/sci/ - Science & Math

Reposting cuz posted when it died
How the fuck do you either
>Wake up
>Win over your brain desire to stay in bed
I am having trouble coming up with reasons other than I can be productive more time, which is not good enough for my brain. My train of thought usually goes
>"Why do I have to wake up?"
>>"To write for 8 hours instead of 6"
Then I don't give a shit and go back to sleep

Help me bros

I was thinking of having a cup of coffee over my alarm clock to drink it whenever I am about to put off the alarm but I fear of spilling it over important notes or something like that

>>10887370
Well I just responded in the other thread, but I'll add here that there are other things you could do too. If your alarm is loud enough, you could move it up / away from your bed so that you need to stand up to turn it off. Other stuff like that.

how do i learn calculus

>>10887384
You read a book on it or watch some videos on it. It's really not a big deal.

>>10887384
I did by learning their applications other than just memorizing formulas

>>10887384
>>/sci/thread/S10667733

Unsanswered questions:
>>10861301 was half answered by >>10861322 (me)
>>10861883
>>10862808
>>10865758
>>10868241
>>10868366
>>10868818
>>10871171
>>10871459
>>10872163
>>10872372
>>10876252


How do I better myself tally:
>>10861714
>>10861806
>>10861880
>>10887342


How do I build muscles:
>>10861885

Apparently millions of years ago Antarctica was filled with trees and forests and was home to 5-7ft tall penguins.
If all the glaciers there were to melt today, could we possibly see the rebirth of forests and 5-7ft tall penguins?

Posting ITT to avoid the /mg/ chads berating me first

How do I show that [eqn]-\lim_{h\rightarrow{0}}\frac{f'(c-h)-f'(c)}{h}=\lim_{h\rightarrow{0}}\frac{f'(c+h)-f'(c)}{h}[/eqn]?

>>10887653
You just pass the minus to the h, set j=-h, swap for j, and notice that both equations say the exact same thing.

>>10887653
Also there is an assumption that [math]f[/math] is twice differentiable at [math]c[/math]

>>10887680
Damn I'm a retard, didn't even think about just giving the negative to the denominator, cheers.

>>10887689
That doesn't matter, the identity only makes sense when f' and f''(c) exist.

>>10887653
>/mg/ chads

>>10887653
literally just two definitions of the derivative of f' depending on which side of c you draw the secant line

>>10887405
10871171 got answered in the chemistry general thread.
You can skip this one.

Just got email back from professor after asking about undergrad research project for course credit and he basically just said "yes, i can do a project with you". what do respond to this? i dont even know how this shit works and just want to do it because no other classes to take. am i supposed to come up with the project or will he probably get me one to do? or should i ask him in the reply?

>>10887744
Typically, your advisor will have something in mind, and that topic will usually pertain to their own research interests. In this way, they will act as a mentor of sorts, showing you how research 'works' while also getting you into their field.

For this reason, you'll want to outline some of your own interests, to make sure that you guys will have the same goals from the get go. It helps if you've taken one of their courses and have an interest in the subject.

>>10887744
Any shitty undergrad can say he wants to research, actually suggest a subject, fool.

>>10887756
>>10887767
i took a class with him already about lasers and talked about that in the first email along with his research i learned about in his class but i didnt really say anything really specific like a project topic or outline. really i just dont know if i should reply to him about it or just say thanks, or maybe talk about meeting when school actually starts or what because no social skills

>>10887370
Dude. If you aren't too shy to be OP, (I am,) this would be a great topic on /adv/. I cruise around there sometimes and haven't seen it. Try sleeping next to an apple.

>>10887779
Suggest a meeting in person about possible areas of study. If there was anything in particular about optics or lasers that you wanted to study, then suggest that. Otherwise, this is (an essential) formality to establish that you two both want the same thing, so he can go ahead and start writing up a project for you.

>>10887805
ok thank you for the help

I am an autist that wants to make maps and stumbled upon graph theory.

So far all the programs I've found that let you make graphs (Gephi, graphviz) don't seem to have any way of changing the length of edges? I've been trying to do research on graph theory to figure out if that's even important or if I'm way off base with the sort of math I need to use, but everything I'm reading is either not exactly reliable or dense as molasses. Am I way off base or am I just missing something flashing brightly in my face because I haven't studied math this in depth?

>>10887827
The length of the edges is not really a concern. Topologically speaking, they can be shrunk down to any arbitrary size.

What you may be thinking of are *weights*. A weighted edge may be useful for mapmaking, as a weight could signal distance from one vertex to another.

>>10887832

I had a feeling it might be a terminology issue.

Would it be possible for there to be multiple, differently weighted edges in between the same pair of nodes?

>>10887839
Absolutely. In fact, there may even be "loops," which are edges that start and end at the same vertex, and these can also be weighted. And you can have as many as you'd like.

Many important theorems and algorithms, however, may specify that the graph at hand is simple, in which case there are no loops and multiple edges between any pair of vertices is not allowed.

>>10887848

Holy shit alright, thank you, this should hopefully make this way more manageable. I started out googling "graph map" or something similar and it just gave me a thousand xy plots.

Does co2 in the atmosphere eventually turn into something else?

>>10888118
ye

Can anyone recommend any resources on amazing and preventing cascading failure in mechanical systems? Everything I've found online has been about power grids.

>>10887363
I need some good touhou music to listen whilst performing mindless labor bordering on janitorial work, what do you recommend?

>>10889010
learn a good substitute for whilst, maybe read a book, listen to someone articulate speak for a few minutes that is probably going to benefit you more greatly than any music that could be recommended for you to listen to whilst you perform your obligate labors.

>>10887370
I had a very similar problem in highschool. My solution was similar to one posted previously. I got an alarm clock and put it in one corner of the room, and put my phone in another corner. Then I set the two alarms 1 minute apart. The trick is to make it difficult to just hit snooze and go back to sleep.

>>10889033
Unfortunately this mindless job requires me to use my eyes. The job is not wholly mindless and does require some thinking and juggling numbers in my head.

