/sqt/ /qtddtot/ - stupid questions thread

[Anonymous No.11671932]

Handy edition.

Formerly >>11656811

>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
>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
>look up the Tex guide beforehand
>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

Resources:
Good charts: https://imgur.com/a/kAiPAJx
Shitty charts: https://imgur.com/a/1Q1LIMk (Post any that I've missed.)
Verbitsky: https://imgur.com/a/QgEw4XN
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.11671985]

Are there any charts for electrical engineering? I'm due to take a course in August-December and want a head start. I already know linear algebra and multivariable calc.

[Anonymous No.11672009]

Unanswered questions:

Math questions:
>>11659903
>>11661487
>>11662016

Probability and Statistics:
>>11660026
>>11664367
>>11671351

Physics questions:
>>11658062

Engineering questions:
>>11660740

Biology and Medicine questions:
>>11661048
>>11661208
>>11662557
>>11664769
>>11668771
>>11669690

/g/ questions:
>>11662723
>>11663770
>>11665439
>>11668092

Advice requests
>>11657888 (Strictly speaking not an advice request.)
>>11668172

Stupid questions
>>11656815
>>11657636
>>11661266
>>11666196

>>11671985
If there are, I haven't seen them.
Just use the wiki.

[Anonymous No.11672238]

What's with the touhou fascination in this board in general and in this threads in particular? I know that the touhou group consists of very smart people that always give answers to tough questions, but are they that numerous?
Also, what's the fascination with touhou? the girls, or the gameplay? I've never played a touhou game before, but after starting frequenting this board I want to try it because now I think it's some sort of game for intellectuals.

[Anonymous No.11672298]

Just how difficult is it to get into a school like Berkeley or MIT for a nuclear engineering PhD? Like what sort of GPA and GRE scores are considered passable and what additional things do they want?

What are the next tier of nuclear graduate programs and how hard are they to get into?

[Anonymous No.11672398]

>>11672238
the people posting touhou here are using it to avatarfag
touhou is perfect for that purpose because there's a whole bunch of cute characters with very distinctive, easily recognizable designs and they all have like 30-40k pictures of fanart each

[Anonymous No.11672414]

>>11672238
This board is just full with trannies.

[Anonymous No.11672670]

>>11672238
Everybody who gets into Touhou gets in via the music. It's catchy EDM without being heavy on bass or distortion and every track has over a hundred different youtube covers.
There's something about the STEM or just autism-adjacent mindset of having to classify things that leads people who like the music to absorb everything else. I don't think it's specific to Touhou, I think that any series of cartoony video games with fairly good music and some critical mass of sheer quantity of fanart becomes a mind virus for some groups of people.
Thankfully, I prefer Rareware media properties liked a civilised person.

[Anonymous No.11672704]

>>11671932
How decent are 2.5M masks for not spreading Corona virus? I work retail and uber eats. I know its not going to be as good as n95, but I don't want to keep health professionals from getting them. I just want to make myself less of a vector.

[Anonymous No.11672870]

>>11671932
Can you help me? there are two buckets; A with 5 balls and B with 3. A dice is trown and if the numebr is even, bucket A gives one ball to the other and viceversa if it is odd. The process ends when one bucket has all the balls. What is the probability of the box A to accumulate the 8 balls?
I thought is was: P(A)=(0,5)^3+(0,5)^5+(0,5)^7....=1/24
but it can be that cause then it P(B)=(0,5)^5+(0,5)^7....=1/96
so P(A)+P(B)=/=1 AND THATS IMPOSSIBLE

[Anonymous No.11672957]

>>11672870
sounds like markov chains and limiting distributions

[Anonymous No.11672959]

>>11672870
Essentially, the geometric sum is *almost correct*, but you forgot to account for permutations (or multiple routes, so to say).
So there's a [math]0.5^3[/math] chance of it finishing in three steps, that's correct, because the route is unique.
But there are quite a few routes for it finishing in five turns. It can start with a ball going from A to B, and then B gives A four balls in a row, which has [math]0.5^5[/math] probability of happening, or B can give A a ball, A gives a ball back, and then B gives all three of its balls to A, which also has [math]0.5^5[/math] chance of happening, and so on.

[Anonymous No.11673030]

Does this seem right? The example problem in the book doesn't involve torque so I'm worried I did something stupid.

[Anonymous No.11673093]

>>11672704
Thing is there's not really empirical testing to answer your question, but the answer is "probably good enough" and certainly better than nothing. What will make the biggest difference is keeping your distance, and not coughing or sneezing when you're around people, also try to keep conversation brief, and talk more with your mouth pointing down and into your shoulder, that way if anything gets through, it is hitting you rather than traveling towards the other person.

[Anonymous No.11673151]

Hey bros, how do I find the range of the function? I know that I need to find the greatest value of the denominator but I don't exactly understand what that means.

[Anonymous No.11673156]

I’m in schooling to be a aviation electrician to work on chinooks,blackhawks,Etc. As I build a background in electricity as a wire chaser what schooling do you recommend? I’m interested in everything from Crispr/Pharma to aerodynamics. I don’t have training in really any field so I’d have to start at the basics.
>TLDR becoming a wire chaser for aircrafts and I’d like to peruse more schooling/knowledge after training is over for all Math/Sci subjects looking for recommendations

[Anonymous No.11673169]

>>11673151
>I know that I need to find the greatest value of the denominator but I don't exactly understand what that means.
look at the denominator. what is the largest value it could possibly be?

[Anonymous No.11673188]

What's the largest size mankind could get a pyramid to, using modern tech?

[Anonymous No.11673254]

>>11673156
That's a weird question, where there isn't really even an answer. I think you need to just hang around the board and find out the topics you're interested in and keep working out from there. I'd say to look into engineering technology since it would be a great addition to your current training but sounds more like you're hoping to be eclectic and branch out into generally unrelated subjects. I could recommend kinesiology, and human ergonomics, since the machines you're working on rely on human interfacing to control many aspects of operation.

[Anonymous No.11673308]

>>11673188
Is there literally any reason at all why we couldn't just keep building indefinitely, aside from the curvature of the earth making it technically not a pyramid or just a lack of materials?

[Anonymous No.11673327]

>>11673308
I think in a solid pyramid the limit is in the strength of the materials you use closest to the base, because they have to hold the weight of everything above without crumbling
Maybe someone could run up some numbers on it

[Anonymous No.11673331]

>>11673327
But what if we just put it in space?
Or on the moon?
What if we make it out of a light weight superstructure so that it doesn't collapse on itself too

[Anonymous No.11673341]

>>11673331
stacking solid blocks is way simpler than building something like a skyscraper, and more stable as well

[Anonymous No.11673366]

>>11673331
>But what if we just put it in space?
eventually it would create its own non-negligible gravitation field, and would collapse into more of a sphere shape than a pyramid
>What if we make it out of a light weight superstructure so that it doesn't collapse on itself too
nothing is indestructible, eventually if you made it big enough the material would succumb

[Anonymous No.11673390]

>>11673341
>>11673366
Would pic related work?
How big could the concrete core get to before destroying itself?

[Anonymous No.11673398]

>>11673254
Thanks for the suggestion.
I’m interested in starting a business in 6 years and haven’t decided what I wanted to do yet but everything interests me. I don’t really have that much knowledge other than basic GED background. I was thinking of creating cheap generic medications or figure something out with the schooling I’m getting now.
I just don’t know where to start but I’ll get paid $4,500 extra for college a year so I can study something

[Anonymous No.11673418]

>>11673390
this here says that at best, concrete has a compression strength of 8000 psi, and another google search tells me that concrete has a density of 2400 kg/m^3, or about .039329 kg/in^3, or about .385817 lb/in^3
assuming uniform density and gravity, you would have to stack concrete 20735.2 inches high before the base began to fail. this is about 1728 ft, or 0.327 miles high

[Anonymous No.11673425]

>>11673390
>>11673418
forget about concrete, anon. earth-fill.

[Anonymous No.11673433]

>>11673418
Nice, anon
Do you have any numbers on steel reinforced concrete as well, or some other suggestion on the materials that could be used in its place?

[Anonymous No.11673442]

>>11673425
Would earth-fill be strong enough to build a 200m layer on top of?

[Anonymous No.11673450]

>>11673418
This is assuming a cilinder shape, where the whole base gets equal load, right? Wouldn't it be different on a pyramid, considering that the middle would be getting the most forces, but even if the concrete there starts failing, it doesn't have anywhere to spread to, so it still holds everything together?

[Anonymous No.11673463]

>>11673433
wikipedia says that porcelain has a compressive strength of 500 MPa, nearly 10 times that of concrete
fortunately, coincidently, porcelain has a near identical density to concrete, so the highest porcelain pyramid you could build is 10 times higher than the concrete one, so 3.27 miles
>>11673450
it assumes no shape, the only relevant idea is that the concrete on the bottom has 0.327 miles of concrete on top of it (of course in a pyramid, this would only be true for the center of the base, and the pressure would decrease as you moved out)
>even if the concrete there starts failing, it doesn't have anywhere to spread to, so it still holds everything together?
the molecular structure of the concrete itself fails at this pressure, and the volume of the concrete decreases, resulting in instability of the entire structure

[Anonymous No.11673479]

>>11673463
>porcelain
really nice to know, but how would someone bake a massive porcelain pyramid to being with? Would it be feasible to build from porcelain blocks instead? Is it even possible to bake a solid block of porcelain, or only thin stuff, like plates?

>>11673463
>the molecular structure of the concrete itself fails at this pressure, and the volume of the concrete decreases, resulting in instability of the entire structure
oh, that makes more sense
thank you anon!

[Anonymous No.11673482]

>>11673442
Mountains.
>>11673433
I'm not the same guy, but reinforced concrete is better under an axial load. The forces on an element near the bottom of the pyramid are compressive everywhere. You want something with isotropic strength. Prestressed or dispersion-strengthened concrete.
I don't know all the physics of mountains, but probably look there to answer this question.
>>11673450
something like that, yes
>>11673463
The problem with porcelain is it is more brittle than concrete. You must carefully much more [math] carefully [/math] examine for cracks and imperfections. The nature of ceramics is such that
>>11671832
I forgot about the existence of solutions. Thank you anon.

