention multi cored rectangles and nested cores

>multi cored
Refers to a cut with 2 or more cores. and this retains the same irrational side length problem

>nested core
Should be self explanatory
>>
Not enough math symbols.

Post it on math stackexchange, overflow, or /r/maths.

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a problem for the bored guys, have fun.
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>>8479599
That was fun OP 8/10

keep reuploading because I keep making brainlet mistakes
>>
>>8479599
bump OP tell me if this is right cunt
>>
>>8479706
OP has to hand it in to the teacher and wait for them to mark it first

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Is there a scientific reason why it would be desirable to shoot a man before throwing him out of a plane?
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Some people have survived pretty high altitudes. Using newton's law of better be safe than sorry, it follows.

I hate this place
>>
>>8479361
Showing off accuracy
>>
Dead body will flop loose and tumble

Live body may try to stabilise and steer in a vain attempt to soar out of going splat.
Thus may not be an accurate indicator of crosswinds etc

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Do Nuclear Weapons prevent invasion from foreign forces?
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>>8479345
When was the last time someone invaded a nuclear weapon state?

Oh right
>>
>>8479349
correlation =/= causation

>>8479345
Yes and no. It depends.
It depends on the likely hood of a counter value or counter force attack and the chances of preventing launch or preforming a shootdown. It also depends on the collateral. Nuclear weapons are the boogymen of modern warfare, the fact of the matter is nuclear warheads are more efficient than ever and produce hardly any radiation. It's why (other than the fact that using nuclear weapons removes...
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>>8479360
>correlation =/= causation

Yeah, tell that to Saddam.

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Climate Change will affect the continent of Africa the worst. What could be done to save Africans?
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>>8479316
Nothing we need to put mines in the mediterrean and build a wall in turkey to stop the flow of niggers.
All we need to do is to trap them in their continent until they all die.
>>
>>8479316

Slavery, but they didn't wanted to be saved, and the ones we saved are now making riots.
>>
Sink the continent.

No really. We need to go back to pre-industrial population. It's the only way the species as a whole can survive. Bill Gates HATES this idea. But Bill Gates is a moron.

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This stuff work?
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>>8479194
Is it an amphetamine? If not then no.
>>
>>8479208
According to the webpage it's made of Bacopa Herb Extract, Alpha-GPC, Yerba Mate Leaf Powder, Phosphatidylserine, L-Theanine, and Vitamin B12. Not sure if those are legit ingredients.
>>
>>8479194
Yes, you dumb nigger it's like lubricating a gear

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I really think the fact that you hear "calc/Ochem/Pchem/(whatever challenging course here) is just SOOO hard" constantly is what trips more people up than anything else. People go into a lot of these courses thinking they'll never understand, so they don't try, they fail, and then they perpetuate that line of thinking.

Is this why normalfags don't get into math beyond highschool levels?
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>>8479173
>calc/Ochem/Pchem/(whatever challenging course here) is just SOOO hard
Only Americans ever say this
>>
>>8479173
I don't think that's true
I think it's because those courses are the first ones you run into where you actually have to put some thought into what you're doing
so they end up weeding out all the people who lack the ability to think critically or follow more than a single step of logic

and that happens to be a whole lot of people
>>
lainposter pls go

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How do you nerds deal with presentations in school? I'm actually pretty good socially and take care of my appearance and seem normie as fuck but when it comes to being in the spotlight of strangers my social anxiety really kicks in. Like I have benzos and beta blockers lined up just too deal with this shit. I know I won't get through University without doing at least one alone presentation, group presentations i have no problem with.
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Experiences? Tips?
>>
>>8479095
>>8479098
Practice.
Speech therapy, and just do as many presentations as you can. Stop caring what others think.
>>
>>8479095
>pretty good socially
>seem normie as fuck
>but when it comes to being in the spotlight of strangers my social anxiety really kicks in
????

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Any scientifically proven method to treat dark circles under eyes? I don't want to follow women blog shit

Pic related, mines is way worse than that
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Get enough sleep.
>>
>>8479091
Not be Indian.
Solved.
>>
>>8479091

There may be a couple of things to consider:

>genetics
Yes, this can be genetic. It can either be a racial trait or a non-race-specific trait that you could have even if you're the palest white person you know.

>sleep disturbances
Even if you seem to be getting a solid eight hours of rest, you may not be getting restful sleep. A lack of restful sleep doesn't mean you're tossing and turning or having other apparent sleep...
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Why do dryers take so long to dry?
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>>
Science. Sometimes not enough, sometimes too much
>>
>>8478972
You keep forgetting to empty the lint filter.
>>
>>8478972
Because you can't put a dryer into another dryer.

What's the best search engine for free, primary-source literature?

I've tried le google scholar take pity on me /sci/toplasms
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>>
most literature is free
http://sci-hub.bz/
>>
>>8478895
Much obliged.
>>
>>8478892
>pnas

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Helloooo smart-asses. I'm looking to study some MATH! Does anyone know of an online resource that teaches you everything from the basics to university + beyond level?
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>>8478426
>>
anyone oppose to this site? http://www.gcflearnfree.org/
>>
I did khan academy for a while but it didn't do that much for me

>>8478441
hey that looks pretty good actually

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>3D biological printing
>darknet access to various infection disease genomes
>induced mutation

How fucked are we in twenty-thirty years?
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>>
we've been fucked for the past 50 years so who give a fuck
>>
>>8478335
But you can literally make a dangerous pathogen at home. It wouldn't be that difficult.
>>
>>8478360
my dorm is a haven for dangerous pathogens i tell you what
no one gives a flying fuck about cleaning anything!!!

last time i ever live with strangers.

