/sqt/ /qtddtot/ - stupid questions thread

[Anonymous No.11919362]

Previously >>11903346

Reminder that the most basic problem solving technique is actually writing the problem down.

>what is /sqt/ for
Questions regarding math and science, plus appropriate advice requests.
>where do I go for other SFW questions and requests?
>>>/wsr/ , >>>/g/sqt , >>>/diy/sqt , >>>/adv/ , etc.
>books?
libgen.is (warn me if the link breaks)
https://stitz-zeager.com/
>articles?
sci-hub (you'll have to google for a link, unfortunately)
>book recs?
https://sites.google.com/site/scienceandmathguide/
https://4chan-science.fandom.com/wiki//sci/_Wiki
http://math.ucr.edu/home/baez/physics/Administrivia/booklist.html
>how do I post math symbols?
https://i.imgur.com/vPAp2YD.png
>a google search didn't return anything, is there anything else I should try before asking the question here?
https://scholar.google.com/
>where do I look up if the question has already been asked here?
>>/sci/
https://boards.fireden.net/sci/
>how do I optimize an image losslessly?
https://trimage.org/
https://pnggauntlet.com/

Question asking tips and tricks:
>attach an image
>if you've made a mistake that doesn't actually affect the question, don't reply to yourself correcting it. Anons looking for people to help usually assume that questions with replies have already been answered, more so if it has two or three replies
>ask anonymously
>check the Latex with the Tex button on the posting box
>if someone replies to your question with a shitpost, ignore it

Stuff:
Good charts: https://imgur.com/a/kAiPAJx
Shitty charts: https://imgur.com/a/TpiinBE (Post any that I've missed.)
Verbitsky: https://imgur.com/a/QgEw4XN
https://pastebin.com/SmBc26uh
Graphing: https://www.desmos.com/
Calc solver: https://www.wolframalpha.com/
Tables, properties, material selection:
https://www.engineeringtoolbox.com/
http://www.matweb.com/

[Anonymous No.11919405]

Unanswered stuff:
Math stuff:
>>11905759
>>11911229
>>11915126
>>11915976

Physics stuff:
>>11905016
>>11908671 with correction >>11908678
>>11909343
>>11911365
>>11911365
>>11915484
>>11915612

Biology questions:
>>11916611

/g/ stuff:
>>11906256
>>11916141

Stupid stuff:
>>11904235
>>11908507
>>11909987
>>11910886
>>11915655
>>11915685
>>11916003
>>11916151
>>11918612
>>11918629
>>11918965

[Anonymous No.11919496]

Is it just me, or are chemistry problems more diffcult at googling for an answer? It feels like with anything else, it's easy or at least straightforward to find out a specific fact by googling for keywords, then honing the search terms as necessary. But when it comes to chemistry, you can formulate a very precise question whose answer would be common knowledge if asked to a chemist but not plainly stated anywhere, neither or academic books nor on internet communities of chemists. Do I have a point here? Maybe such specific knowledge is known but simply paywalled behind crap like Reaxys?

[Anonymous No.11919665]

How do i calculate force at terminal velocity, and also when im doing drag coefficients do break an object thats a cube and a cylinder into two parts for easy calcs or do i need some type of new model for calculating it?
Im trying to figure out if catching a camera at terminal velocity is safe.

[Anonymous No.11920015]

Are BJT transistors used anymore?

[Anonymous No.11920129]

>A point estimator [math]\hat{\theta}_n[/math] of a parameter [math]\theta[/math] is consistent if [math]\hat{\theta}_n \rightarrow \theta [/math]
How do we know our point estimator will converge to our parameter if the parameter is unknown?

[Anonymous No.11920236]

>>11919665
it depends how you catch it.
if you know the terminal velocity you can use the approximation
[math]F=\frac{\Delta p}{\Delta t}[/math] where [math]\Delta p, \Delta t[/math] are the change in momentum (momentum of falling camera at terminal velocity) and the time it takes you to fully stop its motion.

[Anomynous No.11920438]

Dust explosions, I read, are caused by igniting particles with a high surface-area-to-volume ratio. But why does rapidly burning all that dust cause an explosion?

[Anonymous No.11920512]

>>11920438
burning stuff causes heat
heat causes the air pressure to increase
if you burn a lot of stuff in a small area you create a local source of very high pressure that has to go somewhere, so it travels away from the fire like a shockwave. it's the exact same mechanism of a bomb

[Anonymous No.11920778]

>>11919362
ok lads i require college advice
i have to choose between two fields: first is robotics and second is electronic engineering, telecommunications and information technology
im quite knowledgeable in both mechanical and electrical physics
which one do ya think will land me a more dynamic job because i dont want to be a office monkey my whole whole life ;_;

[Anonymous No.11920947]

Is it possible that gravitons, if they exist, might actually be really huge? Like stretching to the ends of the universe huge?
Would that explain why they're so low energy and hard to peturb?

[Anonymous No.11920950]

>>11920778
EE is always a more lucrative field, if not a bit more boring.
if you're super invested in robotics then go there, but if you're 50/50 or even close to that then do EE.
>which will land a more dynamic job
EE is the only one that will land you a job in the first place

[Anonymous No.11921011]

how do i solve this? what's the answer?

[Anonymous No.11921042]

>>11921011
its all linear so, express the transformation from the point (x,y) to the point T(x,y) as a matrix, invert the matrix, done.

[Anonymous No.11921059]

Is the whole “gravity is a bend in spacetime” thing another one of those scientific lies that are close enough when the truth takes too long, like entropy as randomness? GR provides nothing as far as what gravity actually is only equations so where does this come from? Is it an experimentally derived idea? I occasionally see stories about research on the mechanisms for gravity which surely shouldn’t be happening if we figured out at least that it’s curvature right? Or am I completely wrong here?

[Anonymous No.11921063]

>>11921011
https://www.wolframalpha.com/input/?i=invert+%28%288%2C+13%29%2C+%2817%2C+2%29%29

[Anonymous No.11921072]

>>11920947
no, point particles are all sizeless

[Anonymous No.11921079]

>>11921059
>Is the whole “gravity is a bend in spacetime” thing another one of those scientific lies that are close enough when the truth takes too long, like entropy as randomness?
No.
>GR provides nothing as far as what gravity actually is only equations so where does this come from?
IIRC there are some no go results that show that gravity can't be formulated classically in a way compatible with special relativity.
Also, read about the Equivalence Principle.
>Is it an experimentally derived idea?
GR has strong experimental backing.
>I occasionally see stories about research on the mechanisms for gravity which surely shouldn’t be happening if we figured out at least that it’s curvature right?
IIRC that's because GR isn't compatible with quantum mechanics.

[Anonymous No.11921084]

>>11921011
turn it into a matrix and ask wolfram alpha for the answer

[Anonymous No.11921139]

I know you guys dont like compsci here but i have a python question

I used to know some formating trick to use instead of inserting a bunch of tabs in a print statement, it went something like ("{a}\t{b}\t{c}").format("a","b","c")
except the word isn't format and i'm not sure what the data structures were

[Anonymous No.11921141]

>>11921063
>>11921084
shit.. duh, thx

[Anonymous No.11921147]

>>11921072
sizeless, sure, but what about their probability distribution? something like >90% an electron is constrained to a region of a few picometers, but what is >90% of a graviton was AU or galaxy or cluster sized?

[Anonymous No.11921149]

>>11921141
>https://www.wolframalpha.com/input/?i=invert+%28%288%2C+13%29%2C+%2817%2C+2%29%29
just kidding, I still don't get it. what' s the 'rule' here?

[Anonymous No.11921154]

>>11921079
>No
So then what is its position as a scientifically verifiable real (as in, not just a part of the math involved) phenomenon on a scale from string theory to...I don’t know something unquestionable like alpha-beta hierarchy.
> no go results that show that gravity can't be formulated classically in a way compatible with special relativity.
Sorry I didn’t understand the implication here.
> GR has strong experimental backing.
That’s not what I was saying there. What I meant was that relativity seems to not actually be affected by what mechanism ultimately creates gravity, only that the resulting effect behaves in certain ways. Put another way relativity doesn’t need curvature either conceptually or mathematically and wouldn’t be disproven if we discovered a different mechanism of action. If I’m not wrong about that, or tell me if I am, then what direct proof is there for gravity as curvature, since in that case experimental support of relativity =/= experimental support of curvature.

[Anonymous No.11921194]

>>11921149
He literally linked you the answer. Just format it like the second like.

[Anonymous No.11921201]

>>11921149
Think about what you did to to turn the mapping [math]T(x,y)[/math] into a matrix. Now do that but in reverse for your inverted matrix.

[Anonymous No.11921218]

>>11921201
I tried entering the second line. I just don't really know these terms well enough to know what I'm looking for in that answer

[Anonymous No.11921233]

>>11921218
they gave you the first rule in terms of ax + by

[Anonymous No.11921241]

>>11921233
pls

[Anonymous No.11921251]

>>11921218
You're not entering the answer in the proper format. But more importantly it doesn't seem you actually understand what the point of this problem is.

They give you a linear transformation [math]T : \mathbb{R}^2 \to \mathbb{R}^2[/math] defined by, for every [math](x,y) \in \mathbb{R}^2[/math], [math]T(x,y) = (8x + 13y, 17x + 2y)[/math]. One of the main reasons for studying linear algebra in the first place is that every linear map [math]\mathbb{R}^n \to \mathbb{R}^m[/math] can be represented by an [math]n \times m[/math] matrix, with the action of the map being matrix multiplication on "column vectors" of [math]\mathbb{R}^n[/math], yielding column vectors of [math]\mathbb{R}^m[/math]. In this case [math]n = m = 2[/math], so we have a [math]2 \times 2[/math] matrix. How do we figure out this matrix representation? Well let's write it down: [eqn]T(x,y) \equiv \begin{pmatrix}
T_{11} & T_{12} \\ T_{21} & T_{22} \end{pmatrix} \begin{pmatrix} x \\ y
\end{pmatrix} = \begin{pmatrix} 8x + 13y \\ 17x + 2y
\end{pmatrix}.[/eqn] Perform matrix multiplication between the [math]T[/math] matrix and the [math]\begin{pmatrix} x \\ y
\end{pmatrix}[/math] vector:
[eqn]\begin{pmatrix}
T_{11} & T_{12} \\ T_{21} & T_{22} \end{pmatrix} \begin{pmatrix} x \\ y
\end{pmatrix} = \begin{pmatrix} T_{11}x + T_{12}y \\ T_{21}x + T_{22}y
\end{pmatrix}.[/eqn] Compare this to the equation above. Can you see how we got the matrix elements of [math]T[/math]?