[Anonymous No.11673488]

>>11673482
But mountains are made of rock, not just earth
How strong are rocks, like the ones egyptians used? are they stronger than concrete?

[Anonymous No.11673491]

>>11673488
the eygptians used granite, which is about 4 times stronger than concrete

[Anonymous No.11673496]

>>11673482
**The nature of ceramics is such that they are susceptible to different modes of fracture. Concrete is fairly tough stuff, porcelain shatters.
>>11673463
>it assumes no shape
Yes, it fucking does. Concrete strength is tested in a very specific way. I used to watch civvie cucks do it all day long at my school.

[Anonymous No.11673500]

>>11673491
>Granite
so now we're pushing for 6900 feet already? Nice

[Anonymous No.11673504]

>>11673500
Anon, the tallest mountains are nearly 30k feet.

[Anonymous No.11673511]

>>11673496
>Yes, it fucking does.
does this only apply to solids? i know that fluid pressure is shape apathetic
>>11673500
granite is actually a bit more dense than concrete, so you cant just multiply the number by 4

[Anonymous No.11673521]

>>11673511
>granite is actually a bit more dense than concrete, so you cant just multiply the number by 4
how would that work out, then, smaller or bigger?

[Anonymous No.11673525]

>>11673521
a bit smaller, because a mile of granite is a bit heavier than a mile of concrete

[Anonymous No.11673531]

>>11673511
Yes, it applies to solids only. Idk if compressive strength for a fluid exists. We aren't talking about pressure, btw.

[Anonymous No.11673535]

>>11673531
>We aren't talking about pressure, btw.
im not a civvie so i wouldnt know, but since compressive strength is measured in pressure (psi, MPa) i assumed they were somewhat related
if you want to redo my retarded calculations be my guest

[Anonymous No.11673554]

>>11673525
I understand, thank you again, anon!

[Anonymous No.11673560]

>>11673554
no problem, pyramid-kun
you might want to stick around, tho. that other guy might explain what compressive strength actually is

[Anonymous No.11673569]

>>11673560
Based anime poster, can you double check the math/physics for the picture of the problem I posted earlier? It had been buried under the pyramid discussion

[Anonymous No.11673577]

>>11673560
Oh, I was just thanking you, I have no intention to leave just yet, still want to see what else comes out of this

>>11673569
I'm sorry anon, it wasn't my intention to bury anyone else, hope someone reaches out to help you (If I weren't so dumb I'd help you too)

[Anonymous No.11673591]

>>11673569
>Based anime poster
i hope youre not confusing me with 2hu-kun
unfortunately, i dont know anything about mechatronics or whatever the fuck that is

[Anonymous No.11673600]

>>11673591
It is brainlet mechanical engineering applied to an engineering technology control systems course. It isn't the formula I'm worried about since the book supplied it just that I may have screwed up somewhere on the basic conversions to balance the units. Thanks though Anon, I'm sure to someone familiar with the subject it will be a very simple problem to double check.

[Anonymous No.11673634]

>>11673188
I dunno, but on the Moon it could be even bigger because gravity.

[Anonymous No.11673643]

>>11673030
>>11673600
Looks fine.
>>11673569
desu not much anime gets posted in these threads
>>11673535
They're similar. If a pyramid is [math] H [/math] tall, then average normal stress at a layer at elevation [math] z [/math] from ground is [math]
\sigma=\rho gH(1-z/H)/3 [/math]. So at the ground layer, the building material needs to withstand [math] \rho gH/3 [/math] But this is average over the layer. Stress concentrations are to be expected around corners.
>>11673634
Yes, it could.
>>11673560
force/area in a solid

[Anonymous No.11673648]

>>11673366
Keep making it bigger. Would it eventually become a star?
"While you can't turn Jupiter into a star, it is not ruled out that you could turn Jupiter into a catastrophic thermonuclear bomb."
That could be cool too, tho.

[Anonymous No.11673659]

>>11673643
Thanks, Anon! Makes me feel better.

[Anonymous No.11673669]

>>11673560
I actually just now read your question. Force/area is stress. Compressive strength is the maximum stress attained in a substance as it is strained. When you see stuff like this >>11673418 it is almost certainly referring to an axial or 1D load.

[Anonymous No.11673929]

Gigabrainlet here, can someone explain buoyancy to me. Does it really boil down to there being more pressure at the bottom than the top?
Would a thin sheet lying horizontally on a fluid not experience buoyancy at all?
Would a ball that is extremely smooth at the bottom, and rough at the top experience more pressure at the top?

[Anonymous No.11674000]

>>11673929
basically, yeah. You can show that the hydrostatic pressure in a fluid is proportional to depth and its specific weight. Pascal's principle is the hydrostatic pressure at any point on a plane of constant depth is the same. Considering that the infinitesimal pressure force is normal to every point on a body, you integrate over the whole surface to get the total pressure force, aka "buoyancy." When you got thru the motions, you find that buoyancy only cares about the volume of fluid displaced.
>Would a thin sheet lying horizontally on a fluid not experience buoyancy at all?
If by "thin" you mean that it has no thickness, then that means it has no volume. So no, it wouldn't.
>Would a ball that is extremely smooth at the bottom, and rough at the top experience more pressure at the top?
no

[Anonymous No.11674021]

>>11673929
basically, yeah. You can show that the hydrostatic pressure in a fluid is proportional to depth and its specific weight. Pascal's principle is the hydrostatic pressure at any point on a plane of constant depth is the same. You integrate pressure over the whole submerged surface of a body to get the total pressure force, aka "buoyancy." When you got thru the motions, you find that buoyancy only cares about the volume of fluid displaced. All else constant, orientation and shape doesn't matter.
>Would a thin sheet lying horizontally on a fluid not experience buoyancy at all?
If by "thin" you mean that it has no thickness, then that means it has no volume. So no, it wouldn't.
>Would a ball that is extremely smooth at the bottom, and rough at the top experience more pressure at the top?
no

[None !!yW1EeZjtTJb No.11674274]

e

[Anonymous No.11674573]

What's the algebraic way to understand the Schrodinger equation for a time-dependent Hamiltonian?

By this I mean, in the case of a time-independent Hamiltonian [math]H[/math], the SE is just a restatement of Stone's theorem: [math]\{ e^{-i H t} \}_{t \in \mathbb{R}}[/math] is a strongly continuous one-parameter abelian unitary group.

When we have a time-dependent Hamiltonian, we have two problems: we don't really get to use the exponential map by itself anymore, but rather we need to invent the "time-ordered" exponential [math]\mathcal{T}\mathopen{}\exp[/math]. Also, the Hamiltonian may not commute with itself at different time points, so we lose the abelianity. I suppose we also need to specify a starting time [math]t_0[/math]. Nonetheless, we can consider the solution set [eqn] \left\{ \mathcal{T}\mathopen{}\exp\mathopen{}\left( -i \int_{t_0}^t H(t') \, dt' \right) \mid t \geq t_0 \right\}. [/eqn] What algebraic properties does this set have? It can't even tell if it's a semigroup because the time-ordered exp fucks with me. Are its continuity properties inherited from those of the Hamiltonian (i.e. as a map from the reals to self-adjoint operators on a Hilbert space)?

[Anonymous No.11674873]

>>11663770
>Lets say we have a Turing machine that is just like a regular TM, but with the difference that its tape has finite length (i.e. 100 symbols) so if it reaches the left/right-most cell and tries to move further it doesn't. How do I go about proving that a TM of this type recognizes a class of regular languages?

CS majors are retarded. They even tell you the answer in the question by giving away that it's a DFA. Let the DFA's states = FauxTurning's states x (tape lang set)^#length x tape position.

[Anonymous No.11674889]

>>11656815
>What's the most addictive substance on Earth?

[Anonymous No.11674934]

>>11671932
How can photons be massless but still have momentum?

[Anonymous No.11674956]

>>11674934
E^2 = (mc^2)^2 + (pc)^2

[Anonymous No.11674979]

>>11674573

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

[Anonymous No.11675045]

>>11674889
Based

[Anonymous No.11675065]

hi guys, forgive my brainlet question but could someone explain to me what's the exact basis we put the charges like that?
((ORGANIC CHEMISTRY // CHEMISTRY)

[Anonymous No.11675412]

>>11674889
Based.

[Anonymous No.11675418]

>>11675065
wtf is Nu?

[Anonymous No.11675589]

>>11674889
yeah, im thinking based

[Anonymous No.11675612]

I need ideas.

[Anonymous No.11675629]

>>11675612
Basically, as long as it's better than something like this, I'm content.

[Anonymous No.11675660]

>A binary source generates digits 1 and 0 randomly with probabilities 0.6 and 0.4, respectively. a) What is the probability that two 1s and three 0s will occur in a five-digit sequence?

Is it just 0,6^2 * 0,4^3 or do I need to multiply that by 2?

[Anonymous No.11675695]

>>11675660
You need to multiply that by five choose three.
So [math]10 \times 0.6^2 \times 04.^3 = 0.2304[/math].

[Anonymous No.11675701]

>>11675695
You got it man thanks

[Anonymous No.11675712]

i've had a free matlab online license for 3 months because of a course that i've been on and it should've expired 2 months ago, yet i'm still able to use it normally
i didn't give any credit card info or something of that sort on matlab, can i continue to use it without a worry or will they want payment later?

[Anonymous No.11675910]

Who the fuck came up with the "Feynman technique"? I've read a lot of stuff by Feynman and nowhere he mentions something like it.

[Anonymous No.11675945]

What algorithms are used to generate the tool-path so that the CNC machine mills the desired shape. Any idea is appreciated. pic related.Video related
https://www.youtube.com/watch?v=jbIU7l_8pR8

[Anonymous No.11675961]

>>11675910
literally anyone who has taught can figure it out independently

as far as feynman himself, idk.

[Anonymous No.11675967]

>>11675961
Yea I know. But I want to know who started calling it the "Feynman" technique.

