/sci/ - Science & Math

Newbie. I keep seeing t. _____. What does that mean?

>>9940534

t. noobie

>>9940534
>I keep seeing t. _____. What does that mean?
terveisin
https://en.wiktionary.org/wiki/terveisin

>>9940526
why does the tip of my dick burn for half an hour if I fuck up the timing between pissing and jerking off?

http://www.chrobotics.com/library/understanding-euler-angles

the matrix to get from inertial frame to vehicle-1 frame obviously makes sense, and so does the matrix for getting from vehicle-1 to vehicle-2. but I don't see how simply multiplying them together gets you a matrix to get from inertial frame to vehicle-2 frame. the first matrix is just a rotation about x. the second is just a rotation about y. multiplying them together second*first means "rotate about x, then rotate about y". meaning "rotate about inertial frame x, then rotate about inertial frame y". it doesn't mean "rotate about inertial frame x, then rotate about vehicle-1 frame y".
so it seems like theres a missing step.
how does multiplying the matrices mean a rotation about vehicle-1 frame y and not inertial y?

>>9940548
Miksi?

>>9940526
When using the law of signes. Why does multiplying both sides in the denominator come out so,it's a fraction times the sine.

So let me give you an example. Say you use the law of signes and set up a problem.

Sin 73/12= sine b/11.

So the answer is multiply both sides by 11 then take the inverse sine of the left to find b.

When you multiply sine 73/11 by 11. Why does that equal 11/12 x sine 73. Is it just rearranging the fraction? Wouldn't it be more like solving the fraction first then multiply by 11?

>>9940687
Sorry meant sine73/12 x 11.

>>9940526
So for this integral, I know that if I substitute the 1/2 part for anything with abs value between 0 and 1 it will evaluate to 0, 1 and it's not defined while > 1 it will be nonzero.

However I don't understand how the results are obtained when I try to explicitly evaluate the antiderivative to get nonzero.

http://www.wolframalpha.com/input/?i=int+(+1%2F2+*ie%5Eit+%2F+(1%2F2+*e%5Eit-1)+)+dt,+t%3D0..2pi

http://www.wolframalpha.com/input/?i=int+(+1+*ie%5Eit+%2F+(1+*e%5Eit-1)+)+dt,+t%3D0..2pi

http://www.wolframalpha.com/input/?i=int+(+2+*ie%5Eit+%2F+(2+*e%5Eit-1)+)+dt,+t%3D0..2pi

Is it possible to reduce lat/long coordinates to XYZ spherical coordinates into a matrix?

would it be strange to email professor about interest in getting undergrad research experience (unpaid) with him only a week before the semester starts? I would probably suggest an in person meeting too in case he wants to do something like that. Should I attach my resume or something?

>>9941125
It’s totally to ask a prof for u dergrad research position a week before, even during the semester is fine. If he is interested, he will ask for a resume himself and then you wil most likely discuss research in person. Also, try to either get credit hours for you research (most colleges have that option) or get payed (valid option if the prof is rich. I got payed 14/hour for three years of undergrad research).

>>9941145
>totally to ask
Totally ok to ask

>>9940599
This, I need to know this too

>>9940747
You're missing that it's an improper integral

How do I find mean squared error of 2D angles in a relatively fast way? I also have additional weight/accuracy for every measurement which could be used too, but it's not that important.

>>9941113
>xyz spherical coordinates
wut

Roughly how fast could i lern all of math that is taught basicly from scratch (im not old and i want to be ahead of my peers but i never really paid attention at school i just did it then somewhat forgot the topic like i was in a trance) all the way to the general level they teach at the universetyes assuming that these three are true.

Slightly above average memory. ( If the average person would remember lets say X% id be able to remember 50% more.)

Not being as dumb as the average joe (infact not being that domb at all im even worse (philosophy joke)9 but sadlly currently not having enough processing power to just immitate von neumann.

Profound motivation to lern it. (Doing it evry day for round 8 hours if the need should arise)

I would wanna hear your opinions because im courious and i know this isnt the place for seriuos questions but i have limited resouces currently.

Also sorry for the stupidity of this question and spelling (not english).

>>9941165
* I mean how to find an angle that minimizes mean square error, not just mean of squared errors.

>>9941175
You need to go back all the way as far as you find easy. If that means math at a 5th grade level, then start there. Start doing problems, don't guess, don't cheat. Every week you should start moving up grade levels and topics. Spend longer on the introduction to major topics, particularly exponentiation, polynomials, the concept of functions, and trigonometry. Spend a lot of time graphing things by hand once you're comfortable with functions.

I've taught first year calculus for a while, and the vast majority of why people do badly is their basic algebra/trig skills, not failing to understand rate of change.

>>9941177
Angle of what? Draw a picture? I can't grasp what you're looking for yet.

>>9941186
OP here. Yes that is my intention starting from scratch since a holled wall isnt exactly sturdy.

But lets say you would have to start from scratch roughly howlong would it take you?

And howmuch time did you dedicate to lerning math howmany years (example: 5 years 3 hours a day or something...)

I find it usefull having a timeframe and cause im serious.

>>9941175
If you already have a profound motivation, as you say, why should it matter how long it takes? Why is everyone always concerned with how long something will take as opposed to it's feasibility. Go out and get started now, that's the first step in making it take less time

>>9941201
Well since by knowing time it is more economic and endorphines get released if you are back petted. But yes i apreciated your advice and thanks.

>>9941194
Well, there isn't much to draw.
I have n angles, all starting from some common ray. I need to find such an angle α that has minimum sum of squared errors, where error is difference between angle α and given angle. The tricky part is that difference between angles is never over 180 degrees, eg 355° and 5° is just 10° apart.
Sorry if my terminology is a little off.

>>9940675
pls help
I feel like I must have some fundamental misunderstanding of linear transformations

Going through some old analysis notes and my brain isn't working at all. How do I prove that a closed and limited real interval contains it's maximum and minimum value?

>>9941250
ok i get it now thanks to http://web.cse.ohio-state.edu/~wang.3602/courses/cse5542-2013-spring/6-Transformation_II.pdf
that slideshow makes a distinction in thinking about transformations with respect to the global frame (inertial frame in the other page) vs the local frames (vehicle frames) and says you just do the multiplication "backwards" if you're doing it the latter way. which I swear I never learned taking linear algebra. but i see how it kind of works now.

>>9941321
Meant to type closed and bounded here.

>>9941349
Since it's bounded, it has a sup and inf (this is thanks to the spanking completeness of the reals). And since the interval is closed it contains all of its limit points, so it must also contain its sup and inf.
Or something like that.

>>9941358
Thanks. I didn't realize sup and inf are also limit points, but that's trivial to show.

>>9941235
Sounds like you need some edgecase-roundtrip algorithm like simplex-tableau.

>>9941370
well not necesarily, a bounded discrete set has sup and inf, but they are not limit points. anyway, you don't need any topology really, just show that the supremum of [a,b] is b, but that's trivial.

>>9941113
Your question is poorly worded

I don't know what you're asking, but you should read up on spherical coordinates (r, θ, φ) in general, and if you know Trig you should be able to figure out how to convert to xyz CARTESEAN coordinates. You can put any set data into a matrix, spherical or cartesian.

Why does everything under the radical become 4? Shouldn't they all stay with the 2 coefficient?

>>9941575
Length is [math]\sqrt{x^2+y^2+z^2}[/math]. Two squared is four.

