/sci/ - Science & Math

Any Idea where I can download
Fundamentals of Physics (2018) 11e Student Solutions Manual
https://www.amazon.com/Fundamentals-Physics-Student-Solutions-Manual-ebook/dp/B07F7KC5R9

>>12108439
I DL'd 10th edition, I think that most exercises should be there.

Any reputed Uni where I can get a Maths undergrad degree online? Physics would be impossible online due to lab work being required right? But what about Maths, bros?

If yes what course should I try?

I'd say I'm retarded and can only do trigonometry from 0 to 90* without looking at tables, great at algebra, pretty decent at advanced calculus but shit at basic limit functions, set theory pisses me off. I can do geometry at decent level too.
But I want to work hard at getting good. Help me.

How many bones could you remove from a person without killing them?

I'd categorize them:
No harm to remove
- coccyx, floating ribs, portions of facial bones

Debilitating but survivable
- All limb bones, clavicle, a few more ribs, most of the pelvis, the mandible

Probably too hard to do without killing them
- Spine, essential chest cavity structural elements

I want them to be able to breath and eat without machine assistance

why is the integral of csc x so stupid

>>12108539
No jesus christ, but there is hope for you yet. It is almost certain that schools will be online only for spring 2021. The CSU system made it official yesterday, UC will likely follow. So what you can do is enroll in any in-state CC and take your classes online. CC's will usually offer calc 1-3, linalg, ODE, and discrete math.

there's already a thread >>12103457 with the exact same title
at least wait until the bump limit, jesus

>>12108436
For EE, specifically systems and signals, what's best? Master's or PhD?

>>12108436
Software, give us free physics software that can simulate plasma up to quantum properties, I need a link for that.

>>12108436
Good job transposing the previous format for the new thread. It might not seem too significant but quite a few people will check these links and it not only helps them get valuable resources that are very hard to come by in isolation but also cuts down on retarded repeat posts.
>>12108439
solutions for Haliday and Resnick and Hugh D Young's books are available on Slader I believe. Remember to attempt the problem in earnest before checking or you learn nothing.

>>12110572
>plasma up to quantum properties
How many super computers do you have access to?

>>12110054
I checked the catalog and nothing comes up when I type "sqt" "qtddtot", etc., I don't know why. Okay, let this thread die, then.

Thoughts on hormonal anticonception?
Is there a reason I should tell my gf not to take it if we're paranoid about her getting pregnant and it doesn't seem to fuck up her cycle?
Reading about it, I didn't find anything scary, but still.. better ask some real professionals here.

I am hoping someone will respond to me at the post linked here: >>12108565

why do people refer to single numbers such as 1.618 or root 2 as ratios? slashes not good enough for science folk

My CV is shit but I have publications.
How badly did I mess up? I thought I'd do research instead of internships and now nobody replies to my grad school applications.

>>12113024
>now nobody replies to [literally anything]
that's normal
they like enthusiasm. figure out how to get people jumping with anticipation and you'll get accepted

>>12113088
You can't be a soijack in your email. That's not professional

>>12113093
you'd be surprised. I did it once for a school I didn't care about for a professor I didn't care about. Less than 1month later, I got accepted with him as my primary contact, along with a sizeable bonus and an awkward situation to navigate out of.
I still cringe to this day. Being an ass kissing cheerleader faggot is absolutely being selected for these days.

>>12113124
Would you do it for the best research group leader in the country?

>>12113129
anyone who allows themselves to be called that is likely a huge egomaniac so yeah.
Get on your knees and start sucking.

If earth was split in two, with both bodies staying very close to each other in synchronized orbits, what would gravity be like on both bodies? Would there be no noticeable change if they were close enough?

What creates the brown spots in avocados: oxidation or bacterial growth?

Hi, I'm trying to find the root system of the Lie algebra [math]\widetilde{\mathfrak{so}(9)} = \mathcal{B}_4[/math]. I've found 13 roots, so the dimension should be [math]4 + 13 + 13 = 30[/math] (4 for the Cartan algebra, 13 positive roots and 13 negative roots). However, [math]SO(9)[/math] has dimension 36. Which roots am I missing? It should be three of them.
The Cartan matrix is
[eqn]
\begin{pmatrix}2 & -1 & 0 & 0\\ -1 & 2 & -1 & 0 \\ 0 & -1 & 2 & -1 \\ 0 & 0 & -2 & 2\end{pmatrix}.
[/eqn]
I've found the following roots using root strings:
[eqn]
\alpha_1 \\
\alpha_2 \\
\alpha_3 \\
\alpha_4 \\
\alpha_1 + \alpha_2 \\
\alpha_2 + \alpha_3 \\
\alpha_3 + \alpha_4 \\
\alpha_3 + 2\alpha_4 \\
\alpha_1 + \alpha_2 + \alpha_3 \\
\alpha_2 + \alpha_3 + \alpha_4 \\
\alpha_2 + \alpha_3 + 2\alpha_4 \\
\alpha_1 + \alpha_2 + \alpha_3 + \alpha_4 \\
\alpha_1 + \alpha_2 + \alpha_3 + 2\alpha_4
[/eqn]
Thanks.

>>12114601
Ok I'm stupid, they were
[eqn]
\alpha_2+2\alpha_3+2\alpha_4 \\
\alpha_1+\alpha_2+2\alpha_3+2\alpha_4 \\
\alpha_1+2\alpha_2+2\alpha_3+2\alpha_4
[/eqn]

This is probably braindead tier for most of the people here but the only subject I've really struggled with so far in physics is uniform circular motion and kinetic/potential energy, any other brainlets who had trouble with it know any good resources?

>>12108436
why did you have to use that s oy filled Erlenmeyer as a pic?

>>12114748
dw I'm with ya breh, left my job of 5 years to start studying and been struggling with my introductory physics unit the most out of all my classes. I'm using a book called Physics Principles by Giancoli to teach myself as the lecturer I have barely explains anything and just vaguely rushes through 5 year old slides, and scribbles some diagrams on paper. After reading the book and understanding the concepts I go to https://www.youtube.com/c/MichelvanBiezen/

and work through the playlist he has of whatever topic I'm working on, try to answer the questions before without using the help of the video, then watch the video through to check your reasoning and see where you went wrong, after that I just work through the worksheets provided by my lecturer.

>>12108436
How do I tell if a function is real-only, complex, or imaginary only?