[Anonymous No.11675986]

Is this right? I thought 3.14... = 3.15 so in their example it would be a false statement

[Anonymous No.11675995]

>>11675986
nvm i'm retarded

[Anonymous No.11676157]

>>11675910
>>11675967
I'm pretty sure the first person to actually call it the "Feynman technique" was Scott Young, the blogger who did that MIT challenge thing a few years back. He was calling it that as far back as 2011.
It's not made-up or apocryphal, though. This is apparently a quote from his biography by Gleick:
>“[He] opened a fresh notebook. On the title page he wrote: NOTEBOOK OF THINGS I DON’T KNOW ABOUT. For the first but not last time he reorganized his knowledge. He worked for weeks at disassembling each branch of physics, oiling the parts, and putting them back together, looking all the while for the raw edges and inconsistencies. He tried to find the essential kernels of each subject.”

[Anonymous No.11676196]

Why isn't [math]\forall x(Px \implies Px)[/math] a tautology?

[Anonymous No.11676330]

>>11676196
It is.

[Anonymous No.11676591]

>>11674934
Because momentum is a more general concept than the [math]p=mv[/math] formula you learned in physics 101.

[exmedfag No.11677089]

I hit the wall again Bros.
for context
>2 months ago I was @ Med School, But I didn't liked to get shitted and pissed on, So I decided to drop out and go to Chem, so I have to Relearn All math and physics because of the UNI exam.

>Arithmetics Done
>Algebra 1 Done
>Algebra 2 Done

>Geometry Done/Trigonometry pending
Ok so this happened yesterday I started with Geometry, I was Happy measuring angles, drawing lines, doing goofy proofs and BORING algebra conversions between angle measures (Hexa,GMS, Radians with the π as a factor) BY HAND.

The problem came when the bitch from the Course I'm taking Jumped me with this "six circular functions" table and gave no explanation at all, and because I don't understand that I Can't move on.

Question 1:
I get the Sine and Cosine ones but The hell is up with the Domain of the Last 3, What is that Weird ass looking U symbol, WHAT DOES IT MEAN? Where does it derive?
I searched for U symbol in google but the only thing that comes up is the one used for unions of sets.

Question 2: How bad is it to do the Geo/Trigonometry exercises With a Calculator? it's just tedious to do all shit by hand, It isn't as fun as Algebra.

Resources to learn more of Trig are Appreciated.

[exmedfag No.11677095]

>>11677089
>BORING algebra conversions
I meant Arithmetic conversions, with multiple decimals.

[Anonymous No.11677257]

Is there a spontaneous, strongly endothermic rxn that can be reversed electrolytically? I'm imagining it for a refrigeration system, or like a chemical ice pack that can be recharged

[Anonymous No.11677262]

Brainlet here who needs help with this problem: The diagonals of quadrilateral ABCD intersect inside the figure. Show that the sum of the squares of the sides of the quadrilateral is equal to the sum of the squares of its diagonals, plus four times the length of the line segment connecting the midpoints of the diagonals
I've drawn a figure here, and I know I need to use the law of cosines, but I don't know how to start on this

[Anonymous No.11677621]

If a GPU can process, say, 10 teraFLOPS, is it reasonable to assume it can produce 10 trillion integer operations per second too?

[Anonymous No.11677692]

Could someone explain what this question is asking for in particular?
My interpretation of the question is that it's asking for a value of y=kx^n that when substituted into the original equation, removes (x) so that the rest of the equation is a constant??? I'm honestly not sure, sorry.

[Anonymous No.11677758]

Bros, in the last step, couldn't he had just cancelled out the cosines so that the limit as r->0 becomes 2?
Also, when we convert limit (x,y) -> (0,0) into limit (r) -> (0), does the theta also become 0 or can it be anything I want since it's not a part of what the limit approaches?

[Anonymous No.11677783]

>>11677758
>couldn't he had just cancelled out the cosines
Read the bottom line of the proof. Most of the time, yeah, [math]\frac{\cos \theta}{\cos \theta} = 1[/math] . But it's possible that [math]\cos \theta = 0[/math] , and in that case you can't cancel out 0/0 to be 1. Which means there are two choices of angle for which the limit doesn't exist.

[Anonymous No.11677862]

>>11677783
>But it's possible that...
Oh fuckkkkkkkkkkkk, that makes a lot of sense.
I didn't know that was what he meant.
Thank you!

[Anonymous No.11677999]

>>11672298
plz

[Anonymous No.11678010]

>>11677692
>My interpretation of the question is that it's asking for a value of y=kx^n that when substituted into the original equation, removes (x) so that the rest of the equation is a constant??? I'm honestly not sure, sorry
duh, what do you get for b

[Anonymous No.11678026]

>>11672298
>>11677999
>Just how difficult is it to get into a school like Berkeley or MIT for a nuclear engineering PhD?
Hard. Grad admissions rates at top schools tend to be somewhere in between 5 and 10 percent, keeping in mind you're competing with people who thought they were good enough to apply to MIT in the first place.
>Like what sort of GPA
4, preferably. One or two decimal points lower is probably fine.
>and GRE scores
GRE general is a complete meme. They almost literally don't matter at all. A 10th grader interested in math/physics could get 170 on the quantitative, and the verbal is just to make sure you're not a FOB chink who can't speak English. You do need to be careful on the quant though, because it looks really bad if somebody misses more than like 1 question on what's basically a high school math test.
>and what additional things do they want?
Rec letters and research experience are the most important things on a grad application by far. Other stuff is just hoops to jump through to not get rejected.
>What are the next tier of nuclear graduate programs and how hard are they to get into?
Ask your profs for this kind of advice. They know you better than we do, they'll be better at judging where's a good match, and they also know people. Your profs will not say "go to X, the reputation is good" they'll say "go to X, Dr. Y is there, I know him, he'd work well with you" which is much more useful.

[Anonymous No.11678189]

>>11672298
>for a nuclear engineering PhD
Bait or actually retarded?

[Anonymous No.11678205]

I know this might be more accurate to ask on /his/ but I can't make image posts, so I'll ask here.

I am having issue with this argument.

A person makes a claim that I made an X claim

I ask them proof where I made X claim

They don't provide proof

I call them out on it.

They then claim "Absence of evidence is not the evidence of absence".

How do I proceed? I know simply throwing out generic statements about burden of proof/proving a negative might muddle this argument further. Any advice?

[Anonymous No.11678215]

>>11678205
>Any advice
you're being trolled

[Anonymous No.11678223]

>>11678215
Let's just say this person is serious for arguements sake. Trying condescend me for being less intelligent.

I know the gist of what to respond, I just want to make sure it's clear and incisive.

[Anonymous No.11678233]

>>11678205
Absence of evidence can be a complete proof of absence when the domain that you're talking about is finite. You're not saying that no post in the universe exists where you said X, just that you didn't say X in that particular thread in that particular conversation with him, which is easy to check and verify directly.

[Anonymous No.11678239]

>>11678205
>>A person makes a claim that I made an X claim
"distorted perception of reality"

Common happenings when having an emotional charged debate where you auto fill/complete your opponent's arguments and not even realize it.

>They then claim "Absence of evidence is not the evidence of absence".
Oh, you're making shit up to start an anti-religous circle jerk.

[Anonymous No.11678241]

>>11678233
>You're not saying that no post in the universe exists where you said X, just that you didn't say X in that particular thread in that particular conversation with him, which is easy to check and verify directly
Nope he is claiming that I had made an X claim sometimes in the past in said forum.

[Anonymous No.11678245]

>>11678239
This has nothing to do with religion. I'll be bit more specific to what that individual is accusing me of claiming.

He says I had in the past claimed/implied that people belonging to particular region are lazy and uneducated

[Anonymous No.11678248]

>>11678245
Burden on proof is on him to justify his claim.

[Anonymous No.11678251]

>>11678248
I know. I just want to avoid any loopholes before making that generic statement.

[Anonymous No.11678264]

>>11678251
A good way to counter him is to call him a faggot because there is no evidence that he's not.

[Anonymous No.11678266]

>>11678264
in fact he has admitted to being one on a previous occasion

[Anonymous No.11678300]

Can the BRST current couple to a gauge boson? What happens to the BRST symmetry after SSB?

Also, another question: I was trying to calculate the beta function of Yukawa interaction between two left fermions and a scalar, but I noticed that the divergent part of the loop I was calculating vanished. Is there a deep reason to why this happens?

[Anonymous No.11678339]

>>11677621
No. It may have separate ALUs for integers and float, and may have more float ALUs (as those operations are more common). Apart from anything else, a fast multiplier for single-precision floats can be made with far fewer gates than one for integers, particularly if you don't need exact rounding (you can ignore products between low-order bits as the results will be dwarfed by the overall rounding error).

[Anonymous No.11678443]

[math]\sin\beta =[/math] simp

[Anonymous No.11678765]

>>11673093
Damn. Alright, I guess I'll just figure out if I'll get pic related or the ones with the valves. I hate how most of the masks available don't really do shit besides a false sense of security.

[Anonymous No.11678782]

>>11675712
>can i continue to use it without a worry or will they want payment later?
Have you tried asking the course's professor?
I'd usually assume that matlab is extending licenses because of corona, but I couldn't find anything about that on google.
Either way, I doubt they'll demand some form of payment, since they'd need to literally take you to court on a bullshit case so they could have a minuscule shot at 60 bucks.
>>11677262
Have you tried using muh vectors? This really looks like a muh vectors exercise.
>>11678266
LMAO THIS NIGGA IS LITERALLY A FAGGOT

[Anonymous No.11678797]

Is it true that [math] M_n(\mathbb R)\otimes_{\mathbb R}\mathbb C\cong M_n(\mathbb C) [/math]?

[Anonymous No.11678807]

>>11671932
Why is 5 rounded up instead of down?

[Anonymous No.11678819]

>>11678807
0,1,2,3,4 are rounded down, 5,6,7,8,9 are rounded up. That’s an even split

[Anonymous No.11678824]

>>11678819
0 is truncated not rounded

[Anonymous No.11678834]

>>11678797
yes

[Anonymous No.11678846]

>>11678797
Yes.
Choose the base [math]E_{ij}[/math] of matrices with a [math]1[/math] in entry [math](i, j)[/math] and zero everywhere else, and the base of [math]\mathbb{C}[/math] given by [math]\{1, i \}[/math].
Then, define the isomorphism by extending [math]E_{ij} \otimes 1 \rightarrow E_{ij}[/math] and [math]E_{ij} \otimes i \rightarrow iE_{ij}[/math], and use [math]E_{ij}E_{jk}=E_{ik}[/math] (note: indices might be fucked) to check the multiplication for the base.