Now that you have the matrix representation for [math]T[/math], you can invert it. If you don't know how this is actually done, google it. For [math]2 \times 2[/math] matrices it's very simple and you should actually understand why the result is what it is, rather than just telling WolframAlpha to spit the answer out. Assuming you've done that, you now have a matrix representation for [math]T^{-1}[/math]:
[eqn]T^{-1} \equiv \begin{pmatrix}
[T^{-1}]_{11} & [T^{-1}]_{12} \\ [T^{-1}]_{21} & [T^{-1}]_{22} \end{pmatrix}.[/eqn]

[Anonymous No.11921260]

>>11921251
(cont.) What is the transformation rule for [math]T^{-1}[/math]? Well let's do the same thing we did at the beginning but in reverse: [eqn]T^{-1}(x,y) \equiv \begin{pmatrix} [T^{-1}]_{11} & [T^{-1}]_{12} \\ [T^{-1}]_{21} & [T^{-1}]_{22} \end{pmatrix} \begin{pmatrix} x \\ y \end{pmatrix}.[/eqn] Perform the matrix multiplication with the proper matrix elements [math][T^{-1}]_{ij}[/math] and look at the output vector you obtain.

[Anonymous No.11921269]

>>11921218
I hate when people get mad at a stupid question on an sqt thread, but you’re not even asking a question. You’re telling people to just give you the answer because you can’t be bothered to even know the basics of what you’re asking about. Even the damn answer bot basically told you the answer and you still can’t get it right. “The answer isn’t a formula”. What do formulas have given it’s obviously not constant?

[Anonymous No.11921275]

>>11921269
I asked what the rule was supposed to mean, I still don't know but I'm reading the other anons' quality reply

[Anonymous No.11921280]

>>11921269
and for the record, my book didn't mention this it all, and I couldn't find out what was meant by 'rule' of the inverse via googling

[Anonymous No.11921298]

>>11921251
>>11921260
thanks for the quality reply, fren

[Anonymous No.11921332]

is real world too primitive for pure math?

[Anonymous No.11921392]

>>11920129
Even though the parameter is unknown, it is a fixed number. The idea is that the estimator will resemble the unknown value more and more the more number of elements in your sample. It can be proven mathematically, it's a sort of probability convergence. I don't see why not knowing the true value of the parameter matters at all.

[Anonymous No.11921451]

>>11921139
>("{a}\t{b}\t{c}").format("a","b","c")
("{a}\t{b}\t{c}").format(a="a",b="b",c="c")

[Anonymous No.11921917]

how big of a deal is it if my degree is from a university's satellite campus instead of the main one?

[Anonymous No.11922072]

What's the difference between centre of lift and centre of pressure?

[Anonymous No.11922455]

>>11921154
>So then what is its position as a scientifically verifiable real (as in, not just a part of the math involved) phenomenon on a scale from string theory to...I don’t know something unquestionable like alpha-beta hierarchy.
"It works really well whenever we can describe a situation with it, but it doesn't work when we can't even use it to describe the situation."
>Sorry I didn’t understand the implication here.
Imagine you could formulate gravity as a force generated by a field that acts between objects with mass, in Minkowski space.
This immediately hits a problem because light curves under sufficient gravity.
But besides that, I recall it still having some other problems.
>That’s not what I was saying there. What I meant was that relativity seems to not actually be affected by what mechanism ultimately creates gravity, only that the resulting effect behaves in certain ways. Put another way relativity doesn’t need curvature either conceptually or mathematically and wouldn’t be disproven if we discovered a different mechanism of action. If I’m not wrong about that, or tell me if I am, then what direct proof is there for gravity as curvature, since in that case experimental support of relativity =/= experimental support of curvature.
Light bending is by far the strongest argument, but I recall there being mathematical stuff too.

[Anonymous No.11922540]

>>11920950
thank you anon
i'll have to break up with my gf because of your answer..

[Anonymous No.11922910]

How bad explosion would be caused by 1g of antimatter?

[Anonymous No.11923044]

>>11919362
Would it be possible to make a logic gate that uses non-boolean logic?
What would such a thing do?
How would it work?
How would it be used?

[Anonymous No.11923074]

>>11923044
What did he mean by this?

[Anonymous No.11923076]

I don't wanna make an iq thread. I'm assuming my iq is 105-125 but only have done the meme online tests. I've been stuck in this constant mental loop of having absolutely 0 confidence with anything I do, because my iq is too low and there are a lot of people way smarter. I think "Well yeah, this sounds right, but I'm not smart enough to know 100% if this is correct or if I even have all the options." It has been taking over my life constantly thinking about how inefficient I am and what's the point if someone else smarter can do it more efficiently? I'll sit here all day trying to be "productive" but won't because I'm always worried what I'm doing is low iq/wrong. Which most likely that is true, but it's getting to the point where I've reverted back to playing video games all day long to not think about it.

[Anonymous No.11923108]

>>11923076
use descartes method: anything you perceive perfectly clearly is correct

[Anonymous No.11923114]

>>11923044
it just takes non boolean inputs and outputs. it deos whatever you want to.

For example: a voltage multiplier that can be set to integer values, for a multiplication calculator

[Anonymous No.11923115]

>>11923076
>and what's the point if someone else smarter can do it more efficiently?
This was the only question mark I saw in what appeared to be a diary entry. It shouldn’t matter what someone CAN do more efficiently, it only matters IF they do it. I had the the opposite problem and it made me really lazy. Once you’re out of academia though, you quickly realize no one gives a fuck how smart you are, only how your intelligence directly affects them. And they’re right. Wasted genius is as abundant as instant noodles. Just put the work in and you’ll be better than any other genius at most fields you could choose to be in. Except theoretical research, I mean just give up.

[Anonymous No.11923121]

>>11919362
How do I do this? The professor had a really short, abnormal online lesson about it.

[Anonymous No.11923126]

>>11923108
But how do I know it's perfectly clearly when there could be unknown unknowns?
>>11923115
>Diary
Yes, because that's the backstory of the problem. How do I want to "put in the work," when most likely the work I'm putting in is inefficient and most likely incorrect due to not being able to ever grasp it fully?

[Anonymous No.11923128]

>>11923076
Get an ego large enough to crush someone to death from half a kilometer away.
>>11923121
Dude line that goes through two points.
[math]y = 4-x[/math], I think.

[Anonymous No.11923153]

Is this proof wrong?
>Null T^n is a subspace of null T^n+1
>null T^dimV+n = null T^dimV
>v is a generalized eigenvector, so it is in null (T-LI)^j
>thus it is in null (T-LI)^dimV
>thus the set of generalized eigenvectors is equal to null (T-LI)^dimV
but what if j is less than dimV? Then we know the set of genral eigenvects is in nullT-Ldimv, but we dont know that the null space doesnt contain other stuff, so how does he say the sets are equal? Is it a wrong proof?

>>11923126
if everything fits within your model, then those unknown unknowns are outside your system and aren't a big deal until you stumble into them. if they are within your system, then your system will clearly not fit together

[Anonymous No.11923159]

>>11923044
one way to do it would be to have the gate trigger randomly.
wala.
or do you mean a gate that's not on your chart?
'Cause that can work too, there are only 8 possible outcomes on your chart, there could be much more.

[Anonymous No.11923163]

>>11923126
>the work I'm putting in is inefficient
Again, it’s not a race or pissing contest. You either contribute or you don’t. Einstein’s work means fuck all to an economist. That one chick with an iq over 200 works as a writer for some housewife magazine. No one gives a fuck what she thinks about how we should handle corona. The inefficiency question is irrelevant, just accept some people are better than you but that you can still be useful. The incorrect question is, well, incorrect. Unless you’re actually far dumber than you’re making it out to be, the right or wrong question in most fields is an easy. The hard part is formulating a sensible answer. What are you even trying to work in anyway?

[Anonymous No.11923167]

Is[math]f: x\mapsto x+1[/math] a linear function? Linear map? Why or why not?

[Anonymous No.11923172]

>>11923128
I still don't get it but your answer is right.

[Anonymous No.11923191]

>>11923153
If [math]j \leq dim ~ V[/math] you have that [math]T^{dim ~ V} v = T^{dim ~ V - j}T^j v = 0[/math] and then [math]v \in ker ~ T^{dim ~ v}[/math], so there's no problem.

[Anonymous No.11923193]

>>11923167
f(1) = 2
f(1+1=2)=3, f(1)+f(1)=4

it is not linear. the rate of change along one dimension is not constant. each unit effects the output differently depending where it is added. the effect of the function on each unit on average varies depending on how many units enter the function

[Anonymous No.11923197]

>>11923167
Linear function? Yes.
Linear MAP? Nope.
AFFINE map? Yes.

[Anonymous No.11923198]

>>11923172
What part don't you understand, finding the line that goes through two points or piecewise functions?

[Anonymous No.11923199]

>>11923191
i know that v is in the kernel, but hes saying that the set of v equals the kernel set. but we dont know that the kernel doesnt include other vectors

[Anonymous No.11923209]

>>11923199
Yah, but you aren't claiming that [math]ker ~ T^j = ker ~ T^{dim ~ V}[/math], right? For it to be a generalized eigenvector it just needs to be in the kernel of some power of the matrix. There's no issue with passing to a larger power.

[Anonymous No.11923242]

>>11923198
Finding the function for the piecewise I suppose. I get how to use it, I get how to graph it when given, but I can't seem to deconstruct what's in front of me when it's just the graph. I understood this problem just fine.

[Anonymous No.11923252]

>>11923209
oh i see. because if its in null(T^dimV), it is a generalized eigenvector, even if its not in the kernel of a lower power, so adding new vectors to this set poses no issue

thanks anon

[Anonymous No.11923256]

>>11923163
I'm not doing anything right now. I've wanted to get a "smart" college degree (STEM) because money/prestige but am too stupid for one. I feel like getting a business degree is a waste of time/money. If I tried to do something entrepreneurial I will always be decimated by smarter people and lose my money for not being smart enough. I'm also getting older at age 26 and am way passed up by my peers. Don't have the iq to catch up. I do need to figure out how to do "something" with myself though.

