/sqt/ stupid questions thread

[Anonymous No.9816387]

This thread is for questions that don't deserve their own thread.
>give context
>describe your thought process if you're stuck
>try wolframalpha.com and stackexchange.com
>How To Ask Questions The Smart Way http://www.catb.org/~esr/faqs/smart-questions.html

previous thread >>9800402

[Anonymous No.9816392]

Hi, brainlet here.

Prove that [math]|\sin(t)|^{-1/p}[/math] is of weak [math]L^p(\mathbb{T})[/math]-type. Definition: [eqn]|\{t:|\sin(t)|^{-1/p}\geq \lambda\}|\leq C\lambda^{-p}[/eqn]for some [math]C[/math] and all [math]\lambda>0[/math].

(Or equivalently [eqn]|\{t:|\sin(t)|^{-1/p}\leq \lambda\}|\geq 2\pi -C\lambda^{-p}[/eqn]for some [math]C[/math] and all [math]\lambda>0[/math])


I tried: if [math]|t|\leq \lambda^{-p}[/math], then
[eqn]|\sin(t)|^{-1/p}\geq |t|^{-1/p}\geq \lambda[/eqn]But this only shows that [math]|\{t:|t|^{-1/p}\geq \lambda\}|\leq |\{t:|\sin(t)|^{-1/p}\geq \lambda\}|[/math], but I want the reverse inequality.
I also tried [math]\frac{2}{\pi}|t|\leq |\sin(t)|[/math] to obtain [math]|\{t:|\sin(t)|^{-1/p}\geq \lambda\}|\leq |\{t:K|t|^{-1/p}\geq \lambda\}|[/math] with [math]K[/math] some constant, but this only holds for [math]|t|\leq \frac{\pi}{2}[/math], so I cannot prove anything for the other [math]t[/math].
Chebyshev/Markov doesn't work either, since you need it to be in [math]L^p(\mathbb{T})[/math], while it's not.

Help me out pls. Thanks

[Anonymous No.9816468]

>>9816392
I may be wrong but C = 4 seems to work.
For [math] \lambda \leq 1, \\ | \{ t: |\sin(t)| \geq \lambda^p \} | = 2 \pi - 4\arcsin(\lambda^p) \leq 2 \pi - 4 \lambda^p \leq 4 \lambda^{-p} [/math]

[Anonymous No.9816547]

If 0/0.1 is zero, and 0/0.001 is zero, then why is 0/0=infinite?

[Anonymous No.9816563]

>>9816387
What is this creature

[Anonymous No.9816582]

Playing with the idea of trying my hand at a somewhat hard sci-fi novel, and one thing that has been bothering me when trying to deal with FTL travel without breaking relativity is how the typical warp drive deals with traveling through information at superluminal speeds while being encased in a relativistic bubble.

Take for example, the premise. A vessel is capable of FTL travel by warping a bubble of space; contracting in front, expanding behind itself, letting it 'surf' through space. However, information (radiation, light, debris etc) hits the contracted point much faster than it can travel through the bubble of realtime. Kind of like a bartender's nozzle on a bottle of liqour.

The question is; How would you percieve information coming in exponentially faster than it could pass by you? Would it be blue-shifted? Or would you just percieve a blinding light of cosmic radiation and photons out the windshield?

[Anonymous No.9816616]

>>9816547
Because you only get [math]\lim\limits_{n\to\infty}\frac{0}{10^{-n}}=0[/math].
This only says something about the limit, and so you don't know anything about [math]\frac{0}{0}[/math],
which is undefined, as [math]0\cdot 1=0[/math] would imply that [math]\frac{0}{0}=1[/math], but so does [math]0\cdot 2=0[/math] imply [math]\frac{0}{0}=2[/math], but then we have [math]2=1[/math], a contradiction. This is just using the definition of multiplicative inverse, but there are also examples using limits that contradict each other.

Anyway, [math]\frac{0}{0}[/math] is undefined.

[Anonymous No.9816621]

>>9816563
It's a real-life-lookalike statue in the Neanderthal Museum in Mettmann, Germany. Probably supposed to show what a cultured Neanderthal would look like nowadays, or it's just purely a joke like something you would find at the entrance.

[Anonymous No.9816630]

>>9816468
Wow, I checked every single inequality and everything looks legit. Thank you so much. Can't believe how easily I could just have taken the inverse. The last inequality is not something I could have come up with though.

I believe (sketching the function in google) the tightest bound with this estimate is [math]\pi [/math] (to make sure that the last inequality still holds).

[Anonymous No.9816644]

So if an A.C. circuit produces and emits an electromagnetic wave, where does the energy come from? And how would you change the circuit to adjust the wavelength of the radiation?

[Anonymous No.9816645]

>>9816468
>>9816630
My conjecture was wrong due to a dumb mistake, but I calculated that the tightest constant is [math]\frac{\pi^2}{4}\approx 2.46740110027[/math].

[Anonymous No.9816661]

>>9816468
NOOOOO. I now see a mistake right from the start. It should be
[math]| \{ t: |\sin(t)| \geq \lambda^{-p} \} | = 2 \pi - 4\arcsin(\lambda^{-p}) \leq 2 \pi - 4 \lambda^{-p}[/math], which only works for [math]\lambda>0 [/math].

>a simple example
REEEEEEEEEEEEE. I HATE KATZNELSON. HE IS A HARMONIC ANALYSIS CROOK. REEEEEEEEEEEEE

[Anonymous No.9816664]

>>9816661
[math]\lambda\geq1[/math]*

[Anonymous No.9816681]

TLDR; How much does your average Joe know about mathematics? How does this vary from America, to Europe, to Asia?

I ask because I want to know how much math I need to know before I can stop feeling so ashamed of my ignorance. Without exaggeration, I grew up surrounded by people who barely even knew grade school arithmetic and geometry, with zero knowledge of Algebra or beyond. Zero. They didn't even know what the Cartesian Plane was. I was also home schooled by these same people and got a GED. Thus, for a long time, I had a severely warped perspective of what constitutes "adequate proficiency in math." Once I started perusing /sci/, I began to realize that I was severely misinformed. I'm not interested in becoming a mathematician, I just want to get up to par and maybe even a little bit above par, relative to ordinary people, but I don't know what ordinary people know.

[Anonymous No.9816691]

>>9816681
The average American elementary school math teacher can't even do algebra of one variable. I would imagine the average American is just below that.

Don't worry about catching up to the rest of the world, just learn enough math to be personally satisfied with your own understanding

[Anonymous No.9816693]

>>9816691
>The average American elementary school math teacher can't even do algebra of one variable.
How do they get through high school then? Let alone college.

[Anonymous No.9816697]

>>9816681
Didn't they know just the word Cartesian Plane, or really the whole concept of plotting the graph (of a function) in an x-y-coordinate system?

[Anonymous No.9816703]

>>9816697
None of it. They had never seen it nor heard of it before. Zero algebraic knowledge. As if it didn't even exist.

[Anonymous No.9816707]

>>9816703
Goddamn, that's retarded. They should all be kidnapped and be force-fed logic and basic math before being released to continue their miserable lives.

[Anonymous No.9816709]

>>9816707
Want to be even more disturbed? One of them was a 5th grade teacher for 15 years.

[Anonymous No.9816718]

>>9816661
>>9816468
Lel. That was a pretty brainlet mistake I made. It should be [math]| \{ t: |\sin(t)| \leq \lambda^{-p} \} | [/math] though. Now [math] | \{ t: |\sin(t)| \leq \lambda^{-p} \} | = 4\arcsin{\lambda^{-p}} \leq 2\pi \lambda^{-p} [/math] using [math] \frac{2x}{\pi} \leq \sin(x) [/math]. At least this is hopefully correct.

[Anonymous No.9816721]

>>9816709
>>9816709
Well, I don't think elementary school teachers should HAVE TO know that. They only need to be able to read and write, do simple arithmatic and teach discipline. A high school teacher like that should be lynched tho.

[Anonymous No.9816735]

>>9816718
I have doubt about that last inequality.
Google function gives [math] \frac{\pi}{2}x \leq\arcsin{x} [/math] for [math]0<x<\text{something}[/math]. However, taking a bigger constant (like 2) seems to work. Do you know what how to argue that [math] \frac{\pi}{2}x \arcsin{x}\leq2x [/math]?

[Anonymous No.9816738]

>>9816735
Correction for last tex: [math] \arcsin{x}\leq2x [/math]

[Anonymous No.9816745]

>>9816735
[math] \frac{2x}{\pi} \leq \sin(x) [/math]. For [math] 0 < x < \pi/2 [/math]. Now you can let [math] x = arcsin{ \lambda^{-p}} < 1 < \pi / 2 [/math] for [math] \lambda > 1 [/math]. For [math] \lambda < 1 [/math], the measure of the subset will always be [math] 2 \pi [/math] anyway.