>>12114817
Giancoli is the one my course uses too but I hardly use it, since my lecturer does an alright job. I'll check out the channel though, thanks man.

For part b, would this simply be the expectation with the highest value? I.e. [math] E(X|a) = 3p + 2(1-p) [/math]?

>>12114830
From its definition. Any polynomial with real coefficients has a real value for any real argument, and that extends to any analytic function (a function defined by a convergent Taylor series) over the region of convergence. Such functions will also be defined for any complex argument.

Functions which are only defined for a portion of the reals (e.g. square roots, or more generally nth roots for even n) are often defined for the entire complex plane (or the entire plane except discrete singularities), although they're typically multi-valued (e.g. any real has n nth roots; between zero and two of these will be real).

About the only "typical" functions which are defined for reals but not complex numbers are those which are defined piecewise, as comparisons (x>0 etc) aren't meaningful for complex numbers.

>>12108439
tfw you aren't learning anything

>>12114938
what'dya mean

Anyone well versed in biology/organic chemistry who can tell me which solvent is best to get opium out of poppy straw in an aqueous solution for further process into morphine base via slaked lime and ammonium chlorid?
Can I just use water for it? I read that morphine/codein is very soluble in water and the other unwanted alkaloids are not that much so that water is just okay. Or maybe some kind of alcohol? Or is this too much and solves too many unwanted alkaloids?

I'm probably gonna embarass myself with this question here but what the hell, I have nowhere else to go. Sorry

If one of the properties of an indefinite integral is that you can move a constant factor (-1) across the integral sign, why isn't pic related true? When I move the minus in front of the integral and solve it via substitution, I get log(2x+1) instead of log(-2x-1). What am I doing wrong?

>>12115043
[eqn]\int \frac{1}{x}\mathrm{d}x = \log|x|+C.[/eqn]
You can't take the logarithm of a negative value.

can someone explain how Im supposed to find V_ad?
I knoew V_ac is -10 but idk how to find the rest

>>12115236
forgot pic

>>12115239
calculate the equivalent resistance of the parallel resistors and then multiply by the current in the circuit (V=IR)

>>12115245
I dont know the current

>>12115250
wait I can calculate it my bad

Where did the solution sqrt(x)=-10/6 come from?

>>12115273
x - 1 = 9 + 6sqrt(x) + x

>>12115282
Ok my bad, I typed x - 1 = 9 + 6x + x^2

Given Onsager's use of Kramers–Wannier duality method to solve the 2D Ising model:
[eqn] \sinh{2K}\sinh{2L}=1 [/eqn]

Can I stretch it to the equations below to solve
for [math]H\neq0[/math]?

[eqn] \sinh{2K}\sinh{2L}=1/4 [/eqn]
[eqn] \sinh^2{2K_c}=1/8 [/eqn]

I have worked out everything else, I just need to know if this duality can be extendable.

I feel like this is an easy question, but I'm stumped.

>>12115597
How tf can a function be unbounded on every open interval? I can't think of anyone, but I'm probably just a brainlet.

What is this question even asking me to do? If it was asking me to solve a problem using integration by parts that would be one thing, but it just says to "show this to be the case" and gives me the formula for integration by parts? The answer is the question itself? Is it asking for a proof? If so, where do I even start?

>>12115768
>Is it asking for a proof?
yes
Just use vector calc identities and gauss theorem

I've been working on my own steganography tool, and I want to make sure it's robust against steganalysis. Pic related is mcafee's steganalysis method, which is found at https://www.mcafee.com/enterprise/en-us/downloads/free-tools/steganography.html from some google searches, I found that they use Amazon S3 bucket servers, but the only definition for SDI I could find was spectral differential imaging. Is that what they are using, or is it possibly a proprietary secret? Because it seems like SDI was used for other purposes not relevant to my project.

>>12115597
>>12115609
I'm thinking in Thomae's function to the -1, that is, 0 for any irrational and q for any rational p/q, with (p,q)=1

how does [math]121x \equiv 165 \text{ mod } 20[/math] reduce to [math]x \equiv 5 \text{ mod } 20[/math] here?

>>12115768
demonstrate via identities and standard calculation techniques that the lefth side is equivalent to the right side. It is a sort of straightforward proof where the only thing left to the imagination is precisely what steps you'll carry out for the manipulation of the identities.

>>12114946
low iq. very common and very sad

>>12116433
ok

>>12116412
[math]121 \equiv 1 \text{ mod } 20[/math]
[math]165 \equiv 5 \text{ mod } 20[/math]

>>12115821
Look at the URL you posted. The top of the page says "Steganography Defense Initiative" in 60pt type. Spectral Differential Imaging doesn't appear to be remotely relevant.

Their algorithm almost certainly contains proprietary elements. If you want to guard against steganalysis, you need to analyse the statistics of the bits you're going to change and ensure that the changed bits fit the same profile. Measure the correlation between the bits being used and the other bits of the same pixel and the bits of the surrounding pixels. Once you have a statistical model for those bits, you need to figure out how to encode the hidden stream to fit that model. I'd suggest using the principles behind arithmetic compression.

From Apostol.
Why isn't (1.12) a strict equality? Isn't the right side of (1.11) equal to the lower integral of f+g?

>>12108436
How do I go around solving
Axf''(x) + Bf(x) + Cxf(x)=0?
Already tried Laplace transformation but I end up with an arctangent in an exponential that I don't know how to go about reversing.

>>12116753

Wouldn't you have equality if [math]s_1 = f[/math] and [math]s_2 = g[/math] for some [math]s_1,[/math] [math]s_2[/math]?

>>12108436
I don't quite get the relationship between compactness and continuity. Can someone pls explain?

>>12116753
Simple logical statement. If 1.11 defines the least upper bound and one has that [math]I(f+g)[/math] is an upper bound of all members of the set defined by the sum of the two integrals, then simply [math]I(f+g)[/math] is geq 1.11 by definition of the least upper bound. Just nothing else

how can I measure the rate of change of sine, its derivative is cos, but that's begging the question

read about a NASA program that would tap the yellowstone supervolcano for energy while also relieving pressure from it to stop it from spontaneously blowing up. they said it would cost 3.5B dollars which seems like chump change especially considering you're tapping into a huge source of energy and preventing a cataclysm. why aren't they doing this? is it just that the risk of triggering an eruption is too high?