[Anonymous No.11923313]

>>11919405
I'll repost my genemod question
How long is it until gene modding becomes widely popular? And what are the limits of it?
I've watched a man on youtube cure, now reduce, his lactose intolerance by genetically modifying himself. Now, it's worn off after a few years.
But if you were to do something like that to height, what would happen? How do you even get started modifying your own body parts? I guess I'm looking for an answer on how to change myself, like becoming 6'7" extreme as an example, or other bodily changes. Hell if someone could even point me to an underground biohacking community I'd be grateful.

[Anonymous No.11923317]

>>11923242
>but I can't seem to deconstruct what's in front of me when it's just the graph
Fuck this is really hard to explain.
It really isn't any different from finding the function normally. If it's piece-wise a line, you take two points in the interval, you find the line equation, and that's your answer for what the function is in the interval where it's a line. The fact that it's piecewise is, in a sense, irrelevant to its local behavior.
You might want to just use the Talk to a Tutor button.

[Anonymous No.11923334]

>>11923317
I will but first I just want to say thank you for the assistance. I really appreciate it.

[Anonymous No.11923394]

In the original question of pic related, there was an 'h' in the third row of the last vector (where I have 26). We were just presented with the three vectors and asked to find a value for in 'h' that resulted in linear dependence.

Why did I get this wrong? I described the resultant vector as a combination of the other two.

[Anonymous No.11923420]

If I wanted to write pic related in parametric vector form, it'd just be

[eqn]\matrix{-9 \\ 4 \\ 1 \\ 0}x_3 + \matrix{8 \\ -5 \\ 0 \\ 1}x_4 [/eqn]

right?

[Anonymous No.11923423]

>>11923420
forgot pic

[Anonymous No.11923438]

>>11923420
>>11923423
Yes.
[eqn] \left ( \matrix{-9 \\ 4 \\ 1 \\ 0} \right ) x_3 + \left ( \matrix{8 \\ -5 \\ 0 \\ 1} \right ) x_4 [/eqn]

[Anonymous No.11923442]

>>11923438
That should be a bracketed nx1 matrix, parentheses are inappropriate and aesthetically displeasing

[Anonymous No.11923448]

>>11923442
Fuck off.

[Anonymous No.11923451]

>>11923076
The only place raw intelligence matters is with shit like pure math research or quantum physics or whatnot. Most places in the world depend more on your willingness to do work.
Example: suppose a company hires you to do work for them. You may think, hey, maybe there's someone smarter/harder working/more good looking they could have hired instead. But they didn't, anon. They're betting you're the best person out of the batch, and who are you to disagree?
Just play to your advantages and try to do something with your life. Unless you wanna be a famous mathematician, then thassa ripper bro

[Anonymous No.11923467]

>>11923438
ok, now can you look at this question >>11923394


thx

these were exam questions I got wrong I guess

[Anonymous No.11923504]

>>11923451
I would like to have a better understanding of how things work in the world math/science wise, but I realize I won't ever get to the point of "understanding" like those smarter and will always be in the dark. Very scary thought! That's what I'd be doing if I didn't have to worry about money, so yes it's a ripper. Yeah, I do want to be good at something (that makes money), but that absolutely seems reserved for the highest iq. Millionaires are definitely all 130+ unless they're in entertainment/sports.

[Anonymous No.11923517]

What has sci done with their major? I'm going into my fourth year for mathematics and have not made connections at all. Am I fucked?

[Anonymous No.11923529]

>>11923467
[math]v_1 \left ( \matrix{1 \\ -1 \\ 3} \right ) + v_2 \left ( \matrix{-5 \\ 7 \\ 8} \right ) + v_ 3 \left ( \matrix{1 \\ 1 \\ h} \right ) [/math].
And then you ansatz [math]v_1 = -6[/math], [math]v_2 = -1[/math] and [math]v_3 = 1[/math].
tl;dr your professor was being finicky for no good reason.

[Anonymous No.11923538]

>>11923504
>but I realize I won't ever get to the point of "understanding" like those smarter and will always be in the dark
The only difference with those smarter is that they realize that no matter how "smarter" people get, they'll always be in the dark. That's part of the appeal of sciences and maths, every answer you find just opens up even more questions that are probably even harder to solve. It's not like you are missing out on "the truth" for not being as smart as you think you should be. There's a huge amount of things not even the brightest people in the history of humanity could be able to figure out, and in that regard you are no different than them or the rest of us.
>Millionaires are definitely all 130+ unless they're in entertainment/sports.
Connections are way, way more important than intelligence if you just care about money. Also if you throw your ethics out the window like a pretty big amount of them it's even easier regardless of how smart you are.

[Anonymous No.11923614]

>>11923529
was I right still though? also couldn't [math] v_1 = 6, v_2 = 1 [/math]? rather then them both being negative (this is what I had in my asnwer)

there were a few similar things on this exam. I basically got every problem right but only got 84%, kinda pissy about it desu

[Anonymous No.11923655]

dz = ((dz)/(dx))*dx + ((dz)/(dy))dy


Why.

[Anonymous No.11923716]

>>11923614
>was I right still though?
Yeah, you were pretty much correct.
>rather then them both being negative (this is what I had in my asnwer)
Sure, then [math][v_3 = -1[/math].
Judging from the comment, your professor was literally just finicky with definitions.
>>11923655
Because that's how exterior derivatives work.

[Anonymous No.11923772]

>>11923394
You got the right answer, but the intermediate steps are either missing or incoherent.

[Anonymous No.11923799]

>>11923716
Why can't [math] v_3 = 1 [/math] as well?

>>11923772
Basically I just looked at this and immediately saw that if you multiply the first vector by 6, then add them both, you get 1 in the first two rows, as required. So I just did the arithmetic for the last row as well. Did I do this wrong?

[Anonymous No.11923820]

>>11923799
>Why can't v3=1 as well?
Because then the sum doesn't zero.

[Anonymous No.11923827]

This one also really bothered me. I just wrote that the standard matrix is [eqn][\matrix{1 & -5 & 4 \\ 0 & 1 & -6}] [/eqn], but I only got 20% on this question for 'not showing my work'. There is no work to show, however. It was a question you answer by glancing at the equation and immediately recognizing.

[Anonymous No.11923842]

>>11923820
Ok, I guess I did misunderstand this then. Wikipedia describes linear independance as "a set of vectors is said to be linearly dependent if at least one of the vectors in the set can be defined as a linear combination of the others;", so I thought I was just supposed to fnd [math]v_3[/math] such that it was a combination of the other two vectors.

For reference, I've attached the actual question on the exam.

[Anonymous No.11923844]

>>11923827
Going to be honest desu, your teacher is a faggot

[Anonymous No.11923851]

>>11923827
>show your work for that
Oh boy.
Those are some very high work showing standards.
>>11923842
>Wikipedia describes linear independance as "a set of vectors is said to be linearly dependent if at least one of the vectors in the set can be defined as a linear combination of the others;", so I thought I was just supposed to fnd v3 such that it was a combination of the other two vectors.
Yeah, that's the definition wikipedia uses.
Your professor uses the "there exist numbers [math]v_1, \cdots , v_n[/math] not all zero such that [math]v_1x_1 + \cdots v_n x_n = 0[/math]." definition and he got on your ass about it.

[Anonymous No.11923852]

>>11923820
Oh wait, I see what you mean. I was saying
[eqn]v_1 + v_2 = v_3 [/eqn]
while you're saying
[eqn] v_1 + v_2 - v_3 = 0 [/eqn]

but the statements are equivelant.. so obviously when written as it is in the last line, it'd be -1(v_3).

hopefully I'm understanding correctly

[Anonymous No.11923907]

>>11923851
>>11923844
Ok, so this is my last complaint, I've shown you guys all my mistakes on the exam now. I was docked 40% on this question for not having the parametric form he desired. I didn't know what he wanted exactly so I just went with what I've been entering on the online homework, since it's been working. AFAIK, this is not a universally standardized term, and my vector _was_ still in fact in parametric form, despite what his comment implies. Also, it is dead easy to see that I could split into his desired format like up here: >>11923438


Though pic related was the most agreeable docking of points, all in all I feel as though I should've gotten an A on this exam, since I got all the answers right and showed my work wherever it involved more than a glance. I was given an 84%, nearly a C, and I think I'm gonna email him tonight after I'm done building my case.

[Anonymous No.11923912]

>>11923907
and pic related was how the question was posed

any tips on how to approach my email dialogue would be great, I've never done this before

[Anonymous No.11923919]

>>11923842
a[1,-1,3]+b[-5,7,8]+[1,1,h]=0
a-5b+1=0
-a+7b+1=0
=> 2b+2=0 => b=-1
=> a+6=0 => a=-6
-18-8+h=0
=> h=26
Alternatively, find the determinant of
[ 1 -5 1]
[-1 7 1]
[ 3 8 h]
which gives 2h-52; this is zero when h=26.

Generally speaking, pulling numbers out of your ass and demonstrating that they satisfy the equation(s) isn't considered sufficient. Apart from anything else, it doesn't demonstrate that the solution is the only solution.

[Anonymous No.11923951]

>>11923827
>It was a question you answer by glancing at the equation
There's a lot of retards who have no idea of what they're doing (and judging from last thread, you're one of them), so unless your teacher knows you're not one, you can't just write the solution without explaining shit. Still, your teacher sound a little bitchy, though, so you should've been extra rigorous with your work.

[Anonymous No.11923968]

>>11923907
Parametric vector form:
[eqn]
x3 \begin{bmatrix} -9 \\ 4 \\ 1 \\ 0 \end{bmatrix} + x4 \begin{bmatrix} 8 \\ -5 \\ 0 \\ 1 \end{bmatrix}
[/eqn]

[Anonymous No.11923979]

>>11923919
>pulling numbers out of your ass doesn't always work
right, I don't remember what I was thinking at the time, but it looks like I did forget to show h=26 is the only soluton. Right now it is not apparent to me 'just by looking at it' theat h=26 is the only solution, but if I'm going to try to earn points back on this I'll need a good arguement for why it was obviously the only solution at just a glance.