>>9941575
no, because you square. if a vector has coordinates (x,y,z) then its magnitude is sqrt(x^2 + y^2 + z^2)

>>9941586
>>9941589

Of course. I guess I was just expecting to see
sqrt((2t)^2+etc). He just skipped past an intuitive step. Thanks anons

If a resin is UV resistant and doesn't turn yellow, does it mean that something under the resin that is not resistant will also stay pristine?

I mean does UV resistance blocks UV rays or just UV rays dont affect the material?

what trickery happened to the k term?

>>9941731
double angle identity

>>9941746
>tfw bad precalc performance is still biting me 3 classes later

does the Ni(en)4 2+ complex chelate exists?
nickel ethylenediamine

>>9941642
Its a pretty vague question desu. It depends on the amount of UV you're putting on and for how long you're putting it on the target you aim for.

Why does thinking about something really cute give me a feeling similar to drowsiness?

Are there any specific resources you guys use/used to improve your academic writing and/or fluency in the use of citations?

>>9942354
Normal everyday exposure to sun, it's a keychain, would like it to stay pristine for years or even decades

Please bear with me number theorists, I'm just an applied brainlet.
I was thinking about prime gaps and how 2 and 3 are the only consecutive primes. Is there anyway to prove this, without prior knowledge of 2 and 3 being prime?
I tried using Fermat's Little Theorem but to no avail.

okay i thought i figured it out but i didn't

to describe the orientation of an axis you can use three angles, and people use lots of different standards for the order and name of these angles. that isnt important to my question exactly. the point is that, for example, let's use the yaw pitch roll standard. first we rotate around z by an angle yaw, then using the coordinate frame that rotation produces, we rotate about y' by an agle pitch, and finally using the coordinate frame THAT produces, we rotate about x'' by an angle roll. this makes sense and the page http://www.chrobotics.com/library/understanding-euler-angles has very good pictures about it.
HOWEVER
they say that the matrix for a linear transformation to describe that orientation is done by simply multiplying the familiar rotation matrices.
I don't see how that's true, because those matrices are for rotations about the global frame; what that page calls the inertial frame. not the local frame post-rotation.

as in like, Ry*Rz (where Ry and Rz are the matrices for rotation about y and z) I would think make a matrix for a transformation that says "rotate about z, then rotate about y". on that page though, they have it to mean "rotate about z, then rotate about the new y axis that that rotation created". they even specify explicitly that it's not a rotation about the inertial y axis, but the local y axis. I don't fucking get it.

>>9942482
When you multiply the matrices, you're composing the rotations. So when you multiply by Rz and then Ry, you actually are rotating about the new y axis that the z rotation created.

>>9942469
2 divides all even numbers greater than 2
t. complete moron

>>9942502
I get that I'm composing the rotations but doesn't Ry*Rz*v mean "rotate v about z, then rotate that resultant vector about y"? it doesn't mean "rotate v about z, then rotate that resultant vector about the new y created by that rotation about z"

>>9940678
no vittu miksei

are tennis balls yellow or green?

>>9942517
it's not sequential, you could combine Ry*Rz into one matrix R and do R*v, both rotations apply simultaneously to v

>>9942621
what the fuck
then i have a fundamental misunderstanding about how transformation composition with matrix multiplication works

I mean it is associative though, R*v is the same as Ry*(Rz*v)

>>9940526
Sleeping Beauty will participate in a little experiment. She will be put to sleep on Sunday. The experimenter will flip a coin. If it lands heads, he will wake her up on Monday. If it lands tails, he will wake her up on Monday, and then before she goes to sleep, will wipe her memory of the past day, so that when she wakes on Tuesday she won't know whether it's Monday or Tuesday.

Sleeping Beauty wakes up. The experimenter asks her what the probability is that the coin landed on heads. What should she answer?

>>9942621
like listen fucker,
Rz*v produces another vector v'.
Ry*v' rotates v' AROUND THE FUCKING Y AXIS
NOT AROUND THE NEW LOCAL Y AXIS FORMED BY THE FIRST ROTATION

>>9942616
Greenish Hue.

>>9942636
>>9942668
nvm, i fucked up, i just woke up
i checked the link and the author could communicate better since it's complicated, but maybe you should think about it in "inverse" compared to what the picture shows, like you're not taking an neutrally oriented airplane and pointing it in its actual direction, you're rotating the airplane to put it into a local frame of reference

>>9942672
whaaaat
how do you discern that

>>9942674
like pic rel instead of >>9942482
the relevant coordinate system that you're doing the next rotation in is the red one

>>9942675
I still dont see how the basic rotation matrices are used for these local coordinate frames

>>9940526
>>>/wsr/551858

>>9942668
> NOT AROUND THE NEW LOCAL Y AXIS FORMED BY THE FIRST ROTATION
Yes, around the new local Y axis formed by the first rotation.

(Rx*Ry)*v = Rx*(Ry*v)

Imagine Ry*v not just as the point obtained by rotating v by Ry, but as a set of points forming a diagram illustrating the rotation. Rx*(Ry*v) rotates the entire diagram by Rx. So Ry is a rotation about the local Y axis established by Rx.

Each transformation transforms the entire coordinate system. Any subsequent transformations are interpreted in the coordinate system established by the previous transformations.

Note that matrix multiplication isn't commutative: A*B isn't (in general) equal to B*A.

>>9943112
>Ry is a rotation about the local Y axis established by Rx.
That's backwards from how I was thinking
I can't really think of this in terms other than sequential operations on a vector, in your example it's "rotate about y then rotate about x". But you're saying more like "Rx*Ry*v gives a vector that can be thought about as having been rotated around x THEN around the y' axis formed by Rx, but that vector is not what would result if you took v, rotated it about y, then rotated it about the new local x".

Because I mean, objectively speaking, Rx*Ry*v rotates around the global y then rotates around the global x. But you're saying you can think about it differently; it gives the same result as if you thought about it rotating about x, then rotating about the new local y formed by that first rotation.

>>9943205
and if this is the case, that website I linked is doing it in the wrong fucking order still.

>>9943226
unless the website just didn't bother to fucking add the detail that the plane is in some weird orientation to start with, and we use first roll, then pitch, then yaw to tell us how to get it back to its "regular" position facing north (on inertial x axis, as in just pic related)

and we use yaw then pitch then roll to describe a weird orientation if we start from pic related, but the matricies the website gives are not FOR that. right? it's been over 2 whole fucking days that I've tried to figure this out. I'm going to kms

>>9943256
and I forgot the pic
fuck literally everything

>>9943256
well yea the web page is for how to use a sensor so i think that's the point, the plane or robot or someth is what it is and you're interpreting the sensor data from the plane/robot point of view

>>9943262
okay so what would the matricies be for starting at the inertial position like in that pic, THEN yawing, THEN pitching, THEN rolling, as they SEEM to show in the page? is it just reverse the order of multiplication?

So the Heine-Borel covering theorem states that for every compact [math] S \subset \mathbb{R}^n [/math] that is covered by an union of open sets, there exists a finite subcover.

What if the original cover is made up of a finite number of open sets in the first place? In that case can the original cover itself be considered a valid subcover? Because if you remove a set from this original cover you might in some cases end up with only a partial cover of [math]S[/math].

what am I doing here?
I thought that I would take the derivative of f and y and plug those values in but im not getting the right answer with that

>>9943378
By differentiating you get the velocity vector (sint , 1-cost). At time 1.25*pi this is (-1/sqrt(2) , 1 + 1/sqrt(2)).