>>12116893
Make clearer what you want to do.
Do you want to have a real time measurement of a sine waves rate of change? Then implement a derivative filter.
Do you want to analytically find the derivative? Then use the definition of the derivative and a bit of trig identities

>>12116893
rate of change is just the finite difference approximation of the derivative. Rate of change from [math]f(x[/math] to [math]f(x+\Delta x)[/math] is
[eqn]\frac{f(x+\Delta x)-f(x)}{\Delta x}
in the limit [math]\Delta x \to 0[/math] it is the derivative

>>12116861
Compactness is a property of sets (in a topological space) and continuity is a property of functions (between topological spaces). Depending on the topic there may be many different relationships so it's hard to tell which one you mean specifically. I guess the most basic one is that continuous functions preserve compactness (generally only in one direction).

Also most of their relationships come from their topological definitions, so you'll need to work with those if you want to know why they behave so nicely with one another. For compact sets, that would be the fact that for every cover of the set with open sets, you can extract a subcover that is just made up of a finite amount of those open sets, no matter how many elements your original cover has. And for continuity, the definition would be that if you have an open set in the image space, then its preimage will also be an open set, every time. Both definitions pretty obviously restrict a lot of properties through the use of open sets, so the way a continuous function affects open sets in one space will have an immediate consequence on the other space, which is where most of the properties between compact sets and continuous functions come from. That includes the fact that continuous functions defined on compact sets are uniformly continuous, and a bunch of other stuff that can be deduced from these

>>12116893
rate of change is just the finite difference approximation of the derivative. Rate of change from [math]f(x)[/math] to [math]f(x+\Delta x)[/math] is
[eqn]\frac{f(x+\Delta x)-f(x)}{\Delta x}[/eqn]
in the limit [math]\Delta x[/math] to [math]0[/math] it is the derivative

>>12116928
So it's just a matter of preservation?
Hmm

>>12115089
log(-1) =
1.36437635 i

>>12116886
I see, thanks anon.

>>12116985
This.

>>12116977
At least its probably the most fundamental relationship between those. If you add other conditions you can get more interesting results, but at the end the idea is that some properties that hold in compact sets in one space will imply other properties in a different space through the use of a continuous function. Sometimes you can get some properties about the functions themselves, too, like in the property I mentioned earlier about continuous functions in compact sets, or Dini's theorem.

In general there's just too much stuff you can say regarding continuous functions defined in compact sets, that's why I kinda just pointed out where most of those come from at their core, and that is from their effect on open sets in both spaces.

>>12116985
I would have thought the [math] e^{i \pi} = -1 [/math] would imply ln(-1) = i * pi. Is your log base ten?

>>12117033
I think he's just a brainlet

>>12116893
https://youtu.be/HVvCbnrUxek?t=1m

>>12117033
lg(x) base 10
ln(x) base e
log(x) generic

>>12117032
Hmm I see thanks!

>>12110049
They absolutely will not, just like for the fall term they're all going to announce in-person classes to get people (read: chumps) registered then they're going to flip to online at the last second when everyone will be affected by sunken cost fallacy. I work in academia and most institutions I deal with are already building our Fall 2021 online plans if there isn't a vaccine already in place

in this question, is [math]Z_{in}[/math] (which i think is the impedance of the input?) supposed to be equal to [math]Z_s[/math]? i have such little understanding of what it is im actually doing here so please dont bully

>>12117033
[math]\log (x) = \ln (x)[/math].
Only ph*sicists assume base 10.

I know this is a tall ask but is anyone willing to solve this and explain how there is no Um1 or Um2 in the final answer?
I cant into latex so Ill post a pic of what I got next

>>12117120
different in different places
it's sloppy to use just 'log'

>>12117270
[math]\log (x)[/math] always means base e in math, unless specified otherwise.

>>12117094
I'm pretty sure Zin is the impedance between the quarter wavelength load, and the source. The source impedance itself is the impedance from the AC supply.

>>12117258
what I got

>>12117283
this is 4chan, look at board name

>>12117270
log means natural log unless you're in compsci

>>12117094
probably match the load to the line

einstein summation notation makes shit 10x quicker, why didnt they teach us this earlier

Question raised by The Martian/this thread
>>>/tv/139279891

How permafucked is Martian soil by perchlorates? What's the likeliest final solution to the Martian toxicity question?

>>12117904
They did, you just weren't paying attention.

>>12117258
Is it incompressible flow?

>>12116799
Axf'(x)=-(B+Cx)f(x)
f'(x)/f(x) = -(B+Cx)/Ax
Integrate both sides w.r.t x [*]
log(f(x))+k = -(B.log(x)+Cx)/A
f(x) = K*e^(-(B.log(x)+Cx)/A)
This approach can be used for anything which satisfies f'(x)/f(x)=g(x), to get f(x)=ce^G(x) where G is the antiderivative of g.

[*] [eqn]\int {({dy \over dx}) \over y} dx = \int {1 \over y} {dy \over dx} dx = \int {1 \over y} dy[/eqn]

>>12117258
[eqn]
u(x,z)=U_m(x) \left(1-\frac{z^2}{\delta^2}\right)\\
U_m =-\frac{\delta^2}{4\mu}\frac{\Delta p}{L} \\
F=\int_l\int_S \tau \,dA \,dx =-\int_l \mu\, U_m \,2\pi \delta\frac{2z}{\delta^2} \,dx |_{z=\delta}=-\int_l \,4\pi\mu\, U_m dx\\
=\pi \delta^2 \Delta p
[/eqn]

>>12117871
>source: my ass

>>12115337
Anyone?

>>12108436

>Was super excited to start this
>https://www.goodtheorist.science
>every fucking link is dead

goddamn what happened is there a backup of his stuff or a new source which is equally as good

Is there a relatively safe cure for eye floaters yet?
They're only getting worse as I get older, I hate it.

med bros, my penis head has grown too wide for my foreskin. I can't get it past half my penis head. what steroid cream should I buy for making it retractable again?

>>12108439
libgen?

I feel like this shouldn't be hard but it is for my brainlet brain. I need to draw a decision tree for this problem. Can someone check if I did it right? I'm getting hung up on the logic of the problem

>>12118914
here is the decision tree I cooked up

Can someone explain what they mean by this in more detail? I understand integration by parts* but Im not quite grasping what they mean by the highlighted text.