[Anonymous No.9816748]

>>9816745
ah, I mean [math] x = \arcsin{ \lambda^{-p}} < \pi / 2 [/math]

[Anonymous No.9816758]

>>9816547
>If 0/0.1 is zero, and 0/0.001 is zero, then why is 0/0=infinite?
In which wheel?

[Anonymous No.9816761]

>>9816693
Yes but the average American probably retains 15% of what they learned in high school

[Anonymous No.9816764]

>>9816745
O haha, I wrote the function wrongly in google.

Thank you thank you thank you for solving this Katznelson conspiracy.

[Anonymous No.9816768]

>>9816764
Haha, you're welcome. Your post reminded me that I have to revise some functional analysis before the semester starts.

[Anonymous No.9816961]

If i'm measuring earth's gravity at it's core, should i consider the entire earth's mass or only the mass of it's core?

[Anonymous No.9816997]

>>9816547
because it isn't
where did you get this retarded idea from?

[Anonymous No.9817225]

still hoping for an answer
>>9814840

[Anonymous No.9817236]

>>9816961
Consider the space-time being curved.

[Anonymous No.9817657]

What's the best online resource for learning python?

[Anonymous No.9817873]

>>9817236
Question mark

[Anonymous No.9817908]

Does it ever bother you that you're limited by your genetics how smart/fast/strong you can be and that if you were born stupid you can't hope to be anything better than mediocre?

[Da mole No.9817910]

>>9817657
A book...

[Anonymous No.9817928]

>>9816387
Already posted on /wsr/ but no one helped me.
Some dude asked if this shit was phd level physics and thats the only reply ive gotten.

given a cylindrical shell of radius a, superficial charge density sigma, and infinite length, that's encompassed by a non-conductive tube of inner radius b, outer radius c, volumetric charge density rho and infinite length; answer the following:

[all numeric data and schematic on pic related]

> 1) for the region in between both cylinders, (a <= r <= b), prove that the electric field at a distance r is given by E = A_2/r and find the value of A_2 in meters

> 2) in the aforementioned region, an electron is spinning with a circular and concentric to the cylinders trajectory, whats its speed?

> 3) whats the electrons kinetic energy?

> 4) knowing the electric field between the cylinders, prove that the interior cylinder of radius a and the innermost face of of the large cylinder (radius b) have the same electric potential. compute the potential difference between them (V_b - V_a).

> 5) whilst inside the larger cylinder (b <= r <= c), prove that the electric field is given by: E = (A_3) + A_4/r find the value for A_3 in meters.

> 6) find the value for A_4 in meters.

> 7) knowing the electric field between the cylinders, find the potential difference between the innermost face of the large cylinder (radius b) and its outermost face (radius c).

dont actually do the homework for me, just help me get what I need to do, i dont fucking understand how im I supposed to compute the areas (A_2, A_3 and A_4) when the cylinders are fucking infinite.

appreciate any help, tell me if anything is unclear.

[Anonymous No.9818056]

>>9817908
yes

[Anonymous No.9818065]

is there an objective way for an optometrist to find the optimal prescription for your lenses (i.e. not relying on self-reporting)?

[Anonymous No.9818069]

these threads sure are slow

[Anonymous No.9818318]

>>9818056
It's a shame that Adderall can only do so much. I guess I can put hope into the Singularity.

[Anonymous No.9818344]

>>9817928
1) Gauss's law, use a cylindrical surface between the tubes. Make the length L arbitrary; it will cancel out. Infinite cylinders just means you don't get any weird edge field effects.

2) Standard expression for centrifugal force on a circular orbit, equate to force from E-field, get velocity

3)KE from velocity, I'm sure I don't need to walk you through this

4) Potential is the path integral of the E-field

5) Gauss cylinder again, but now the enclosed charge changes with radius.

7) Path integral again

[Anonymous No.9818349]

>>9818344
By centrifugal, I of course mean centripetal.

>>9817928
Also A_2 etc. are not areas.

[Anonymous No.9818374]

>>9818318
i wish i had access to Adderall

[Anonymous No.9818378]

>>9818344
Thanks anon.

[Anonymous No.9818426]

>>9818374
It's not really a miracle worker. If you're already a simpleton like me, it's just going to make you into a simpleton with better reflexes. Unfortunately, there's nothing that can make someone like me more intelligent or solve my problem solving deficiencies.

[Anonymous No.9818427]

>>9818426
Oh not to mention you die earlier because of the increased daily strain on your heart.

[Anonymous No.9818441]

>>9818427
Wrong.

[Anonymous No.9818528]

Trying to find the limit of this sequence as n approaches infinity. I know it converges to 3 but I don't know how I would get to the answer or prove it.

[Anonymous No.9818607]

My uni is offering a course on Lebesque Integration in the fall. I have taken real analysis I/II but it's been a while since I've look at my notes. What should I brush up on before considering registering?

[Anonymous No.9818626]

>>9818528
trying writing a function [math]f:\mathbb{R}\to\mathbb{R}[/math] defined by [math]\displaystyle \left(\frac{3^{x}+1}{x}\right)^{\frac{1}{x}}[/math]. Hint: use logarithms.

[Anonymous No.9818636]

Espero que alguien sepa español:
¿Cómo se traduce esto: «Any set can be embedded as a basis into a free monoid»?

[Anonymous No.9818656]

>>9818636
"Cualquier conjunto puede ser incorporado como una base a un monoide libre"

[Anonymous No.9818854]

>>9818528
>suppose the limit exists
>take the logarithm of that limit
>apply the fact that logarithms are continuous to commute the sequence limit, with function composition
>so the logarithm of the terms of the sequence converges to the logarithm of the limit, as n approaches infinity
there you go, try that

[Anonymous No.9819137]

>>9816681
In most of Europe, everyone is pretty much forced to take all of what americans call precalculus. That includes topics like trigonometry, some linear algebra /vector geometry, elementary probability and statistics, coordinate geometry, algebra and a couple other small topics.

In some countries (predominatly mediterranean side), they also make students learn some calculus, more vector geometry, complex numbers and linear algebra in their final two years. Students also get to "specialize" in science and then you do more math, mostly just more advanced things of the previous stuff.

In the UK it depends on the school, although i think most schools force you to do GCSE math, which is the same as the first thing i mentioned. You then can opt to do math in your last two years, with the choice to do on top of that "further math" (and in some examination boards, even "advanced further math"). The normal math is the same as earlier, but the further math goes quite deeper into some math topics. You start to actually do "proofs" too.

I think most of US people cover "precalc", with the option to take calculus in highschool too for "advanced" students.

[Anonymous No.9819166]

>>9816387
I've a classical mechanics and electrodynamics exam in 40 minutes and I'm turning up without underwear. Anything to look out for?

[Anonymous No.9819199]

>>9819137
Calculus is a requirement in most non-inner city high schools, most go up to Calc II (mostly integrals for the entire year) whereas Calc II and Calc III are advanced in high schools, depending. I know Yuros love to use black kids as their standard for American education but there are white schools in America, as well.

[Anonymous No.9819205]

>>9818441
Explain to me how increasing your heart rate daily with amphetamines doesn't lead to an early heart attack?

[Anonymous No.9819225]

>>9819199
>calc is the be all end all of math
you guys don't touch any linear algebra/vector geometry either, and im pretty sure you dont see induction proofs or properties of polynomials

[Anonymous No.9819229]

>>9819225
Most of that are considered separate disciplines so you can either go into calculus, algebra or proofs. Most people choose calculus.

[Anonymous No.9819285]

>>9819229
you are so dumb dude dont reply again

[Anonymous No.9819304]

>>9819285
No.

[Anonymous No.9819383]

>>9819205
I don't know. Explain how it does. The research doesn't match your claim.

[Anonymous No.9819519]

I still don't understand polar, spherical and cylindrical coordinate systems. Why are they so confusing?

[Anonymous No.9819524]

Do prions have genetic material? Can there be protein genes in this example?

[Anonymous No.9819527]

>>9819519
Only spherical should be confusing. Any point on a plane can be described by the distance form the origin and the angle. Adding the 3rd dimension, it's the same but we slide over z: cylindrical. Spherical is cancerous with those two angles, but it's still logical. Shit can be generalized to n dimensions for differential geometry induced tumors.

Just take a look at pic and note that the second angle only needs to take values between 0 and pi in order to describe every point on the sphere.

[Anonymous No.9819547]

>>9819519
Also, for a more intuitive purely geometric approach, observe how you could fill a plane with only circles with center (0,0). Add the 3rd dim and extend these circles to infinitely long cylinders. Spherical coordinates is filling space with balls with center (0,0,0).

If this makes sense to you, then I suggest you try to think of a way to fill the 3dim space with circles only (you may bend/shape the circles, but no points though). This is possible, but not in the 2dim space. The answer is due to Andrzej Szulkin called "R^3 is the union of disjoint circles".