[Anonymous No.11678865]

>>11678807
i think technically 5 is supposed to be rounded different ways depending on whether the following digit is even or odd, but everyone just rounds up because no one cares enough i guess.

[Anonymous No.11678881]

>>11678846
I was thinking that perhaps there is a canonical isomorphism derived from the fact that [math]M_n(\mathbb R)\cong\mathbb R^{n^2}[/math] and so the tensor [math]M_n(\mathbb R)\otimes_\mathbb R \mathbb C \cong \mathbb R^{n^2}\otimes_\mathbb R\mathbb C\cong \mathbb C^{n^2}\cong M_n(\mathbb C)[/math], but was worried that perhaps the multiplication algebra structure would fuck things up.

[Anonymous No.11678897]

>>11678881
That's some very healthy paranoia, but it does work in this case.
Also, such an isomorphism wouldn't be canononical because it depends on the base choice.
See this page: https://en.wikipedia.org/wiki/Complexification for more stuff.

[Anonymous No.11678901]

>>11678865
Whoa, that's awesome. Thanks, anon. I never knew we were doing it wrong this whole time. Definitely going to impress someone with this at at cocktail party some day.

[Anonymous No.11678936]

>>11678901
>As a general rule, any numerical figure ending in a number greater than five is rounded up and a number less than five is not rounded up. The rules for rounding off numbers are best illustrated by examples. Suppose the number 3.5587 is to be rounded off to three significant figures. Because the fourth digit (8) is greater than 5, the third number is rounded up to 3.56. Likewise 0.5896 becomes 0.590 and 9.3866 becomes 9.39. If we round off 1.341 to three significant figures, because the fourth digit (1) is less than 5, then we get 1.34. Likewise 0.3762 becomes 0.376 and 9.871 becomes 9.87. There is a special case for any number that ends in a 5. As a general rule, if the digit preceding the 5 is an even number, then this digit is not rounded up. If the digit preceding the 5 is an odd number, then it is rounded up. For example, 75.25 rounded off to three significant digits becomes 75.2, 0.1275 becomes 0.128, and 0.2555 becomes 0.256.
from a textbook i used

[Anonymous No.11678956]

>>11677089
1) It is the union. It's just a slightly obtuse way of writing the collection of all points in the domain.
2) Look up the unit circle. It tells you a lot. If you want to do stuff by hand just remember the most important values on the unit circle.

[Anonymous No.11678971]

>>11678026
>Ask your profs for this kind of advice. They know you better than we do, they'll be better at judging where's a good match, and they also know people. Your profs will not say "go to X, the reputation is good" they'll say "go to X, Dr. Y is there, I know him, he'd work well with you" which is much more useful.
This is almost certainly the best way to handle things. Getting some research work done in the meantime will definitely be to my advantage. Thanks for telling me about the GRE too.
>>11678189
What's wrong with going for a Phd in nuclear engineering?

[Anonymous No.11679003]

>>11678865
>following digit
i think you mean preceding digit
https://en.wikipedia.org/wiki/Rounding#Round_half_to_even

[Anonymous No.11679007]

>>11679003
yeah

[Anonymous No.11679096]

Engineerlet incursing into applied math (control theory specificaly).

Should I go trough a Proof book then Linear Algebra Done Right or the other way around?

Also, is Spivak a good book after those two?

I'm aspiring to get into differential geometry by the time I'm wrapping my master's (in about 2 years)

[Anonymous No.11679164]

When I studied philosophy in school, the Stanford encyclopedia of philosophy and the Internet encyclopedia of philosophy were great resources to learn about an idea or author and then start following citations to do research. Now I'm studying chemistry. Is there a resource like that for wikipedia's. Is pubchem good? I need to research a chemical for a class and cite things more favorably looked upon than wikipedia.

[Anonymous No.11679175]

>>11679164
Start with the greeks

[Anonymous No.11679362]

>>11674956

wait how can this be true and E=mc^2 also be true?

[Anonymous No.11679364]

>>11675418

Nucleophile

[Anonymous No.11679379]

>>11679175
hello fellow crossboarder

[Anonymous No.11679386]

>>11679362
[math]E = mc^2[/math] isn't true, it's just an approximation to the other formula in the classical case (when speed is small).

[Anonymous No.11679387]

Are the uses and hazards of common chemical compounds just something to be memorized and referenced?

[Anonymous No.11679395]

>>11679386
the p is momentum right? of which mass is a component? my question about photons being massless still stands

[Anonymous No.11679401]

>>11679395
Photons have energy, and thus have momentum.
See >>11676591

[Anonymous No.11679414]

>>11679386

ooh I see

[Anonymous No.11679424]

>>11679175
I'm not studying philosophy anymore. I'm studying chemistry now. I'm not looking for philosophy of chemistry or micro structural essentialism or anything like that. I'm in gen chem III and I am doing a project on isopropyl alcohol. I made a typo in my earlier post, but what I want to know is if there's a handy resource for chemistry similar to philosophy's iep and sep.

[Anonymous No.11679509]

Here are several notions of "structure preserving maps" in different mathematical contexts:

1. A group homomorphism between groups [math]G,H[/math] is a map [math]\phi:G \to H[/math] such that [math]\phi(ab) = \phi(a) \phi(b)[/math].
2. An order embedding between posets [math]X,Y[/math] is a map [math]\phi: X \to Y[/math] such that if [math]x <_{X} x'[/math] then [math]\phi(x) <_{Y} \phi(x')[/math].
3. A measurable map between measurable spaces [math]X, Y[/math] is a map [math]\phi: X \to Y[/math] such that if [math]B \in \Sigma_Y[/math] then [math]\phi^{-1} (B) \in \Sigma_X[/math].
4. A continuous function between topological spaces [math]X, Y[/math] is a map such that if [math]B \in \tau_Y[/math] then [math]\phi^{-1} (B) \in \tau_X[/math].

It seems natural to me to divide these 4 notions into two sets: 1,2 correspond to some "push forward" property, whereas 3,4 correspond to some "pull back" property.

I have two questions:
1. Does category theory give a name to the above distinction I made between "push/pull" structure-preserving maps? (I have 0 knowledge in CT so go easy on this if possible, all I know is that CT is the common mathematical framework for this kind of questions)
2. Can we always express one type in terms of the other? (For example, it's known that the notion of a structure-preserving map between metric spaces indeed can be expressed in both forms: a continuous function may be defined in the topological way (pulls back open sets to open sets), or as a function that commutes with limits i.e. if [math]x_n \to x[/math] then [math]\phi(x_n) \to \phi(x)[/math].)

[Anonymous No.11680185]

I dont get it are them all or only b?

[Anonymous No.11680196]

>>11679509
I'd just like to point out that a good reason to use preimages is that they preserves unions, intersections, inclusions, and set differences, while forward maps only preserve unions and inclusions in general, so a structure of a sigma-algebra or a topology could only be preserved realistically in the reverse direction.

Another good reason I could think of is the fact that most algebraic structures have the really nice property that a bijective homomorphism is automatically an isomorphism, but this fails in topology - except in the famous case where [math]X\to Y[/math] bijective with [math]X[/math] compact and [math]Y[/math] Hausdorff. Eliminating bijectivity, we still get that the map is closed, ie it takes closed sets to closed sets, thereby preserving structure in the forward direction.

Perhaps you could think that algebraic structures impose strong constraints, or that a topology is an excessively general object, which is why we can only think in preimages. Also, I could imagine that maybe the following could work as a definition for a group homomorphism (but I'm just conjecturing here): a set function between groups [math]\phi:G\to H[/math] is a group homomorphism iff for every subgroup [math]K\subseteq H[/math], [math]\phi^{-1}(K)[/math] is a subgroup of [math]G[/math].

[Anonymous No.11680220]

>>11680196
Nope.
Take [math]G= H = \mathbb{Z}_p[/math], [math]p \geq 3[/math].
Any map which sends the identity to the identity satisfies the property you've given (because cyclic groups of prime order have no non-trivial subgroups).
>>11680185
Yeah, just b).

[Anonymous No.11680277]

>>11675065
conservation of charge.
You're probably confused by the product on the top, right? The + isn't on the nucleophile itself, it's distributed across the molecule.
Generally, nucleophiles and leaving groups are (-) or neutral, and electrophiles are (+) or neutral.

[Anonymous No.11680323]

>>11680196
>>11680220
BTW was flipping through some stuff and just found this.
https://groupprops.subwiki.org/wiki/Lattice-determined_group_property

[Anonymous No.11680630]

is there anything technical that's preventing us from making an artificial uterus?

imagine women crying and losing 88% of their value overnight

[Anyone familiar with electrici(...) No.11680928]

Is BTU synonymous with electricity? Like, if I get an air condition with 7,000 BTU, is that going to be using more electricity than one with 5,000 BTU? I've heard yes and no respectively and don't know who to turn to. We need an air conditioner and my family thinks that higher BTU = more electricity strain.

Please help me

[Anonymous No.11680970]

>>11680928
BTU is a unit of energy. The electrical cost is going to be proportional to the power the unit draws, so you need to look for BTU/hr. 7000 BTU/hr is going to be a higher strain than 5000 BTU/hr, for sure. You need to look at the coefficient of performance of the unit too tho.

[Anonymous No.11680988]

How did he get from the 2nd last step to the last step? I know that he factored out the constant of 1/2 outside of the integral which should've left (u+1)-1 into just (u) right? How come the -1 still remains?
Sorry for the writing on textbook

[Anonymous No.11681017]

>>11680988
[math] \frac{1}{2}(u+1)-1=\frac{1}{2}[(u+1)-2]=\frac{1}{2}(u-1) [/math]

[Anonymous No.11681021]

>>11681017
Ohh, thank you!

[Anonymous No.11681032]

>>11678936
what a pointless and arbitrary rule

[Anonymous No.11681049]

>>11681032
the entire concept of any "rule" for rounding numbers is pointless and arbitrary

[Anonymous No.11681138]

>>11681032
i imagine its intended to create as close to a balanced number of over-rounding and under-rounding as possible for any given set of measurements

[Anonymous No.11681184]

ok, ima baby programmer, and this is cool stuff I'm enjoying learning, but how can I write a program to do algebra, like..
(3x^3 + 2x^2 + x + 1)^4
in C or lisp

resources?