>>11923951
Well, I know now, fwiw.. I've been pretty slammed this term and this prof dropped this exam at the bottom of an email that was waaay too long to actually read - he didn't even announce he had done so on the class website. I didn't know it was available and due until it was already crunch time. This was the first exam so I had no clue he was going to be this uptight about everything, next time I guess I'll have to show work for every single step, but then again I should have the time to do so. Grateful for everybody's help and sorry for the round of underresearched questions last time.

>>11923968
Right, but the other one is still 'parametric vector form', it's just the addition of those two vectors after all. I only wrote it the way I did on the exam because the online homework has been accepting it like that.

[Anonymous No.11924003]

>>11923979
>>11923919
ok, well I've got my explanation for why it was immediately obvious h=26 was the only solution:
[eqn]x1-5x_2 = 1[/eqn]
[eqn]-x1+7x_2 = 1[/eqn]
add eqn1 and eqn2 and we have 2x_2 = 2, so x_2 = 1. Plug in and we see x_1 = 6

so continuing the mental arithmetic from there leads to h=26.


so I guess I'll start typing up my email to the prof. I think I'm basicaly just gonna rewrite and repost what I've done here.

[Anonymous No.11924009]

>>11924003
>so I guess I'll start typing up my email to the prof. I think I'm basicaly just gonna rewrite and repost what I've done here.
Would not recommend doing it.

[Anonymous No.11924013]

>>11924009
You think it's better to say nothing and jsut accept the grade, or are you just memeing? the exam is worth 10% of our grade, i think it's worth an email to try and get into the 90%+ range

[Anonymous No.11924021]

>>11924013
>You think it's better to say nothing and jsut accept the grade, or are you just memeing?
I think that your email brings no real new information to him and is extremely unlikely to change his mind, so you shouldn't annoy him over this.
The parametric vector thing is the only one I see as working out, but you'll have to properly look through the books in the bibliography to see what they consider parametric form.

[Anonymous No.11924036]

>>11924021
I agree, but I've consistently been shocked at what a simple request can do, especially from professors, even when they've expicitly stated in their syllabus or elsewhere that such a request will be denied.

I'll at least request the parametric vector thing then, and maybe I'll treat the others as a post-script. I don't want to be rude or come off as a beggar, but do feel a lot of these marks were super unfair.

[Anonymous No.11924079]

What are the ideas behind Commutative algebra? I mean in topology you study homeomorphism, homotopy, and such because you want to study the proprieties of "distance" and "continuity", what's the point of commutative algebra?

[Anonymous No.11924152]

>>11924036
>a lot of these marks were super unfair.
They weren't and I also agree it'd be a waste of time for you and your teacher. But you do what you feel is best.

>>11924079
Geometry.

[Anonymous No.11924169]

>>11924152
I'm just phrasing it as a question of why I lost points on the questions I'm concerned about, along with submitting what I _now_ think would get full points, and kind of leaving it open to him.

[Anonymous No.11924184]

what's a book I can read to learn about lunar geology

[Anonymous No.11924231]

Is The C Programming Language too outdated to be worth reading?

[Anonymous No.11924485]

Why is this even a thing?

[Anonymous No.11924499]

>>11921451
I can't believe i was this close

[Anonymous No.11924510]

>>11924231
No.

[Anonymous No.11924511]

Suppose you have a scalene triangle in 3d space, the coordinates of its three corners, the distances between the points, and the angles.
how do you find the corrdinates of the point on the hypotenuse of this triangle, such that drawing a line perpendicular to this one, through the third point, divides the triangle into two right triangles?

[Anonymous No.11924574]

>>11924511
Let your triangle be ABC, with AB the side your considering. Your point is the intersection of the line through AB and the plane perpendicular to it that passes through C.

[Anonymous No.11924666]

For normed vector spaces and inner product spaces, the fields are usually the reals or complexes. What other fields are possible? Easy guess would be subfields of reals or complexes, but can we use finite fields, for example?

[Anonymous No.11924736]

>>11924666
As long as your field is characteristic zero, it's okay to use. Problem with finite fields / fields of nonzero characteristic is that the norm isn't homogeneous, i.e. say you're in Z_p, then for some nonzero vector v we have p||v|| = ||pv|| = ||0||, so ||v|| = 0 (since norms are valued in R, where p is not zero. Can you value your norm in Z_p? If you do this, I believe you'll violate triangle inequality somewhere).
But with things like Q, you'd be fine.

[Anonymous No.11924748]

>>11924736
I see, thanks for the explanation with the positive characteristic.

[Anonymous No.11924779]

>>11924666
You can do stupid shit wherever you want, but IIRC you can only do meaningful stuff over the reals, the complex, the quaternions and, in a pinch, the p-adics.
You can define a norm over whatever ordered zero characteristic field you want, but it might not even be complete in the trivial case.
>>11924736
Z_p isn't ordered, so you can't even state the triangle inequality if you value the norm in Z_p.

[Anonymous No.11924807]

I'm in a mechanical engineering program at college, I'm doing well. I have an internship at a small company under my belt and another internship at a big company lined up. The problem is I probably won't graduate until I'm almost 30 and I really don't have any experience except for the internships. My question is, how do I appeal to employers and compete in the job market with the younger guys from better schools? I was thinking about starting a notebook and filling it with various projects that I will complete. Are there any mechanical engineers that can tell me what kind of thing employer's are looking for besides a degree?

[Anonymous No.11924817]

is there something special or a reason that our world has 3 spatial dimensions instead of literally any other number?

[Anonymous No.11924897]

Anyone know how can I proof a function is negative (semi)definite.

I know that you can proof functions are positive defintie with the gradient and Hessian matrix , but what about the other way around? I tried it and I get a 0 and can't use Sylvester's criterion.

[Anonymous No.11924901]

>>11924897
I get a 0 in one of the minors of the Hessian and thus Sylverster's criterion is inconclusive i meant to say.

[Anonymous No.11924910]

>>11924485
They are summerfags and reddit tourists. They click on science and mathematics because they feel this is closer to their native identity irl and that the experience would be like reddit.

[Anonymous No.11924931]

In short channel MOSFETs there is an effect of velocity and the drain current becomes dependent of the gate voltage in a linear fashion. Is there a similar phenomena for BJTS?

[Anonymous No.11924932]

>>11924931
...an effect of velocity saturation*

[Anonymous No.11925045]

I'm the fag who was complaining about my LA professor earlier and posting screenshots from my exam.

So far I've haggled my way up from an 84 to an 87. Still waiting on another email back to hopefully push it into the 90s, fuck the naysayer from earlier.

[Anonymous No.11925067]

>>11924779
I was putting on some stupid order but yeah obviously there's no order that works with the group structure.

[Anonymous No.11925259]

what would you assume I'm supposed to do here? We're using the chain rule for composition functions and partial derivatives.

[Anonymous No.11925265]

>>11925045
you had better do well on the next exam desu...

[Anonymous No.11925328]

Are there actually scientists who study "spiritual" shit like life after death, or is that just not taken seriously/not given funding? Like is some of the topics seen as pseudoscience actually researched behind the scenes by real scientists or is it just left up to reality TV and schizo /x/-posters?

[Anonymous No.11926047]

Can anyone identify what kind of bone abnormality this is?
It's a pork rib bone.

[Anonymous No.11926051]

>>11924897
>>11924901
A matrix [math]A[/math] is negative semi(definite) if and only if [math]-A[/math] is positive (semi)definite.

[Anonymous No.11926238]

Was I supposed to take Linear Algebra before taking Calc 3? Seems like Calc 3 was all vectors, all the time.

[test No.11926309]

>>11926238
No. The stuff you need for calculus is very basic and should've been explained to you in that course.

[Anonymous No.11926436]

>>11919362
Is there a group of infinite order where every subset of the group, except the identity, is a generator for the group

[Anonymous No.11926490]

>>11926309
I hadn't dealt with vectors or matrices since pre-calculus. The teacher didn't explain jack shit.

[Anonymous No.11926599]

>>11926436
No.
Proving there isn't is left as an exercise to the reader.
In case you meant "every infinite subset", then I don't know and the problem looks pretty hard.

[Anonymous No.11926600]

Did I do this right? The problem was "find the direction of maximal increase from(1,2,1) and the value of the directional derivative in that direction from that point.", where the original function was
[math]f(x,y,z) = 4x^2y+2xz^2−3yz+ 4[/math]

[Anonymous No.11926610]

>>11926600
forgot image

[Anonymous No.11926647]

>>11926610
Why did you write down in the last line that the gradient equals the gradient divided by its norm?

[Anonymous No.11926728]

>>11926647
>why did you
I'm not certain, but maybe I meant to put a [math] \vec{u} [/math] next to it, as that would more closely resemble something sensible (the directional derivative). Though I don't know if that'd be correct.

[Anonymous No.11926735]

as in,
[math] \nabla f \cdot \vec{u} = ...[/math]

[Anonymous No.11926744]

>>11925328
no. when someone funds your experiment they intend for you to get results. unless you can think of an experiment that conceivably demonstrates "spiritual" shit then you'll never get funding.

[Anonymous No.11926770]

>>11926728
You probably want to just write something like:
"The direction of maximal increase is [eqn]u = \frac{\nabla f (1, 2, 1)}{|| \nabla f(1, 2, 1)||} = \frac{1}{\sqrt{329}} \langle 18, 1, -2 \rangle [/eqn] and the value of the the directional derivative in that direction at that point is [eqn]\nabla f \cdot u = \langle 18, 1, -2 \rangle \cdot \frac{1}{\sqrt{329}} \langle 18, 1, -2 \rangle = \sqrt{329}[/eqn]."

[Anonymous No.11926821]

why does FTL travel cause time travel? does warp drive, shifting spacetime rather than moving FTL, have the same effects? where is this time travel localized to?

[Anonymous No.11926838]

>>11926821
I literally explained this to you in the last thread you asked.
Two planets, A and B, 1 light year away
If A looks at B through a telescope it sees B as it was when it emitted the light that is currently reaching A, so it sees B as if it was 1 year ago.
Now if someone on A travels to B in a FTL ship that gets there in 1 second, you're getting there BEFORE the light from B made it to A. So you're at planet B at an earlier point in time than you observed.
If you were looking at B as you traveled to it, you would essentially be watching the light from B played backwards.