*or at least I thought I did. I understand it enough to use it to compute an integral with it

>>12118958
That's ... just completely useless information.
It just states that you can change between integrals of g df/dx to f dg/dx by changing sign and adding f*g

>>12118975
>That's ... just completely useless information.
I was wondering about that. I hadn't seen anything like this before, but then I hadn't seen it in the context of vectors and dot products, cross products, del operators, etc before.

Wait, does that make a difference, or is that still just useless information?

>>12118991
In vector calculus you just use gauss' theorem. Integration by parts is a special case of that.

You need integration by parts a few times when it comes to integrating distributions, but other than that I haven't used it in a long time.

It looks like the PDF given here is wrong, and actually 2x/(b-a), but even then how does one get (b-a)^2 in the divisor?

>>12119046
Or wait it's not the PDF, but the marking on the graph from which you get the PDF, though that still doesn't explain why the CDF divisor is squared

Damn a lot of high level math here, I hope you guys don't mind my brainlet question.

Need to calculate at what meter/second the train has to go to stop at exactly 1000m. Function is
v(t) = 30 - 0,8t (v = m/s, t = time)
I did:
v - 0,8t = 0
-0,8t = -v
t = 1,25v
But not sure where to go from here. I know I have to set it to = 1000 somehow, but if I do that from the start (v - 0,8t = 1000) the answer makes no sense.

>>12119089
x=v*t

>>12119151
Like
1000 = v * 0,8t ?
I think I'm doing something wrong because I'm not sure how to get to the answer from here.

>>12119216
I think so too
I don't even understand the question
You're asked to calculate v0 or v(t)?
Because v0 is 30 m/s and calculating v(t) seems stupid

>>12119234
v is 30m/s, yes, but when v is 30m/s the train stops at 562,5m. Now the question is, what speed does it have to be so the train stops at exactly 1000m?

>>12119089
You need to use the SUVAT (also called UVAST) equations. These equations describe motion in a straight line with constant acceleration. Given 3 of the following: S (displacement), U (initial velocity), V (final velocity), A (constant acceleration) and T (time), you can calculate either of the other 2.

You have 3 of these quantities (S, U and A) and need to find V. Use the second equation.

>>12119280
>You have 3 of these quantities (S, U and A) and need to find V. Use the second equation.

I mixed up U and V here. That said, the answer conflicts with the equation for velocity you gave in >>12119089

>>12119280
>>12119297
Hmm we haven't learned these equations yet but there's a first part to this problem that I have already solved that includes the letter "s", maybe it is relevant for the second part?

>>12119270
Oh I see

v(t)=v0-0.8t
=0 when the train stops
-> v0/0.8=t

Integration gives you the displacement
x(t)=v0*t-0.4*t^2
=1000
Inserting
-> v0^2/0.8-0.4*(v0/0.8)^2 =1000
-> v0 = 40 m/s

>>12119338
>v0 = 40 m/s
This checks out with the second equation given here >>12119280: [eqn]0^2 = 40^2 + 2 \cdot -0.8 \cdot 1000[/eqn]

>>12119338
Perfect, thank you. So the first part I wrote above was right (v/0.8 = 1.25v), just didn't know how to continue as I'm seeing this integration formula for the first time.

My fucking Casio fx-82AU keeps shitting the bed whenever I want to put a number with a power before a fraction, the fraction just takes the power spot when I hit x^()

>>12118991
it's not useless as other anon suggested, but it's kind of immediately apparent in the application of integration by parts. they're trying to give you a "practical" understanding of integration by parts, whereby your integral over u dv is changed to v du.
if you're looking at the integral of two terms and you're like "ugh, if only the derivative was on the other term, then I'd be able to integrate it easier" then that's what they mean. but nobody really thinks this way, idk the book didn't phrase it great.

Learning some chemistry stuff and I'm woefully under equipped for this.

I'm looking at a text book and it gives figure one with a 1:1 concentration of KCl and how it stays at equilibrium. Okay, simple enough.

Figure two shows that at a 10:1 concentration, the K+ atoms flow to the 1 side from the lesser side.

Figure three shows that with a certain charge on the 1 side, the K atoms on the 10 side stay there, meant to show electrochemical balance or something.

What I'm curious about is, why would the K atoms flow from the greater to lesser solution, and not both the K and the Cl atoms?
If both diffuse the charge would remain neutral, which I would assume it would want.

>>12119584
use more brackets

>>12119584
Grow up and take the rpn pill

>>12119760
I can't I have to use this piece of shit for exams

This is eating me up from the inside
from -pi/2 to pi/2
dy = sqrt2
But from pi/2 to 3pi/4
dy = 2(1-1/sqrt2) = 0.6

Wtf is going on here this graph is insanely nonlinear
The Taylor series is helpful, but insufficiently explanatory

>>12119793
I have no idea what you're asking

>>12119809
How to describe the rate of change of sine. When position is max so is accel, but when pos is min velocity and jerk are max
What is going on here? This level of complexity from such simple periodicity?

>>12119857
>How to describe the rate of change of sine
cos
>When position is max so is accel, but when pos is min velocity and jerk are max
No, look at your graph again

Now with all this Venus talk I have a question. When is said that "x planet's condition is such that there cannot be life there", what do they mean with "life"? human life? or is there an universal concept of life?

>>12119908
usually refers to life as we know is possible of existing on earth, or analogous systems that we think could exist in other places (silicon-based life forms, for example). there's no one answer though.
it's a pretty bold thing to say and unless they're talking about a fucking black hole I take it with a grain of salt.

>>12119882
That's why its such a mindfuck, the derivative explanation no longer satisfies me. I can see how the derivatives are determining the change, or really its what the change will be in the future, as accel = 0 velocity = 1, but describing this change of sin in terms of cos and sin does not really explain whats happening to sin

Sin changes as sin changes doesnt describe how sin is changing, do you see? Saying its cos like sin and cos describe one another, theyre the same thing, so its this circular begging the question situation

>>121199316
[math] \text{cos}x= \frac{e^{ix}+e^{-ix}}{2} [/math]
what is the rate of change of the exponential function? is it unsatisfying to you for [math] \frac{d}{dx} e^x = e^x [/math] ? because by your logic the rate of change of the exponential function is even worse than circular

>>12119946
meant as a reply to
>>12119931
accidentally added a number

>>12119931
>describing this change of sin in terms of cos and sin does not really explain whats happening to sin
I really don't know what sort of miracle explanation you expect.

does "ivy league prestige" work for phd degree? or would i be better off just going to a better group in my field at a non ivy university?