[Anonymous No.11681194]

>>11680630
Feminists and moralfags. The technology to make test tube babies has been around for a while, but no scientist wants to be the first to try it on humans because that would be career suicide.

[Anonymous No.11681246]

I attended a mock class for someone applying for a job at my university a few days ago, and in a few days I'm going to have a follow up meeting with the department head and the other people who attended. During the meeting we had directly after the mock class another student and I both criticized the applicant pretty harshly for his performance during the class. Frankly, he did very poorly. However, he also seemed very nervous and I think it severely affected his performance, and I want to give him the benefit of the doubt that he'd be better in a real classroom. I also liked the thorough and holistic approach he gave the topic in question, and explicitly told our department chair that the lack of thorough and holistic approaches was something I felt was a weakness in our program.

The applicant did poorly by every metric upon which I would normally judge a professor, but at the same time I think he can improve and his teaching style is exactly what I think the school needs. Should I give him a bad recommendation or a good one?

[Anonymous No.11681256]

>>11681246
couldn't you say what you have just said here? sort of a recommended with reservations?

[Anonymous No.11681272]

>>11681256
I'm unsure if his positive qualities outweigh his negative ones and want additional opinions.

[Anonymous No.11681324]

>>11681272
You should have recorded the lecture so we could watch and give feedback

[Anonymous No.11681378]

>>11681032
The rule that "ties" (where the number is exactly half-way between the two candidates) round to the nearest even value is used to avoid systemic bias. This results in the sum or mean of a sequence of rounded values being much closer to the sum or mean of the original values than if ties are consistently rounded in one direction.

[Anonymous No.11681389]

>>11681184
> how can I write a program to do algebra
Do you mean evaluate expressions for particular values of their variables, or solve equations for a variable?

The former is straightforward, except that you'd normally use Horner's method to evaluate polynomials:
double f(double x) {
double y = ((3*x+2)*x+1)*x+1;
return pow(y, 4.0);
}
If you're talking about solving: Newton's method is simple and usually fast but requires derivatives. Bisection is slower but doesn't require derivatives. Beyond that, you could fill a library with what's been written on the topic of "numerical methods" for solving equations.

[Anonymous No.11681404]

>>11679362
E=mc^2 is for the rest frame or when m is the relativistic mass

>>11679386
> isn't true, it's just an approximation to the other formula in the classical case
No

[Anonymous No.11681406]

>>11678971
>What's wrong with going for a Phd in nuclear engineering?
Dead field

[Anonymous No.11681777]

i think i more or less understand (cubic) spline interpolation, but i'm not sure how to create the matrices for it with [math]n[/math] and can't really find a source that represents it nicely or gives an algorithm for it, anyone knows where i could find something like this?

[Anonymous No.11681821]

Eyy /sci/ finally got a scholarship, which country should i go NZ or US? The uni is irrelevant for now.

[Anonymous No.11681984]

>>11671932
Is confidence interval the same thing as degree of belief? I'm a brainlet who can't really understand the latter.

[Anonymous No.11682055]

>>11681777
Work it out for yourself. You have f(x)=a+bx+cx^2+dx^3 (where a,b,c,d may be scalars or vectors). Typically you have desired values for f(0), f(1), f'(0) and f'(1) (i.e. the value and derivative at each end of the segment). Differentiating gives f'(x)=b+2cx+3dx^2. Evaluating at x=0 and x=1 gives
f(0)=a
f(1)=a+b+c+d
f'(0)=b
f'(1)=b+2c+3d
This gives you a system of linear equations; for scalar f, it's 4 equations in 4 unknowns. For n-dimensional vectors it's 4n equations in 4n unknowns.

If you're fitting a piecewise-cubic curve to a sequence of points p[i], for each segment you typically have f(0)=p[i] and f(1)=p[i+1], and f'(0)=(p[i+1]-p[i-1])/2 and f'(1)=(p[i+2]-p[i])/2, i.e. the tangent vector at a point is half the difference between the points on either side. This ensures that where points are equally spaced, the function is just linear interpolation, f(t)=p0+t*(p1-p0).

[Anonymous No.11682059]

Anyone got a hint for how to prove that if
[math] E \subseteq \omega \text{then} \cap E \in E [/math]

[Anonymous No.11682070]

>>11682059
The integers are well-ordered, every subset has a least element. E has a least element. The intersection of E is the least element.

[Anonymous No.11682085]

>>11682070
>the integers
Mean the natural numbers.

[Anonymous No.11682114]

>>11681246
>he also seemed very nervous and I think it severely affected his performance
>I want to give him the benefit of the doubt that he'd be better in a real classroom.
>I think he can improve
Do you actually think that or are you trying to be optimistic?
Honestly, I'm not some mind reader or a psychoanalyst, but I'd guess it's the latter. I'd recommend either trying to gauge his character a second time (by, for example, stalking his online profiles) or giving him a bad recommendation.

[Anonymous No.11682135]

>>11681246
>his teaching style is exactly what I think the school needs
Why do you think that? Tell us more about his qualities, you just focused on the bad side.

[Anonymous No.11682412]

>>11682055
ok thanks, i've kinda implemented it, but for some reason it after a certain point, the interpolation function just starts decreasing, not sure why

[Anonymous No.11682513]

>>11682114
I do think he can improve, but if I'm wrong I don't want to give a good recommendation and subject a bunch of undergrads to him.

>>11682135
>explicitly told our department chair that the lack of thorough and holistic approaches was something I felt was a weakness in our program.
This is for an ME program. The candidate gave a lecture on gear selection. Many ME professors focus entirely on number crunching when it comes to this topic, only bringing up things like manufacturing processes or gear geometry in the context of the effect those things have on the strength of the gear.
This guy took the time to bring up things like cost, noise generation, the pros and cons of different manufacturing processes, all things that a lot of our current professors don't give enough information on when I comes to selecting parts.

[Anonymous No.11682547]

is magnetic confinement "real" and does ITER have reason to exist? or is it another "big science" project for the sake of loosely defined science?

[Anonymous No.11682708]

>>11682513
>I do think he can improve, but if I'm wrong I don't want to give a good recommendation and subject a bunch of undergrads to him.
In that case, you shouldn't concern yourself so much, and you might as well recommend him. You're not the only person involved in the decision, you don't need to be an impeccable judge of character capable of determining exactly what's good and what isn't. It's not just an issue of it not being entirely your fault, it's also a situation of him getting the position because other people agree that he'll probably improve.
Unless your opinion pretty much determines the whole thing, then you probably shouldn't recommend him.

[Anonymous No.11682771]

>>11681821
A full scholarship? Than I would probably go for USA since the unis are better recognized. Otherwise New Zealand. Kiwis are really nice people.
New Zealand is basically Australia without the bad stuff.

[Anonymous No.11683138]

I'm trying to prove, and seek out what exact typical axioms are necessary, to prove

[math] \forall X.\ \mathcal{P}[\{X\}] = \{\emptyset, \{X\}\} [/math]

I'll refrase this to it's fundamentals first.
So this expands to

[math] \forall X.\ \forall x.\ (x\in \mathcal{P}[\{X\}]) \leftrightarrow (x\in \{\emptyset, \{X\}\}) [/math]

which expands to

[math] \forall X.\ \forall x.\ [ x\subseteq \{X\} \implies (x=\emptyset\lor x=\{X\}) ] \land [(x=\emptyset\lor x=\{X\}) \implies x\subseteq \{X\} ][/math]

The right conjunct is evident by binary case analysis. What remains to be proven is

[math] \forall X.\ \forall x.\ (x\subseteq \{X\}) \implies (x=\emptyset\lor x=\{X\}) [/math]

which expands to

[math] \forall X.\ \forall x.\ (\forall y.\ (y\in x\implies y\in \{X\})) \implies (x=\emptyset\lor x=\{X\}) [/math]
which expands to

[math] \forall X.\ \forall x.\ (\forall y.\ (y\in x\implies y=X)) \implies (x=\emptyset\lor x=\{X\}) [/math]

Now I think at this point we need to use LEM (not 100% sure, but I think there's no other way), namely

[math] \forall x. (x=\emptyset) \lor \neg(x=\emptyset) [/math]

which should be equivalent to

[math] \forall x. (x=\emptyset) \lor \exists y.\ y\in x [/math]

But that's as far as I got right now.

Also, my rewriting with the all-quantifiers outsides aren't super formal, but I think that's effectively allowed.
I'm grateful for help.

[Anonymous No.11683159]

New shitty charts imgur: https://imgur.com/a/TpiinBE

[math]\mathcal{Now ~ accepting ~ reviews.}[/math].
Post them and I'll add them here:
https://pastebin.com/65142q6X
Note: if no name is specified, I'll use Anonymous.

[Anonymous No.11683160]

Without looking at it's graph, how can I tell that the absolute value of this would eventually go to infinity?
When first took a look at it, I thought it'd go to zero but it actually shot up to infinity. Can anyone explain how simply by looking at this, or doing some form of calculation, tell that the abs value of this goes to infinity at some point?

[Anonymous No.11683166]

>>11683159
Also keeping a pastebin for this is absolutely retarded, does anyone have a better idea?

[Anonymous No.11683195]

>>11683138
The issue I have is how to use
∀y. (y∈x ⟹ y=X)
from just having
∃y. y∈x.

Probably the above two mean
∃!z. z∈x.

I suppose
x={X}
should be translated to exactly that.
Question mark.

>>11683166
Using git or directly the /sci/ threads.
But I'm not sure if you have any criterium by which you can make sure those reviews are good, or if people actually properly reading it.

>>11683160
I recognize this as Li(3, -3/2), so maybe look up discussions of the PolyLog (or use any of the nice strategies for alternating series.)
https://en.wikipedia.org/wiki/Polylogarithm

[Anonymous No.11683199]

>>11683160
This isn't even defined. In particular it cannot have an absolute value. Where did you get this from?

[Anonymous No.11683217]

>>11683160
Well, the modulo of the summands is [math]\frac{1}{n^3} \left ( \frac{3}{2} \right )^n[/math], and the term on the right grows a lot faster than the one on the left, so the sequence of summands diverges, and so does the series.
I couldn't tell you whether it diverges to plus infinity, minus infinity or in some other way without testing numerically, tho.
>>11683195
>But I'm not sure if you have any criterium by which you can make sure those reviews are good, or if people actually properly reading it.
I don't, the plan is copying in everything that seems either serious or funny.