>>10887386
>>10887388
>>10887393
how do i learn calculus

>>10888118
> Does co2 in the atmosphere eventually turn into something else?
Some of it gets absorbed by plants (mostly trees), some of it gets absorbed by oceans (an increase in CO2 in seawater results in an increase in acidity).

It doesn't undergo chemical reactions while in the atmosphere (unlike e.g. methane which breaks down into CO2 and water over time).

Brainlet learning baby math here.
Why is [math]0^0[/math] considered indeterminate rather than undefined?

When working with rational polynomial functions, why does simplifying and dividing out terms or rationalizing the denominator change the original function's domain?

>>10887363
for medfags:

I looked at a blood type compatibility chart and it was clear after a couple minutes that there's an obvious rule. A, B, and + are all things you can have, and if you have any of those, you just can't give blood to anyone who doesn't have it. So O+ can give to any type that doesn't have a + for example, or AB- can't give to anyone without an A and a B.

Question is, why is +/- notated that way instead of just using C? Seems needlessly confusing.

>>10889010
Just search Touhou remix on youtube.

Are there any logical objections to defining the Probability as the cardinality of the set of the desired event/events divided by the cardinality of the set containing all possible outcomes?

>>10889830
as long as the possibility of each thing occurring has the same weight, I don't see why not

>>10889203
Once you get into higher maths you'll learn that functions that output values like 0^0, 0/0, infinity/infinity and so on are actually missing a variable, you can't determine if they are undefined or not, hence indeterminate.

For instance:
[math]\lim_{x\to\infty} x/(x+1)[/math]

gives infinity/infinity as is, l'hopital's rule tells us the limit is 1. Undefined terms, such as 1/0 can't be reduced in such a way. Recognizing indeterminate forms is essential in higher maths.

I'm trying to understand renormalization in QFT, can anyone recommend an introductory text or paper? In particular something about the beta function would be helpful.

>>10890104
>renormalization

>>10889169
Thanks!
The answer I was looking for

How do i choose between mathematics and physics if both interest me?

>>10890518
what are your end goals and career? do you want to become a scientist or mathematician? do you want to work on more applied shit or more theoretical?

>>10890536
>what are your end goals and career?
I want to be an academic
>do you want to become a scientist or mathematician?
I don't see why the label itself is important
>do you want to work on more applied shit or more theoretical?
Theoretical

I want to do a small scientific paper on how Twitter forces verification based on any activity on your account that could be linked to the so-called rightwing (obviously these people are not all rightwing, its just that Twitter is super progressive).
Is there a resource out there that explains in brief what the basic requirements of a good scientific paper are?
I don't care if it gets accepted to journals or whatever, I just want it to be good enough to get some exposure so that Twitter will come under greater scrutiny plus it will be an interesting exercise into how these things work.

Is theoretical computer science still important when it comes to developing new technologies?

>>10889203
>Why is [math]0^0[/math] considered indeterminate rather than undefined?
Because there are several plausible definitions for what it may be that do not yield the same result.
If you think of this in terms of calculus, you could say that it stems from the fact that the limit [math]\lim_{(x,y) \to (0^+, 0)} x^y[/math] does not exist.
In fact, taking the limit along appropriate paths, you can make it anything you want: For any [math]\alpha > 0[/math], you have [math]\alpha = \lim_{x \to 0^+} (\underbrace{e^{-1/x}}_{\text{converges to }0})^{\underbrace{(\ln \alpha )x}_{\text{converges to }0}}[/math]
Now there are arguments for why it should be 1 (as Bourbaki, for example, suggests).
For example, [math]\lim_{x \to 0}x^x =1[/math], which seems like the most natural limit-based definition of [math]0^0[/math] (but, as I explained above, a limit-based definition not really satisfying).
Another reason, more algebraic, is that any empty product (so product with zero terms) "should" be 1 by convention, for the same reason that a sum of no terms should be zero.
It allows one to defined products over any set and many formulas only extend if we set it like this, for example if [math](x_i)_{i \in I}[/math] is a finite collection of real numbers and we have a partition [math]I = I_1 \sqcup I_2[/math], we would like to say [math]\prod_{i \in I} x_i = \prod_{i \in I_1} x_i \times \prod_{i \in I_2}x_i[/math].
For this to work even when one of the sets is empty, we need to set [math]\prod_{i \in \emptyset} x_i = 1[/math]. With this convention, we might reasonably say [math]0^0 = \prod_{i \in \emptyset} 0 = 1[/math]

>>10889203
>Why is [math]0^0[/math] considered indeterminate rather than undefined?
Because there are several plausible definitions for what it may be that do not yield the same result.
If you think of this in terms of calculus, you could say that it stems from the fact that the limit [math]\lim_{(x,y) \to (0^+, 0)} x^y[/math] does not exist.
In fact, taking the limit along appropriate paths, you can make it anything you want: For any [math]\alpha > 0[/math], you have [math]\alpha = \lim_{x \to 0^+} (\underbrace{e^{-1/x}}_{\text{converges to }0})^{\underbrace{-(\ln \alpha )x}_{\text{converges to }0}}[/math]
Now there are arguments for why it should be 1 (as Bourbaki, for example, suggests).
For example, [math]\lim_{x \to 0}x^x =1[/math], which seems like the most natural limit-based definition of [math]0^0[/math] (but, as I explained above, a limit-based definition not really satisfying).
Another reason, more algebraic, is that any empty product (so product with zero terms) "should" be 1 by convention, for the same reason that a sum of no terms should be zero.
It allows one to define products over any set and many formulas only extend if we set it like this, for example if [math](x_i)_{i \in I}[/math] is a finite collection of real numbers and we have a partition [math]I = I_1 \sqcup I_2[/math], we would like to say [math]\prod_{i \in I} x_i = \prod_{i \in I_1} x_i \times \prod_{i \in I_2}x_i[/math].
For this to work even when one of the sets is empty, we need to set [math]\prod_{i \in \emptyset} x_i = 1[/math]. With this convention, we might reasonably say [math]0^0 = \prod_{i \in \emptyset} 0 = 1[/math]

>>10889203
>When working with rational polynomial functions, why does simplifying and dividing out terms or rationalizing the denominator change the original function's domain?
It does not change the original function's domain.
Another thing you should keep in mind is that, if you are doing things properly, then a function comes together with a domain that is specified, and operations are only defined for functions with the same domain and return functions on that domain.
That is why, when you divide a function by another one, you may first need to restrict the domain to a subdomain where the denominator does not vanish. For example, x/x is defined over R \{0} and equal to 1 everywhere on this domain.
This is sort of nitpick-y but it seems like the sort of nitpicking that you may find helpful.