>>9943360
>for every compact [math] S \subset \mathbb{R}^n [/math] that is covered by an union of open sets, there exists a finite subcover.

That's the definition of compact. Heine-Borel says a subset of [math]\mathbb{R}^n[/math] is compact iff it's closed and bounded.

>What if the original cover is made up of a finite number of open sets in the first place?

Then that's your finite subcover.

>>9943360
Yes, obviously. A set is a subset of itself

>>9943427
>>9943429
Thanks. Yeah I messed up, should have wrote closed and bounded instead of compact there.

https://en.m.wikipedia.org/wiki/Davenport_chained_rotations
ok I think this answered whatever else I was confused about

>>9942658
I would say 50%. It's a fair coin and there was a single coin flip, so she knows the probability is 50%.

If she wakes up on Monday and knows that it's monday, the coin landed heads so she can add that to her answer. However the probability of landing heads was still 50%.

If she wakes up and doesn't know what day it is, she knows the coin landed tails, so she can add that to her answer. The probability was still 50%.

>>9942658
1/3

>>9942658
>>9943452
>>9943516
well fuck it's a trick question, it depends on how you want to interpret it, from an outside point of view it's 1/2 because it's a fair coin toss, but from her point of view she would get waken up twice if it's tails, so there are three different cases where the experimenter could ask her the question, hence 1/3

Profitable fusion reactor WHEN

Can someone explain this to me

>>9943548

Let's say I have a random vector with multivariate Gaussian distribution. Is there some quantitative way to judge how many random samples of this vector I need so that the sample mean and sample covariance are reasonable estimates for the actual mean and covariance matrix? Note that the actual mean and covariance matrix are not known.

About to start my sophomore year. I want to start applying for work in my field, but I've never applied for a lab before. Could I get suggestions/ripped to shreds please?

Friends, I need to learn some calculus topics (Limits/Derivatives up to Taylor and Mac Laurin) in the next 72 hours, what's the to-go resource for this situation? bear in mind that I have some calculus knowledge but I'd prefer to follow something structured instead of trying to fill the gaps.

thanks.

I don't know whether I should major in Physics or Chemistry. Any advice?

>>9943644
Chemistry if you want a job where you do practical stuff. Physics if you want to be truly enlightened but also either jobless, teacher or research slave.

>>9943644
chemistry if you want to be a titration cuck

I'm having problems understanding why z = 0 is the only branch point of the logarithm function. It's clear why it's the case for that point, but why isn't it true for every other point of the complex plane? Wouldn't you get a different value of log if you go around a loop around z = 1, for example?

>>9943685
>Wouldn't you get a different value of log if you go around a loop around z = 1, for example?
Why would you?

>>9943762

Let's say I go around a loop around z = 1 of radius [math]\epsilon[\math]. From the definition [math]\log z = \log re^{i\theta} = \log r + i \theta[\math], you start with [math] \log z = \log r [\math], since the phase is zero and end with [math] \log z = \log r + 2\pi i [\math], since the phase is [math]2\pi i[\math]. There's clearly a mistake with this rationale, but I can't see where.

>>9943762

Let's say I go around a loop around z = 1 of radius [math]\epsilon[\math]. From the definition [math]\log z = \log re^{i\theta} = \log r + i \theta[/math], you start with [math] \log z = \log r [/math], since the phase is zero and end with [math] \log z = \log r + 2\pi i [/math], since the phase is [math]2\pi i[/math]. There's clearly a mistake with this rationale, but I can't see where.

Let's say I go around a loop around z = 1 of radius [math]r[/math]. From [math]\log z = \log re^{i\theta} = \log r + i \theta[/math], you start with [math] \log z = \log r [/math], since the phase is zero, and end up with [math] \log z = \log r + 2\pi i [/math], since the phase is [math]2\pi i[/math]. There's clearly a mistake with this rationale, but I can't see where.

>>9943762
Let's say I go around a loop around z = 1 of radius [math]r[/math]. From [math]\log z = \log re^{i\theta} = \log r + i \theta[/math], you start with [math] \log z = \log r [/math], since the phase is zero, and end up with [math] \log z = \log r + 2\pi i [/math], since the phase is [math]2\pi i[/math]. There's clearly a mistake with this rationale, but I can't see where.

>>9943956
Sorry, I messed up. I meant:

From [math] \log z = \log (1+r) e^{i\theta} = \log (1+r) + i\theta [/math], you get [math] \log z = \log (1 + r) [/math] at the beginning of the loop and [math] \log z = \log (1 + r) + 2\pi i [/math] at the end of the loop.

As far as notation goes, aren't these the same thing? Like the partial derivative with respect to x, just different notation?

In a class I'm taking, the professor asked us to take the partial derivative of a function with respect to x, then take the partial derivative with respect to y, and then df/dx, so I'm trying to figure out if df/dx is something different, or if he's just 'avin a giggle.

>>9944006

mechanically, they are essentially the same, that is taking a partial derivative involves holding all variable save one constant. Notationally the curly d symbol is used when the function is a function of several variables.

>>9944006
https://en.wikipedia.org/wiki/Total_derivative

Why does this integral have 2 different solutions?

>>9944057
[eqn] \ln (a \cdot b) = \ln (a) + \ln (b) [/eqn]

>>9944073
So the ln(2) disappears into the C?

Why is 11/12*sin 73 = 11*sin73/12

>>9943956
theta is the argument of z, i.e. the angle relative to zero, not relative to the point you're looping around.

Why aren't we sending remote controlled rovers to the moon? Why send them to mars whit all the lag and other communication issues when we have a perfectly valid, easy to land on planetoid just next door?

So I do not really get why the product rule makes sense.
The definition of conditional probability makes a ton of sense to me intuitively, just the proportion of (a and b) constrained to the outcomes where b is true

But why does the product rule make sense? Do not get me wrong, I am totally aware that you can easily derive it from the definition,
I just do not get why multiplying the conditional (on b) with b makes sense.
Even if probabilities are unitless, could P(A, B) be seen as having "higher dimensionality" (and consequently something like P(A,B,C) being higher again)?
I realize I do not really get why multiplying probabilities makes sense (even if division sortof does).

>>9944311
the moon sucks

>>9944412
Don't judge a book by its cover, also don't judge a celestial body by its surface layer.

Seriously though, the thing is tidally locked to us, there's also a Lagrange point between us that would make it even easier for an astronaut to control any equipment sent there, if it was necessary. And telepresence is becoming a thing now with all the VR craze going on, we may no longer need to send any expensive life support for astronauts to work there, just some RC droids that can work even better than a dude in a clumsy suit. Just because the moon is a wasteland doesn't mean we can't take advantage of it, hell maybe we'll discover something revolutionary if we're lucky.

HOW DO I CONTAIN MY AUTISTIC SOUL-YEARNING FOR MORE SPACE EXPLORATION GOD FUCKING DAMNIT?

WHERE IS THE JAMES WEBB TELESCOPE AND WHY HASN'T IT ALREADY BEEN IN SPACE FOR TWO YEARS ALREADY?

WHY DON'T WE HAVE TEN DIFFERENT KINDS OF SPECIALIZED HUBBLE 5.0 TIER TELESCOPES ON THE MOON AND AT EVERY LAGRANGE POINT ALREADY?