[Anonymous No.9819551]

>>9818854
>>9818626
Thanks. I wrote it as e^ln(...) and used L'Hopital's for anyone else wondering

[Anonymous No.9819562]

>>9819519
But they're pretty handy in quite a few circumstances, such as the magnetic field from a long wire, or the electric field from a point charge, and more complex renditions of.

[Anonymous No.9819895]

I don't know how relativity works, how would these scenarios work out?
If nothing can move faster than the speed of light from anyone's perspective, then how can these problems be resolved?
>Scenario 1:
2 planets launch a ships at each other at more than half the speed of light, say, .75 the speed of light.
How fast does each ship measure the other as they pass? Why don't they measure each other as going 1.5c?
>Scenario 2:
A ship leaves buoys as it accelerates.
It leaves a buoy at the start of its journey, then accelerates itself to half the speed of light to the first buoy,
drops another, and then accelerates itself to half the speed of light relative to the second buoy,
and then drops another.
How fast does each object measure each other object? More specifically, why doesn't the first buoy perceive the ship as travelling at the speed of light?

[Anonymous No.9819904]

How does seasons occur? Why is it Winter at Southern hemisphere and Summer on Northern hemisphere if Earth is at the same distance of sun (therefore both hemispheres) and also still has rotation movement?

[Anonymous No.9819951]

>>9819904
The axis on which the earth spins is tilted. This means that a random location on the surface of the spinning planet might spend an uneven time in day or night. During Christmas, the south pole is tilted towards the sun, meaning that days are longer in the southern hemisphere, shorter in the northern hemisphere, and stay the same on the equator. it also stays day all day at the south pole, and stays night all day at the north pole. The longer days mean more time storing heat from the sun in the soil and water, and less time losing it into the night sky. the inverse happens in the northern hemisphere. the distance from the sun does not matter as much as the amount of time spent in it. additionally, the sun shines hardest on the place where it is shining head-on, as apposed to places where the light is entering at an angle, because it gets scattered and reflected by the air it passes through, so the area in the center of the circle of daytime gets the most heat, with that being the hemisphere that is tilted towards the sun.

[Anonymous No.9820004]

Why can you just invert the Jacobian here, is there a gap in my knowledge of a rule that says you can just do that whenever?

[Anonymous No.9820222]

>>9820004
They are not inverting the Jacobian, they are taking the inverse of the determinant of the matrix. The inverse exists since 1 <= xy <= 2 so neither x nor y can be 0

[Anonymous No.9820228]

What is the best introductory book on differential topology?

[Anonymous No.9820674]

ez

[Anonymous No.9820723]

shoud i study physics og maths?

[Anonymous No.9820737]

Where do I start in biology?

[Anonymous No.9820740]

>>9816387
Will fluoride/toothpaste kill my braincells?

[Anonymous No.9820745]

Why do my eggs smell like eggs

[Anonymous No.9820812]

>>9819895
>Scenario 1
You have to consider what the speed of each ship will be in the reference frame of the other ship, which will be less than the speed of light after you apply the proper transformation.

>Scenario 2
I only understand special relativity which does not describe accelerating reference frames.

>>9820723
It's a lot easier to learn physics from mathematics, then mathematics from physics.

[Anonymous No.9820845]

Help pls
>>66428821

[Anonymous No.9820888]

>>9820845
it's gone. Type it again here please.

[Anonymous No.9820905]

What the fuck happened to WolframAlpha for Android?
Even with the easy integral, the step by step answer is fucked up

[Anonymous No.9820923]

>>9820905
Also, there is the classic timed out error for any tricky integral

[Anonymous No.9820981]

>>9820905
What's wrong with it?

[Anonymous No.9821067]

>>9820981
The step by step solution only shows a part of the answer and the quality is pretty bad, like some upscaled low res picture

[Anonymous No.9821135]

what do you guys do about the topics you never mastered in high school, For eg i dont know much of stats, probability and complex no and so if i go to college, will i get fucked?? Or will learning high level stuff in college will automatically fill in the gap left by my poor high school knowledge?

[Anonymous No.9821191]

>>9821135
You're better of studying what interests you on your own rather than lining Professor Shlomo's pockets with your shekels. Unless of course you are going to college to become a wagecuck.

[Anonymous No.9821204]

Somebody explain voltage to me in brainlet terms.

[Anonymous No.9821215]

>>9821204
Work done(on the charge) to move charge from point A to point B is the voltage between point A and B

[Anonymous No.9821217]

Someone explain to me van Kampen's theorem.

[Anonymous No.9821439]

>>9820228
milnor's topology from a differentiable viewpoint
>>9820723
maths
>>9821217
you can compute the fundamental group of a union of spaces by concatenating their loops in novel ways, modulo concatenating the loops in the path connected intersection.

[Anonymous No.9821453]

>>9820723
I think you should try learning english first.

[Anonymous No.9821823]

>>9817657
coding bat

[Anonymous No.9821959]

how do electrons become free in metal? i read stuff and undestand that it goes like this:
>have a metal
>metal has a crystal structure
>structure has knots or nodes
>atoms are situated in nodes
>their furthermost orbits overlap
>they become positive ions
>electrones become free
>add voltage
>get current

did i get it right? i don't understand the overlapping part

[Anonymous No.9821971]

>>9816387

In zoology, are there examples of two species that: live in proximity, and don't predate or prey on one another, but instead have a general lack of interest in one another, and simply move around each other, not even having a sympathetic or symbiotic relationship, nor the usual antagonistic one?

Is there a formal name for such an indifference between two species? Does this even happen in the animal kingdom?

[Anonymous No.9821987]

>>9816387
Why does manganese oxide breakdown hydrogen peroxide quicker than copper oxide, iron oxide or lead oxide. Manganese (IV) Oxide

[Anonymous No.9821994]

>>9821959
Ken Wheeler explains;

https://www.youtube.com/watch?v=dnEx3JjeGGg

[Anonymous No.9822023]

>>9816387
Should geologically important federal lands be given away? How economically viable are these lands?

[Anonymous No.9822027]

>>9821959

Further reading to understand the transfer of energy, waves and dielectric properties - underlying principle; Field interaction, aka magnetism, light and electricity in it's true form.

==============================

Two good books on the topics;

John Oneill - Nikola Tesla Biography - Prodigal Genius (Digitized version)

https://archive.org/details/pdfy-beZtsHoLHWtnnj9n

------------------------------

Ken L. Wheeler - Uncovering the missing Secrets of Magnetism (2014)

https://archive.org/details/magnetism1small

==============================

Fundamental principles on the topic include looking at physics with new eyes; Waveform vs. Particles, aka "atomic orbitals" vs "atomism", or field-interaction vs. "mechanical" particle-interaction;

1) Article;
https://en.wikipedia.org/wiki/Atomic_orbital

2) Examples
http://www.bing.com/images/search?q=Atomic+Orbital&FORM=IRIBIP

==============================

Perhaps not an exact answer to your question, but information is non the less provided for a more intimate understanding on the topic, as "electrons" pr. today's physics are classified as "particles", which they are not - which must be understood to comprehend electron-flow and ionization in it's true form.

Ken's got a bunch of videos on the topic at large worth checking out, if you can spare the bits where he rambles a bit.

[Anonymous No.9822095]

i'm so fucked for my calc and lin algebra exam tomorrow. why the fuck am i such a brainlet. fuck i really wantted to do well. fuck fuck fuck

[Anonymous No.9822133]

I was seriously thinking about dedicating my time to make an application to an foreign uni. But the thing is that i used to be bellow average on maths (around a mean 5,5/10, i think that's a D on American grade system) and the other STEM subjects weren't spectacular too. I only came to have an actual interest on STEM related stuff recently

How could i fix my curriculum on terms of taking extra activities and doing good SAT/TOEFL tests ? What kind of other certifications/tests should i pursue ?

[Anonymous No.9822171]

Let's say that you have a research lab and have to test some machines used for alternative medicines by another company.

How much do you ask for?
How much would it cost?
How much time would it take?

Anyone could point me toward an example of a similar research that detailed all the methods, the tools they used? The costs and personnel?

[Anonymous No.9822227]

>>9816961
Gauss' law applies.

[Anonymous No.9822257]

>>9821994
>>9822027

thank you very much

[Anonymous No.9822393]

>>9822227
explain

[Anonymous No.9822502]

Alright /sci/, how the FUCK do I search through/view patent information, especially pharmaceutical stuff?

[Anonymous No.9822553]

>>9822393
>explain
"The net "gravity flux" through any hypothetical closed surface is proportional to the net mass within that closed surface."

If you consider as surfaces spheres center at the center of the earth, each of them will contain less and less mass. At the center there would be no sphere, hence no mass, hence no gravity.


Other more visual way to see this is that each piece of the earth is pulling you, in the center of the Earth there exist an antipodal piece of the Earth whose pulling counteract the one of the former piece, hence rendering a net effect of zero force.

[Anonymous No.9822618]

>>9816387
>Get a "statistics" job for summer
>It's literally just data entry into spreadsheets

How do I make the suffering stop? t. Theoretical physics grad student.