>>10887363
Since this is a brainlet question undeserving of its own thread, what math should I study if I wanted to become a meteorologist?

>>10887363
What would be taught in a class titled "combinatorial analysis"?
Brainlet undergrad here, I'm not familiar with the field of combinatorics, is it anything like discreet math? How is a "combinatorial analysis" class different from discrete math?

>>10891103
Unironically major in geography and take some statistics classes on the side

>>10891311
It might just be a different name for combinatorics. In French, there is no noun for "combinatorics" so the field is formally known as "combinatorial analysis". (the word analysis does not refer to what we call mathematical analysis, but more to the general idea of "inquiry")

>>10891354
don't call yourself a brainlet friend, it is not going to help you in any appreciable way but does make me sad for you.

>>10891311
how about google first

>>10891400
So would the class basically be discrete math with the graph theory removed?

>>10891311
I read a book about combinatorial analysis, once.
It went through permutations, arrangements, cyclic permutations, other specific issues that show up in permutations, the pigeonhole principle, etc.

>>10890518
Major in both?

What is the uncertainty [math] \Delta E_n [/math] of the quantum harmonic oscillator?

>>10890615
Yes

>>10891451
danke

>>10889010
https://www.youtube.com/watch?v=Ty2wQU3PEoo
>>10890104
In general renormalization is the procedure of integrating out high-energy/hard modes, or coarse-graining out short-range modes in real space. Let [math]\psi\in \Gamma(M,E)[/math] be a section of an appropriate vector bundle [math]E\rightarrow M[/math] and [math]\mathcal{L}\in\Omega^d(J^\infty E)[/math] the Lagrangian density. By integrating along the fibres of [math]J^\infty E[/math] we get the action [math]S[/math] as a functional on jets of the space of sections of [math]E[/math].
Decompose [math]\psi = \psi_< + \psi_>[/math] such that [math]\psi_>\in L_\text{loc}[/math] has compact support on the momentum shell [math]b\Lambda < k < \Lambda[/math] for some RG parameter [math]b[/math]. Suppose a functional Liouville measure [math]\int_\mathcal{D} d\mu[/math] on the space [math]\mathcal{D}[/math] of sections of [math]E[/math], we may write [math]d\mu = d\mu_> d\mu_<[/math] such that the partition function reads [math]Z = \int d\mu_< e^{-S_0[\psi_<]}\int d\mu_> \exp\left( -S[\psi_<,\psi_>]\right) = \int d\mu_< e^{- S_0[\psi_<] + W_\text{eff}[\psi_<]}[/math], where [math]W_\text{eff}[/math] is the effective quantum action that takes into account the "average" interaction of hard modes with soft modes [math]\psi_<[/math].
By computing [math]W_\text{eff}[/math] perturbatively, you may bring [math]S_0 + W[/math] into a form [math]S_\text{eff}[/math], which belongs to the same polynomial class of [math]S[/math] as a functional on jets. You can now rescale the jets of [math]\psi[/math] and the parameters [math]\alpha[/math] in [math]Z[/math] such that [math]Z = \int d\mu' e^{-S_0'}[/math], where the prime indicates dependence on rescaled parameters and fields.
This rescaling then generates a flow [math]b \mapsto \alpha(b)[/math], for which [math]\frac{d\alpha}{db} = \beta(\alpha)[/math]. This is the definition of the [math]\beta[/math] function, as the generator of RG flow.

>>10889830
>>10889972
this. You either will, or will not, get struck by lightning with a winning lottery ticket in your hand tomorrow. That's two outcomes, doesn't make it 50/50.

>>10891488
checked

absolutely based yukarifag

>>10889830
This is the naive definition of probability that's intuitive but doesn't do you much good outside of toy examples with casino games where you essentially assume your probabilities are what you want them to be. It's not very useful for say giving a weather forecast or predicting stock prices. Learn Bayesian statistics.

>>10889313
cause scientists are cunts with naming shit

>>10889313
Rh is different gene to ABO

>>10891472
here's a quick and inexact way:
energy-time uncertainty principle is [math]\Delta E \Delta t \approx \hbar[/math]
characteristic time of an oscillator is [math]2\pi/ \omega[/math], and thus we get [math] \Delta E \approx 2 \pi \hbar \omega [/math]
to be exact, just calculate [math]\Delta E = \langle H^2 \rangle -\langle H \rangle^2 [/math] for the particular state you're interested in. As expected, in an energy eigenstate you obviously get [math]\Delta E = 0[/math].

>>10892077
oops, that should be \Delta E \approx \hbar \omega / 2 \pi on the third line.

>>10892077
oops, that should be [math]\Delta E \approx \hbar \omega / 2 \pi[/math] on the third line.

How do I get the expression of this for all even natural numbers? How do you even tackle such a problem?

>>10892408
You just recall that [math](-1)^{n+1}=-(-1)^n[/math] and go slashy slashy.

hey /sci/
is there a way to show that I have listed all possible factors of a number?
I'm not talking about prime numbers exclusively

for example, if I have 9 I can write 3*3 or 1*9 and I know that those two are all there is
but what if the number is higher? is there some theorem that limits the number of factorizations?

>>10892552
Ye. Just use the prime decomposition, go through all permutations, and then through all associations of said permutations.