[Anonymous No.11926854]

>>11926490
You should've checked the syllabus.

[Anonymous No.11926936]

When you drink with an empty stomach, or say a couple hours after you've eaten, do you get the same amount of drunk only it hits you faster, or do you get more drunk than if you drink the same amount of booze while or immediately after eating?

[Anonymous No.11926994]

>>11926599
Small update for the infinite set thingy.
If one element has infinite order, we can use all of its powers as a set, so the group is the integers, and the integers don't satisfy the necessary conditions, so we can assume all elements have finite order.
Zorn's lemma guarantees the existence of minimal generating sets. If one of these is infinite, you can remove one element to get an infinite subset of the elements that doesn't generate the group.
Otherwise, all of these are finite, that is, the group is finitely generated.

To sum up, we have a finitely generated group where all the elements have finite order. Unfortunately, the Burnside conjecture is wrong, so this just simplifies the problem/example hunt instead of solving it.

[Anonymous No.11927064]

>>11926936
you get more drunk cuz no food is helping to absorb the alcohol

[Anonymous No.11927117]

>>11926770
looks reasonable, thanks!

[Anonymous No.11927150]

What book should I read to review precalc? I'm gonna starting calc 1 soon and its been a few years.. I forgot it all, or I guess if I forgot I didnt learn it at all.

[Anonymous No.11927217]

I'm trying to build a volume indicator, but I've gotten stuck. I have the audio's frequency spectrum. I've applied m-weighting to adjust for human perceived loudness hearing. Now how do I combind the spectrum into a single db level? Root mean squaring the data is obviously wrong because if I'm just playing a single tone at 200hz, and take 32 samples over 48000hz, I'll get a much higher volume level than 2048 samples when I average.

Anyone know the correct way to derive a single "total decibel" from a frequency spectrum of decibels? Google has failed me.

[Anonymous No.11927255]

>>11927150
Khan academy.
https://stitz-zeager.com/
Lang's basic maths.
Flip through the chart links in the OP.
Look in the wiki.

[Anonymous No.11927298]

>>11927217
http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/db.html is this what you are looking for?

[Anonymous No.11927319]

>>11927255
Looking more for a review type book.. stitz would be great if it was my first time with the material. I like serge lang, but I feel like I'm doing a disservice by not doing his proofs, I'm trying to just cram the computations not the concepts if you know what I mean.

[Anonymous No.11927364]

>>11927298
Sorry, not really. I can convert between intensity and decibels, but my questions is how to combine decibels at different frequencies.

For example, there's a sound at -50 decibels at 200hz and a sounds at -60 at 400hz, what would you say the decibels are for the combined sound of the two?

[Anonymous No.11927420]

Hi anons, stupid question about radioactive decay. If I have two isotopes, X and Y, with given decay times tX and tY, and I know that the abundance of X is f, how can I calculate when the abundance was or will be g? Thanks.

[Anonymous No.11927527]

>>11927319
>review type book
Never heard of any.
Does a reference book work? There's https://libgen.is/book/index.php?md5=E8C280904FDC5A19900986BA5004B8B8 .
Covers ~80% of all mathematics that a bachelors should know, but you can just read the stuff you want to remember.

[Anonymous No.11927544]

Anyone here know how to expand the first term in the Laplace equation in spherical coordinates?

We begin with the expression:
[eqn] \frac{1}{r^2} \ \frac{d V}{d r} \ (r^2 \ \frac{dV}{dr}) [/eqn] and should obtain the following expression once expanded [eqn] \frac{d^2 V}{d r^2} + \frac{2}{r} \ \frac{d V}{dr} [/eqn]

How does one perform the expansion of the first expression though? It is clearly incorrect to simply assume regular algebra i.e. [math] a^{-2} \ b \ (a^2 \ b) [/math] . Is it necessary to use the chain rule in some form due to the differential operators?

[Anonymous No.11927545]

why is there an obligatory topology course in my CS major?

[Anonymous No.11927569]

>>11927544
I think that the expression you should begin from is
[eqn]\frac{1}{r^2}\frac{\text{d}}{\text{d}r}\left(r^2\frac{\text{d}V}{\text{d}r}\right).[/eqn]
Notice how you have a [math]V[/math] in your first derivative, which i don't think should be there.

[Anonymous No.11927572]

>>11927544
You've written it wrong, anon. That's literally just [math](\frac{dV}{dr})^2[/math].
It's [math]\frac{1}{r^2} \frac{\partial}{\partial r} (r^2 \frac{dV}{\partial r} )[/math].
Then you use the product rule.
>>11927569
Bingo.

[Anonymous No.11927597]

>>11927545
Topological analysis is important in CS you goof!

[Anonymous No.11927605]

>>11927545
IIRC it isn't the math topology, it's this:
https://en.wikipedia.org/wiki/Network_topology

[Anonymous No.11927612]

>>11927605
no, I mean the math topology
>>11927597
how

[Anonymous No.11927637]

>>11927612
>no, I mean the math topology
Oh.
I dunno, then. The lads who were drafting your curriculum got bored and added meme stuff in.
Happens sometimes.

[Anonymous No.11927660]

>>11927569
Thanks man, got it done right now

[Anonymous No.11927802]

should i learn inverse functions or function's composition first?

[Anonymous No.11927821]

>>11927802
Composition.
Inverse functions literally only make sense if you understand composition.

[Anonymous No.11927903]

>>11925265
i will lol

[Anonymous No.11928001]

How would you solve this ODE? My book just says multiply by [math] x^2 [/math] and integrate, but I don't see the full path:

[eqn] \frac{d^2 X(r)}{dr^2} + \frac{2}{r} \ \frac{d X(r)}{dr} = 0 [/eqn]

If I multiply by [math] r^2 [/math] I get

[eqn] r^2 \ \frac{d^2 X(r)}{dr^2} + 2 \ r \ \frac{d X(r)}{dr} = 0 [/eqn]

If I attempt to integrate now I get the expressions [eqn] \int r^2 \ \frac{d^2 X(r)}{dr^2} \ dr + 2 \ \int r \ \frac{d X(r)}{dr} \ dr = \int 0 \ dr [/eqn]

The integral on the right hand side will obviously just equal a constant but for the integrals on the lefthandside; should I use integration by parts?

[Anonymous No.11928004]

>>11928001
*correction

my book says just multiply by [math] r^2 [/math] not [math] x^2 [/math]

[Anonymous No.11928006]

>>11928001
>>11928004
Sure. Integrate the first integral by parts first and see what happens.

[Anonymous No.11928014]

>>11928001
Compute [math]\frac{d}{dr} \left ( r^2 \frac{ dX(r)}{dr} \right ) [/math] (with the product rule).
I didn't pull this out of my ass, I pulled it out of the Laplacian computation from earlier.

[Anonymous No.11928032]

>>11927545
So you can learn about homotopy

[Anonymous No.11928038]

How come in Complex Analysis, we always integrate a function on a contour instead of on a region? If [math]\Omega \subseteq \mathbb{C}[/math] is open and connected, what does [math]\int_{\Omega} f(z) \, \mathrm{d}z[/math] mean?

[Anonymous No.11928119]

I'm confused about what we can and can't do with averages over a group. If I have a group [math]G[/math] and a function [math]f : G \to \mathbb{R}[/math], is it true that [eqn]\sum_{g \in G} f(g) = \sum_{g \in G} f(g^{-1}) ?[/eqn] I suspect not. I know we can translate by any fixed [math]h \in G[/math], but that's not the case here. Unless there's some other reason that makes the sum over a group invariant to taking inverses specifically? What about if [math]f[/math] is a class function?

[Anonymous No.11928122]

>>11928038
C is 1-dimensional as a vector space over itself

[Anonymous No.11928127]

>>11928119
Those two sums are exactly the same, [math]g \mapsto g^{-1}[/math] is a bijection.

[Anonymous No.11928134]

>>11928127
Ohhh, I see. Dang I'm dumb. Thanks a bunch.

[Anonymous No.11928138]

Is it possible to get into a PhD program without having a master's degree? If so, why do so many PhD's that I've met also have a masters degree?

[Anonymous No.11928146]

>>11928138
In the US (and Australia I believe) it's common practice to go from BS to PhD. In the rest of the world, usually the institutions require an MS first.
Either way, even in the US the university often offers a masters "on the way" to completing the PhD. Typically it just involves passing classes, qualifiers, and getting a couple of research credits, all stuff that you're doing as a PhD student anyway.

[Anonymous No.11928508]

is the CDF for Y simply the product of the CDF of each Xi? If so, how in the world would I differentiate such a beast to get the pdf for Y?

[Anonymous No.11928533]

>>11928508
>is the CDF for Y simply the product of the CDF of each Xi?
Yeah. The probability of getting a value smaller than some fixed value is the probability of getting a smaller value for all individual probabilties.
>how in the world would I differentiate such a beast to get the pdf for Y?
Have you tried using the product rule?

[Anonymous No.11928780]

>>11928508
[math]P(Y\leq y) = P(X_1\leq y)\times \cdots\times P(X_n\leq y) = \left(\int_0^y \beta e^{-\beta x} dx\right)^n.[/math]
The CDF of Y is still a single variable function, so it's a lot simpler than you think.

[Anonymous No.11928791]

>>11928533
>>11928780
thanks i looked at it and honestly was too lazy to try

[Anonymous No.11929335]

It seems like on this board the only thing that people know is math.

[Anonymous No.11929378]

I want to learn the biosynthetic pathways for exotic plant alkaloids, the kind organic chemists like to make, but I don't know what words to search for. plant biochemistry? plant biosynthesis?
Does anyone know the subject, or a textbook that just covers a bunch of mechanisms for alkaloid biosynthesis?

[Anonymous No.11929410]

If [math]a>1[/math], how do I show that [math]a-\sqrt{a^2-1} > 1[/math]?

[Anonymous No.11929446]

Do snakes have arses?

[Anonymous No.11929819]

>>11919362
based patrick suppes
no gay marriage for me thank you.