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>as you mature you realize scientific advancements are temporary bullshit and mathematics is the only field worth pursuing
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>>8478309
Your thinking is completely backwards.
>>
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too bad there is no actual advancement in mathematics, just people investing ever more time in arcane, arbitrary, and meaningless thought-inventions. Mathematics has long passed the point where mathematicians were dealing with primary or tangible notions of quantity and space, nowadays 'mathematicians' concern themselves with mostly secondary or tertiary notions; doing mathematics about mathematics or mathematics about the mathematics they do about mathematics. It is totally artificial and concerns only the peculiarities of the human mind and speaks to no deep truths...
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>>8478329
sounds perfect for an autist to be quite desu

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Biofags what could this be? Cultured on nutrient and taken from normal ground. Hope somebody can help me out
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>>8478240
A very small ikea fruit bowl
>>
A dickhole
>>
>>8478240
Dirt

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Who do you think will get it and why?
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>>8478179
George church because he's a boss
>>
>>8478179
the woman because she worked so hard to get where she is and is an inspiration to little girls and little boys everywhere showing that a woman can be president too
>>
>>8478179

Nobel prizes get shared all the time.

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>will the earth heal if humans go extinct
>terra is a live thing
>humans are a problem
>species traitors in charge of logic
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>>
>animals have rights
>it's wrong to kill animals for fun
>animal experimentation needs to stop!
i hate these hippie faggots
>>
we need to take care of our environment but the whole gaia na'avi "dude, humans are a disease like that guy said in the matrix! lmao" thing is a meme
>>
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life isn't worth perpetuating or conserving.

My candidacy exam is in 4 hrs. Any advice ?
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>>
>>8478139
Candidacy for what?

Probably stop shitposting and collect yourself though.
>>
>>8478140
materials chem
>>
Sit down and relax and clear your head until about 30 minutes before hand when you start to get into the right mindset

goodluck bro

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Which answer gets me into a STEM course?
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>>
>>8477942
>nth repost of retarded garbage
>>
>>8477945
how is it retarded garbage. came across it for the first time and I legitimately want to know before I go trashing it on Facebook.

don't want to post the wrong answer and get btfo
>>
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>>8477942

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Solve N when P = NP

I will pay handsomely for the correct solution
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N=1 :)
>>
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>>8477865
You missed a solution you absolute fucking brainlet.
>>
>It's another interpreting P vs NP as an algebraic problem episode

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I was thinking about curvature(k) a little the other day. If the circumference of a sphere changes, from lets say C to C+1, should the curvature change in respect to the circumference at all? Or should it remain constant. I was thinking we could use the point ((C/2pi), 0,0) and ((C/2pi)+4,0,0) to describe the 2 changing points and constructing our r(t) curve, if following the curvature formula after finding T, the curvature would not change at all. Is this true? I've never seen any problems like this and I was just wondering if it's even possible to find curvature...
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lol Christ I'm a moron, I just remembered k=1/R. So smaller spheres have much larger curvature and visa versa. sorry /sci/ I din't need you after all.
>>
What a fucking retard...
>>
>>8477856
Why +4? I'd just do (rcos(t),rsin(t),0)
Differentiate twice to get -(rcos(t),rsin(t),0)
Then the curvature is
1/sqrt(r^2(cos^2(t)+sin^2(t))=1/r
So the curvature has an inversely proportional relationship to the radius, and therefore to the circumference. This makes sense since a large circle starts looking like a line locally.

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Out of all the planets in the Milky Way that contain life there is a handful that contain intelligent life. Out of all the planets that contain intelligent life there are few with advanced civilizations. The most advanced civilization lives on the other side of the galaxy, is thousands of years older than ours and already has a technology that lets them travel at 1% c.

And it means nothing, because it is still impossible for them to even detect us, not to mention fucking contact us and vice versa.

Why is it even "controversial" to claim that humans and...
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>>8477815
because based on projections if even 1 civilization went space age and began colonizing, assuming they got a headstart of just 10,000 years on us, they should be all over the place and we should be detecting radio signals from their vast empire

the fact it's completely quiet out there is spooky, to say the least. it implies we're the only ones because the odds of finding a race at our exact level of technological advancement is miniscule.
>>
>>8477815
Can someone who is smarter than me chime in and answer this: if a civilization on one edge of the galaxy could broadcast a radio signal strong enough that it would reach earth, would we even be able to recognize it as something not natural? or would it be so degraded it would be indistinguishable from the rest of the noise in the universe?
>>
>>8477815
>that image
>Central Bulge

LMAO

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how did mathematics go from basic addition and subtraction to abstract structures in multiple dimensions/spaces with notions of infinity/greater-than-infinity slapped all over the place?
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>>
Idk. Why is Cocoa so cute?
>>
>>8477803
Green Tea
>>
>>8477803
You can thank Galois and the early 1900s revolution in formal logic and foundational mathematics.

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Does the ISS appear to wobble when viewed with the naked eye, and if so, why?

I'm in Melbourne, Australia, and a couple of times recently when I've gone out to watch the ISS flyover, it appeared to have a very visible 'wobble'. Last night in particular, the ISS flew roughly 90 degrees above me, and it had this very pronounced wobble to it. I've had other people in Melbourne tell me they've seen the same thing, though a quick google only showed up one result:

https://www.quora.com/Why-would-the-ISS-appear-to-be-wobbling-when-viewed-with-the-naked-eye

Is...
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>>8477791
Seeing as how the ISS is much further up than the plane and thus the light from the ISS has to pass through a lot more atmosphere, that's probably the wobble your describing.

The whole reason we put a telescope is orbit was to eliminate artifacts caused by the atmosphere.
>>
>>8477802

Thanks. Is there a reason, though, why the 'wobble' seems significantly more pronounced that the degree to which stars 'twinkle', or am I imagining this?
>>
it is impossible to see the ISS if its going past mach speed over the earth.

sage

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