>>10887363
reminder to wait to ask for help until you’ve spent a good deal of time thinking over the problem. remember to check the chapter, earlier chapters and other resources in the book; the author may have demonstrated a method for solving that problem or a related problem you have overlooked! this will make you better at self teaching, strengthen the will and most importantly you can feel proud knowing you worked the problem all on your own. good luck

Say your consciousness exists as a separate entity that inhabits your body. If your consciousness is randomly placed in a body then you are most likely to be alive at a time when there is the highest population. So can you use the fact that you are alive today to generate a probability distribution for the apocalypse?
I think this may be bayesian probability related?

Can compression beat encryption?
If we compress any information as far as possible it appears to be randomness.
If we encrypt some information wouldn't the "randomness" that appears after maximum compression be the same as if we compressed the original information?

>>10892077
just noticed another mistake, that should be [math]\Delta E^2 = \langle H^2 \rangle -\langle H \rangle^2[/math] on the final line

How should I put down the research lab that I'm in on my resume?

University of Autism, Department of Autism Studies
Undergraduate Researcher, [Professor's last name] Group

latex test
$\epsilon \geq 0$

how?

If I want a crack at the smoothness and existence problems of the Navier-Stokes equations, I'm assuming I have to be an analysis wiz? Are there any other fields that I should at least have a grasp on? I get that no one knows what fields the final solution will end up utilizing, but what does everyone seem to be working with right now?

>>10894410
iutt seems one of the more promising approaches, as well as theory of barnett integrals

Why do scientists sit by and let people be exposed to 5G radiation?

Why should we trust you?

>>10894455
I'm guessing we can model turbulence by bitcoin values as a function of time

>>10887363
Why do atheistic arguments eventually get to a point where there is a significant leap if "faith" to explain the nature of creation & existence (primordial soup for example). Hemoglobin is the most complicated molecule out there and do you think that just happened to assemble on its own after so many trials and error? I renounced any semblance of faith and went down that 'theres no god' phase for a decade after watching dawkins and hitchens and their like, turns out that they were the fools that professed to be wise in the biblical sense. Thoughts?

>>10894461
I dont think the frequency is high enough to cause radiation/harm to the body

>>10895326
How long ago do you think god created hgb

>thermo question I thought of at random
I am fairly certain that springs experience a small increase in thermal energy when compressed. This would dissipate into the surrounding environment over time. If you allow a compressed spring to reach room temperature, then let it decompress, does it increase, decrease, or remain the same temperature immediately after the decompression? What are the mechanism that cause the change in temperature/thermal energy during compression/decompression?

>>10895496
Answered one my question. A metallic spring likely cools when decompressed, and this is known as the barocaloric effect. Also found this near article, that there is a material that shows the opposite effect:
https://www.nature.com/articles/ncomms1606

Since smoke is unburned fuel, would running a blue-hot propane torch in front of your face in a house fire reduce smoke inhalation hazard? Or is asphyxiation a more pressing concern?

Why is the sky blue? I know that Rayleigh scattering goes as [math]\omega^4[/math], so higher frequencies are preferentially scattered, but wouldn't that result in the sky being violet because violet is the highest frequency of visual light?

>>10887363
What is a good introductory book on algorithm analysis? Preferably with an emphasis on functional programming, but imperative is fine too.

>>10887363
How do I boxed in answers using latex? How do I use different alphabets in latex? Is there another command for \displaystyle that does the same thing?

>>10896574
I think the atmosphere would need to be much thicker, there's not enough gas for it to violet. I dunno mate.

>>10896574
Yeah, but apparently our sun's too wimpy to produce much violet, so the blue-green peak is what you get

Cheers. Is the deviation from an ideal black body all due to absorption in the solar atmosphere?

>>10896924
mean for >>10896914

Is it even possible to get a job in 2019/2020 as a self-taught web dev?

Or did I fall for the Learn To Code meme

>>10896927
Dunno. Those blue spikes kind of look like the hydrogen/helium emission spectra though, don't they?

What's the best degree if I just want to make good money without actually doing work.
t. smart but lazy

>>10896950
How self taught? Indy engineer, only took most basic web and programming courses formally in school, but I have had an affinity for coding since late high school and done informal tutoring for floormates back in college. Been hired as a software engineer by Boeing for above and develop my own software for a pharmaceutical manufacturing company as an intern. I bet the coding in a work environment was the strongest factor, and I only volunteered my skills because mandatory testing and data was being recorded and managed on probably a near literal ton of paper, and no one new anything beyond excel, not even VBA

>>10897000
Become a financial parasite off your parents and friends with a self-taught degree in social engineering. If you're not attractive or charming, this will be an uphill climb. Maybe a professional gaming career if you can make people laugh and you are willing to commit to playing on a days where it is more like work than play.
Smart and lazy meme needs to die though. Laziness is not a smart strategy outside of planning your actions in order to maximize efficiency and effectiveness. Avoidance of effort or investment into oneself is sloth and nihilistic depression.

>>10897289
>Avoidance of effort or investment into oneself is sloth and nihilistic depression.
Or ADHD

>>10887363
Struggling to understand the difference between these two standard deviation formula. Any lead ?

>>10897376
Pic related. Laziness is not a symptom of ADHD, the doctor said so.

>>10897641
I have only known for the coefficient for the 's' to be 1/(n-1), not '+'. Assuming this is true, sigma represents the standard deviation of a sample size that is comprised of all relevant data (aka there is no missing data, or it includes everything). 's' is the deviation for a sample size of which is only partial accounted for. The n-1 term denotes that there is an additional degree of freedom to account for (the unaccounted data). You'll notice this increase 's' relative to sigma in a sample of equal size, indicating that sigma is more precise than 's' due to its full account of the dataset.