[Anonymous No.11683248]

>>11683217
Never mind, forgot that the modulo actually becomes monotonic when n is large enough.
It does the thing where it shoots up a bunch and then shoots down a bunch.

[Anonymous No.11683251]

>>11683217
let's work through a book on /sci/ and write the exercise solution in a nice LaTeX file, or something fun like that

[Anonymous No.11683276]

>>11683251
What book are you thinking of?

[Anonymous No.11683279]

>>11683276
Lang's algebra

[Anonymous No.11683298]

How does the series of (n)/(n^2+1) from n=1 to infinity diverge via the limit comparison test?

[Anonymous No.11683308]

>>11683298
Yes. Compare with n/(2n^2)=1/(2n)

[Anonymous No.11683313]

>>11683279
That sounds like an absolute pain.

[Anonymous No.11683360]

>>11683276
It must be some common denominator thing.
I think it can be successful, if people can go wild on it. It doesn't have to be super hard to get hard things out of it.
I'm totally on board, as soon as other people do it too.

>>11683138
I think I've cleaned it up now

For all [math]X[/math], [math]\mathcal{P}[\{X\}] = \{\{X\}, \emptyset\} [/math]

Prove: This reduces to the claim that for all [math]X[/math] and for all [math]x[/math],

[math]x\subseteq \{X\}\ \leftrightarrow\ x\in \{\{X\}, \emptyset\}[/math]

The [math]\leftarrow[/math] direction is evident by case distinction, so we really want to prove the [math]\rightarrow[/math] direction.

And this simplifies to

[math](\forall y.\ [y\in x\implies y\in \{X\}]) \implies (x=\{X\}\ \lor\ x=\emptyset) [/math]

and further, using a defining property of the empty set,

[math](\forall y.\ [y\in x\implies y=X] ) \implies (([\exists y. y\in x] \land\ \forall y. [y\in x\implies y=X])\ \lor\ \neg[\exists y. y\in x]) [/math]

We can eliminate the second appearent of the premise and simplify this to

[math](\forall y.\ [y\in x\implies y=X] ) \implies {\mathrm {REM}}[\exists y. y\in x] [/math]

where the Restricted Excluded Middle for a property [math]\phi[/math] means [math]\phi\lor\neg\phi[/math].

LEM says that all instances of [math]{\mathrm {REM}}[\phi] [/math] are true, so all instances
of [math]\psi \implies {\mathrm {REM}}[\phi] [/math] are true as well, so we're done.

[Anonymous No.11683369]

>>11683138
I've thought long and hard about this.
Pretty sure you just use the axiom of extensionality to conclude that any nonempty subset equals [math]\{ X \}[/math].
>elaborate
If it contains an element, it contains an element of [math]\{ X \}[/math] (this isn't contradiction, this is just the definition of a subset). Thus, it contains [math] X [/math], and equals [math]\{ X \}[/math].

[Anonymous No.11683373]

>>11683369
THEN AGAIN, you might actually need LEM to conclude that a set that doesn't equal the empty set contains an element.

[Anonymous No.11683384]

>>11683138
>>11683360
this is your brain on foundations
not even once, kids

[Anonymous No.11683400]

>>11683373
Yeah, I came to the conclusion (>>11683360, still happy if someone points out potential errors) that
[math] \forall X.\ (\exists x.\ x\in X)\lor \neg(\exists x.\ x\in X) [/math]
will be needed.
In a theory without type constructors, no, [math] \exists x. \Psi(x) [/math] can be true for free.

However, now I wonder if you can assert
[math] \forall X.\ (\exists x.\ x\in X)\lor \neg(\exists x.\ x\in X) [/math]
as an axiom without that implying excluded middle for all properties.

>>11683384
What's your favorite field?

[Anonymous No.11683445]

I have spent over an hour on this question, and I am convinced that the software marking this is wrong. I have changed so many things I have gotten so many different answers but none are correct. I plugged this into multiple derivative calculators as well, still nothing has been shown to be correct.

Initially I got -1/96, and then diverging infinities. I just don't know any more.

Also, when using l'hopital rule can I make that 4^-1 constant a 0? or because it's in the numerator I can't do that?

[Anonymous No.11683450]

>>11683445
what are you talking about

[Anonymous No.11683454]

>>11683445
Picture got removed somehow when doing captcha

[Anonymous No.11683513]

>>11683454
[math]\frac{ \frac{1}{4+h} - \frac{1}{4} }{6h} = \frac{ \frac{4-(4+h)}{16+4h}}{6h} = \frac{-1}{96+24h}[/math]
So I'm gonna invest in -1/96.

[Anonymous No.11683524]

>>11683513
Wolframerino agrees.
https://www.wolframalpha.com/input/?i=limit+as+h+goes+to+zero+of+%28%284%2Bh%29%5E%28-1%29-1%2F4%29%2F%286h%29

[Anonymous No.11683527]

>>11683454
[math]\frac{\frac{1}{4+h}+\frac{1}{4}}{6h} \rightarrow \frac{\frac{1}{4}+\frac{1}{4}}{6h} \rightarrow \frac{1}{12h} \rightarrow \infty[/math]

[Anonymous No.11683559]

Let g be a concave function and h is the squared 2-norm of g. Is h a convex function?

[Anonymous No.11683563]

>>11683559
>2-norm
Dunno what you mean.
[math]f(x)=x^{1/4}[/math] is concave, innit?

[Anonymous No.11683564]

Quadrilateral:Triangle=Circle:?
Options are Ball, Cone, Oval, Pentagon and Parabola.

[Anonymous No.11683622]

>>11683563
I mean the euclidian norm.

[Anonymous No.11683657]

>>11683622
Then [math]f(x) = x^{1/4}[/math] works as a counter-example, doesn't it? It's concave, and [math]f(x)^2 = x^{1/2}[/math] is not convex.

[Anonymous No.11683797]

>>11683657
I see, thanks anon.

[Anonymous No.11683834]

>>11683454
[math] lim_{h\to 0} \dfrac{ (4+h)^{-1} - 4^{-1} } {6h} = \dfrac {1} {6} \frac{d}{dx}_{x=4} \dfrac{1}{x} \dfrac {1} {6} \cdot -\dfrac{1}{4^2} [/math]

[Anonymous No.11683839]

>>11683454
[math] \lim_{h\to 0} \dfrac{ (4+h)^{-1} - 4^{-1} } {6h} = \dfrac {1} {6} \dfrac{d}{dx}_{x=4} \dfrac{1}{x} = \dfrac {1} {6} \cdot -\dfrac{1}{4^2} [/math]

[Anonymous No.11684012]

>>11683839
I don't get the x=4 part but it looks like the solutions match the others. I hate online classes. Thank god this is my only one left.

[Anonymous No.11684044]

Cryptography related. In an SSL handshake process, when using the server's public key (from a certificate) to encrypt the pre-master secret key, what does this encrypting process actually entail? Is there a website to demonstrate this process?

[Anonymous No.11684076]

>>11678807
15 is 50% more than 10, but
15 is 25% less than 20.

[Anonymous No.11684228]

The other day I spent an hour digging through textbooks for a project, only to discover that the solution was something really basic that I had learned in a sophomore level class and subsequently forgotten about from not having used it in a while. How do I avoid this problem in the future?

[Anonymous No.11684238]

>>11684228
>how do I not forget things ever
enjoy your Nobel if you ever figure out the answer to this one

[Anonymous No.11684251]

I guess this counts as a stupid question...

So /sci/, I was inflicted with a bit of mania a few months ago and applied for a few master's programs overseas, not really thinking that anything would come of it. You can probably guess where the rest of this is going. Well, the mania gave way to standard depression and I forgot about it for a while. Now months later I learn I was accepted into a master's for neuroscience. What the fuck.
I guess I'm going to accept and go for it, but what the fuck am I getting myself into? I haven't done any education related stuff in years.
Can this even go anywhere career wise?

And for anyone who has done a graduate program, is the 50 page paper at the end or whatever difficult?

[Anonymous No.11684267]

>>11684251
you'll be fine

[Anonymous No.11684280]

This was in a Guardian article about something, something, global patent pool, something, coronavirus vaccine "for the people".

Anyway, whether it's "real lab technique" or a stupid-science staged photo, what is this?
I'm not familiar with the equipment and haven't seen that type of specimen container either.
I've worked in a wet lab but only to use the computers for bioinformatics stuff, not wet work.

[Anonymous No.11684285]

>>11684280
Of course, I'm not ruling out that it's just an update of pic related.

[Anonymous No.11684315]

wtf am I doing wrong here?

[Anonymous No.11684326]

>>11684315
You are confusing wolfram. When you ask to convert to degrees, it assumes ALL the units are radians, i.e. it's calculating sin(40 radians) instead of sin(40 degrees)

[Anonymous No.11684339]

>>11684326
ah ok. thanks.

if i didn't include "to degrees", it was giving me the results in radians. i didn't check to see if the radians were actually equal between the two

[Anonymous No.11684342]

>>11684238
I just want to be able to remember basic concepts from my field.

[Anonymous No.11684347]

>>11684228
You need to use the skills to bed them down, and then keep on using them from time to time to prevent the memory fading and keep the neural connections strong.

To start with, do your homework.
Like, whatever the exercises are in the book, do them, don't just read over them, decide that you know them, and move on.
Then, either repeat those exercises from time to time or find ways to use the skill. Even tutoring a student in the subject for beer money would help.

[Anonymous No.11684416]

Help a brainlet out. I figured out the first part but domt know how to start with the second.

[Anonymous No.11684733]

>>11684416
#2. The angular momentum of a particle is r*M*v, so the angular momentum of the piece of wood prior to impact is (L/2)*(M/100)*v = M*L*v/200. Post-collision, the angular momentum of the rod is Ir*ω with Ir=M*L^2/12 while the angular momentum of the piece of wood is Iw*ω with Iw=(M/100)*(L/2)^2, so the total angular momentum is (Ir+Iw)*ω = (M/12+M/400)*L^2*ω = (103/1200)*M*L^2*ω. This assumes that the centre of mass is at the centre of the rod (the mass of the wood is ignored).