[Anonymous No.11929842]

>>11929819
He's making mistakes all over the place!
Hasn't he ever heard a little song called "I'm my own grandpa", where he thoroughly explains how you could be your own grandfather?(And then, in just one or two more steps, you can get a family tree where you're your own grandmother)

[Anonymous No.11929846]

When smoking a joint, if I use the lighter a bit on the filter, can it kill the coronavirus that might be in there from someone else’s saliva?

[Anonymous No.11929880]

>>11929842
And here, he denies the existence of genderfluid individuals! How can he keep getting away with it?

[Anonymous No.11929884]

>>11929846
yeah bro, it works for needles too btw but the needle manufacturer jews dont want you to know that so you keep buying fresh needles every time

[Anonymous No.11929886]

>>11929846
saliva can get deep into the filter paper and around the outside surface further along the joint, additionally they were holding it in their hands presumably, you are also making contact with the same surface. If you’re worried stop sharing joints, actually stop sharing them if you don’t want HPV and significantly higher flu risk in the fall and winter as well its fucking disgusting.

[Anonymous No.11930430]

Explain the total differentials to me like I'm retarded, because I am. Why is it the sum of the partial derivatives multiplied by their respective change in x or y? I just don't get it. I understand what a derivative is. I understand what a partial derivative is, with respect to a multivariable function. It's this weird formula that I'm not able to follow the logic of. What is it telling me?

[Anonymous No.11930455]

>>11929410
Rearrange as [math]a-1 > \sqrt{a^2 - 1}[/math], then square both sides.
You'll then reach [math]2 > 2a[/math], which is patently false.
You may then proceed to ask your calculator what is your expression for [math]a=2 > 1[/math], [math]2 - \sqrt{2^2 - 1}[/math] and observe how it returns a number smaller than 1.

[Anonymous No.11930459]

>>11929335
It seems that most of the questions are math too.

[Anonymous No.11930478]

>>11930430
The differential gives you the best linear approximation of the function f, int the sense that [math]f(x+dx,y+dy,z+dy)=f(x,y,z)+\partial_x f(x,y,z)dx+\partial_y f(x,y,z)dy+\partial_z f(x,y,z)dz +R(dx,dy,dz) [/math] and R has the property [math] \frac{R(dx,dy,dz)}{\sqrt{dx^2+dy^2+dz^2}} [/math]

[Anonymous No.11930483]

>>11930478
Sorry [math]\lim\limits_{\sqrt{dx^2+dy^2+dz^2}\to 0} \frac{R(dx,dy,dz)}{\sqrt{dx^2+dy^2+dz^2}}. [\math]

[Anonymous No.11930639]

>>11929335
Everyone knows math. From engineers to physicists and economists.

[Anonymous No.11931015]

Why doesn't this work?

[Anonymous No.11931023]

>>11931015
[math]\exp (x^2) \neq \exp (x) \exp (x) = \exp (2x)[/math]

[Anonymous No.11931034]

>>11931023
Ah fuck me. Thanks

[Anonymous No.11931054]

"A radioactive substance decays exponentially over time. If we start with a 250 gram sample there will only be 20 grams 300 years later. Create a function to model the amount of substance that remains in terms of time, measured in years. Show all work."

Y=Pe^rt

P->250 Grams
e->e
r->?
t->300 years
Y->20

20=250e^r*300
2/25=e^r*300
ln(2/25)=r*300
(Ln(2/25)/300)=r
r≈-0.008419≈0.842%

and this is the part I get tripped up on.
is this the answer? Is asking for more?

f(t)=250e^-0.00842(t)

[Anonymous No.11931074]

>>11930639
You are right, but few physics questions get answers.

[Anonymous No.11931303]

I seem to have misunderstood this question. My work is the following post.

[Anonymous No.11931321]

>>11931303
I have no clue what the reduced row echeleon form has to do with part a.

Also, the matrix, before reduction, would simply be the following, right?
[eqn]\begin{bmatrix} 1 & 2 & -1 & 1 & 2 &
3 \\ 5 & 12 & 3 & -5 & 6 & 5 \end{bmatrix}
[/eqn]

Where the RREF is
[eqn]
\begin{bmatrix} 1 & 0 & -9 & 11 & 6 &
13 \\ 0 & 1 & 4 & -5 & -2 & -5 \end{bmatrix}
[/eqn]

I'm just not seeing the connection here.

[Anonymous No.11931334]

>>11931321
I think what they meant was look at the augmented matrix [math] \left[ A \, \mathbf{b}_i\right] [/math] for [math]i=1,2,3,4[/math], but that's really confusing that they put it that way.

[Anonymous No.11931391]

would companies like sigma aldritch deliver to university housing? I want to buy my hairloss compounds on the cheap.

[Anonymous No.11931411]

>>11931334
I think I've got it now, but I don't really have a good explanation as to 'why' this worked, and it's required for the question.

[Anonymous No.11931414]

>>11931391
Is Nair really that expensive?

[Anonymous No.11931416]

>>11931334
>>11931411
oh and this is my updated answer to a)

[Anonymous No.11931420]

>>11931414
on the off chance you were serious, i am talking about stuff like minoxidil, tretinoin, finasteride etc

[Anonymous No.11931424]

>>11931420
I knew what you meant, it was just a joke.
Guess it wasn't very funny...

[Anonymous No.11931435]

Fuck it, I'm lazy, and I have the min respect for the board to avoid cluttering the catalog...

To the question: supernovae at 1k lightyears are extiction level events on surface of earth.

How much lower is the flux density if sheltering within the sun,? How much extiction resistance is gained, in other words?

[Anonymous No.11931474]

>>11931054
Your answer is correct. However:

For exponential decay in general, it's more common to put the constant (with units of time) in the divisor: e^(-t/τ), where τ is the time taken to decay by a factor of 1/e. If y=e^(-t/τ), dy/dt=(-1/τ).e^(-t/τ)=-y/τ. IOW, if you draw the tangent line at any point <t,y(t)>, <t+τ,0> is where it intersects y=0.

For radioactive decay, it's more common to use the half life, i.e. 2^(-t/λ) rather than e^(-t/τ) (they're equivalent besides a factor of ln(2) in the constant).

Y(t)=250*2^(-t/λ)
Y(300)=20 => 250*2^(-300/λ)=20
=> 2^(-300/λ)=20/250
=> 300/λ = -log(20/250)/log(2)
=> λ = -300*log(2)/log(20/250) = 82.33

2^(-t/λ) = e^(-t*ln(2)/λ) = e^rt where r=-ln(2)/λ = -0.00842 or e^-(t/(λ/ln(2))) = e^(t/τ) where τ=λ/ln(2) = 118.78.

[Anonymous No.11931488]

>>11931416
OK, I think I see what's going on. When you row reduce the full augmented matrix ,[math]\left[ A \, \mathbf{b}_1 \, \mathbf{b}_2 \, \mathbf{b}_3 \, \mathbf{b}_4 \right][/math] you are solving all four systems simultaneously.

[Anonymous No.11931493]

>>11931474
Holy shit this is wonderful. Thank you.

[Anonymous No.11931524]

Is it possible to recover my cognitive ability?
i'm early 30 and i have been neet for almost 10 years and i can feel that my memory and attention has declined, i have difficulties remembering names.

[Anonymous No.11931533]

>>11931524
no. use it or lose it is a thing. it doesn't flow the other way though

[Anonymous No.11931562]

>>11931533
KYS retard

[Anonymous No.11931577]

>>11931562
kill yourself pathetic faggot

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3191246/

[Anonymous No.11931580]

>>11931524
PAY ATTENTION NIGGER

[Anonymous No.11931599]

>>11931577
>it doesn't flow the other way though
you're wrong

[Anonymous No.11931676]

>>11931488
Ah ok, thanks. (duh!)

[Anonymous No.11931753]

man linear algebra is the most tedious and stupid class I've ever taken, I thought I'd like it since I enjoyed self studying linear and abstract, but they make this all about extremely mundane and tedious calculations

[Anonymous No.11931774]

>>11931074
People post some pretty stupid physics questions here tho.

[Anonymous No.11931799]

An inverse function is inverse if
[math](f \circ g)(x) = x[/math] & [math](g \circ f)(x) = x[/math] right?

but what if, for example, [math](f \circ g)(x) = x-3[/math] & [math](g \circ f)(x) = x-3[/math] ?

Is it still valid? or IT HAS to be [math]x[/math] alone for it to be inverse? if the output in both compsitions is [math]x-3[/math] isn't that the same thing?

[Anonymous No.11931806]

>>11931799
>Is it still valid?
no
>>11931799
>or IT HAS to be xx alone for it to be inverse?
yes>>11931799
>if the output in both compsitions is x−3x−3 isn't that the same thing?
no

[Anonymous No.11931813]

>>11931806
So if i'm doing [math](f \circ g)(x)[/math] and the output is something that is not [math]x[/math] i can safely say that the function is not inverse?

[Anonymous No.11931819]

Ohhh so if [math]f(x)[/math] has its inverse [math]f^{-1}(x)[/math] then [math]f^{-1}(x)[/math] has to be injective unequivocally?

[Anonymous No.11931821]

>>11931813
yes

[Anonymous No.11931823]

>>11931599
No im not coping retard

[Anonymous No.11931840]

>>11931819
f has an inverse iff f is bijective
if f has an inverse then [math] f^{-1} [/math] also has an inverse which is obviously f, and [math]f^{-1}[/math] has to be bijective as well (and is therefore injective/surjective of course)

[Anonymous No.11931953]

>>11931823
The study you posted literally says otherwise you dunce!

[Anonymous No.11931964]

>>11931840
ohh, i got it, thanks man

[Anonymous No.11931982]

>>11931953
The study I posted is only meant to establish that synaptic pruning is real and experimentally verified. If you look further there is zero, absolutely zero evidence of cross-domain benefits to cognitive training. Under no circumstances without neutrophics and unsustainably aggressive cognitive training regiments can you possibly increase iq whether that be executive function, short term memory, visual-spatial reasoning or any other key component of higher reasoning. It is genetically determined, what isn't genetic is only plastic prior to puberty. At 30 you are done, it is over, you can mitigate against brain fog and senescence but you cannot reverse it. Just as you cannot undo brain damage and damage to cartilaginous tissues so too can you not increase the complexity of neural circuity to an appreciable and useful degree past puberty. It is completely unfounded physically and would not make sense from an evolutionary perspective where hard wiring highly calcified behavioral patterns to optimize social status and mating opportunity would necessitate rigid thinking and less energy spent on growth. You are retarded, you are coping, you are a faggot.