[Anonymous No.9822658]

I can't see LaTeX anymore on /sci/.
I'm using Chrome. I restarted and still can't see LaTeX.
How do I fix this?

[Anonymous No.9822662]

>>9822618
write a program to automate your "job" then sit back and get paid to jack off

[Anonymous No.9822667]

>>9822662
what if data is from paper? le visual recognition neural network?

[Anonymous No.9822697]

>>9822667
OCR my dude

[Anonymous No.9822715]

>>9821439
>by concatenating their loops in novel ways, modulo concatenating the loops in the path connected intersection.
Explain this to me in retard terms

[Anonymous No.9822834]

>>9822658
Try to pause adblocker on this page. That works for me at least.

[Anonymous No.9822837]

>>9822834
It worked! Thanks mate!

[Anonymous No.9822866]

how to concentrate on study for long hours?

[Anonymous No.9822907]

>>9819519
Polar coordinates:
Every point v in the plane can be uniquely determined by its angle θ and its radius r.
v= r (cosθ,sinθ) = ||v|| v/||v||.
(cosθ,sinθ) is the point on the unit circle which your reach when you have traveled distance θ along the circle having started from the point (1,0).
In short, instead of using two lines (the x and y axes) to describe a point, you use a circle and a half-line (the unit circle and the non-negative reals).

Cylindrical coordinates:
They are for the 3D space.
You use Polar Coordinates for the (x,y) part of (x,y,z), and you keep using z for z.
So, here you use a circle, a half line (combined they are a plane) and a line.

Spherical coordinates:
You use a circle, a line and a semicircle.
First, you project the point v onto the xy plane.
That projection has length r sinφ, where r is the length of v and φ is the angle v makes with the z axis (you start measuring from the z axis. the angle ranges from 0 to π).
Let the angle of the projection of v be θ.
Combining the above, the projection is equal to r sinφ (cosθ,sinθ,0).
The only thing remaining to be found is the projection of v onto the z axis which is easily seen to be r cosφ.
So
v = Projection onto xy + Projection onto z = ( r sinφ cosθ , r sinφ sinθ , r cosφ)

[Anonymous No.9822926]

>>9821439
>>9822715
NVM, thanks so fucking much. ^_____^
I think I have a solid grasp of algebraic topology, is it worth studying algebraic geometry now or not? What's the main study of algebraic geometry?

[Anonymous No.9822936]

>>9822926
>algebraic geometry
polynomials

[Anonymous No.9823175]

>>9822257

Any time. Hope it helps.

https://www.youtube.com/watch?v=5IwgRNS1Frs&index=3&list=PLTMm2h0hniVIvITS68zKz8mz1E7y36-id

[Anonymous No.9823295]

>>9822553
So i can't just 10=5.97e24*6.67e-11/x2 to discover a point on Earth where the gravity acceleration equals 10 since the mass will vary depending on the radius

[Anonymous No.9823500]

>>9817910
what book you fucking goon

[Anonymous No.9823644]

What kind of math comes after differential equations? The most complex thing I've done were fourier transforms or laplace transforms in class and those weren't bad. Where do I go from here?

[Anonymous No.9823647]

People talk about how beautiful math is and what not. I suppose I don't understand. I like math, but when does did it become beautiful to you?

[Anonymous No.9823653]

>>9823644
Integral equations

[Anonymous No.9823660]

>>9823644
PDEs

[Anonymous No.9824144]

Fuck me, why are there two different standards for Fisher F-tables? On one table under F(0.95; 5, 7) I get 3.97, but according to the solution to an exam problem this is the value of F(0.05; 5, 7). An online calculator tells me the latter is right. So my table is showing me the values for 1 - α instead of α, as in left-tail quantiles vs right-tail quantiles, correct? Or something to that effect.

[Anonymous No.9824174]

>>9816693
Normalfags memorize some rules for passing the tests, make cheatsheets, get given the exact same tasks in the lessons and homework as in the examinations and still barely pass. Then they forget everything they aren't using.

The average person knows pretty much nothing outside arithmetics and (if they're a man) usually some basic geometry like what a square is and how to find its area. Or at least where to look for for the formula in a table. Hell, even most technical fields don't actually require you to do anything besides plug numbers into expressions. I had a classmate in 3rd year mechanical engineering who didn't know what a cosine was, and probably still doesn't because he flat out said he doesn't give a shit.

[Anonymous No.9824233]

>>9824144
Most tables clarify about whether they're showing "c such that P(X>c)=a" or "c such that P(X<c)=a".
Look again.

[Anonymous No.9824265]

>>9824233
And my table just so happens not to give me that information. But I think I've cleared things up now.

[Anonymous No.9824290]

I was doing fine In mech eng at notts uni UK (2nd year) then one day I woke up & decided I didn't want to be here & dropped out that afternoon.

I've struggle since then to take responsibility or do anything, even now I have a work deadline for 3 (it's 2:15) & I've not started it dispite having everything ready & prepared & open. I've missed every single deadline, appointment, meeting etc since then.
Do I have a disease or hormone imbalance or some shit? why did this randomly happen and why can't I break out of this ever since then?

[Anonymous No.9824297]

>>9824174
>I had a classmate in 3rd year mechanical engineering who didn't know what a cosine was, and probably still doesn't because he flat out said he doesn't give a shit.

if it makes you feel any better, most engineers like that get weeded out in industry and end up as "cost analysts" or "project managers" instead of doing any actual technical work.

[Anonymous No.9824371]

>bra-ket notation is brought into physics one day without background
>figure it can't be that tough to learn about afterwards
>try to figure it out from the wikipedia page but the rabbit hole only grows deeper
Fuck

[Anonymous No.9824389]

>>9824371
if you want to have a rigorous understanding, take a functional analysis class.
just thinking about them as row and column vectors should be enough for babbies first qm though

[Anonymous No.9824411]

Is there a relation between autism and math enthusiasm?

[Anonymous No.9824431]

Is the expression x/yz taken as (x/y)*z or x/(yz)?

[Anonymous No.9824467]

>>9824431
>Is the expression x/yz taken as (x/y)*z or x/(yz)?
You'd have to ask whoever wrote the expression

[Anonymous No.9824547]

>>9824431
it would mean (x/y)*z but chances are they meant x/(yz) otherwise they would've just said xz/y

[Anonymous No.9824649]

I'm reading Spivak's Calculus, chapter 5. Got stuck on ii), I remember using L'Hospital's when working through Stewart's, but I'm not sure how to compute this limit using Spivak's epsilon-delta methods. I've read, scanned, and rescanned and reread the chapter many times (before and after this question cropped up). Any help would be superb!

[Anonymous No.9824653]

>>9824649
Theorem 2, for reference.

[Anonymous No.9824656]

>>9824653
the real theorem 2, for reference

[Anonymous No.9824667]

>>9824649
>>9824656
samefag, is it just as simple as multiplying the numerator by it's conjugate? Is there's no method Spivak discussed that I should be utilizing?

[Anonymous No.9824710]

>>9824649
[math] x^n-y^n=(x-y)(x^{n-1}+x^{n-2}y+\cdots+xy^{n-2}+y^{n-1}) [/math]

[Anonymous No.9824743]

>>9824667
x^3-8 = (x-2)(x^2+2x+4)

[Anonymous No.9824754]

>>9824411
no, however there is a strong relation between autism and asking questions on /sci/

[Anonymous No.9825036]

>>9824389
It's condensed matter, not QM, though I guess it's the quantum part of condensed matter.

[Anonymous No.9825086]

i feel like a utter brainlet but i can fuking solve this, i know its x1=x2=x2

but i cant see the way to the solution

[Anonymous No.9825143]

>>9825086

Take the first equation, divide everything by x_3, then multiply by both divisors to arrive at x_1 = x_2.

[Anonymous No.9825148]

Ok so modern processors were made to process mathematics. Series of numbers in base 2 are operated on by the CPU in order to complete calculations. We have different CPUs for different types of processes, utilising the same basic principles, mathematics and logic, in order to process complex things such as sound and video.

What if there was a CPU that didn't rely on transistors? A CPU that instead of using mathematics, operated on colours? Or chemical reactions? Is it possible to produce a CPU using things other than binary transistors? This idea came into my head because, in essence, our brain is a CPU, and instead of binary transistors we use Neurons to process the world through chemical reactions.

[Anonymous No.9825157]

>>9823644
>finally shit fucking holy
?????

[Anonymous No.9825161]

>>9825143
god fuking damn, i should just neck my shit

thx

[Anonymous No.9825167]

>>9824710
>>9824743
Did Spivak tell me in chapter 5 that a 0/0 limit is indeterminate and thus requires manipulation? I know 1/g was discussed for when g is 0, but not directly dicussing indeterminate limits. Perhaps it was implied from the lemma and theorem.

Anyhow, thanks.