Conservation of angular momentum gives
M*L*v/200 = (103/1200)*M*L^2*ω
=> ω = (M*L*v/200)/((103/1200)*M*L^2)
= (v/200)/((103/1200)*L)
= 6*v/(103*L)

[Anonymous No.11684756]

How do I induce autism to counteract and inhibit my ADHD? I've already tried vaccinating and it didn't work.

[Anonymous No.11684802]

>>11684756
climb up a 5G tower and sit on top of it for a few hours

[Anonymous No.11684837]

>>11684756
>How Are They Different?
>
>Keep an eye on how your child pays attention. Those with autism struggle to focus on things that they don't like, such as reading a book or doing a puzzle. And they may fixate on things that they do like, such as playing with a particular toy. Kids with ADHD dislike and avoid things they'll have to concentrate on.

[Anonymous No.11684880]

How in the hell do they do this shit?
Did they get help from aliens at area 51?

[Anonymous No.11685080]

Had a doubt in modular arithmetic.
I know that (Ax + B) % N = ((A%N * x%N)%N + B%N)%N
But is there any such rule to simplify A % (Mx + N) ?

In general I am trying to find an O(log A) algorithm for finding A % B where A and B are very large integers( thousand digits) and are stored as strings. Is there any efficient algorithm for this?

[Anonymous No.11685196]

what is Hausdorff's definition of a product of two sets? And further,

[Anonymous No.11685197]

>>11685196
How does does kolmogorov extend it with the arbitrary set of numbers that assign probability to events?

[Anonymous No.11685250]

>>11685196
Most likely [math]A \cap B[/math]. I'm basing this deduction on [math]AB = 0[/math] being possible and context.
>>11685197
I don't really understand your question. Do you mean "How does Kolmogorov extend the notion of a probability to other fields?"
In that case, you have the field and you have a function from the field to the reals which associates to each event its probability. This function satisfies some axioms, namely every probability is non-negative, the probability of the set of all outcomes is [math]1[/math], and the probability of a union of disjoint events is the sum of the probabilities.

Also, what text is that? It looks ancient.

[Anonymous No.11685261]

i am royally fucked right now since my textbook still hasn't arrived (or even sent by the publisher) and I need help not only to solve but to understand how to solve exercises like this one:

An ideal Rankine cycle uses water in its gas phase as the working fluid. The pressure at which the boiler operates is 28 bar and the pressure at which the condenser operates is 14 bar.

Given that the water vapour entering the turbine is saturated, calculate the following:

1. the efficiency of the cycle
2. the heat that the condenser removes

(it's a translation, so I might have mistranslated something)

is there anyplace that explains in detail how the 1st and 2nd law of thermodynamics works along with rankine cycles?

khan academy doesn't have much in thermodynamics and all I have to work with are some shitty notes in .ppts written in fucking comic sans.

[Anonymous No.11685445]

what is more efficient:
>read math textbook for 2~3 hours straight in the morning
>read math textbook for 1.5 hours in the morning and then more 1.5 hours in the evening or later in the same day
said textbook is more theorical and doesn't have much problems to solve, but another options would be:
>read math textbook and then straight out jump to solve exercises
>read math textbook and then solve exercises later that day

[Anonymous No.11685457]

Why is log with base 1 undefined?
I mean I understand there are no solutions for log_1(2)
But shouldn't log_1(1) be exception and equal to 1?

[Anonymous No.11685477]

>>11685261
*it's 14kPa not 14bar on the condenser

[Anonymous No.11685534]

>>11685457
No, that's completely wrong, [math]\log_1 1 = 8[/math].
This is so for two(2) reasons. The first one is that [math]1^8 = 1[/math]. The second one is that eight is my favorite number.

[Anonymous No.11685550]

How do I find the formula for when functions [math]\log_a{x}[/math] and [math]a^x[/math] cross for any a? Is it possible even, or do I need to know a first

[Anonymous No.11685563]

>>11685550
or let's just say that a=0.05
There are 3 intersections
how do I find them?
[math]\log_{0.05}{x}=0.05^x[/math]

[Anonymous No.11685581]

>>11685563
log_a(x) = a^x
is equivalent to
x = a^a^x
There is no closed formula to solve this for x. You can only do is numerically with stuff like the bisection method.
https://en.wikipedia.org/wiki/Bisection_method

[Anonymous No.11685725]

What is a "maximal linearly ordered subset"?

[Anonymous No.11685754]

Chemfags, how do I determine if a sample of sodium hydroxide is pure? I checked the manufacturer's website but there's little info I can make sense of.

[Anonymous No.11685761]

>>11685754
titration

[Anonymous No.11685763]

>>11685754
flip through an analytic chemistry handbook (a-chem is all about proving a sample matches expectations in both quality and quantity). pH test sounds like it would be simple enough. Do you have a pH probe or a titration setup?

[Anonymous No.11685771]

>>11685761
>>11685763
I don't have a setup. I just need to know if the small white crystals contain only sodium hydroxide or if there's other shit added in. It's not industrial grade.

[Anonymous No.11685774]

I am looking for a way to import generic clemastine furamate into Canada from an overseas pharmacy in order to treat my MS. How do I find such a pharmacy?

[Anonymous No.11685782]

>>11685771
well without any equipment you can use a shitty pH paper like >>11685763 said but that would be a guesstimation at best

[Anonymous No.11685788]

>>11671932
can anyone prove this or is it just bullshit? makes no sense to me

[Anonymous No.11685809]

I need someone to tell me the answer to this so I know if I did it ok or if I am retarded

[Anonymous No.11685823]

>>11685771
>I don't have a setup
buy some srynges then

[Anonymous No.11685837]

>>11685782
What other components are usually added in? Is there no way to separate them?
>>11685823
What for? I have very little knowledge of chemistry.

[Anonymous No.11685840]

>>11685725
bumping this. I can imagine one maximal linearly ordered subset of R^2 would be
[math] Q = {(a,a) \in \mathbb{R}^2} [\math] but IDK what a second one would be. MAXIMAL means not contained by any other subset right? Every linearly ordered subset of R^2 would be contained by Q innit

[Anonymous No.11685841]

>>11685837
he wants you to use a syringe in lieu of a burette to perform a titration along with ph paper, which isn't incredibly difficult 2bh

well if it's in some small white-ish balls it's probably decently pure

if it's coloured then no

[Anonymous No.11685848]

>>11685837
>little knowledge of chemistry
>tryna start meth lab

[Anonymous No.11685865]

>>11685841
Yeah it's a bunch of very small white balls. But "decently pure" won't cut it.
Are there any retard-proof tutorials for titration using this method?
>>11685848
It's nothing so impressive and definitely nothing illegal.

[Anonymous No.11685888]

>>11685865
What's your budget like buddy? For you to do a titration, you're going to need to buy a strong acid, which you'd add dropwise to a measured sample of your NaOH, measuring pH of the solution for *literally* every single drop for possibly hundreds of drops.

if time is money that will be a problem it'll also be less precise if you are using pH paper. If you got your hands on an electronic pH probe you'd have a better time but either way you're going to be buying some strong acid.

[Anonymous No.11685889]

>>11685840
[eqn]
S \cup \{ (a,0) | a \geq 0 \}
[/eqn]
is another maximal linearly ordered subset of R^2.

[Anonymous No.11685899]

can a bro explain to me how transistors work and how are they useful .
I understand diodes, but what's the point of transistors. Also can you build computers with just diodes?
Thanks in advance

[Anonymous No.11685902]

>>11685889
thanks anon, but isn't that a subset of the Q I defined, and therefore not a maximal subset?

[Anonymous No.11685906]

>>11685888
>strong acid
Hydrochloric is pretty cheap last time I checked, but I don't have a lot of money right now, so an electronic probe, the appropriate glassware and so on might be a problem.
I just need to isolate any possible impurities that could contaminate the pretzels I'd like to make using that lye.

[Anonymous No.11685993]

>>11685906
>>11685906
you dont need any special glassware

just take a glass jar

measure how many g of NaOH you put in it along with a known V of water

add dropwise HCl of a known concentration

buy a pH probe from ebay or whatever for like 10 bucks

they're usually +-0.5 pH accurate

we even tested a cheap handheld pH probe with a expensive lab grade one and the cheaper one was consinstely about 0.5-0.7 pH from the expensive one

[Anonymous No.11686024]

>>11685993
Thanks.

[Anonymous No.11686031]

>>11686024
also, for the love of god, please read e.g. a lab guide for titrations something like a chem undergrad before doing this

[Anonymous No.11686043]

>>11685261
>>11685477
Okay, so apologizes that the work is pretty messy. The cycle at the top is exactly what is given. The most important thing to realize with ideal Rankine is that the boiling and condensation processes are at constant pressure, and that the compression (pump) and expansion (turbine) processes are isentropic. Dotted lines are lines of constant pressure on the TS diagram. The goal is to find the enthalpy at 1, 2, 3 and 4. You need a table of fluid properties. Use http://homepages.wmich.edu/~cho/ME432/Appendix1Udated_metric.pdf . Then, [eqn] \eta_{\text{th}}=\frac{w_{\text{net}}}{q_{\text{in}}}=\frac{w_{\text{turb}}-w_{\text{pump}}}{q_{\text{in}}}=\frac{(h_3-h_4)-(h_2-h_1)}{h_3-h_2)}\approx 28\% [/eqn]
Heat transferred in condensation is h4-h1=1784.02 kJ/kg.
>is there anyplace that explains in detail how the 1st and 2nd law of thermodynamics works along with rankine cycles?
Go to libgen and snag textbook. I use Cengel. With respect to Rankine cycles, just remember the normal version of 1LT and that the change in energy of a fluid (by heat or work) is change in enthalpy. For 2LT, just remember the area under the TS curve is heat transfer.

[Anonymous No.11686140]

Can someone explain me why the solution uses alfa/2=0.01 instead of 0.005? Is it wrong?

[Anonymous No.11686409]

Can i use thin film spectrum interferometry to measure the thickness of (some 100nm thick) SiO2 coated particles?

[Anonymous No.11686498]

Can the Fredholm equation for charge distribution in a straight wire segment be solved analytically? What about the charge distribution of a line with one ending and the other end stretching to infinity?