>>12119984
PI/research group prestige matters more for sure. if you really have the opportunity to go to a "better group in your field" and you want to do this field for your life, then that's definitely the better option.
e.g. the best school in the world for my field is colorado university, boulder. if you're in the field everyone knows this.
but if you want to transfer fields at some point or really don't want to do your PhD work for the rest of your life then the name of the school is important still.

>>12119908
probably just self-replicating bacteria.
Complex multicellular life like arthropods didn't seem to appear until large amounts of a high energy oxidizing molecule flooded the atmosphere (cambrian explosion, great oxidation event), so It's fair to say complex life should be fairly rare.
Throughout most of life's early history, life was dependent on reducing sulfur compounds (H2S) as an energy source. For whatever reason, these early life forms were constrained to single celled archaea.
PH3 is chemically similar, in that it is a moderately high energy reducing energy source, and many planets have reducing atmospheres rather than oxidizing.

So simple life is most likely. Complex life, probably not.

>>12108436
I am a fucking brainlet, i tried to solve this:

Two players, A and B, draw two balls each without replacement, only once, in turn, from a deck with 2 red balls and 6 black ones. Player A starts. Any player wins if he draws at least 1 red ball and the opponent draws none. Otherwise they tie. Compute the probabilities of A winning, B winning, tie.

Only thing I think I found is P(A wins)=31/84 but i am not completely sure of that.

>>12120095
how did you arrive at this answer

>>12119946
holy mother of mind melting

thats not e^ix thats e^iz with constant change in z and the graphs are looking straight down on x and y

>>12120203

>>12120212
So the roc is in the rate of change of signs in the expansion, and the change of sings is due to the distance between even and odd numbers, and e is ofc the ratio between exponentiation and division by factorial of same number

>>12120241
What the fuck are you smoking

>>12120291
The good stuff.

>>12120136
P(A gets two red)+P(A gets exactly one red AND B gets none)

Sounds good but I might have messed up the computation of the second member

>>12120477
how can a player draw only one red ball without the other player drawing any?

>>12120487
o nvm i cant read
there are four possibilities regarding the top two cards of the deck
red then black
black then red
red red
black black
just calculate the probs of each of these

>>12120487
since the balls are 8, if A gets one red one black, B can get one black, no?

>>12120498
nvm still cant read
seven possibilities regarding top four cards, compute those

>>12120498
I understand, I read that you saw what I meant now.
Thank you, I will compute now.

>>12120509
ohhhhh damn I feel retarded... TY

>>12120509
scratch that, 11 possibilities

its easier to break it down into cases:
no reds in top four = tie
one red in top four = 50% who wins
two reds in top four = 25% A, 25% B, 50% tie
it may be counterintuitive, but P(A) = P(B)

>>12120537
I had that goddamn suspicion because I thought at first:
A starts, so A has an advantage
but then I told myself that conditioning that can be done even future events (condition on an event in the future) and so I started thinking that it might very well be the case.
Thank you very much it was very good.

>>12120537

so P(A wins)=0.25*P(two reds in top four)+0.5*P(only one red in top four)

correct?

>>12120554
yep

>>12120560
ty

actually you may want to redo the two reds case
now that i think about it, theres 4 cases that result in a tie, 1 where A wins, and 1 where B wins

>>12120598
I tried summing the probabilities of the following sequences to see when A wins:
RRBB
RBBB
BRBB

I obtained 9/28 since the first is 1/28 and the other two are both 9/56.

>>12115002
Ask erowid for different extraction techniques for opium. I believe I read that water works pretty well which is why they make poppy tea

Does mathematica have something to split a function into its real and imaginary parts

When is the smoke from the fires going to clear? When do the fires stop? Days, weeks, months still?

>>12121216
South California, I mean.

>>12121216
few weeks

>>12121189
ComplexExpand[ReIm[f(x)]] will give you a tuple of your real and imaginary parts

ComplexExpand[ReIm[a+bi]]={a,b}
if you input a function like Sin it won't work, you need to write it out explicitly with complex values
ComplexExpand[ReIm[e^ix+e^-ix]]={2Cos[x],0}

>>12121216
november

Is there any point in self study if I'm a NEET dropout who is barred from entering academia? I studied math and cs for a few semesters but now I'm on NEETbux and heavy medication. What I do have is lots of time though, is there any field that would maybe let me make a tiny contribution or will I just end up as a schizo?

>>12121347
You're not prohibited from doing any independent work. You'll have trouble though for certain fields.
I can say that any experimental field is probably out, so I'd narrow it down to theory. And from there just think about what you like the most and what you could dedicate the most to.

You'll not be regarded as a schizo as long as your work is legitimate. No "numbers in the neighborhood of infinity"

>>12116458
>Steganography Defense Initiative
Well now I feel stupid. Thanks though, anon. And this website checks JPG, so it's a bit more complicated than LSB or pixel manipulation. Once I get a working model though, if anyone's interested I'll report back.

>>12121341
thanks

>take weeder class sophmore year
>lots of memorization and study time required
>do well and pass
>a year later someone is asking me for my notes for that class
Is it ethical to give him my notes? I've never had this situation before, thanks.

how do i get better at mathematical induction proofs? any resources?

BRO PLEASE I NEED HELP
I used the formula:
mass = (4 * Length^2 * Frequency^2 * Linear Density)/(Nodes^2 * Gravity)
Putting in my numbers, the formula becomes:
(4 * 1^2 * 140^2 * 0.0015) / (4^2 * 9.80) which gives me 0.75, is this not the right answer?

>>12121726
nvm they wanted me to put in 0.750 (which i had on the screen but didn't put in yet) instead of 0.75

>>12121543
yup as long as it is not for free
you payed something (time) for this result, as long as he pay too (one way or another) then you will both have payed something to get a result (and he need also to learn your notes)
you don't need to ask for money, favor, introducing you to a girl, beers work too and is often received a lot better

>>12121543
only if he pays you and you write someone elses name on it

I feel like an idiot, but can someone explain to me how I'm supposed to derive [math]m_{theory}[/math] from this?