[Anonymous No.9825170]

>>9825148
Binary is used for a reason though anon, it’s the most simple construction for advanced logic

[Anonymous No.9825176]

>>9825170
This is correct but what if you didn't want advanced logic? What if, say, you were programming emotions, empathy, or morality? These things aren't logical at all.

[Anonymous No.9825183]

>>9825167
The expression [math] \frac{x^3-8}{x-2} [/math] is equal to the expression [math] x^2+2x+4 [/math] for all x different from 2.
Recall the definition of the limit.
[math] \forall \epsilon>0 \, \exists \delta>0 \, \forall x : \quad 0<|x-x_0|<\delta \implies |f(x)-l|<\epsilon [/math]
The x's that you care about are different from [math] x_0 [/math] .

[Anonymous No.9825386]

Is this study valid?
http://www.bearconflict.org/wp-content/uploads/2016/11/firearms-and-bears.pdf

>We compiled information on bear attacks from readily accessible state and federal records, newspaper accounts, books, and anecdotal information that spanned the years 1883–2009.
I mean specifically the fact that they reference newspapers and "Anecdotal information"
Does that invalidate the study?

[Anonymous No.9825625]

The velocity (v) of sound in the air is 1087 when it is 273 k (t), but it gets higher when t rises.
Experiments show that the variation of v in relation to t is (variation or delta of v)/(variation or delta of t) (1087/2.(√ 273)). t^(-1/2).

I need to express v in function of t, how do I do that?

[Anonymous No.9825633]

>>9825625
I am sad...

[Anonymous No.9825851]

>>9825176
how do you represent them then? this doesn't have to do with transistors, CPUs or binary necassarily.

If not logic, at the lowest level, then what else could a computer process? All of it's processing is possible via electrical current.

[Anonymous No.9825853]

>>9825183
I'll digest this tomorrow morning, when my browser hopefully renders your latex. thanks in advance anon.

[Anonymous No.9825983]

>Apostol
>Courant
>Spivak
>Stewart
>Hass, Thomas Jr., Weiss
>Keisler
>Kline

assuming I've done pre-calc and read How to Prove It (Velleman), which is the best book that has a mixed approach (pure math and applied math) and good exercises to learn calculus if I'm self-studying and it's my first exposition to the subject?

[Anonymous No.9826036]

>>9825157
Manga is read right to left

[Anonymous No.9826038]

>>9825983
Courant&John

[Anonymous No.9826310]

some basic calculus here lads
the question is:
For [math]y=Ax^3-Bx^2[/math], find [math]A[/math] and [math]B[/math] if the curve has a stationary point at [math]({\frac{1}{2}}, {\frac{-1}{4}})[/math]
(note that it doesn't say whether the point is a maximum or minimum)
I tried solving and got the following simultaneous equations:
[math]3A=4B[/math] and [math]A=2B+2[/math]
which gives [math]A=-4[/math] and [math]B=-3[/math]
but the answer says that [math]A=4[/math] and [math]B=3[/math]
which tells me that i've misplaced a -1 or something, i couldn't find any place where that happened though. tell me that i'm not crazy plz.

[Anonymous No.9826390]

>>9826310
as it turns out, i was misplacing a -1, got the correct answer now

[Anonymous No.9826476]

If I have a toroidal transformer with a known turns ratio, relative permeability, and core area is it possible to take that information and somehow plug it in to one or more of Maxwell's equations and find out what level of magnetic flux will saturate the core AND by extension find out what the minimum peak current is that will saturate said core at a given switching frequency and duty cycle?

[Anonymous No.9826573]

Can someone check my resolution? It's a thermodynamics exercise about air compression and I think I may have over-complicated it, but I didn't know how to solve it so...

[Anonymous No.9826619]

>>9825625
You have dv/dt = f(t). Integrate it, but make sure your equation is correct.

[Anonymous No.9826632]

>>9822133
Do tons of online practice for the SAT. The test is not designed for you to finish the whole thing unless you are in the top 10%. Anyways, even though I got a 99%ile score, it's still in the 25%ile for Harvard and MIT. I wouldn't bother with applying to Ivy League schools unless you get 1450+. If you really want to go international, many schools outside the USA also accept the SAT as part of their application (think Oxford or Canadian schools). American schools pile you with debt unless you apply for scholarships.
One thing I noticed on the SAT itself was that the English sections are particularly difficult (maybe because I'm good at math). Grammar should not be a problem unless you are mentally deficient, but the reading comprehension was hell. Like I said, do tons of practice online at Khan Academy SAT prep, and focus on the sections that need work. Good luck mate. I'll answer any questions if I remember to check this thread.

[Anonymous No.9826688]

>>9826573
Nevermind that. The integral is completely wrong, and after I corrected it I got an even wronger answer.

[Anonymous No.9826779]

Yo /sqt/, was pointed to here from /g/'s /dpt/. I'll copy and paste my post.

>* 2 - 1
Why does this sum appear so often in my code? I'm a math brainlet but this sum is able to attain a consistently incrementing number, + 2 of the previous number, and I'm amazed how it does this.

>4 * 2 - 1 = 7
>5 * 2 - 1 = 9
>6 * 2 - 1 = 11

It always increments by 2 each time. Math amazes me but I sucked at it back in school, so....

[Dank_Nugg €€££¥¥¥ No.9826794]

>>9816387
Alright /sci/, you're all fairly intelligent. I have a dumb question. Do "probiotic" foods ever make it to the gut without being purged of all bacteria? Don't get me wrong, I enjoy fermented foods, yogurt, beer, etc. It just boggles my mind to think that stomach acid somehow wouldn't absolutely obliterate all of the "health benefits" that people look for in that kind of stuff.

[Anonymous No.9826800]

>>9824411
I don't know about math, but I knew this one guy who was good at chess, (the only thing he took joy in) would go to chess tournaments, etc. And he was definitely aspergers.

[Anonymous No.9826844]

>>9816387
CAN SOMEONE HELP ME MAKE A FUCKING CUBE IN MATLAB

I KNOW IT'S JUST CIRCLES STACKING ON TOP OF EACH OTHER AND I'VE MADE A CIRCLE BUT I CAN'T FIGURE OUT HOW TO STACK THEM

CODE:

imageSizeX = 500;
imageSizeY = 500;
[columnsInImage rowsInImage] = meshgrid(1:imageSizeX, 1:imageSizeY);
centerX = 250;
centerY = 250;
radius = 100;
circlePixels = (rowsInImage - centerY).^2 ...
+ (columnsInImage - centerX).^2 <= radius.^2;
image(circlePixels) ;
colormap([0 0 0; 1 1 1]);
axis('equal')

[Anonymous No.9826847]

I'm studying intro physics and I hate optics. I think it's so stupid and unintuitive. Maybe it's because my textbook is shit. Can someone inspire me to like it somehow? Can you tell me something cool that will make me want to study it?

[Anonymous No.9826850]

>>9826844
CYLINDER******


NOT CUBE

[Anonymous No.9826939]

Brainlet here
Got a function f(x,y,z)
I calculated the gradient and figured out the tangential plain on a specific given point on the surface described by f(x,y,z)=0

Now I'm given a vector and am asked to calculate the point on the surface at which the tagential plain is orthogonal to that vector and I'm having trouble

Where I'm at is that if the vector is orthogonal to the plain it has to be some multiple of the normal vector of that plain, which I know
But I don't know if it's orthogonal, I want to know where (?)
Also got something in my head about the cross product and how that would describe a vector that's orthogonal and all but it just doesn't make sense

I feel like I'm almost there but just can't wrap my head around it, any advice on how I might figure this out would be greatly appreciated

[Anonymous No.9827081]

do math major or physics majors learn mathematical physics

[Anonymous No.9827104]

>>9826939
You are given a vector v. You need to find where on the surface the gradient is a scalar multiple of that vector. Find x y z and k such that

f(x,y,z)=0 and
grad f (x,y,z) = k v
Simultaneously

[Anonymous No.9827158]

>Random number generator
>Generates numbers from 0.00 - 99.99
How likely is it to roll 1,2,3,4,5,6,7,8 in a row ?
Please help a brainlet
Is there a website where you can calculate such problems ?

[Anonymous No.9827173]

>>9827158
[math] \frac{1}{10^4})^8 [/math] = 0.(thirty zeroes)1 % [/math]
>Is there a website where you can calculate such problems ?
There isn't any.
Just study basic combinatorics. It's quite useful for real life anyway.

[Anonymous No.9827208]

>>9822936
>polynomials
That doesn't sound different from what I learned in high school though, how does it differ then?

[Anonymous No.9827298]

>>9827104
Thank you Anon
Just putting it down like that makes it all seem less complicated and confusing, I'll try and find some answers

[Anonymous No.9827314]

>>9822027
>>9821994
Who is Ken Wheeler and why does anything he has to say hold any weight besides him quoting Tesla, Thomson, and others about why electrons aren't real?