[Anonymouse No.11686533]

>>11685788
Are you sure that's correctly transcribed? If I set x=0, I get e^{-m} = 1.
It sort of looks like the derivation of the Poisson distribution as a limit of Binomials, but the exponent on (1-(m/n)) is wrong.

[Anonymous No.11686535]

>>11686043
this is an excellent explanation.

thank you.

[Anonymous No.11686542]

How can I solve a problem that's too large to hold as a single mental model? I've not experienced this before.

[Anonymous No.11686568]

>>11686542
use paper nigger

[Anonymous No.11686638]

why does 0^0=1, when 0^(any other number)=0?

[Anonymous No.11686660]

>>11686638
A^B in set theory is the set of all functions f:B -> A
0 in set theory is the empty set
so 0^0 is the set of all functions from the empty set to the empty set which only the empty function fullfills
so 0^0 = {0} = 1 in set theory

[Anonymous No.11686720]

>>11675945
Im guessing offsetting the desired part surface with a tool geometry you are machining with. And using inverse kinematics to move the tool center point on this offset surface.

[Anonymous No.11686980]

Does anybody know what is the difference between poisson and binomial distribution? I cant make any sense of it. How does the probability of an event beig small in comparison to the number of experiments change the formula??


>>11686533
yeah that was what i was trying to prove. obviously that equality is false though.

[Anonymous No.11687109]

Drugs make you either lazy as fuck (weed), a hyper spaz(coke), or hallucinate (shrooms)
Do they do anything else, category theoretically?

[Anonymous No.11687125]

I like how the artist for the OP image just completely gave up on the hands

[Anonymous No.11687138]

Got the following:

Prove that:

[math]0*1+1*2+...+(n-1)*n = \frac{n(n-1)(n+1)}{3}[/math]

\forall n \in \mathbb{N}, n \geq 2

Proved that 2 = 2 and proceed with [math]n+1[/math], and this is what i got:

[math]n(n+1) = \frac{n(n+1)(n+2)}{3}[/math]

Is this correct?

[Anonymous No.11687157]

Got the following:

Prove that:

[math](n-1)n = \frac{n(n-1)(n+1)}{3}[/math]

[math]\forall n \in \mathbb{N}, n \geq 2[/math]

Proved that 2 = 2 and proceed with [math]n+1[/math], and this is what i got:

[math]n(n+1) = \frac{n(n+1)(n+2)}{3}[/math]

Is this correct?

[Anonymous No.11687172]

Got the following:

Prove that:

[math]0*1+1*2+...+(n-1)n = \frac{n(n-1)(n+1)}{3}[/math]

[math]\forall n \in \mathbb{N}, n \geq 2[/math]

Proved that 2 = 2 and proceed with n+1, and this is what i got:

[math]n(n+1) = \frac{n(n+1)(n+2)}{3}[/math]

Is this correct?

[Anonymous No.11687252]

>>11685445
2-3 hours in the morning but with short breaks in between

[Anonymous No.11687256]

>>11687109
they can make you dissociate, go buhhhhhh, not lazy but just completely numb. they can make you happy or sad. they can make you fall asleep. they can make you chilled out but not lazy. they can make you terrified or pained

[Anonymous No.11687258]

>>11686542
which problem is it? break it into model pieces and work with those

[Anonymous No.11687262]

>>11687125
how an artist doesn't understand hands in extreme detail is beyond me, they are literally the tools of their trade

[Anonymous No.11687269]

>>11687172
[math]\sum n(n+1) = \sum n^2+n = \sum n^2 + \sum n = n(n+1)(2n+1)/6 + n(n+1)/2 = \frac{n(n+1)(2n+4)}{6}=\frac{n(n+1)(n+2)}{3}[/math]

[Anonymous No.11687293]

>>11685445
study 2-3 hours in the morning
take a break, chill, read and reflect until afternoon
make a pot of coffee at 7p then study another 2-3 hours

fuck sleep and its cousin

[Anonymous No.11687319]

I have a very dumb group theory question: Let G be a finite group. Then is every homomorphism from G to itself necessarily bijective?

[Anonymous No.11687323]

>>11686980
you hit the head there. poisson is for rare events, it is the limit of the binomial distribution as the number of events goes to infinity. we specify "rare" events because you want n*p to be finite in the large n limit

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

[Anonymous No.11687335]

>>11687125
Same.
>>11687319
No.
Consider, for example [math]\mathbb{Z}_2 \oplus \mathbb{Z}_2[/math]. First, project onto the first entry. Then, use the inclusion of the first entry into the group.

[Anonymous No.11687350]

I have a bakery and can make cake A and cake B, to do cake A i need 1/2 kg of sugar and 8 eggs and the cost per cake is $400.

To make cake B i need 1 kg of sugar and 8 eggs, the cost per cake is $500

I have 10 kg of sugar and 120 eggs in left in the store

how many units of each cake can i produce to make the most money

is this solved combining or something like that?

[Anonymous No.11687376]

>>11687350
They use the same amount of eggs, so you know that [math]120/8 =15[/math] cakes will be baked.
Then you compute how many of those you can make type B.

[Anonymous No.11687377]

>>11687335
By
>use the inclusion of the first entry into the group.
do you mean map [math]z_1[/math] to [math](z_1, z_1)[/math] where [math]z_1[/math] is the first entry?

[Anonymous No.11687385]

>>11687350
Linear convex optimization problem, you can do it easily using CVX or even Excel.

[Anonymous No.11687388]

>>11687377
Okay I can see that it is the only choice to make it a homomorphism. Thank you!

[Anonymous No.11687390]

>>11687377
I meant [math]z \rightarrow (z, 0)[/math], but sure, that works too.

[Anonymous No.11687403]

>>11687390
Oh oops. Now I feel embarrassed about my last statement.

[Anonymous No.11687606]

>>11671932
microbio question: 1/2 cup per gallon anhydrous citric acid. is this concentration good enough for sanitizing containers and supplies for hombrewing? picrelated actual product i'm using. anyone got a link or resource that can help help me understand concentrations and what kind of sanitization power different stuff has? i also have access to iodine. trying to stick to products that are safe to consume for obvious reasons.

[Anonymous No.11688084]

>>11687606
there's a homebrew general on /diy/ right now. they might be able to help.

[Anonymous No.11688098]

Can we copy spiders' method of flight on a larger scale?

[Anonymous No.11688116]

>>11687606
Wow the pictures look so similar

[Anonymous No.11688394]

i just got through an ML course and i'm really pumped up and digging all of this but i'm really not sure how to start applying all of it
what's a good way to start actually writting neural networks etc.?
start to pick up pytorch and just write some simple stuff like digit recognition?

[Anonymous No.11688433]

>>11684076
Using that logic, 14 should be rounded up as well.

[Anonymous No.11688435]

>>11687350
>half a kilo of sugar and few eggs make the cost of the cake to be $400
This is why USA will fail

[Anonymous No.11688448]

>>11685080
Modulo is just the remainder after division. You can't make it any faster than division, and you can't simplify A/(B+C). For very large numbers, the fastest division algorithm is to find 1/B by using Newton's method to solve 1/x-B=0 for x then A/B=A*(1/B)=A*x. The iteration is x'=x+x*(1-B*x), which requires two multiplications and an addition. For numbers of this size, multiplication would typically use the Schönhage-Strassen algorithm.

[Anonymous No.11688457]

>>11685809
would this be correct?
y/x=G1G2G3 / 1+G1G2H1+G2H2+G2G3H3

[Anonymous No.11688483]

Why don't the planets pull each other out of their regular orbits?

[mco No.11688521]

Hey, my stupid question is where can I download a copy of this book? More Than Words: A Parents Guide to Building Interaction and Lanuage Skills for Children with Autism Spectrum Disorder or Social Communication Difficulties

[Anonymous No.11688631]

>>11686720
alright that much I understand, but say a whole chunk of the volume has to be removed, how do I go about generating a path such that this volume is removed in as little moves as possible, and to minimize the time the tool is not in contact with the material?

[Anonymous No.11688902]

when doing a linear interpolation, how should I round up the result?

[Anonymous No.11688921]

Can somebody tell me where I'm going wrong?

Suppose a = 3, b = 4
1) clearly holds, for m,n = 1,0 and = 0,1 respectively
2) I can understand it being the smallest subgroup containing both a and b. That is intuitive.
3) *does not hold*
"Denote by (a,b) the smallest positive integer in G."
okay, 3 (m = 1, n = 0) is the smallest positive integer in G. (a,b) = 3 divides 3 with no problem, but (a,b) = 3 does not divide 4.

How should I be reading this instead?

[Anonymous No.11688951]

>>11688921
m=-1, n=0. So 1 is in G....

[Anonymous No.11688952]

>>11686043
I downloaded the book you mentioned and I am now trying to solve this by myself, but I have trouble understanding the part in pic related.

The fluid that exits the turbine is wet steam, correct? Which thermodynamic properties and what kind of table do I need to use to find the h of water+steam mixture?

[Anonymous No.11688954]

>>11688951
n=1*...on ios so typing is hard

[Anonymous No.11689036]

>>11688952
nvm retarded question

[Anonymous No.11689071]

>>11688951
I'm a brainlet thank you senpai

[Anonymous No.11689118]

guys im a bit retarded and need a hand on this question: i. If two numbers between 1 and 100 are randomly generated, what is the probability that the first number
exceeds the second number?

[Anonymous No.11689144]

>>11689118
50%, it either does or it doesn't.

[Anonymous No.11689161]

>>11688084
thanks, anon.

>>11688116
similar to what?

[Anonymous No.11689217]

>>11689118
Write down all the possible outcomes and count how many are valid

[Anonymous No.11689335]

>>11689118
49.5%
>>11689144
Nice try

[Anonymous No.11689424]

>>11688457
That's the answer I get (assuming that the right-most G2 should actually be G3).

[Anonymous No.11689445]

>>11689118
Explanation: there are 100^2=10000 possible pairs. 100 of them have the two numbers equal, leaving 9900 having the two numbers unequal. By symmetry, half the unequal pairs have the first larger than the second. 9900/2=4950, 4950/10000=0.495=49.5%.

[Anonymous No.11689622]

>>11688483
Source?

[Anonymous No.11689659]

>>11689424
yes it is, ok tnx

[Anonymous No.11689972]

how do I find the resonant frequency of any arbitrary rlc circuit which is not just series or parallel?