WHY ARE WE TAKING WHOLE GENERATIONS TO MAKE TINY B-GRADE UNSATISFYING DISCOVERIES, WHEN REAL HARDASS NIGGA SPACE EXPLORATION IS WAITING FOR US AND WE COULD BE FIGURING OUT WHAT THE COSMOS ITSELF IS

WHY IS ELON MUSK SPENDING TRILLIONS OF DOLLARYDOOS TO MAKE A TUBE THAT TRANSPORTS FAT PLEBS AROUND TO LIVE THEIR PLEB LIVES, AND COMMERCIAL SPACEFLIGHT SO FAT PLEBS CAN LITTER THE ATMOSPHERE WITH MORE MICRODEBRIS AND FAST FOOD CONTAINERS, AND WASTE COSTLY ROCKET FUEL, WHEN WE COULD BE USING ALL THOSE RESOURCES FOR AMAZING INTERESTING THINGS

>>9944006
If [math]f=f(x)[/math], then [math]\frac{\mathrm d f}{\mathrm d x}=\frac{\partial f}{\partial x}[/math].

If [math]f=f(x,y)[/math], then [math]\frac{\mathrm d f}{\mathrm d x}=\frac{\partial f}{\partial x}+\frac{\partial f}{\partial y}\frac{\partial y}{\partial x}[/math].

In short, taking the partial derivative is like taking your normal derivative (holding all but the variable constant), and taking the total derivative will require you to invoke the chain rule. In functions of one variable, both notions will coincide.

>>9944057
every time you see the same antiderivative with different answers, the answer to your question is
>it's in the constant

>>9944472
pitch it on shark tank

>>9944510
Shart Tank

>>9944488
I think that's what the professor is wanting us to do, thanks!

>>9944041
Thanks!

Do numbers exist?

>>9944647
My digits exist, check em

Why is engineering so gay?

lmao, what is wrong with these sickos, they say a 50% margin on office supplies is normal, but do they even realize how many potential customers could just click the next google result, when you're selling bags in packs of 1000, even a big-budget company is going to be wary of spending $50-100 on bags that actually cost $10 to buy in bulk, buying online instead of retail isn't even inconvenient, the good online stores have a 1-2 day delivery time and you don't have to drive to some obscure store and deal with those douchebags in person

>>9944914
50% minimum that is

and well yeah i have high margins but i'm more specialized than office supplies and packing materials and i have competitive prices

Can any atom be turned into an ion? You take the atom's name and add ions to it? Ionized cobalt would then be cobalt ion?

Can a ionic bond be formed between all atoms? All they need is the opposite ion charge of each other?

Are there any special attributes to a positive hydrogen ion as it has no electrons at all?

Why don't atoms change into different atoms when ionized?

>>9944412

And Mars doesn't?

I took apart a car battery yesterday to get the sulfuric acid and lead. I accidentally got a few little cuts on my hand which began to sting while handling the innards. This morning, my hand is a bit swolen and stinging.

I'm just wondering how dangerous it is handling sulfuric acid and lead?

>>9945114
Dangerous enough that you should see a doctor.

...Also, far too many posts on 4chan require a response that ends with those five words.

>>9945117
Please elaborate? I kept handling the materials to a minimum and thoroughly washed my hands afterward. It's shocking how heavy lead is.

Another point. I tried melting the lead about 1/4 of the plates on the stove top, but only got a few small bits.

If photons are the force carries of electromagnetism, how come magnets don't glow in the dark?

>>9945135
quantum memes

>>9945135
They do just not in a visible wavelength.

>>9945187
no they don't

How much energy does a single thought use up

>>9945439
>How much energy does a single thought use up
depends on whether you're a brainlet or a brainiac

>>9945441
then what would be the average

Why don't humans have tails?

>>9940747
Again

If I have something measured to be 2.5inches (2 significant figures). And convert it to centimeters, how many significant figures does it have now? 2.5*2.54=6.35 but im not sure how many signings it would have.

>>9945528
We reached a point where the utility of a tail no longer outweighed the resources it takes to grow and maintain it. Evolution doesn't like expensive vestigial elements, the movement is always towards optimization

>>9945771
The conversion factor is assumed to have infinite sigfigs (because an inch is EXACTLY 2.54000... cm). So your answer needs 2 sigfigs. (6.4 cm)

>>9945135
Permanent magnets do not release energy. I know it seems like they do, but they don't.

And AC electromagnet could in theory be made to glow in the dark. The ones you power up at home glow in radio waves.

>>9944647
That's a matter of opinion. You are discussing the Platonist vs. Formalist schools of thought in mathematics.

>Be Math graduate student
>Get sick 2nd semester in, fail a class
>Somehow adviser(god bless him) and I pull off a hat trick and get my Masters before the school can kick me out of the PhD program(they literally gave zero fucks about my situation)
>Want to get my PhD and do math research but I'm sure that that graduate class F has eternally tainted my prospects
>Literally me
What should I do now? I was advised to go teach at a community college and do research on my free time, but I never garnered any math research skills during my time in graduate school

CS with data science major here

Should I stay on track to make bank as a data scientist or follow my heart and get into bioinformatics research?

I'm a brainlet, I barely passed my GED science test by guessing, where I can I learn what was actually on the test so I don't feel so dumb.

>>9946045
you could probably do bioinformatics research with a data science degree, just make more money. all data science is, is the ability to perform statistical analysis without understanding the principals or maths behind the analysis

Do all things with energry and/or mass exert and are affected by gravity?

Do elementary particles have a set gravity constant?

Asked in gravity thread as well. Not sure I fully understand what gravity is.

>>9946040
are you not able to retake classes 1-3 times to attempt to improve the grade (even if the old one might still be printed on your already attained degrees) ?

>>9946050
coolmathgames.com

>>9946211
Not for graduate level classes I'm afraid, it's permanent.

>>9946152
>Do all things with energry and/or mass exert and are affected by gravity?
Yes.

>Do elementary particles have a set gravity constant?
No.

>Asked in gravity thread as well. Not sure I fully understand what gravity is.
Science hasn't stuck the pin on that one yet either.

Most of matter's mass is caused the dance between massless bonded quarks in its atomic parts, which also grant its internal clock, and is why you need energy to make this mass move, and why matter can't reach the speed of light (as opposed to massless things, which always travel at the speed of light when in a vacuum). The pace of this dance changes in a gravity well. Energy not involved in this dance o'mass can also create gravity.

Questions remain as to whether are not there are gravitons, what their nature might be, and how to make gravity work in a way that agrees with both relativity and QM, and stick that all into the standard model, hopefully for a working TOE.

>>9946152
>>9946239
>Do elementary particles have a set gravity constant?
>No.
Wait... Misread that as "do all elementary particles have a se gravity". Many particles are massless, and thus no, but they also have energy. This pales in comparison to the mass created by the bound particles in protons and such, but, if ya get enough in one place, then ya got yourself some gravity, and, for non-half spin particles, ya can get as many in one place as ya want - at least until they go all singularity on ya.

I don't understand the second fundamental theorem of calculus

Can someone confirm that this answer?

Basically set the moment around B to zero. w*2 = NAsin60*(4+3cos30) + NAcos60*3sin30. I get 804N apparently the answer is 3220N.

I asked someone else for their answer, it uses a different w value but everything else is the same. They followed the same process I did but got the right answer. Either I'm really dumb or this question is fucked.