[Anonymous No.9827366]

>>9827104
>>9827298
I figured it out!
Turns out the z component of the gradient is just a whole number in this case so it was very easy to find k and go from there
I think part of what made this whole thing so inconprehensible to me was that I didn't even properly understand what was actually asked of me

Thanks again!

[Anonymous No.9827378]

>>9816387
What's estimated weigh of a O'Neill cylinder?
Is dropping one on earth worse than a tsar bomba?
Yep, /m/ related shit.

[Anonymous No.9827389]

>>9827378
I started watching Gundman 79 recently
Also saw War in the Pocket before that
Good stuff

Probably very heavy

[Anonymous No.9827404]

>>9827389
I doubt it could make THAT damage.

[Anonymous No.9827493]

How do I know if I'm too dumb for a PhD? Is there a brainlet test I could take?

[Anonymous No.9827786]

Does a tensor have a magnitude for each of its directions or a single magnitude for all of its directions?

[Anonymous No.9827852]

>>9816387
Can someone give an intuitive explanation for why the two definitions of the dot product are equal / related? My book defines it for length-2 vectors, call them a = <x, y> and b = <w, z>, as
a⋅b = ||a|| * ||b|| * cos(Θ) = xw + yz
I see that both of the methods of computation always give the same answer, i just want to understand why they do on an intuitive level.
It makes sense that, if we let a = b, that we have a⋅b = a⋅a= ||a||^2 * cos(0) = ||a||^2, which is intuitively what we would want since dot product seems to be concerned with multiplication of the lengths or magnitudes of the vectors, taking into consideration their directions. So it makes sense, in the general definition above, that we would multiply the two magnitudes by the cosine of the angle between them. What has me confused is the how that is related to the sum of the products of their x,y- components. Does the latter work because, supposing for the sake of an example that
[math]
a = <10, 10>
b = <10, -5>
[/math]
(just wanted to convey here that one of the vectors is oriented in the opposite direction with respect to one of the dimensions), since the y components of the two vectors are oriented in the opposite directions, we get less from them (actually they detract from what the dot product could be were they semi oriented in the same direction)? This probably makes little sense and for that I apologize, thanks to whoever took the time to read it

[Anonymous No.9827975]

>>9827852
If you convert the vectors to polar coordinates, you get:
x1 = r1*cos(a1)
y1 = r1*sin(a1)
x2 = r2*cos(a2)
y2 = r2*sin(a2)
The dot product is
x1*x2+y1*y2
= r1*cos(a1)*r2*cos(a2) + r1*sin(a1)*r2*sin(a2)
= r1*r2*(cos(a1)*cos(a2) + sin(a1)*sin(a2))
= r1*r2*cos(a1-a2)

[Anonymous No.9828155]

>>9827852
Here:
https://www.youtube.com/watch?v=LyGKycYT2v0

[Anonymous No.9828163]

As someone who’s gotten straight C’s in every math Precalc-Calc 2, what should I expect out of Calc 3 and Linear Algebra?

[Anonymous No.9828164]

>>9828163
Zs

[Anonymous No.9828403]

>>9816758
>wheels

[Anonymous No.9828407]

>>9825183
I still don't understand how this particularly covers the case in which the limit is indeterminate. Nothing I've comprehended so far tells me that when it's indeterminate, I need to manipulate. I'd really appreciate a bit of handholding here, if allowable.

[Anonymous No.9828421]

>>9825183
>>9828407
Is it because with x=2, x-x_0 is not greater than 0?

[Anonymous No.9828527]

>>9828421
Yes. [math] |x-x_0|>0 [/math] is the same as saying [math] x \neq x_0 [/math] .

[Anonymous No.9828629]

What is meant by "modulo the action of a groupoid?"

[Anonymous No.9828640]

Does speed reading actually helps?

[Anonymous No.9828690]

>>9816758
Not the same poster, but I have a follow up question: can we define a topology on the [math]\mathbb{R}\cup\{+\infty,-\infty\}[/math] such that "convergent" sequences in [math]\mathbb{R}[/math] have their usual unique limit, "divergent" sequences converge to either [math]+\infty[/math] or [math]-\infty[/math], and sequences whose limit is "undefined" converge to multiple limit points?

[Anonymous No.9828885]

just noticed this thread, oops.
anyway why is 8/5 not 1.3? you're trying to find out how many times you can stick 5 into 8 right?
so place 5 into 8, and take that away as a whole.
then you have 3 parts left over. this makes sense to me

however the actual answer is 1.6? someone please explain

[Anonymous No.9828894]

Can someone explain the wave property of electrons to me?

I understand uncertainty, the double-slit experiment, and how particles can behave like waves. The bit I'm struggling to get my mind around is the form the wave takes.

Is it a wave function plotted 3 dimensionally in the particle's locality? Is it to do with energy it gives off in waves? Or do we simply know that they exhibit traits of waves (interference) and nothing more?

Any explanation or exposition is appreciated.

[Anonymous No.9828960]

>>9828885
8/5 = 5/5 + 3/5 = 1 + 3/5 = 1 + 6/10 = 1.6

[Anonymous No.9829023]

>>9828960
thanks

[Anonymous No.9829271]

this doesn't seem right, where did I go wrong?

[Anonymous No.9829303]

>>9829271
>this doesn't seem right
Why?

[Anonymous No.9829357]

can being out of school while my brain is still developing make me stupider?

[Anonymous No.9829407]

Take a globe the size of A.


If I represent that with a Mercator projection, how do I tell the distance between any 2 points on the map?

[Anonymous No.9829515]

>>9827366
Very nice! Glad I could help.

[Anonymous No.9829580]

[eqn] A = \{5x : x \in Z, |2x| \leq 8[/eqn]


Is this {-4,-3,-2,-1, 0, 1, 2, 3, 4} or {-20,-15,-10, -5, 0, 5, 10, 15, 20}

[Anonymous No.9829768]

if scope = 2r*pie
and pie is irrational
does that make the scope irrational and immeasureable?

[Anonymous No.9829774]

>>9829407
the mercator projection has horizontal and vertical lines
all these areas inbetween them are the dame size in the real world but different on mercator p.
split every such area you need in another grid system
start counting how many smaller squares you cross

[Anonymous No.9829961]

>>9829407
See:
en.wikipedia.org/wiki/Geodesics_on_an_ellipsoid

Note that it's impossible to construct a planar projection where the actual distance (on the surface of a sphere or ellipsoid) between any two points is proportional to the distance on the projected plane.

[Anonymous No.9830060]

What was intended to be said there? Because clearly that's not true when x=2, y=3 and z=1, or in infinitely many cases.
Btw excuse my retardation i created a thread for this and for some reason i can't delete it

[Anonymous No.9830063]

>>9829768
Let r = 1/pi

[Anonymous No.9830064]

>>9830060
I assume they meant to say xz<yz, there is another error in the line above certainly x+0=0 is NOT true for all x.

[Anonymous No.9830068]

>>9830064
That makes the most sense ty!
I did notice that other one tho i assumed it meant to say x + 0 = x.

[Anonymous No.9830104]

>>9829580
{-20,-15,-10, -5, 0, 5, 10, 15, 20}
It's 5x where x ranges from -4 to 4.

[Anonymous No.9830110]

>>9830060
It's a typo. It should be:
"If x<y and z>0, then zx<zy."

[Anonymous No.9830488]

>>9828527
OK, and because x-x_0 = 0, I cannot proceed under the definition of it a limit, and thus must manipulate it? Thanks anon, I think I see how this was defined before me the whole time.

[Anonymous No.9830877]

Why are there fewer polymaths in the age of information?

[Anonymous No.9831017]

What is b type measurement uncertainty of analog (pic rel) clock (note that it does not have seconds clock tip) and digital clock showing time in HH:MM format?
My guess would be:
for analog one ub=60s/sqrt(3)
for digital one ub=30s
is it correct?

[Anonymous No.9831018]

>>9830104
I forgot pic, sry

[Anonymous No.9831196]

>>9819951
Thanks so much anon, I had this query since elementary school and no one ever mentioned the tilt part, that was the point to start off

[Anonymous No.9831653]

What is undergrad research like? I want to ask a professor to get a position for it (unpaid of course) to help my CV/resume before I apply to grad school, but is it just grunt work in undergrad or am I expected to know some wild shit? In EE/physics b.t.w.

[Anonymous No.9831711]

Why is the area under the curve of a continuous function on a given interval equal to the net change of its anti derivative on that same interval? Why does the area of the function correspond to this difference?

[Anonymous No.9831737]

Does everyone can become a physicist?

[Anonymous No.9831763]

NEURAL NETWORKS
anyone got resources for GAN

is there a library or plugin which cuts most the unnecessary shit and just lets me plug parameters in and run a GAN train

[Anonymous No.9831775]

>>9831711

[Anonymous No.9831777]

>>9831775
Fascinating. Thank you very much, this is exactly what I wanted to know.