[Anonymous No.11932088]

>>11931391
How are you gonna impersonate an entire university department when you don't know the account codes and shit that they use to order chemicals? Sounds slightly illegal.

[Anonymous No.11932095]

I'm trying to get rid of (by eating) the old potatoes that I had bought and hoarded since March for the coofening. Some of them are a little bit green. Wikipedia says this can freaking kill me? Does anyone agree?

Fucking plants and their anti-predator defenses.

[Anonymous No.11932100]

>>11932095
>does anyone agree
yes? you retard. don't eat them. potatoes are some of the more dangerous foods when they go bad

[Anonymous No.11932111]

>>11932100
I don't know I've been frying them only a couple at a time and in moderation and I feel fine so I th

[Anonymous No.11932132]

>>11932111
trips for death-by-potato

[Anonymous No.11932317]

I have to take a course in morphology for pharmaceutical chemistry.
What are some good starting books on the subject? and where should I start?

[Anonymous No.11932323]

>>11932095
Green taters are high in solanine. Consuming large amounts of solanine is not a good idea. Supposedly frying causes some of the solanine to leach into the fat, but you're better off just throwing them away.

[Anonymous No.11932329]

>>11932095
if youre gonna eat it at least peel off the green
the green IS poison but its not too bad unless its taken strong root, and cutting off the actual green bits removes most of it

[Anonymous No.11932349]

>>11919362
How don't we have ways to repair brain tissue?

[Anonymous No.11932460]

>>11919362
I have an arbitrary bit length word. I want to alias this word by multiplying by some integer amount and modulate it to provide all possible combinations of that bit length? Is this possible for all bit lengths, using the same value of alias multiplier for each value? If not, which I suspect, is there a paper or proof I can be pointed to?

[Anonymous No.11932481]

>>11932460
Uh, what?

[Anonymous No.11932487]

>>11932481
Sorry it's hard to explain easily. Let's say I have the numbers 1-4. If I first take the number 1, and multiple it by 1 or 2 or 3 or 4 and then take the result, mod 4, I will get a result of
(1*1)Mod4 = 1
(1*2)Mod4 = 2
(1*3)Mod4 = 3
(1*4)Mod4 = 0
If I take 2:
(2*1)Mod4 = 2
(2*2)Mod4 = 0
(2*3)Mod4 = 2
(2*4)Mod4 = 0
For my transformation with initial value 1, I can receive all possible other values. For my transformation with initial value 2, I only receive half the values.

Is there a way to receive all possible values from all inputs utilizing the same multipliers and mod value?

[Anonymous No.11932519]

>>11932487
Your input and the number that you are modding by need to be coprime if you want to get all the numbers through that process.

[Anonymous No.11932533]

>>11932519
Ok I'll try it with the next prime higher than the mod value, as any prime should be also coprime with all other numbers

[Anonymous No.11932571]

>>11932349
because the body doesn't have a way to repair brain tissue, and the only way we currently repair tissue is by having the body do all the hard work.

[Anonymous No.11932944]

>>11931753
is this your first course? sometimes the basic intro to linear algebra can be really tedious

[Anonymous No.11932955]

>Start with Gelfand Algebra, that's the easy one
I bet people who say that didn't even solve problem 42 properly, holy shit this book is hard.

[Anonymous No.11933059]

https://www.craigslist.org/about/best/lax/35274458.html
>Friends, DON'T SHAVE YOUR ASS-HAIR!
is this accurate? i've pulled out my ass and gooch hair with my bare hands and plucked some of it and i never noticed a problem. i also used to shave my armpits before i went into full NEET mode.

now i'm turning 27 and my hair is getting ridiculous on my genitals and on my legs. i've been plucking my genital hair but i seem to have an absurd amount of it now and it grows back very aggressively. i'm sprouting new hairs on my legs and it grows long and thick and it often itches, plus i want to get rid of it for cycling aesthetics and aerodynamics without having to shave it regularly. i have terrible hapa genetics with the quantity of hairs of a nordic person combined with the hair thickness of an asian person.

i was researching the braun silk-expert pro 5 IPL hair removal device and it seems to work well for legs but they say not to use it on your genitals. the tria beauty 4x seems like it might be better since it is real laser but they also say not to use it on your genitals and it takes longer to cover larger areas like your legs. it's difficult to find anecdotes of people using such devices on their genitals rather than getting it done professionally which i don't want to do.

[Anonymous No.11933073]

by genital hair i mean hair that grows on the actual penis and ballsack

[Anonymous No.11933205]

>>11931982
This level of of autism associated with this level of retardation has never been seen before.
i can't tell if you don't understand a paragraph or if you're trolling

[Anonymous No.11933738]

How is this pic topologically possible?

[Anonymous No.11933896]

Can someone explain how they got this answer? It's college algebra.
>For any nonzero numbers a and b and any integers m and n...
[math] a^-m/b^-n = b^n/a^m [/math]

[Anonymous No.11933899]

>>11932533
Try the number right after the mod value, since [math]n+1\pmod{n} \equiv 1,[/math] and 1 always works.

[Anonymous No.11933905]

>>11933896
I mean how do they simplify? First part of the equation is incorrect, it's supposed to be a^-m/b^-n (raised to a negative 'm'-th and 'n'-th power.)

[Anonymous No.11933920]

>>11933905
Sorry for double posting but to my understanding it looks like this:

[math] (1/(a^n)/1/(b^n)) [/math]

[Anonymous No.11933929]

>>11933896
Can you use [math] ( \frac{a}{b} )^n = \frac{a^n}{b^n}[/math]?

[Anonymous No.11933978]

>>11933929
I'm not familiar with LaTeX. To my understanding of the problem it's a fraction of a fraction in a fraction. >>11933920 And it's also college algebra if that helps

[Anonymous No.11933998]

>>11933929
Nevermind it was a complex fraction apparently.
Khan academy helped me.

[Anonymous No.11934116]

>>11933998
Effectively,
[eqn]\frac{1}{a^n} = a^{-n}.[/eqn] Also,

[eqn]\frac{1}{b^{-n}} = b^{n}.[/eqn] So put the two together.

[Anonymous No.11934529]

Why does the concept of degrees, minutes, and seconds exist, when we could just use degrees with decimals?

[Anonymous No.11934543]

>>11934529
It's non-intuitive.

[Anonymous No.11934553]

>>11934543
I found the degrees, minutes, seconds system non-intuitive and the decimals system intuitive. Is my brain broken?

[Anonymous No.11934618]

>>11908671
>>11908678
The flux is zero. The flux through a flat surface in a uniform field is basically the projection of that surface onto the perpendicular to that field times the field, it is the part of the surface that the field "sees". For example imagine shining a light at the surface, the area important is the area of the shadow cast on any other surface perpendicular to the beam of light.

[Anonymous No.11934627]

>>11934529
Because 60 has many divisors for which the ancient greeks knew how to divide the circle with elementary geometric tools.

[Anonymous No.11934638]

>>11934529
Because the ancient Sumerians used it, probably because "60s" made it easier to do astronomical predictions, and they were one of the original sources of numeracy. Historical baggage, basically, same as the imperial system or conventional current.

https://en.m.wikipedia.org/wiki/Sexagesimal

[Anonymous No.11934745]

Free real QFT, we get creation and annihilation operators for momentum eigenstates of momentum math]\mathbf{p}[\math], the lecture notes I'm using denote them [math]a^{\dagger}(\mathbf{p}), a(\mathbf{p})[/math]. Quantum field operators in real position space are denoted [math]\psi(\mathbf{x})[/math] and there conjugate momenta [math]\pi(\mathbf{x})[/math]. We can fourier transform to momentum space, this transformed field operator is denoted with a tilde above.
However the lecture notes then make the puzzling statement:
[math]\overtilde{\psi}(\mathbf{p})=a^{\dagger}(\mathbf{p})+a(\mathbf{p})[/math] with some constants that I won't bother reproducing; the point is that what I interpreted as an arbitrary field operator corresponding to an arbitrary field configuration is being written as a sum of creation and annihilation operators: there is only one creation and annihilation operator each for a given momentum [math]\mathbf{p}[/math], so there is only one result of adding them, and this cannot represent arbitrary states. For these operators, the momentum is a "label", but for arbitrary field operators the momentum is a coordinate over which the field is defined. In order for this statement to make sense there must be some abuse of notation that I am too obtuse to intuit. I first noticed this problem when the fourier transform was taken:
[math]\psi(\mathbf{x})=\int\mathrm{d}^3p\left[e^{i\mathbf{p}\cdot\mathbf{x}} a^{\dagger}(\mathbf{p}) + e^{-i\mathbf{p}\cdot\mathbf{x}}a(\mathrm{p})[/math],
with again some constants forgotten.
Clearly for each position vector [math]\mathbf{x}[/mathbf] there is only one result of this integral, so this cannot represent an arbitrary field operator.
Some answers on stack exchange led me to believe that perhaps the symbol [math]\psi(\mathbf{x})[/math] is meant to represent an operator that when applied to the ground state gives a position eigenstate, so again [math]\mathbf{x}[\math] becomes a "label" for these position eigenstates

[Anonymous No.11934756]

>>11934745
the integral is
[math] \psi(\mathbf{x})=\int\mathrm{d}^3p\left[e^{i\mathbf{p}\cdot\mathbf{x}} a^{\dagger}(\mathbf{p}) + e^{-i\mathbf{p}\cdot\mathbf{x}}a(\mathrm{p})\right][/math]

[Anonymous No.11934788]

>>11934745
>>11934756
But then fourier transforming this operator would not make sense, this operator creates a position eigenstate for a point [math]\mathbf{x}[/math] regardless of which coordinate system you choose to represent it in, or at least the way in which this is written above makes no sense, as the fourier transformed operator [math]\tilde{\psi}(\mathbf{p})[/math] makes no reference to this priveledged position. And if by some weird notation this were meant to denote an operator which creates momentum eigenstates in an analogous way to how [math]\psi(\mathbf{x})[/math] creates a position eigenstate (this of course makes them not the fourier transform of eachother). However isn't this simply what [math]a^{\dagger}(\mathbf{p})[/math] does (with some differing norm'zation constants)?