>>9946395
ok so the function F(x) has been defined, and so below that we want to find F'(x).

Let's say that k(t) = int f(t)
or equally that k'(t) = f(t)

Evaluating that integral in the first line of your image will give us F(x)=k(x)-k(a)

Differentiating with respect to x, assuming a is a constant and then so is k(a), we get:

F(x)=k'(x)

but we already know that k'(x)=f(x)

Thus F'(x) = f(x)

>>9946421
so does the choice of a matter here or do all a's on the interval where f is continuous give same results?

Can i get into paleontology through a history degree?

>>9946421
F(x) is not a function but a number.

>>9946486
x is clearly a variable, so F(x) can't be a number

Is this an incorrect way of expressing this?

What is the scientific reason for European superiority?

>>9946492
no

>>9946496
Widespread homosexuality and the lengths people went to hide it.

>>9946499
Then why do non-European cultures practice, and have always practiced, mass pediohilia and child sacrifice?

>>9946496
better climate, natural resources, access to the sea (not landlocked as much), having to plan for the winter etc, causing europeans evolve to be more intelligent and more harder working, if you didn't have an AC this summer you would know how utterly useless people would be in for example an african climate

>>9946508
also europeans and east asians have up to 20% neanderthal dna and dna from other archaic humans

Good econometrics books?

>>9946507
The church has done the same, so it evens out to become a non factor.

>>9946508
>if you didn't have an AC this summer you would know how utterly useless people would be
True, I could hardly be bothered to lift a finger during that period of hell on earth.

>>9946460
yes it should apply for all a and x such that f is integrable on [a,x]. F'(x) will always give the same value but F(x) will change with choice of a because only F(x) is dependent on a, as shown in my simplified forms of the two functions.

>>9944076
Yep, the C in each solution are not equal

>>9944085
In the order of operations, division and multiplication have equal priority. Try it with any three numbers e.g. a,b,c. a*(b/c) = b*(a/c).

>>9946748
is it because division is just multiplication where one of the numbers is strictly between 0 and 1?

>>9946767
a/b = a*(1/b)

>>9946774
you take that back

>>9940526
Why can't we find a way to use solar power? The amount of energy that reaches the Earth's surface over the course of a single day is something like all of the energy humanity has ever used combined. Or something, some huge amount.

>>9944377
Ok so P(A n B) is the prob. that A and B happen. So if one is statistically dependent on the other, and if one happens first, then you multiply it by the other given the first (which is just the other if theyre independent), since the first already happened (sorry probably a shitty explanation)

>>9946784
>Why can't we find a way to use solar power?
something something oil companies stifling research something something

>>9946801
But I mean practically. I guess solar cells aren't efficient enough yet and there isn't enough land or whatever but there's gotta be a way. We could have floating solar farms on the ocean or GMO biofuel or giant solar farms in subsaharan Africa.
Or energy storage. Or we could include the efficiency of the internal combustion engine (that wouldn't fix global warming but it would help).

>>9945905
How would a tail become useless? What changed in apes that made it so?

>>9946885
bipedalism?

Is there a DNA ancestry test thing that isn't either run by Mormons or a company that freely hands over all my info to a pharmaceutical conglomerate? Am I being overly paranoid about the possibility of big pharma having my genetic data?

>>9940599
this

>>9946885
How many branches do you find yourself needing but unable to swing from on a daily basis, anon?

Why do we commit things to memory and learn methods of doing things when computers and programs can do all those things for us and doing them by ourselves is inefficient?

does econometrics fit in /sci/? I don't know where else I can ask this not even on other sites

https://web.stanford.edu/~gentzkow/research/fakenews.pdf pages 228-229 [don't worry the link is only a 16 page extract of a journal]

I am trying to make sense of how a linear regression is explained. I would appreciate literally any snippet of knowledge about the table on p229 even like what the p-value means or how there are random negative numbers when the range is 0-1 for variable C. Like anything you might be able to offer on this is appreciated as I understand nothing at all

>>9946971
It's generally more efficient to have the knowledge at hand rather than look it up, and you have to understand that knowledge intuitively to apply it in innovative ways.

...and for the most part, we don't. Most people only memorize knowledge that pertains to their field and social circles. Most other things we look up as needed, though we inevitably pick up some "useless trivia" just by being alive. Those who spend time debating on the internet for the sake of debate pick up more than others, but usually just enough knowledge to be a good demonstration of the Dunning-Kruger effect.

>>9946971
computers are stupid, someone has to program them

>>9946496
Maintaining a major overseas trade hub that gave them access to advancements from all over the world and having a culture that encouraged ambition more than most. This, coupled with getting hit by the black plague in a society that tracked inheritance well, lead to massive wealth concentration and redistribution, which created the perfect storm of knowledge spread (via the resulting printing press, encouraged by the Bible) and entrepreneurship that lead to the renaissance followed by the industrial revolution. As a result of all that, Europe was so far ahead everyone else that no other civilization could catch up, nor help becoming resource pools for that machine, regardless of any genetic advantage they may or may not have had.

China and Japan had a slight chance of riding this wave of advancement early on, but both went into isolation at about the same time (which is also was slowed Russia a bit). The key factor is that Europe never went into isolation, and was always ready and eager to adapt foreign concepts and technologies, putting in considerable investment to acquire them.

>>9947221
yeah but why not just program them instead of memorizing those books?

>>9947218
I guess you're right. Is there any point in learning a new language though?

>>9944377
imagine scaling down the conditional a to suffice for all outcomes. the result of the product is the smaller and less magnified outcome in the, usually, entire probability space. like zooming out of the venn diagram from the b condition and zooming out makes your probability proportionally smaller

>>9947463
not everything is suited for a computer, and you need to learn how to use the program, an advanced program like mathematica can certainly be useful for some specialized tasks but you still need to know a ton of math as well as the wolfram language and various quirks of mathematica to be able to use it effectively

>>9947490
eventually the world will get so advanced that regular humans like those of today won't be able to understand the basics and technology will become like magic

Could you smart anons help me with this? I'm at a loss here, and I'm pretty dumb with physics.

>>9947565
I don't see any equations I can form to get those results.

>>9947567
what did he mean by this?

>>9947463
>Is there any point in learning a new language though?
Have you ever *tried* to communicate in another language in real time using a computer as a go between? The tech just ain't there yet.

Now, as to why we haven't settled on a global language yet, and made sure everyone speaks it fluently, well, I suppose that's a more valid criticism of man.

>>9940687
I'm assuming you mean (sin(73))/12, rather than sin(73/12). multiplying then dividing is the same as dividing then multiplying so yes it's just rearranging, they are the same thing.

Is Khan Academy the best resource to start learning math again or are their any good books on for this?

>>9947636
Oh fug. I meant to ask if I could get an explanation as to how it would reach the answers it has.
a) 1/4w1
b) 1/2w1

>>9947662
We have, English. Almost everyone is with the program by now.

>>9947715
You've not travelled much, have you.

>>9947736
Not that Anon, but I have. Shit, even amerindians know the basics like yes or no in Bolivia.

>>9947741
Ya can "get buy" with English as a tourist in most places (just as centuries ago you could with French - albeit, not quite as universally), but you cannot hold a conversation for shit, even in places where they teach English in grade school. (In part because most of the populous doesn't use it after that, and because they tend to teach their own strange variant of it.)