>>10889010
The new game just came out, there's some great tracks:
https://www.youtube.com/watch?v=H8nKIxv0t0Y
https://www.youtube.com/watch?v=ePzB2RTXtWk
https://www.youtube.com/watch?v=g6quAOBCqEM
https://www.youtube.com/watch?v=1KoJxo9mMvA
https://www.youtube.com/watch?v=U1RPODPdvWs
https://www.youtube.com/watch?v=Fjny1bxfyOA
https://www.youtube.com/watch?v=TgunO56ONMA
https://www.youtube.com/watch?v=un48UTV5S9g
https://www.youtube.com/watch?v=xI_xDONzTMY
https://www.youtube.com/watch?v=ZRdXeRkijZI
Really almost every new song is top tier. I'm very partial to the stage themes and Idolatrize World myself. Enjoy.

>>10897705
Thanks!

so like... is global warming real?

How do I solve this I honestly have no idea

>>10898570
0

>>10898570
Here's a few observations:
[math]\lim\limits_{n \to \infty} \frac{(-1)^(n+1)4}{3^{n-1} - 6^{n+2}} = 0 [/math]
[math]\lim\limits_{n \to \infty} \frac{-6^{n+4}}{3^{n-1} - 6^{n+2}} = \frac{6^4}{6^2}\lim\limits_{n \to \infty} \frac{6^{n}}{6^{n}} [/math]

>>10898604
36

>>10898570
nvm I am dumb

Any tips for finding lecture notes that aren't on libgen?

Is neuroscience worth it bros? I have a personal reason that makes me feel very passionate towards the field, but not sure if it's worth it to go for the PhD.

>>10898650
Lay down and cry. Then use this pain to remind yourself to always upload to libgen anything significant you manage to get your hands on. And maybe, just maybe, future generations won't need to needlessly suffer.

>>10898736
I mean stuff like https://dec41.user.srcf.net/notes/ and https://www.maths.tcd.ie/~dwilkins/Courses/
Do I just go through the webpages of mathematicians and fuck around until I find shit?

This is going to be a clusterfuck.
How do I analyze a function that I do not know anything about?
You can calculate the result but don't know the process, so if you give to this function the number 1 it will output 5, you can give any number and it will output the result.
My question is, how can I analyze the input and output and make the inverse function?
I'm a real noob, all I know about this is the regressions in the calculator but you need to know the type of function

>>10898752
I've been there too and from experience, I can tell you are very much fucked. The best you can do is try to email the website about it, see what happens.

>>10898650
>>10898752
Why do you want lecture notes specifically? Is there anything in particular you are looking for? Googling a subject will yield plenty of good quality books about it. I don't see why you would need lecture notes in particular.

>>10898796
They're usually more recent and with better formatting for being printed.
I'm not seeking out any specific subject.

>>10898763
Unless you make some assumptions about the function you are looking for, you don’t, really.

>>10898763
If you literally know nothing then just do a neural network model and meme up the neurons until you get something that's good enough.

>>10898821
What kind of assumptions?

>>10898833
I was thinking about this, and am going to try but it's a function that, for example, if you give 1 it outputs 5 but if you give it 2 it'll output 4423423 and if you give 10142 it'll output 4
What I mean is that it looks to be really ridiculous and I don't know if the neural network will reach any good prediction

>>10898873
>what kind of assumptions
It's a polynomial with degree at most n for some n, it's monotone increasing/decreasing, etc.

>>10898873
>if you give 1 it outputs 5 but if you give it 2 it'll output 4423423 and if you give 10142 it'll output 4

Well, assuming there is an underlying rule, a neural network will eventually get to it. Functions that jump like this are not that uncommon, and you can certainly force even simple function like a cubic to give those precise values you listed. It will just be very fucky.

Why is the Fields Medal only given to people below 40 years old?

>>10898946
Because it symbolizes a hope for future achievements. Giving it to someone at 60 would go against the point.

What's the point of enthalpy since it's essentially just heat transfered at constant pressure? Why the additional name?

How do I get better with differential forms and vielbein? (in the contexts of gravitation and also non-abelian gauge theories)
I can use them, I just always fuck up by a numerical factor and/or a sign.

>>10899024
Because it's one of the legendre transformations of energy that make up the four* thermodynamic potentials. Basically, you can write the first law of thermodynamics as [math]dU = TdS - pdV[/math]. Now define enthalpy [math]H = U + pV[/math]. Taking the differential of H yields
[eqn]dH = dU + pdV + Vdp = TdS + Vdp[/eqn]
and you can see in the final equality that we went (technically legendre transformed) from a quantity, U, with the natural variables S and V, to a quantity, H, with natural variables S and p. There are two other thermodynamic potentials that can determined by Legendre transforming to the natural variables T and p, and T and V, which are the Gibbs and Helmholtz free energies respectively.

*there are more than four thermodynamic potentials if you also allow the number of particles in the system to vary.

>>10899038
Practice.

>>10899024
Internal energy, enthalpy or also Gibbs free energy are related by Legendre transforms, just like the Hamiltonian relates to a Lagrangian. A reparametrization leading to other relevant quantities of the system.
https://en.wikipedia.org/wiki/Legendre_Transformations#Definition

>>10899038
Practice and good books? I don't know if there's a better answer to a general question like that.

>>10898946
I guess it also rules out prices given away for "life's work" kind of honors

>>10897641
https://en.wikipedia.org/wiki/Bessel%27s_correction

>>10896579
bumping 4u

>>10899074
>>10899083
>practice
thanksk. I was hoping /sci/ might recommend me a book or a resource with some questions and answers but I suppose I'm just being a lazy sod and could just google it myself.

>>10899145
>inb4 yukarifag comes back and tells you to practice doing physics problems.

What are some good nonlinear regression methods? I think the book I'm reading emphasizes linear regression and linearization which isn't exactly what I was hoping for.