>>12121795
so you have delta x on the LHS of eq 10, I would assume they're looking for mtheory= the power on the term on the right
if v0=0 then you only have the acceleration term and thus the exponent for time in this term is 2. that's my guess

Am I having a brain aneurysm or is there something wrong with the second paragraph? Can someone translate pls?

>>12121839
"as" should read "has"

>>12121832
Thank you. That makes sense.

>>12121845
Thanks buddy

>>12117094
bump because im still stuck on this
the first thing its asking for is the characteristic impedance of the transformer [math]Z_0[/math]. the only equation i seem to have for this is [math]Z_0=\sqrt{Z_{in}Z_L}[/math] but [math]Z_{in}[/math] isnt explicitly stated and i dont see how to solve for it

I found the optimal solution to be [math] x = [3 \hspace{2m} 2]^T [/math], but I don't know how to prove this by messing around with the constraints. I only found things like [math] x_1 \leq \frac{11}{3} [/math] and [math] x_2 \leq \frac{16}{7} [/math] by manipulating the inequalities. I don't think this tells me anything or "proves" that my [math] x [/math] is optimal. Can someone help a retard?

>>12122064
it says to graphically solve it

>>12122117
Yes, but I need to prove that my answer is optimal. I cannot use logic with the graph, but somehow I need to show this by manipulating the constraints. I do not know how to do this.

What causes one titty to be bigger than the other and is this random or something determines the dominant titty?

>>12108436
What an atrocious choice of image, OP.
What the fuck is wrong with you?

>>12122747
Rogan is söy repellent.

Can I get away with following this on circuit sim software or should I shell out for physical stuff?

Not strictly /sci/-related but the grad schools generals aren't going any more so I don't know where to ask.
When should I start applying for grad schools? I began my senior year of undergrad a few weeks ago and I'm worried I may have missed the opportunity already. None of my family has any postsecondary education and my advisor is unavailable due to covid, so I don't really have anyone to ask about grad school stuff other than 4chan.
Around what time should I start applying for scholarship and the like? Are they as important as they are for undergrad?
I've read that, for the most part, you shouldn't be getting into any debt for grad school and most programs give you a stipend, will that just be a part of the program or are there specific things you need to apply to for that?
This is in the states, by the way.

>>12123108
It helped me getting my hands dirty, so to speak. It's really not that much to get the basic hardware and begin understanding, in fact a lot of stuff you can just salvage from old/dead hardware.

>>12123131
applications are due by the end of this year for next fall. you should take the gre asap and make a short list of schools, begin reaching out to people you want to work with. You need letters of recommendation as soon as possible as well.

I can do the top one just fine, but how do you arrive at 0.23N on the second question? I know that touching them will split the charge equally but no application of coulomb's law I try ever gets me to 0.23N

>>12123165
I get 0.224N.

>>12123187
How did you even arrive at that? I'm way off no matter what I do..

>>12123207
Either you split the charge incorrectly or it's a calculation error.

>>12123215
I think I'm splitting the charge incorrectly. This is the first question I've had to try doing it.

>>12123216
Got it?

>>12123216
The total charge is -4μC, so there's -2μC on each sphere after equalising.

9e9*2e-6^2/0.4^2 = 0.225 N. The value of 9e9 for Coulomb's constant is a slight overestimate (by ~0.1%) so the actual value is slightly less (i.e. it shouldn't be possible to get 0.23 N if the spheres are treated as point charges).

>>12123260
>>12123272
Yeah I got it, I had -2 written on my page for the split charge but ended up inputting +8 for some reason.

Why am I just allowed to cancel the natural logs in this step?

>>12123356
Because ln is bijective

>>12123356
you're exponentiating both sides

>where has the engineering thread gone?
Also, has anyone seen this engineering fail yet?
https://m.youtube.com/watch?v=593KwsfiajI

>>12123607
Also another incident occurred this weekend as a crane collapsed

>>12123611

>>12123617
Some shitty Chinese crane though
https://www.fleetmon.com/maritime-news/2020/30921/3800-ton-crane-chinese-offshore-construction-vesse/
>start worrying US, you're being overtaken by a nation that can't properly construct cranes

A book I'm reading claims that the integral [math] - \int_{(0,1) \times (0,1)} \log \lvert x - y \rvert \, dx \, dy < \infty [/math].
How the fuck is this shit possible.

My stupid question is:
Can you say something that'd make me pick up my textbook and study?
I've been slacking and I need that lil push.

>>12123685
Did you actually try to compute it?

>>12123825
Yeah but the value just goes off to infinity.

How do I achieve this 'mathematical maturity' thing that everyone's talking about? My major is heavily tied to physics which is also heavily tied to mathematics so I want to not be a formula-chugging person.

>>12123855
That's an improper integral. To evaluate you have to take a limit somewhere, and that limit is actually finite.

Hey /sci/ I'm currently doing /sig/ and I'm total dogshit at math, like a learning disability, anyway a tard like me can learn, my math skills are nigger teir, pretty sure I was just let through in high school because the teachers thought I had a carrer in art set in stone

>>12123917
If you have a disability in math why not learn history or something?

>>12123911
Holy fuck you're right. Thanks, I had made a serious error

>>12123927
I know a good bit on that already, I've learned that you burn 300 calories from normal brain function and it's possible to increase it when you learn new things. Math is something i barely know and I'm obviousky trying to get a bit more /fit/ aswell.

>>12123871
do a lot of math

>>12123963
So I don't need to start from basic addition and just do a bunch of math problems starting where I am now? (Calculus 3)

>>12114915
Nah, it's asking what's the best decision he can make as a function of [math]p[/math].
>>12115597
Someone asked this exact same question a couple weeks ago.
>>12118914
I have no idea how to read that.
Wouldn't it be easier to just compute the expected utility from buying it at each week?
>>12123131
>Not strictly /sci/-related
Anon, this is a containment thread.
>>12123765
Every second you spend not studying is a second that some pajeet spends harassing a white woman over the internet.
>>12123990
Yeah, sounds like a good plan.

>>12124039
Holy fuck where had you been bud? Missed you.

>>12124039
>>12114915
Wait, I misread your post, that's right.
>>12124040
>>/sci/thread/S12015457#p12022419

>>12124045
You fucking nigger, welcome back.

>>12124039

>>12124045
welcome back, fag

>>12124040
Glad to have you back, fag

>>12124039
>Someone asked this exact same question a couple weeks ago.
Found it.
>>/sci/thread/S12058471#p12068582
>>12124053
>>12124056
>>12124057
>>12124061
Thanks, lads.