Plus, the policing on the language is so poor, that folks speaking the same English language in the same country often have trouble understanding one another. Which leads to comedy:
https://www.youtube.com/watch?v=HIBQB91iK-g

posted this on another board so i will just copy and paste


I am a CS student that has been up too long and I need some help.

Given a set of characters a-z A-Z 0-9, whats the total amount of combinations if the string is limited to 5.

e.g a valid string would be AbC12

(the total number of usable characters would be 26+26+10 because uppercase and lowercase alphabet plus 0-9 so 62)

I have looked all over the internet and I see a wide range of varying answers, some describing permutations and some combinations and all of them containing different formulas. Can someone give me a decisive answer please?

AAAAA is a valid string.

abc12 and abc12 are counted as the same string (so no repeating combinations)

is it just 62!

(sorry if this post is all over the place, been awake 36 hours and once I sort this I can sleep)

>>9947753
im a retard...

Hi /sci/ would really appreciate a quick response if possible. Basically I'm a university student and ive been unable to attend most of my lab classes and so my lab proficiency is pretty poor. I'm taking repeat lab classes and working on improving but its definitely my weakest area.

I am doing a lab report on Polymerase Chain reaction with gel electrophoresis. Aside from getting messy and generally poor results, I had one participant have no bands appear (as opposed to atleast one expected and present in all other lanes) in the electrophoresis results. What I would like to know is what the potential cause for this could be as I am very weak in this area with not much background knowledge for labs.

PFA my results. Very messy, unclear but this is what i have to work with. Left is 100bp marker, right is pBR322/BstNI marker. 4 participants each with an undigested control and then a digested PCR product. The lanes are A undig/A Dig/ B undig/ B dig ....

Thanks for the help, my report is due soon and I am just trying to finish my discussion section.

>>9947762
Also please note the lanes with the missing bands (ie the 6th and 7th lanes) are where I would like clarification on potential issues that I could include in my report.

>>9946748
I probably need to study that a lot more somewhere.

I'm pretty sure that I was just taught that you solve from left to right when the order of operations is equal.

Does that mean that anything involving multiply and dividing can aways be done in any order?

>>9947712
it's the lazy way.
Not that it's necessarily bad, but if you want to continue doing more advanced stuff you might want to try books instead. You might want to tell us at what level you are so we can recommend something. Gelfand has 4 low level books, Lang has Basic mathematics, axler has precalculus.

How do you guys deal with knowing you've been self destructive since high school, and it's entirely within your power to improve your life. Yet you continue to waste everyday making no progress on your goals?

>>9948242
>Lang has Basic mathematics
Lang is a meme.

>>9948278
>How do you guys deal with knowing you've been self destructive since high school, and it's entirely within your power to improve your life. Yet you continue to waste everyday making no progress on your goals?
I'm not like that.

>>9948278
I remind myself that 40 years from now I will be dead and how "good" or "bad" I lived my life, if these standards exist at all, wont make any difference.

inb4 pickle rick

hey guys, i have a babby tier programming problem that i'm stuck with. just highschool level c++. i have to make an implementation of linked lists. i'm getting a SIGSEGV, and i've been trying for hours to solve it, but no matter what i do, it's not changing.
I know it's a very common and low level topic, but i don't want to just copy-paste someone else's code because i want to sincerely learn programming.
Is this the right board/ thread for this, or do i go somewhere else for my homework help?
and if this IS allowed here, how best do i post my code( ~150 lines), copy paste it here or take screencaps and post it as an image?

>>9948278

always try to do at least one unit of work every day, at least one proof, one page read, one paragraph written, etc.

just sit down and start. if you can only manage an hour, a half hour, it's better than nothing.

>>9948383
Either you're a 40 year old who likes pickle rick or expect to die in your early 60s, you don't seem qualified to give life advice

>>9948476
Go to >>>/g/

>>9948492
thanks my dude

What does this mean and how do i do it?

help I've lost all of my confidence in my math ability out of nowhere
>started college fall 2017 doing intermediate algebra
>aced it, turns out I didn't suck at math after all
>spring 2018 passed College Algebra relatively easily
>Summer A 2018 passed Precalculus relatively easily
>Summer B 2018 take trig as a 6 week accelerated summer class
>Got through first half of Trig relatively easily
then suddenly it all went to shit
when they put tests and quizzes in front of me, I just froze. I forgot everything. Even if I'd studied the night before, I just... completely blanked
it's not that I didn't understand the material, I just start panicking for no reason during the test and forget how to even start problems. This happened with every quiz or test thereafter

I had my first calc lecture today with a preliminary diagnostic quiz, and it happened there too. I don't know what the fuck's going on
I've never had test anxiety before and now it's turning into a positive feedback loop eroding my confidence and skill in math

how do I stop it before it gets out of control? I need to be on my game for Calculus

>>9948789
I guess testing yourself would help. Find old exams on the internet and do them at home without aids.

>>9948736
you have the trajectory as a function of time. The question asks for set of points of the 2D path of the particle (the x,y pairs that satisfy that equation are points the particle passes).

Since you want the points for all times, set x = t-5 and y = t^2 + 2 and eliminate the time from the equations.

Btw, what's the website or program you're using for those questions?

>>9948818
It's a website my school uses. the problems are provided by the professors. thanks for the info.

>>9948789
Stop being a fag, tests are irrelevant. For academia it helps to get a good average, but networking and research are always more important, just focus on getting gud and ignore test results, study what you think it's necessary and don't worry about it

>>9948818
wouldn't the answer be
y = x^2-10x+27?

What's a good cheap balance? I don't need resolution smaller than .001g, really don't NEED less than .01 though mg would be nice (I have a shitty little barely-accurate mg scale around from forever ago, the generic druggie kind you see everywhere that can't do any decent quantity and is a pita to work with). I'm mostly just measuring reagents, making agar mixes, etc

What's the best bang for buck in terms of reliability/accuracy/longevity with Chineseum or used balances? These B30002T are on eBay and various places for pretty cheap and some Amazon folks said it was decent. I suppose I could get a mechanical one as well.

>>9948988
check aliexpress feedback, the popular ones have pics of people testing them with calibration weights and coins

>>9948820
>fag
Why the homophobia?

>>9948242
Basic arithmetic desu

>>9949193
yes, definitely khan academy, dont waste your time reading

is this a scam

https://www.youtube.com/watch?v=YWig9qg1lnE

>>9949272
its not just a scam
its the perfect scam

Can someone explain this to me? I don't math

>>9949669
What exactly don't you understand?

>>9949682
How do subtract 20,000 from both sides then divide by (1.08)^2

>>9949691
Do you know what subtraction and division are?

>>9949712
Yes?

>>9949669
1 = 1 subtract 1 from both sides
1 - 1 = 1 - 1
0 = 0

>>9945124
Washing your hands isn't always enough. You're probably fine just by rite of the type of lead you were handling, but you would be better off making an appointment with a doctor and talking with them about it.

Most likley scenario is they tell you that you're fine and just to try not to cut yourself up in the future.

>>9949734
doctors could be retard expensive where he lives

>>9949733
I don't get it though
Why is the X/(1.08) being taken away from -20,000/(1.08)^2?

>>9949737
True but considering I live in the country that's known for having retard expensive docs I would say that there's a very fair chance that even then a single visit for consultation is probably not going to be the end of the world for them.