>>10899083

>>10898796
Not that guy, but well written lecture notes are much easier to read than the textbooks they reference

>>10899024
>>10899067
The intensive/extensive variables form symplectic coordinates in phase space with the thermodynamic potential giving rise to a contact structure. Legendre transforms then constitute contactomorphisms that preserve the Gibbs contact form.
https://arxiv.org/abs/physics/0604164

Reposting from /g/ since it seems more you guys area of expertise:

This is probably real basic but I got a math related kinda question I was wondering. There's this game I play where you can take your items to an NPC to be refined, which adds a + number to the item's name, and some added stats and other bonus stuff depending on the item. Anyway, going +1 to +4 is 100% chance, but going any higher has a 50% chance of going up, and a 50% chance of going down. If it goes down, there's also an additional 50% chance that the item will break, making it impossible to do further refinements. So basically it's 50% to succeed and go up, 25% to just go down, and 25% to go down and also break.

My question is, how would you calculate the overall probability to do something like going +4 to +8 before it breaks? Like you got the chance of it succeeding every time, but that's easy enough to calculate, but there's all kinds of other cases like going down and back up without breaking so it confuses me... Been a long time since I got out of school so I'm probably forgetting something simple though. Is there some fairly elegant way of calculating this? I attached a rough diagram of the possible outcomes for the first few repetitions to give a better idea of what I'm talking about.

>>10899686
Oh yeah that shoulda been END under +5 (b) as well if it wasn't obvious.

>>10887363
what are this shiny plastic bags called and where is the aluminium that makes them shine?
my guess is aluminum powder??
i want to know if it conducts electricity (my teter says no)

>>10899686
You get a linear equation for each probability in terms of itself, which you can rearrange and solve: x=a+b*x => x*(1-b)=a => x=a/(1-b).

E.g. once you get to +4, the probability of going from +4 to +5 is 1/2 plus 1/4 of the probability of going from +4 to +5.

P45 = 1/5 + 1/4*P45
=> P45*(1-1/4) = 0.5
=> P45 = (1/2)/(3/4) = 2/3
This gives the same result as 1/2+(1/4*1/2)+(1/4*1/4*1/2)+...; sum of an infinite geometric series.

The probability of going up multiple levels is just the product of the probabilities for the individual steps. But for higher levels, you have to take into account the possibility of going down multiple levels then back up, so you get a system of linear equations. E.g. from 4 to 6:

P46 = P45*P56 = 2/3*P56 (P45 was calculated above as 2/3).
P56 = 1/2+1/4*P46
= 1/2+1/4*2/3*P56
= 1/2+1/6*P56
=> P56*(1-1/6) = 1/2
=> P56 = (1/2)/(5/6) = 3/5
=> P46 = (2/3)*(3/5)=2/5

And so on.

What's the best Multivariate Calculus textbook?

>>10887370
I think it’s a myth that everyone needs 8 hours of sleep. I personally need around 9-9.5 hours before I’ll jump out of bed. Maybe you just need to go to bed earlier

>>10899696
https://en.wikipedia.org/wiki/Metallised_film

Is it impossible to revert lossy compression?
I mean, knowing the method of compression, is it possible make a method of decompressing that gets the original state?
This is sort of a technology question but /sci/ seems more appropriate

>>10900794
Sort of. By definition, if it's lossy, then there's a loss of data. However, you can try to reconstruct the original using software like waifu2x.
Ask again on >>>/g/sqt for recs for your specific case.

>>10900794
> Is it impossible to revert lossy compression?
Yes. The fact that it's lossy implies that there are multiple inputs which compress to the same output. If it was possible to recover the original input exactly, it wouldn't be lossy compression, it would be lossless compression.

>>10900877
>>10900850
>The fact that it's lossy implies that there are multiple inputs which compress to the same output.
how about hashing functions? up to a certain massive data size, every input has a unique output, is it really impossible to revert(without trial and error)?

>>10900892
That`d be lossless compression.

>>10887363
>>10887363
Did I have a heart attack? yesterday night I felt a sharp pain in my heart/chest and I thought im gonna croak
didn't call an ambulance although kinda regretting it
I took 4 advils and went back to sleep
but it still hurts

please help

>>10900892
> how about hashing functions? up to a certain massive data size, every input has a unique output,
Only up to slightly less the size of the hash itself. If you have a 128-bit (16-byte) hash, there are 2^128 possible hashes. There are also 2^128 possible 16-byte files, so it's possible to create a 128-bit hash where each 16-byte file has a unique hash. But the number of files of 16 bytes or smaller is greater than 2^128 (1+2^8+2^16+...+2^120+2^128), so it's not possible for every file of 16 bytes or less to have a different 128-bit hash; more possible files than possible hashes.

> is it really impossible to revert(without trial and error)?
It's impossible to revert *with* trial and error. You cannot create an invertible mapping from a larger set to a smaller set. See "pigeonhole principle".

This isn't an issue for lossless compression because it's possible to get an output that's larger than the input. If you try to compress random data or encrypted data with lossless compression, you're likely to end up with an output file which is larger than the input (although it's possible to create a system where the worst case is an output which is only one bit larger than the input).

>>10901136
>Only up to slightly less the size of the hash itself.
so, if I test every 16 byte file with the hash, there will be no repeated output, but with 17byte files, there will?

Better put, is it mathematically possible to create the inverse function of a hashing function? One where you give a 16byte hash and it outputs data, be it a password or random file.

What areas of math/whatever do I need to study in order to understand the equation on top? I know the bottom is vectors but there is some shit on top that I don't understand.

>>10901280
>it's such specific stuff in applied maths that you dox yourself by recognizing it
Nope, not touching that one.

>>10901301
You're making me lose hope here. Is this notation really that specific?

>>10887363
If there was a tub of water suspended in the air with a live wire in it, and you opened up the drain and stood underneath it would that steady stream of water electrocute you?

>inb4 you'd be electrocute by opening the drain

>>10901354
nah

>>10901363
c-could you explain why?