[Anonymous No.9831786]

>>9831711
Short answer given here:
>>9831775

Long answer is that your questions are very good and you should be skeptical about anything you haven't seen proven directly.

You should take a course on real analysis, or read a good textbook. My recommendation to anyone not studying analysis for a university course would be a radical approach to read analysis as it gives historical context, is relatively easy and has lots of pictures and examples which make the subject a bit more approachable.

If you want a more rigorous approach I'd recommend Oxford analysis 1-3 lecture notes or whatever books Harvard recommend for math55.

[Anonymous No.9831795]

>>9831786
Much appreciated. Thank you very much.

[Anonymous No.9831828]

Is it impossible to tesselate or tile a sphere with parralelograms?

[Anonymous No.9831845]

>>9831828
What does "parallel" mean on the surface of a sphere?

[Anonymous No.9831898]

>>9831845
Exactly what the definition says, brainlet

[Anonymous No.9831938]

>>9831898
there are no parallel geodesics on sphere

[Anonymous No.9831971]

is there a theoretical upper limit for the efficiency of the Seebeck/Peltier effect?

[Anonymous No.9831986]

Full blown, 100%, drooling, retarded fool here.
I have a pretty brutal form of epilepsy that is uncontrollable at this point, and has recently become very dangerous. A neurologist has given me a prescription I'll be getting in a couple of days for a benzo called clobazam (UK). I am in a tricky situation because I'm heavily depressive/suicidal on a day to day basis, and I know for a fact I will be getting hooked on these if I'm not careful, though I have no choice but to take them. The idea of course is to rapidly and heavily suppress the nervous system, and stop anything dangerous happening, but I don't trust myself. There is a bit of history cos i spent a large portion of my life living with a dad on base, addiction scares the fuck out of me (though my dad did go cold turkey with no help, a lot of respect for that). I'm fucking rambling now.
I'm probably over thinking it, it would be logical that clobazam is the lowest level benzo to start on. For some reason 'major' benzos are non-addictive, 'minor' are addictive. I'm assuming this is the lowest minor.
Any help/knowledge/resources on this would be great, I know america has had a massive tranq problem for a long time.

[Anonymous No.9832009]

>>9831986
I should clarify, I'm psychologically dependent on weed already, but it really is nowhere near the legitimate level of dependency these will bring, as with other heavy drugs.
I'm not even sure what my question was anymore, just any experiences/info I guess.

[Anonymous No.9832153]

How do I calculate the height between the two 60 degree markers? I feel like I'm missing something fundamental >.>... I have the total arc length what am I meant to do with it?

[Anonymous No.9832213]

>>9831711
The following is handwavery that can be made rigorous using the mean value theorem.
Interpret the [math] \int [/math] symbol as the [math] \sum [/math] symbol and [math] dx [/math] as [math] \Delta x [/math] .
[math] \int_{a}^{b} f(x) dx = \int_{a}^{b} \frac{dF(x)}{dx} dx = \int_{a}^{b} dF(x) = \int_a^b( F(x_n)-F(x_{n-1}) )= F(b)-F(a) [/math]

[Anonymous No.9832217]

>>9831711
>>9832213
Also, watch this:
https://www.youtube.com/watch?v=rfG8ce4nNh0

[Anonymous No.9832284]

>>9831653
Please someone help an autist

[Anonymous No.9832549]

>>9828629
probably the orbits of the action of the groupoid

[Anonymous No.9832619]

>>9831828
>>9831938
By parallel I meant parallel if it was portrayed in 2D space without the curvature. So like lines of latritude are "parallel".

[Anonymous No.9832633]

>>9832619
Although now I see what you mean as Longitude is debately parralel or not...

[Anonymous No.9832657]

Would it be possible to calculate the distance from an object using a spyglass or scope or whatever knowing only how much the magnification is and knowing the height of said object, which occupies the entire height of the lens?

[Anonymous No.9832764]

how would I start 45?

[Anonymous No.9832774]

>>9832619
>By parallel I meant parallel if it was portrayed in 2D space without the curvature. So like lines of latritude are "parallel".
good luck making the rigorous definition

[Anonymous No.9832790]

>>9831775
this doesn't say anything. of course when F(x) is defined to be the area under f between 0 and x, yeah well no shit that F(a) - F(b) is the area between a and b. but how do you know that F is precisely the antiderivative ?

[Anonymous No.9832793]

>>9832764
AD^2 + r^2 = (AB + r)^2
I would assume.

[Anonymous No.9832797]

>>9830877
I would assume that science has become enormously specialized, even trying to stay knowledgeable in one field can require a lot of effort, but if you have to do that for many different fields and different science, then you truly have a problem.

[Anonymous No.9832935]

Good books on combinatorics? Never did it properly at uni

[Anonymous No.9833105]

Do any of you mathfags 'think' through your keyboard? As in, can you use LaTeX as fluently as you could pen(cil) and paper to work through problems?

>>9832935
See Lovas'z work on the topic, it's canonical but probably more than you're looking for.

[Anonymous No.9833107]

>>9830877
cuz we cannot git gud these days

[Anonymous No.9833124]

>>9832764
Find AC by utilizing the Pythagorean theorem and substract AB from it.

[Anonymous No.9833131]

>>9832764

[Anonymous No.9833154]

>>9832935
stanley's enumerative combinatorics

[Anonymous No.9833185]

>>9832764
What a fucking trivial question. The circle isn't even needed. Or they should not have written r everywhere.

[Anonymous No.9833209]

>>9833105
I don't. At least not yet. I am fast, but I don't consider it fluent, usually because I think before typing.

[Anonymous No.9833441]

>>9833209
do you not think b4 u write?

[Anonymous No.9833445]

Interesting problem that came up at work:

I have persons, S, A, B, and C. For each person I have:

-their 3D orientation vector (which way they're facing)
-their 3D position vector relative to some origin somewhere far away.

I want to label persons A, B, C as Left, Center, and Right, based upon person S's perspective, and he is looking at them.

Since there is no rhyme or reason about which direction A, B, and C are facing, the only way to solve this is to:

1. Find A, B, and C's coordinates relative to the coordinate system defined by whichever way S is facing, and then:
2. Sort them by x-coordinate (in S's perspective coordinate system) and label accordingly

The way to do this is to throw an affine transformation at A, B, C's position vectors, yes?

[Anonymous No.9833446]

>>9833441
I mean I think a lot b4 writing. Like in how should I write down this sentence, etc.
It pretty much only wastes time, because improvements of text should come after.

[Anonymous No.9833487]

I have a BS in Biochemistry with a 3.6, will that be competitive enough to get my into engineering masters programs? I feel like I'm last in line since I don't have an engineering undergrad.

[Anonymous No.9833507]

If a big bang happened behind the event horizon of a black hole, would mass be added to it and will it even be detectable?

[Anonymous No.9833681]

Which methods would you guys suggest for analysing this data set? There are ~80 observations.

[Anonymous No.9833717]

>>9816387
Can we really call genetic engineering evolution? In what terms do we even describe conscious manipulation of an organisms own genetic code.

Sapient evolution?

[Anonymous No.9833723]

>>9833487
Some graduate programs look to diversify their incoming student. If you took a good amount of engineering coursework you should be good. But if you didn't I would give it a try but don't expect anything. Maybe go for bioengineering?

[Anonymous No.9833736]

This might be top brainlet but I'll ask anyway.
If you prove that the number of elements in a set is equal to the number of elements in the set of natural numbers (N), and then prove that a part of the first set is also equal to N, do you get a contradiction or no?

[Anonymous No.9833740]

>>9833723
What would be considered "engineering" course work? I took calc 1-3, p chem, analytical chemistry, eng. Phys 1&2. Most of my upper division coursework was protein related though. I never took linear or diff equations.

I want to work in oil/gas/manufacturing/logging type work so bioengineering is a no

[Anonymous No.9833749]

>>9833681
I'm trying to determine which of the DV's (a-d) are significant in predicting sales.

[Anonymous No.9833795]

>>9816387
>describe your thought process if you're stuck
you're*

[Anonymous No.9833943]

>>9831938
t. has never taken a geometry course in his life

[Anonymous No.9833965]

>>9833736
>If you prove that the number of elements in a set is equal to the number of elements in the set of natural numbers (N), and then prove that a part of the first set is also equal to N, do you get a contradiction or no?
No, a simple example of this happening is 'a set' = integers and 'a part of the first set' = the even integers

[Anonymous No.9834125]

This is probabl stupid, but why:
[eqn]
\frac{dP}{ds}(s+ds)=\frac{dP}{ds}(s)+\frac{d^2P}{ds^2}ds
[\eqn]

[Anonymous No.9834127]

This is probabl stupid, but why:
[eqn]
\frac{dP}{ds}(s+ds)=\frac{dP}{ds}(s)+\frac{d^2P}{ds^2}ds
[/eqn]

[Anonymous No.9834129]

>>9834127
The operator is homogenous.

[Anonymous No.9834137]

Please please help an induction brainlet.