I asked /engi/ this but no one replied.
How difficult is it to find an internship? Are applications open for summer openings during fall or spring semester? What do I put on a resume if I have no projects under my belt? I’m only good at math and ciruits with nothing but grades to show for.

Study and note taking tips for math, more specifically 3 dimensional calculus.
Anything important to know? I havent taken calculus in over a year. Last math class was differential equations
and electricity/magnetism.

ik it's dumb but how would you calculate square roots of a complex number with only a simple calculator?
Both real and imaginary parts.

>>9940599
Youre tearing your urethra unknowingly and your piss makes it burn whereas cum does not

>>9949901
[eqn] z = a + bi \\
\pm \sqrt {2z} = \pm \sqrt{\sqrt{a^2+b^2}+a} \quad\pm i\sqrt{\sqrt{a^2+b^2}-a} [/eqn]

>>9940526
Brainlet here confused about the multivaluedness of the complex log.
If we have
[math] n \ln(e^{\frac{2 \pi i}{n}}) [/math]
It seems like we can either bring [math] n [/math] into the exponent getting [math] \ln 1 = 0[/math]
or cancel the log and exponential getting then [math]2 \pi i[/math]. Is the expression just badly defined?

>mathjax not working on both phone and laptop
what do?

>>9950154
> getting [math] \ln 1 = 0[/math]
Should be
[math]\ln 1 = 2 \pi k i[/math]
for any integer k (including but not limited to zero).
If you mean the principal value of the logarithm, then it has to be zero, as that's the only value within the range (-π,π].

For complex numbers, ln e^x either isn't necessarily equal to x (if you're referring to the principal value) or has infinitely many values, only one of which is equal to x. Either way, you can't simplify ln e^x to x. Or e^(ln x) to x.

More generally, you can't simplify f(f^-1(x))=x or f^-1(f(x))=x if f isn't a bijection.

Let [math]R[/math] be a ring. Is the quotient [math]R[x]/R[/math] just the zero ring? Or am I being a brainlet?

>>9950490
turn off adblock

>>9946486
Ok sure F is the function, so F(x) is then a variable but the point remains that F(x) has been defined. You can refer to F(x) as a function mapping x onto the given integral.

newfag to this board
>school dropout neet
>basically skipped all high school years with an exam at 20 (22 now)
>terrible at math if that means anything
>want to start fixing my shitty life by taking trade school at least
>have absolutely no talent or interests
been searching around and the only close to my home (and to catch my eyes) is electrical engineering, no other engineering options in my city
is this a good pick to take a first step?
I have noticed there's an engineering general but I think my stupidity fits better here

>>9950960
Work on your math skill at Khan Academy, starting where you feel comfortable. From there, sky's the limit

>>9951016
will check it out, thanks for the suggestion

>Some plants have toxins for defense.
>Some of these toxins are used as an anti-inflammatory.
>The total opposite of the function.
>Why the fuck.

>>9940526
what does this mean?

f : x |---> 10 x

Can I skydive in an O'neill Cylinder if I'm starting from the axis of rotation?

>>9951210
Cocoa tastes good to humans and is good for our body.
Cocoa tastes good to dogs and will kill them.

Our biology differs in more ways than form.

>>9947244
Mongols giving a wakeup-call surely helped too.

All hail Economic Espionage!

>>9947762
Applies to most competence problems...
>You can read up on the subject matter (and do some exercises from the book) maybe even train basic operations so you won't fuck up?

>>9951220
f(x) = 10x

>>9951289
thanks

>>9951220
as the other anon said, but in general that type of notation (the arrow with the bottom) means or signifies where that element is being mapped to

in this case x is being mapped to 10x

I have the function in pic related and I need to graph its derivative.
I know that if the function is increasing its derivative will positive and if the function is decreasing its derivative will be negative. Extreme values have a derivative of zero.
But how do I find out the concavity of the derivative and its inflection points? Does anyone know?

>>9948789
Check out http://tutorial.math.lamar.edu/Extras/StudyMath/HowToStudyMath.aspx

>>9951220
f := {(x,y) element of RxR| where y = 10 x} = {(x,y) element of RxR| where y - 10 x = 0}

>>9951365
Maybe you should Google those Questions. Looking it up in your Textbook might also work.

>>9951463
>R
what did he/she mean by this

>>9948789
http://professorconfess.blogspot.com/2013/06/all-remedial-classes-in-one-place.html

Applies to College Algebra too, probably as he calls it: "It’s called College Algebra because nobody would pay for a course called The Algebra You Should Have Learned in High School."
>A large minority of students in College Preparatory Algebra II are non-traditional. They took and passed the material years ago, but have simply forgotten it, or at least are extremely rusty. While spending four months reviewing in college is a painfully slow and expensive way to go about regaining these skills, I can appreciate not everyone has the initiative to go down to the library, check out a book, read and re-read and practice for a few hours until the skills come back. I’m sure administration would never suggest such a course of action to a student, not with a sweet student loan check on the line.

>>9951485
real numbers i'm assuming.

>>9951493
>real numbers i'm assuming.
Why would real numbers be involved?

>>9951468
I already did and I couldn't find shit. You will only find khan academy videos telling you trivial shit like what are first and second derivatives used for.
I asked my teacher and he couldn't answer it, he looked like he was drunk or he hadn't got any sleep.
This kind of shit doesn't appear in textbooks either.

>>9951468
If you actually understood my question you will see that you can't find shit on google. My question is equivalent to finding the third derivative of a function by merely looking at its graph.

>>9951365
> I have the function in pic related and I need to graph its derivative.

The function's peaks, troughs and horizontal points of inflection are the zeros of its derivative. The function's points of inflection are the peaks, troughs, and horizontal points of inflection of its derivative.

So you have zeros near -1, 1, 2, 3, 5. Trough near 0, peak near 1.5, trough near 2.5, peak near 4, trough near 5.5, horizontal asymptote tending toward zero from below.

Locating peaks and troughs of the derivative means locating points of inflection of the function, i.e. where the curvature is zero, i.e. where the graph crosses its tangent. Determining the values at peaks and troughs requires measuring the slope.

>>9944486
Thing's aren't so easy. it took us 1400 years to figure out calculus, it will take us much longer to figure out space exploration. It will get faster or slower depending on what we value as a culture. To value science we need to believe as a society that there is a single immutable truth and that there is a greater purpose to everything ( a mystery of meaning). Since our culture has been poisoned by relativism (the belief that there is no single/valid truth) and cutlural-marxism/post-modernism (the belief that truth is unattainable and there is no higher purpose to life) the progress will come MUCH slower, and once THEY have control over STEM, then progress will halt all togher over arguments about how particle physics i sexist because of its asymmetry (or dumb shit like that). Therefore unless this third wave is stopped in its tracks you can expect we will take MUCH longer than we should, or we will stop altogether, or we will go back technologically for "muh nigger voodoo is science too".
/blog

tl;dr - the progressive cool-aid won't let me have sex with space tentacles and /pol/ was right again.

>>9946971
There once was this girl in grade 12
who could not count inside her head
she had a math problem, a child could solve
but she relied or her calculator instead

so once she came to the equation
it brought dread for saying "no calculator"
10 minutes were left
she found out quite soon
that she could not solve
10 * 22
God gave you a brain that can do nearly anything, if you rely on things of mans own creation to do the thinking for you then you've wasted a gift. The greatest mathematicians figured out the most efficient algorithms to solve IN THEIR HEAD, they did not rely on an abbacus, nor a computer. Likewise you should not if you want to achieve your full potential.