>>10887363
if i put 3 volts 2 amps into a boost transformers primaries at 120 hrz do i get 2 times more volts than if i used 60 hrz?

there is no online calculator for this. all the transformer calculators work on a unknown hrz range or expect me to know the hysteresis losses before it will accept frequency added into the fields

Why is our brain good at remembering sequences of words (like a poem or lyrics to a song quote or a paragraph from a book) but bad at remembering something like d2387r2yfF__lJWdFF"3rªªF43ªª?!·$"·¿·ffd

>>10901429
why do you think anon-kun?

Question on probability. Here’s a little background on the scenario.
I’m going to assume you are familiar with gacha games. You have the option of doing single rolls or 10 consecutive rolls. If the chance of you getting someone is .7%, would your odds increase doing single or 10 consecutive rolls?

where are they getting x=0.634d from

>>10901565
rearranging: [math] x=\displaystyle\frac{1}{\frac{1}{\sqrt{3}}+1}d [/math]

>>10901197
> so, if I test every 16 byte file with the hash, there will be no repeated output
It depends upon the hash function, but this is usually the case. E.g. CRC32 will map every 32-bit sequence to a different 32-bit hash; more generally, for sequences of 32+N bits each hash will be used for exactly 2^N sequences.

> but with 17byte files, there will?
Clearly; you cannot assign a different 128-bit number to every possible 136-bit sequence. At least one hash will be used for at least 256 different files. If the hash is balanced, every 128-bit hash will be used for exactly 256 different 136-bit sequences.

> Better put, is it mathematically possible to create the inverse function of a hashing function? One where you give a 16byte hash and it outputs data, be it a password or random file.
Theoretically, you can find some file with a given hash by trial and error, but the number of trials is required increases exponentially with the number of bits.

For any "strong" hash (e.g. MD5, SHA-* family), this is computationally infeasible. Being able to compute some sequence which generates a given hash is known as a preimage attack, and the existence of a practical preimage attack makes a hash function useless for any context where you're trying to protect against deliberate tampering, although it may still be useful for protecting against corruption (preimage attacks against CRCs are quite trivial, but they're still commonly used for error detection).

No practical preimage attack exists for MD5 or SHA-*. The best known preimage attack against MD5 requires 2^123.4 computations (vs 2^128 for brute force). MD5 and SHA-1 do have practical collision attacks, i.e. it's possible to create two files with the same hash, which is potentially an issue for digital certificates.

>>10901617
got it I'm retarded, thanks

>>10901384
No. Assuming normal operating conditions, the voltage/current ratios are equal to the ratios of the number of turns, and independent of frequency.

Frequency may affect the maximum power transfer and/or efficiency. Mains transformers are normally designed (and spec'd) for either 50 or 60 Hz, i.e. they'll operate at 60 Hz without significant hysteresis loss, and the power rating is given for 50 Hz (power transfer increases with frequency). You can get power transformers designed for 400 Hz mains, but they tend to be ridiculously expensive (because the only place that 400 Hz mains is used is on aircraft, and anything used on aircraft is subject to truckloads of regulation).

Efficiency decreases if run above the design frequency, due to hysteresis loss. Transformers designed for higher frequencies tend to use powdered iron or ferrite cores rather than laminated iron; this has lower permeability so they'll have lower power transfer at a given frequency, but this is more than offset by the increase in frequency.

>>10901632
good posts
consider referring to hash function output as digest though

I haven't done math in ~10 years.
I can't derive, integrate, or do trigonometry, matrix calculations, et c. I didn't really spend any time understanding things beyond passing tests a long time ago.
What resources should I use to start again?

>>10901714
Khan Academy for things from elementary to calculus
Lang - Basic Mathematics (easy to google for a pdf) if you want a really thorough brush up on everything from arithmetic and trig until matrix mechanics, complex numbers (but not calculus). Lang - A First Course in Calculus would be a nice follow-on from that. +Lang has lots of problems with solutions to practice with too.

>>10901714
everything you listed can be learned in about two weeks, Lang’s Basic Mathematics and Apostol’s Calculus are what you want.

>>10900917
if you weren't from the 3rd world / US,
you'd go see a doctor

>>10898113
https://skepticalscience.com/argument.php

What's the best way to study for high grades?

>>10902616
compete with someone in your class

>>10902616
Cheat like everyone else.
Be friended with a Chinese,or Albanian student,they usually have complete exams a month in advance.

>>10901887
>>10901893
thank you.

I have to refresh myself on math before I start uni soon, how the hell do I even figure this out? I'm not really understanding this at all.

>>10902988
what have you tried?

>>10903016
Well that's the thing, I don't even know how to work out the number. I know 112 people attended, but that's it.

I tried doing 112 - A,B,C,D divided by 3 but that's definitely wrong.

>>10903036
when working with word problems a good strategy is to try and rewrite them as an algebraic equations. For this problem, try to find two equations that express the same information as what is stated in the problem.

>>10903036
We call the number of employees who brought a partner x, and the number who didn't y. 3y=x.
Assuming all the partners were fellow company employees, this gives x+y=112.
If all partners weren't, we have 2x+y=112.
The remainder is left as an exercise for the reader.

>>10901334
It seems like an interative method for something in applied maths. I don't recognize it, and I should, so it's probably specific shit.

>>10903061
>>10903082
I feel dumb for asking, but I still don't understand. I was never good at algebra in high school and it's also been a long time. How do I work out x and y?

The partners aren't part of the company btw.

>>10903108
Can't you look through an algebra book for examples and oingo boingo copy?

Are 2.87mg/l of nitrates in bottled water too much?

>>10903199
(5, arc tan 4/3)

Babby grad student here, 1st semester.

For NMR, when using TMS as a reference, can you also use that as an integration reference? Can I take the area of that peak, normalize it to 12 and go from there?

I did that but my other peaks don't make sense

[math] If <Q, \leq > is a lattice and x is a maximal element, then y /leq x for all y \in Q. Show this is not in general true for a poset. [/math]
Is this because a poset could potential not satisfy the ascending chain condition so there may be more x that satisfy the property of maximal but that aren't equal to some y?