Proof that for [math] n \in \mathbb{Z} [/math] such that [math] n \geq 0 [/math] and every [math]r \in \mathbb{R}[/math] such that [math] r \neq 1, \sum\limits_{i=0}^n r^k = \frac{r^{n+1}-1}{r-1} [/math]

[Anonymous No.9834138]

Is it me or the tex thing isn't working anymore, i see them all in plain text

[Anonymous No.9834139]

>>9834137
What have you tried?

[Anonymous No.9834140]

>>9834137
What did you try brainlet? This is literally middle school arithmetic.

[Anonymous No.9834154]

>>9833795
Wrong.

>>9834137
Induction base: trivial
Induction step: try to write [math]r^{n+1}[/math] as a fraction of the form [math]\frac{\ldots}{r-1}[/math].

[Anonymous No.9834240]

[math] \frac{\partial^2 u}{\partial t^2} = a^2\frac{\partial^2 u}{\partial x^2}, 0<t<kx, k>0 [/math]
[math] u(0,x) = \phi(x), \frac{\partial u}{\partial t}=\psi(x), u(kx,x)=\chi(x) [/math]
Is the solution well-defined if k>a?

[Anonymous No.9834243]

>>9834240
[math]\frac{\partial u}{\partial t}(0,x)=\psi(x)[/math]
fix

[Anonymous No.9834295]

how flexible is the human mind? can someone of average intellect truly learn anything through hard work?

[Anonymous No.9834326]

>>9834295
Not anything. There are limits (though not fixed) which come from the amount of effort you can do and how much time you have.

[Anonymous No.9834357]

Does anyone know why some physical calculators don't take operator precedence into consideration? Are these hardware limitations? Also, why does the windows standard calculator not take it into consideration either?

[Anonymous No.9834368]

>>9834357
>Does anyone know why some physical calculators don't take operator precedence into consideration?
Designed by idiots.

>Are these hardware limitations?
No, if you use the right hardware, you can do that perfectly fine, it just requires more effort.

>Also, why does the windows standard calculator not take it into consideration either?
The answer is again: "designed by idiots".

[Anonymous No.9834377]

>>9820004
>>9820222

Wouldn't the correct term be "reciprocal", not "inverse"?

[Anonymous No.9834410]

>>9833736
No. This is actually the case for all sets that can be bijected with N, since N itself has proper subsets that can be be bijected with itself (and these subsets are more than N itself).

[Anonymous No.9834419]

>>9834137
Induction is literally doing a bunch of simple operations in this case.

A better way is:
[math]
S:=1+r+r^2+ \cdots + r^n \\
rS=r+r^2+ \cdots + r^n +r^{n+1} = S -1 +r^{n+1} \implies \\
(r-1)S = r^{n+1}-1
[/math]
And if [math] r \neq 1 [/math] then you can rewrite the above as [math] S= \frac{r^{n+1}-1}{r-1} [/math] .

[Anonymous No.9834424]

>>9816387
Hello
Is there a general method to solve a linear system of ordinary differential equations, when the coefficient matrix is NOT constant?

[Anonymous No.9834426]

>>9820004
Because the derivative of the inverse function is equal to the inverse of the derivative of the original function, and the determinant of the inverse matrix/map is 1 over the derminant of the original matrix.

https://en.wikipedia.org/wiki/Inverse_function_theorem
https://proofwiki.org/wiki/Determinant_of_Inverse_Matrix

[Anonymous No.9834427]

>>9834424
>Is there a general method to solve a linear system of ordinary differential equations, when the coefficient matrix is NOT constant?
As long as the coefficient matrix is diagonalizable, there should be no problem.

[Anonymous No.9834433]

>>9834424
I don't know, but maybe getting it to Jordan canonical form and exponentiating it?

[Anonymous No.9834442]

>>9833445

project A,B,C's positions onto the line orthogonal to S's gaze (front-back) and vertical orientation.

[Anonymous No.9834449]

Why is my brain such a bitch? I've been working at this job on/off for 2 years, yet it still has anxiety/panic attacks over fucking work that isn't for 2 days, that thing it has to do because it's too lazy to focus on anything else in it's life.

[Anonymous No.9834523]

>Context
I want to fit Polygon A into Polygon B, my idea was to find the longest line from one edge that goes through the middle of the polygon, do that for both and scale A so the max line of A is the same size of the one from B.
I take the average of the points from each edge to get the middle, but how do I get the length of a line going from one edge through the middle until it hits a side.
There is probably a really easy formula for this, but well. Maybe someone can help.

[Anonymous No.9834566]

>>9833681
>>9833749
Fit appropriate glm to data with respect to sales, then conduct wald test on coefficients where null is coeff=0, and alternative is coeff=/=0. Keep explanatory variables where you reject the null, that coeff=0, but as always use your gut.

[Anonymous No.9835087]

>>9834427
Yes it is diagonalizable but the eigenvalues depend on t.
What comes after diagonalizing the matrix?
Sorry, all sources that I can find are about ODEs with constant coefficients.

[Anonymous No.9835187]

Sorry if this isn't /sci/ related. But I didn't know where else to post this.

I found this old gold ring in the attic.

How do I tell if it's gold-plated or solid gold?
Also what purity and it's value? It's 4.01g in weight.

>precious metals thread I guess

[Anonymous No.9835437]

>>9835187
Just bite it or drill into it

[Anonymous No.9835454]

>>9835187
Use nitric acid on a scratch. If you see any reaction (bubbles, greening) the ring is plated, gold won't react.

[Anonymous No.9835512]

I recently started playing poker and I feel like it's harder to make a straight than a flush, but flush is ranked higher.

How do we count the possible combinations that make a flush vs a straight.

Here is how I tried to calculate it:

Flush: (13*12*11*10*9) * 4 = 617 760
Explanation: different combinations for a flush of any one suit multiplied by number of suits

Straight: (4*4*4*4*4)*10 = 10 240
Explanation: different combinations for any straight (A - 5 for example) multiplied by number of possible straights (10 possible straights; can start with any card from A - 10)

Would someone please explain to me why I'm wrong?

[Anonymous No.9835597]

>>9835512
nevermind, found it on leddit

https://www.reddit.com/r/poker/comments/g4otb/math_question_why_is_a_flush_better_than_a/

[Anonymous No.9835612]

does doing a task while experiencing pleasure positively reinforce that task? for example if I take opiates while doing math or masturbate while doing math while I gain a disposition for and find greater pleasure in doing math?

[Anonymous No.9835627]

>>9835612
You'll gain a disposition for doing math badly because you'll be too distracted to do it well. Then again, I don't know how well you hold your opiates.

[Anonymous No.9835634]

>>9835627
well maybe but that wasn't really my point. I was asking more about the nature of positive reinforcement in general. More abstractly, does combining a pleasurable activity with a neutral one make one more likely to want to do it or find more pleasure in doing it alone?

[Anonymous No.9835735]

Is this a correct way to express the following statement in math notation?

If m and n are positive integers that are also perfect squares then m + n is a perfect square

What I have:

[math]\ S = \{x^2 | x \in N\} [/math]
[math]\forall m \in \mathbb Z_+ \forall n \in \mathbb Z_+((m \in S \wedge n \in S) \rightarrow (m + n)\in S) [/math]

[Anonymous No.9835783]

>>9835735
>Is this a correct way to express the following statement in math notation?
yes

[Anonymous No.9835948]

On another planet that also has an atmosphere, would the sky still be blue due to how light and shorter wavelengths work?

[Anonymous No.9835998]

>>9835948
For Rayleigh scattering (which is the reason why the sky is blue) with the kind of small molecules which are likely to make up an atmosphere, the amount of scattering increases with wavelength. But there may be other factors involved (e.g. absorption) which affect the overall colour.

[Anonymous No.9836448]

On the right side of the (b) part, wouldn't it be possible for A(y) to be TRUE, A(z) to be FALSE, and yet have z = y to be TRUE? How is this possible?

[Anonymous No.9836530]

>>9836448
A(y) =/= y
A(z) =/= z

[Anonymous No.9836544]

>>9836530
if y = z then A(y) = A(z). If x = z is true A(y) = A(z) is also true

[Anonymous No.9836547]

>>9836544
(y = z)*

[Anonymous No.9836685]

>>9834326
got any studies to back this up?
does anyone?

[Anonymous No.9836816]

I use my smartphone in place of a desktop computer. But in this hot weather the battery drains a lot faster and it takes longer to charge. I understand copper and aluminum are among the best thermal insulators. So when I charge my phone I leave it lying on a flat sheet of aluminum I have from an old computer case. It's only 1-2mm thick. But I notice it does bring the temperature down 2-4°C.

My question is, theoretically what would be the best surface to place my hot smartphone on to cool it down most effectively and as fast as possible? I presume a copper surface is more ideal to place the phone on. How thick does the plate need to be? At what point does the thickness of the plate become redundant in changing the temperature of the phone?