I'm lost in trying to simplify the pictured boolean algebraic expression.
Specifically, I have no clue what they're referring to in the second line with "theorem 14", as there isn't any theorem 14 in the book that corresponds to whatever it is they seem to be doing.

What law/rule are they applying to make that simplification?

I had laser eye surgery a month ago and I’m supposed to wear sunglasses outdoors during daytime for another five months even if it’s not sunny. Is this really necessary? I feel like a total tool with shades on when it’s raining or overcast

How do you guys find time to go beyond what your courses are asking you to do? For example, if a Physics class were to cover chapter 2, how do you guys manage to go cover parts of chapter 3 while also doing a bunch of practice problems that aren't even assigned on the homework for chapter 2?

>>12124106
yes idiot. do you want eye cancer? literally nobody besides yourself is caring how you look, and if anyone says anything just say they're prescription sunglasses and you left your glasses at home

>>12124156
>do you want eye cancer?

>>12124156
>if anyone says anything just say they're prescription sunglasses and you left your glasses at home
yeah, or, you know, you could just tell the truth

>>12124106
Just make sure they're really over the top then you can say it's ironic or you lost a bet or something
With flames and shit
>>12124093
Dunno, you should probably look harder. Bound to be somewhere if he writes it next to the formulas.

>>12124175
I've been looking for roughly two hours now

can anyone here help with job advice? I’m trying to get my boomer uncle a job but all the companies seem to be fake posting jobs. He’s had 20 years under his belt for Quality and did major accomplishments. I don’t know how to help him beyond recruiting agencies and LinkedIn. Agencies have also been cutting everyone dry. Pls advice

>>12122064
bumping for my question, thanks lads

>>12124193
What book?

>>12124228
Roth & Kinney's Fundamentals of Logic Design, 7th edition.
That screenshot is from the solutions manual for the 6th edition, but there's almost no difference in question correspondence. Comparing the two books, there isn't any difference in how the theorems and laws are laid out, so whatever "Theorem 14" is, should hold for the 7th edition as well.

>>12124247
This looks useful

>>12124274
for fuck's sake I'm literally retarded

>>12124285
glad to be of help anon

Anyone able to help with this? My first approach was to think of all the different sums you can make with elements from A. I concluded that with the "first" element of A you can make 19 distinct sums, with the second you can make 18, etc. If you look at how many distinct sums that is it's 190. That certainly sounds significant, pigeonhole-wise, but there are 375 distinct sums that can be made with all the integers from 1 to 189 (1+2, 188+189, and all the numbers in between), which is more than 190.

Tell me where I'm being retarded

>>12124342
Have you tried rearranging [math]a + b = c + d[/math] as [math]a - c = d - b[/math], ordering A and then pigeon holing that?

>>12124398
Well I'm stupid. That should basically be it yea. That'd get you to 190 as well, which obviously proves the theorem. Thanks anon

Requesting feedback on this (again, since no one gave any last thread).

Question about waves, a period is the TIME it takes for a full oscillation while the wavelength is the LENGTH of a full oscillation?

>>12124751
Wavelength is the spatial period, so yes.

>>12108436
Why does 4channel suddenly triggers my kaspersky whenever I visit a page? The sound is honestly annoying as fuck.

>>12124748
Maybe include that \begin{} works in the math environment.
I didn't know that, but I'm probably just a brainlet
[math]\begin{pmatrix}\text{op}\\\text{is}\\\text{a}\\\text{faggot}\end{pmatrix}[/math]

I want to get into designing CPUs, embedded stuff, electronics etc. What degree or field of study should I pursue? I already have a computer science degree

>>12124865
EE or solid state physics

>>12124748
explain what detexify is. I think emphasize its importance more
also thanks for using my post as the example desu

>>12124856
Underrated post.

>>12117270
>I am the log base e, thou shalt have no other logs before thee.

>>12124896
>Hole left by the Christian Dark Ages
This one is true, though.

>>12124902
It's really not as bad as the e-scientists make it out to be. Monks preserved many of the writings of the greeks. If anything, they helped preserve that knowledge instead of having it go forgotten and society needing to start over from scratch.

>>12124896
how do I read a scientific paper?

>>12124909
>It's really not as bad as the e-scientists make it out to be.
True, but that doesn't mean it didn't happen.

>>12124909
but religion bad

>>12124910
By realizing that the abstract and conclusion are the only important things.

>>12124910
Read the abstract, look at the pictures, read the conclusion.
If you're still interested/need a source to plagiate from, read from the beginning.

>>12124818
>spatial period
What does spatial mean? Space? How does space relate to those two? Sorry...

>>12124985
relating to space
spatial period means the length for one wave period. also known as the wavelength

>>12124856
>but I'm probably just a brainlet
No, that's actually important, thanks.
>>12124870
Adjusted.
>>12124896
Baste.

>https://www.artofmanliness.com/articles/fall-asleep-fast/
is this medically sound(falling asleep in two minutes)?

>>12124985
A wave can be expressed as [math]Ae^{i(kx - \omega t )}[/math].
[math]A[/math] is the amplitude and [math]e^{i(kx - \omega t )}[/math] is the rotating around the unit circle, so the wavy part.
When you let the time flow [math]\omega t [/math] describes the oscillation in the with the angular frequency [math]\omega[/math].
When you look at the wave at one point in time and move along the x axis, the wave oscillates with [math]k=2\pi/\lambda[/math]. It has the same purpose as the frequency, only in space

What exactly is the difference between the two speed formulas?

>>12125059
their use cases
the bottom equation can give you the speed of a wave on a physical string. the top one cannot from first principles, you'd have to measure omega and k or lambda and T from an already existing wave on the string.

you also can't use the bottom equation for any other waves (EM, sound, etc.)

>>12125059
the first formula is true for all progressive waves
the second formula is true in a specific case (transverse wave on a stretched string)

would it be theoretically possible to stimulate the JAW muscles trough isometric tension?

>>12125080
>the first formula is true for all progressive waves
Is transverse wave (on a stretched string) also considered a progressive wave? So like, I *could* use the 1st formula for transverse waves but it's much easier to just use the 2nd one?
>>12125073
>their use cases
Ooooh that makes sense, yeah I don't think that you'd be able to measure some of the stuff required.