[Anonymous No.11934842]

Why does this function have values such that z < 0? I thought the domain of ln(x) was x>0.

[Anonymous No.11934845]

>>11934842
oh wait im even dumber than i thought, x^2 + 4y^2 > 0, but for small values z goes neg

[Anonymous No.11934884]

>>11934745
>>11934756
>>11934788
Holy shit man format your posts properly.

[Anonymous No.11934892]

>>11934884
no idea what I'm fucking up

[Anonymous No.11934961]

I'm trying to build a simple RC airplane, i get most of the airodynamic concept but i find myself stuck on something i can't find, how much lift do i need?!

For an airplane of 400g how much lift does the wing has to produce and at what speed ?!

I can't find the equasion for that.

[Anonymous No.11934991]

>>11931391
>sigma
>cheap

[Anonymous No.11934992]

>>11934961
400g at operating speeds

[Anonymous No.11935000]

>>11934992
you mean cruise speed?

[Anonymous No.11935018]

>>11935000
don't know what cruise speed is; probably.

[Anonymous No.11935084]

How can a drill battery jump start a car? Isn’t the starting current for even small cars like a few hundred amps? The inside of a drill battery is just a bunch of 1.5a batteries in series.

[Anonymous No.11935132]

>>11935018
You don't really know the answer, do you

[Anonymous No.11935201]

In the real number system, could this expression:

sqrt(p) ^ sqrt(q)

ever evaluate to a transcendental number for some pair of natural numbers p and q? (Where ^ is the power operator).

More generally, is there any way to create a transcendental number from a finite chain of basic operators, starting with only the integers -- where "basic operator" means ONLY addition, subtraction, multiplication, division, power, and root (no logs, no trigs, etc.)?

[ Note that even though we must start only with integers, it is possible that some intermediate values might end up being irrational, since there is no restriction on how sophisticated you can be in chaining the operators. For example: (2^(1/2))^(2^(1/2)) is a legal construction here, because the numbers that we START with are all integers. ]

[Anonymous No.11935239]

>>11935201
I'm not sure but my intuition is no, because any number created by a finite number of operations can be traced to the solution of a polynomial, which by definition is not transcendental.

[Anonymous No.11935246]

>>11935239
>2^2^.5

[Anonymous No.11935267]

>>11935239
>a finite number of operations can be traced to the solution of a polynomial, which by definition is not transcendental.

I know what you mean. For example, the real solutions for x^5 - x - 1 = 0, are all -- by definition -- not transcendental.

Notice something interesting about that polynomial: all the powers of x are natural numbers. (x^0, x^1, x^2, x^3, etc.)

But in my case, I'm allowing the powers to be irrational. If the power is allowed to be irrational, I can't see a way of guaranteeing that you could always express it as the root of a polynomial where the powers of x are all natural. That's what leads me to speculate that an irrational to an irrational power might be transcendental in some cases.

[Anonymous No.11935290]

>>11935267
I see in fact my first answer was totally wrong. look up the gelfond-schneider theorem

[Anonymous No.11935307]

>>11935290
Thanks, I just found it a few seconds before your post. Here's a promising clue:

"using the Gelfond-Schneider theorem, we find that sqrt(2)^sqrt(2) and 2^sqrt(2) are transcendental but raising them to the power sqrt(2) gives 2 and 4 respectively"

Source:

https://www.quora.com/Can-an-irrational-number-raised-to-an-irrational-power-be-rational-How-about-the-square-root-of-2-raised-to-the-square-root-of-2-power

[Anonymous No.11935382]

>>11935132
lift: force that goes upwards
weight: force that goes downwards

[Anonymous No.11935401]

>>11934961
>>11935132
You won’t find an equation, because it’s very obvious. Which is why he answered despite not even knowing what cruise speed is. It’s like buoyancy (actually exactly the same, since flight is still part of fluid dynamics). If you create more upward force than mass*g, you’ll rise, air or water. The speed is irrelevant(Aside from the air resistance it creates), just know that if you drop below that speed you’ll begin to descend so it shouldn’t be at max motor capacity or something unsustainable.

[Anonymous No.11935927]

Will muon-catalyzed fusion ever be viable? I'm sure there's much that I'm unaware of in this subject, but from what I understand, the only things that make it not viable are 1. the energy cost of producing muons vs the energy produced and 2. the amount of catalyzed fusions a muon can cause before it's "used up". However surely these problems can't be more complicated or costly to solve than the amount of research and funding that's been poured into standard fusion generation, right? Is it just a pipe dream or is it just a matter of little interest in the subject?

[Anonymous No.11936044]

If black holes add relativistic amounts of kinetic energy to any infalling matter, wouldn't their increase in mass be significantly more than the mass of the matter that fell in?

[Anonymous No.11936076]

>>11919362
Can someone help with this? The problem might seem easy but when I tried to put the answers not a single one worked

[Anonymous No.11936096]

>>11933059
he's hugely exaggerating for comedy. I dunno how the fuck you'd actually get some kind of shit-glue holding your ass shut unless you literally just forgot to wipe after your last dump.
your experience may vary but I'd personally recommend just trimming it down instead of going completely hairless. I've shaved my asscrack before and while it's not particularly uncomfortable it does feel very weird, and not in a pleasant way. plus it does itch when the pokey little short hairs start growing back. trimming them to not quite smooth gets rid of both of those issues.

using an electric device down there does not sound safe, I doubt you will find one that doesn't say not to do it. Low control/visibility + automatic device + extremely sensitive region sounds like a very bad mixture.

[El Arcón No.11936113]

>>11935927
Is a muon in a muonic hydrogen bound state a stable particle?

[Anonymous No.11936122]

>>11936113
Unless I misunderstand your statement, no I don't believe so. It's always a matter of time before it decays further. It only is bound for a short amount of time before moving onto another hydrogen atom and eventually decaying.

[Anonymous No.11936125]

>>11936044
Those objects only gain that kinetic energy because they lose potential energy as they fall

[El Arcón No.11936150]

>>11936122
I meant does the muon decay to an electron by emitting a muon neutrino and an anti-electron neutrino while it is in the bound state with the nucleon?

[El Arcón No.11936158]

>>11936113
>>11936150
Or, in other words, is muonic hydrogen stable? Not sure what you mean "moving to another atom?"

[Anonymous No.11936185]

>>11936158
Don't really know the technical aspects, but I think he might be talking about this:
https://youtu.be/aDfB3gnxRhc?t=217

[Anonymous No.11936397]

How should I read this?

[Anonymous No.11936406]

>>11936397
We're defining a new function "+" which takes a pair of integers and outputs a new integer.

If you mean how do I literally read this, I would say "define plus as a function from Z 2 to Z".

[Anonymous No.11936753]

am I misunderstanding something obvious, or is this proof just complete nonsense? (I've cropped out the rest of part 1, as it's not relevant)
the [math]\alpha_1 \alpha_2 ... \alpha_n\alpha_k[/math] are clearly not relatively prime if there's more than 2 alphas, no?

[Anonymous No.11936754]

am I misunderstanding something obvious, or is this proof just complete nonsense? (I've cropped out the rest of part 1, as it's not relevant)
the [math]\alpha_1 \alpha_2 \dots \alpha_n / \alpha_k[/math] are clearly not relatively prime if there's more than 2 alphas, no?

[El Arcón No.11936923]

>>11936397
I read that as "Plus is a function from a Cartesian product of Z with itself to Z" or "Plus is a map from pairs of integers to single integers."

[Anonymous No.11936930]

>>11936406
You're wrong, ":=" is the symbol that means 'defined by'.

[Anonymous No.11936942]

>>11936397
I'm gonna have to agree with Tooker on this one, he isn't necessarily defining the function, he could just be determining its domain and codomain.
Depends on context tho.
>>11936930
Listen, you can use CS notation all you want.
But complaining to people that they aren't is just disgusting.

[Anonymous No.11936956]

>>11921147
many particles already have a probability distribution the size of the universe, electrons and photons for example

[Anonymous No.11936970]

>>11921332
math is too primitive for a description of the world

[Anonymous No.11936977]

>>11922910
about as much as both bombs dropped on japan combined together

[Anonymous No.11936984]

>>11936942
That notation was created im CS but is widely accepted in the modern math community, one of the most famous math books (Aluffi's Algebra) is built entirely around it.

[Anonymous No.11937012]

>>11924817
the anthropic principle is the easiest answer to this, i remember reading that stable orbits are impossible in 4 spatial dimensions for example, and there are countless other similar things that probably arise at higher dimensions

so your question is really why humans exist in 3 dimensions, and the answer is probably because 3 dimensions are hospitable to a human evolving and living

[Anonymous No.11937015]

>>11926821
because the speed of light is the speed limit of the universe, if you go faster you are moving faster than causality itself

[Anonymous No.11937018]

>>11919362
Why is there a tohou pic in all of those threads?

[Anonymous No.11937034]

>>11934543
it's perfectly intuitive

[Anonymous No.11937049]

>>11937018
because touhou is stupid

[Anonymous No.11937233]

I'm asked to determine order of pole or removable singularity for.

z/(1-e^z)) Can anyone walk me through it?

[Anonymous No.11937824]

>>11937233
Find the order of the zero of [math]\dfrac{1-e^z}{z}.[/math]

[Anonymous No.11937882]

>>11937824
the order of a singularity or zero is what power of z the function looks like in an arbitrarily small neighborhood of that point, so a dumb method that always works is to taylor expand problematic terms, here the e^z, around the point of interest.

[Anonymous No.11938152]

>>11937233
[math]z[/math] zeroes of order one, and [math]1 - e^z[/math] zeroes of orde one.
So the pole has order zero (i.e. there is no pole), as you can confirm with https://www.wolframalpha.com/input/?i=plot+%281-e%5Ex%29%2Fx .

[Anonymous No.11938939]

>>11936956
Yes, but their density differs. 90% of an electron can be characterized within a couple angstroms, but what if for gravitons, a few angstroms was infinitesimally small? And to get that same 90% characterization you'd need, at minimum, an area the size of a galaxy?