>>10903479
Oh shit that's ugly, you have to add math bars around each individual latex symbol?
Fine, here it is again:
If [math] <Q, \leq > [/math] is a lattice and x is a maximal element, then [math] y \leq x [/math] for all [math] y \in Q [/math] Show this is not in general true for a poset.
Is this because a poset could potential not satisfy the ascending chain condition so there may be more x that satisfy the property of maximal but that aren't equal to some y?

Is there a rigorous definition for Leibniz notation?
And not just for the simplest cases, for things like implicit differentiation, where you basically treat the differentials like fractions.

>>10903487
Maximal element defined as x such that [math]y \geq x[/math] implies x=y?
Try the trivial poset on two elements.

>>10903562
Sort of. Check out infinitesimals.

>>10903446
If you know its concentration, yes, it's called an internal standard

If movement is a 1D spatial transformation, then what is expansion? Does the expanding universe mean that a 3D spatial transformation is taking place?

So we know the definition of the derivative is

[eqn]\frac{d}{dx}\:f\left(x\right)=\lim _{Δx\to 0}\:\frac{f\left(x-Δx\right)-f\left(x\right)}{Δx}[/eqn]

You can plug any function into here, do the necessary algebraic manipulation, and receive its derivative, without fail.

The (riemann) definition of the integral, however, is

[eqn]\int \:f\left(x\right)dx=\lim _{n\to \infty }\sum _{i=1}^n\:f\left(x_i^{\ast }\right)Δx[/eqn]

The integral represents an infinite summation of values of the function. It doesn't not yield a function itself. (in fact I just realized this is one of the ways to state/demonstrate that integration is more difficult/general than differentiation)

It's easy to see how the pioneers of calculus discovered the symbolic derivatives of functions from using the difference quotient.
How, then, did they actually find/discover the symbolic integrals of functions when the riemann integral doesn't provide a function as output? Yeah if you find the derivative of a function you automatically knows its integral, but that's not what I mean.

>>10903840
>You can plug any function into here, do the necessary algebraic manipulation, and receive its derivative, without fail.
That's where you're fucking wrong, lad.
I'm not feeling arsed to showing that the problem of evaluating the limit of a sequence is equivalent to the problem of evaluating a differential, tho, miss me with that shit.

Did the /sci/ mods end up cracking down on the /eng/ general? From what I can tell it's gone and has been gone for quite a while, which is a crying shame because it doesn't appear to have moved to any other board and instead just disappeared off the internet.

Is there anywhere on the internet left where people can give anonymous career advice? Don't fucking say /adv/, if you've ever been there you'll know it doesn't fit the criteria. /eng/ was solid because it had a core of at least somewhat professional people who could at least claim to have seen actual employment in the field, but the posters of /adv/ are lucky to be able to hold down a job at a fast food joint.

>>10904032
>Did the /sci/ mods end up cracking down on the /eng/ general?
I wouldn't know. It's not hard for a general to just disappear because no one's making the threads.
I'll make one, and tell you later if it bans me.

>>10904032
Like the other anon said, pretty sure people just stopped making them. If not, then /biz/ would be the obvious for career advice.

>>10904038
Thanks. I'll drop by in a bit if it doesn't die instantly, then.

>>10904063
It looked at /biz/ and didn't see anything that wasn't just cryptocurrency cheerleading and memes. Maybe they have intermittent threads for this kind of thing, but it seems unlikely to me.

>>10903840
Not every function is a polynomial.
For polynomials, you just need to know the action on x^n and the show linearity of the operation and you're there. But generally you'll find difficult cases for both. E.g.
e^(sin(x))
you'll not have an easy time reducing
e^(sin(x+Dx)) - e^(sin(x))

How do I not forget stuff? Ask me right now what the order axioms for the real numbers are, I couldn't tell you. No fucking clue.

I did linear algebra last year, and I remember very little of it. Almost nothing at all.

Calculus as well, I took last year. I remember more of it, but stuff like proofs I've basically forgotten. E.g. I couldn't prove the FTC to you if you asked me, yet at some point I knew how to.

I don't remember what the Cauchy-Schwartz inequality says, I just remember it's a thing.

I forget like 70% of the stuff I read, or at least the specifics of it. Often I'll get the vague "Oh this reminds me of something" and then I look it up and I'm fine, but I can't do that on exams obviously, and it's still frustrating.

>>10904175
Eat better, sleep 8 hours every night, and exercise. Drink plenty of water

>>10904211
It's really only a math problem though. I have no problem remembering other things.

>>10904248

you don't think about it often enough

Frens, how many higher math classes do I have to take before there are few women enrolled?

>>10904632
I took a maths PhD class for the first time this semester and there's a lass. She isn't cute, but she's there.

>>10904032
it was preferable to the machine learning and programming threads and kept all of you fags contained in one place
>>10904175
low iq

>>10903840
what a dumb fucking post lmao learn real analysis

>>10904632
I'd say Calc 2 and beyond.

>>1090372
How do I use the concentration to normalize against ally other peaks? Say it's 0.001% v/v

>>10904677
now now, don't shame people for asking stupid questions. this is literally the stupid question thread.

I spend most of my free time trying to improve as an athlete, mathematician, musician, /diy/er, with tangential activities/readings in some crossover areas, like programming, electronics, finance, etc. I read up on general western canon as well when I get bored with everything else. I have tried to narrow my primary foci as much as possible to get more considerable skills in what I truly care about, but it will never be enough. On top of that, I have to toil away doing mindless labor most of the day, everyday.

I hope I make it into grad school one day and I finally make it. Or I get shitloads of money or get my time back somehow.

>>10904251
subconscious processing is fairly important, if that's lacking something else is deficient other than just "effort" or "interest". Maybe related to your approach, if they spent more time going over slightly more advanced material that requires recalling earlier results it could help a bit.
>>10905009
You're right I need to stop doing that, thank you.

What is the geometric interpretation of a row vector, as opposed to a column vector?

>>10905211
>I spend most of my free time trying to improve as an athlete, mathematician, musician, /diy/er, with tangential
Vtinge