Thank you both so much!

Does chlorine react with oxygen?

>>12122064
im dying here anons, can someone help? I cannot use simplex method. I cannot solve graphically. I need to verify that x = [ 3 2]^T is the optimal solution using the inequalities in the picture. I have no fucking clue how to do this.

>>12125529
Set [math]z = x_1 + x_2[/math] and [math]w = x_1 - x_2[/math].
The first equation becomes [math]-w \leq 1[/math]. Rewrite it as [math]w \geq -1[/math]. The second one becomes [math]3.5 z - 2.5 w \leq 15[/math]. Pass [math]w[/math] to the other side on the last equation and get [math]3.5z \leq 15 + 2.5w \leq 17.5[/math]. That's [math]z \leq 5[/math].

>>12125529
Sum the second and third equations for [math]5x_1 + 5x_2 \leq 25[/math].

>>12125332
When they're both gases at room temp? No.

>>12125635
So why does that prove that it is optimal? Is it necessarily the case that it is optimal if it is equal to each [math]b[/math] in the constraints?

>>12124912
>it didn't happen
What is "it" anyway that makes the church so bad?
Protestant countries like to pretend Catholicism is wrong and therefore the period the country was catholic must've been awful (it wasn't due to Catholicism)

Any recommendations for books that introduce Analysis from a pure (point set) topological standpoint.
So not on spaces that have more structure like metric, normed, banach, etc. just a topology.

>>12126253
Because if it's =25 its optimal

>>12126937
in other words, you want a book for general topology

>>12125529
> I cannot use simplex method. I cannot solve graphically. I need to verify that x = [ 3 2]^T is the optimal solution using the inequalities in the picture.
It isn't the optimal solution, unless x1,x2 are constrained to integers. The optimal solution is x1=76/25=3.04, x2=54/25=2.16 => z=5.2 (x1=3, x2=2 => z=5).

>>12126253
5x1+5x2<=25
=> x1+x2<=5
So if there's a valid solution with x1+x2=5, that's optimal; any greater value wouldn't be a valid solution (it would necessarily violate either the second or third constraint). The optimal solution isn't necessarily unique, and you have to show that it satisfies each of the constraints in order to actually be a valid solution.

I'm making a table in APA format that measures responses to two question, but theres 3 groups of people and 7 sections to each question, how should I format the table?
I thought two columns for each question and then 7 columns under each is technically the style, but it looks really messy unless I rotate it sideways which idk if i should or not since its for a first year research unit. Would I be better off making two tables, one for each question? I'm worried that since the study is looking at the correlation between the two i should keep it together

Can someone explain how they reached that conclusion? If I just try to calculate the limit outright I get some jumbled nonsense and I'm not sure what the answer is telling me.

>>12127393
l'hospital

>>12127393
[eqn]f'(x_0) = \lim_{x \to x_0} \frac{f(x)-f(x_0)}{x-x_0}[/eqn]

>>12127419
>>12127393
l'occitane

>>12127428
Don't you ever reply to me again motherfucker
I will fucking cut you

>>12127026
I have never seen any general topology book that introduced properties of differentiation, integration or differntial form (ok, there is additional structure there like hausdorff and countable topological basis)

>>12126937
But you can't do analysis on topology alone. You need a more rigid structure.
Rudin covers basic topological aspects of analysis though.

>>12127393
Do you know the definition of a derivative? Do you know the derivative of 1/x and of ln(x)? The limit being taken is essentially the formula for the derivative of 1/x + ln(x) evaluated at x=2. Proving the derivative of 1/x from first principals should be easy. Proving the derivative of ln(x) might be a little more tricky..

>>12127430
l'ol you mad

>>12127419
That's what I thought I was doing before I realised I had fucked it up. Now I got it.

What is [math]\lim_{h\to0} \frac{f(x+h) - f(x)}{h}[/math]?
Well, obviously if we just apply the L'hospital rule we find that
[math]\lim_{h\to0} \frac{f(x+h) - f(x)}{h} = \lim_{h\to0} \frac{f'(x+h)}{1} = f'(x) [/math].
Ez.

>>12127431
none of these things exist without a metric or a measure

>>12127447
is this real|

>>12127447
But wait!
What is [math]f'(x+h)[/math]?
It's nothing but [math]\lim_{j \to 0} \frac{f(x+h+j) - f(h+j)}{j}[/math].
So in reality we have
[eqn]\lim_{h\to0} \frac{f(x+h) - f(x)}{h} = \lim_{h\to0} \frac{\lim_{j \to 0} \frac{f(x+h+j) - f(x+h)}{j}}{1} = f'(x)[/eqn].
Hmmmm but how do we evaluate the upper limit? We apply L'hospital's rule again to find
[eqn]\lim_{h\to0} \frac{\lim_{j \to 0} \frac{f(x+h+j) - f(x+h)}{j}}{1}= \lim_{h\to0} \frac{\lim_{j \to 0} \frac{\lim_{k \to 0} \frac{f(x+h+j+k) - f(x+h+j)}{j}}{1}}{1}[/eqn]
So in essence what we're dealing with is
[eqn] \lim_{n\to \infty} \left[ \lim_{x_1\to 0} \lim_{x_1\to 0} \ldots \lim_{x_n \to 0} \frac{f(x_1 + \dots + x_n) - f(x_1 + \dots + x_{n-1})}{x_n}\right][/eqn]
Now we need to appeal to the theory of infinitely bracketed limits to know where to go next.

How do you complete this sequence:
1 4 40 50

>>12127831
however you want

>>12127831
1 4 40 50 51 52 53 54 55 56 57 58 ...

>>12127905
This is what I thought but fucking retarded answer is 73 for god knows what logic

>>12127907
Yeah I know that meme xd lol when super epic

>>12127912
What meme? I'm being serious. That's how I would complete it.

>>12127419
L'Hôpital

>>12127991

>>12127917
Shut up, reddit.

>>12127991
Ellhospital.

How does an LED create electron holes? I believe they create light by using the fact that when electrons change orbitals, they have to capture or release energy in the form of EM radiation. So when an LED receives a current, electron get captured and light gets released. An amp a lot of current though, there’s no way it just has that many holes stored like some kind of weird battery, so how does it generate them?

new bread >>12128061

Is Linguistics a good major to double major with Applied Mathematics?