In the volume of the human brain sits a supercomputer more powerful than all of the ones that have ever been on the planet or ever will be, and which is dynamic and self-driven/self-directing ontop of that. You are the pinnacle of creation, own it.

>>9951794
This is too defeatist. I hate the (insert post-modernism world) you have described as well, however it's foolish to assume that barriers to scientific advancement are somehow greater than they were circa AD 600. Seriously, people were just trying to not die before the age of 30, contract one of a hundred diseases that will make your limbs rot, or get burned at the stake. To think today is somehow worse than 1400 years ago for science is extremely edgy.

>>9951807
>To think today is somehow worse than 1400 years ago for science is extremely edgy.

didn't say it is worse. Just that without healthy culture and philosophy science will go nowhere. Everything these parasites touch withers:
https://books.google.ca/books?hl=en&lr=&id=y3AHb4dJy30C&oi=fnd&pg=PA21&dq=feminist+science+physics&ots=PVbC6apIl5&sig=uf_sDpDwzvMC8oz6Zj4iW9Q6fEs#v=onepage&q=feminist%20science%20physics&f=false

currently feminist science is its own thing, but if the same cucls who let 5 guys girls fuck her way into good gam ratings have any say, then we will see a temporary of permanent death of scientific progress. Of course this is just a worry for the moment, but if it ever becomes fruition then its gonna suck a lot more then the loss of those other industries.

>>9951847
bad spelling, shit connection.

>>9951509
Why would numbers be involved?

I don't understand how direction of gradient is always perpendicular to the level curve. This isn't true for real shapes like hills, right?

>>9951884
It is.

https://www.reddit.com/r/MathHelp/comments/88gji2/need_help_with_directional_derivatives/
I can't understand the answer, please help

how the FUCK do feelings and perception persist through time

>>9951999
CAREFUL ANON YOU'RE DOING PHILOSOPHY NOT SCIENCE, PULL BACK!!

QUANTITY AND REIFY! QUANTIFY AND REIFY! FEELINGS ARE JUST UHH.. UHH, THEY'RE.. FUCK! FEELINGS ARE JUST FUCKING..... ELECTRONS! YEAH! THEY'RE JUST ELECTRONS AND NEUROCHEMISTRY AND TIME IS JUST WHAT WE MEASURE WHEN WE USE A CLOCK AND IF IT CAN'T BE MEASURED IT'S NOT REAL SO CONSCIOUSNESS IS JUST CLOCKS AND ELECTRONS

PHEW

>>9952003
the more i read the less any of it makes any sense

>>9951365
The zeroes of the derivative are at the local maxima/minima, and also as the function tends to zero, so does its derivative. So the first thing you can do is draw in the point where the derivative crosses the x axis.

It is hard to see exactly when the derivative changes from increasing to decreasing, but it can be seen that it is approximately at the midway point of each peak/trough. Hence you can draw in the vertical line through which the local max/min of the derivative must be in.

Steeper parts of the curve correspond to steeper derivatives since you have to go "more negative faster".

>>9951884
Suppose flat ground is the xy-plane, and a hill is defined by its height function. That is, a hill is a function of two variables and the height at any point depends only on which position of the hill you're looking at.

Now imagine you climb about halfway up a hill and rest there for a second. If you want to move to the other side of the hill without going up to the peak (because it is too tiring for your fat ass), you can instead just go around it without changing your height. This means you're moving precisely on a level set of the hill.

However you're not only lazy, but also clumsy. You trip on a small rock and fall. The gradient tells you precisely in which direction you're going to fall. Hint: you're going all the way down, you're not going to fall along your path

>>9952003
this but unironically

>>9951924
nigga what dont you understand

if you want the directional derivative along some direction, just do the dot product of the gradient with that vector and done.

>>9952051
>if you want the directional derivative along some direction, just do the dot product of the gradient with that vector and done.
wrong in general

>>9951999
Same way everything else does - causal connections.

Maybe - not quite sure how the point of perception thing works. Feelings are a bit more straightforward, we just put more value behind them than the simple fact we experience anything at all.

Closest thing you get to science, in that regard, is asking the question as to why we experience this particular moment and sequence of time - rather than any past or future time we might exist in. Which, I suppose, some of the more fringe GUT efforts are hoping to answer:

https://plus.maths.org/content/why-block-time

But like all caps there (>>9952003) is alluding to, if it ain't empirical, it can't be scienced. Doesn't mean it doesn't exist, as this is true of a number of very fundamental things, just means you can't use the scientific method on it, and it's outside the purview of science. Might change someday, but it may also be some things will always be beyond such analysis.

>>9951863
>Why would numbers be involved?
10 is in the definition of the function.

>>9952058
the gradient is literally defined to be so. if you're referring to some sort of differentiability issues, then go fuck yourself

>>9952127
yes, I'm referring to some sort of differentiability issues. coincidentally the reddit thread mentioned in >>9951924 is EXACTLY about why "nigga just dot product with the gradient" doesn't always work. congratulations on making a complete fool of yourself.

>>9952088
>doesn't have the brain capacity to understand some variables are labelled as "10"

>>9952143
>>9952127
>if you're referring to some sort of differentiability issues, then go fuck yourself

should I copy all proofs when taking notes?

>>9952145
>doesn't have the brain capacity to understand that labelling something by a number means a number is involved

What is the evolutionary benefit of narcissism? Can’t understand why there are still so many of them. Outside, I mean.

>>9952302
>what is the evolutionary benefit of a mental condition
You may as well ask what the evolutionary benefit of schizophrenia is
Also it's important to note the difference between narcissistic traits and full diagnosed NPD, the former having an obvious answer to your question
>what is the evolutionary benefit of looking out for myself
Pretty straightforward

>>9952317
Thanks! I meant the condition itself, but mental health stuff ain’t hereditary, right?

What do I need to do in order to find these angles? the book I'm using doesn't mention it at all.

>>9952375
https://www.varsitytutors.com/precalculus-help/find-the-measure-of-an-angle-between-two-vectors

>>9952161
You should pay attention to them and make an effort to understand them in class. All of the proofs can be found in your textbook, so there's no point in laboriously copying them all down during lecture. I've found it to actually be counterproductive, since it distracts me from the main ideas of the proof itself.

>>9952343
It depends on the disorder in question. Many can be caused by acquired experiences, but there are biological factors that influence mental health as well. For example, there's an autism blood test currently being researched that has 88% accuracy so far, and they're trying to fine tune it up to at least 95%

When trying to prove an implication in logic do you only have to prove for the assumption that the right hand side is correct? Like if I'm to prove A -> B I just prove that is true assuming A is true since if not then the implication is true anyways?

>>9952610
Should clarify that I'm talking about natural deduction.
To prove that the following is a tautology

∃x¬P(x) -> ¬∀xP(x)

I should asume ∃x¬P(x) then instantiate to a constant, asume ∀xP(x) state that it is in contradiction with our constant which in turn proves ¬∀xP(x)

Is that it or am I missing somthing?

Why are vector fields in Calc 3 so confusing to me

>>9952638
Typical symptom of brainletism

>>9952547
thank you, anon

Is doing undergrad research in analytical chemistry worthwhile? I'm going into molecular biology/biotechnology.

is langs basic mathematics a good refresher before going to uni

>>9953036
plz translate pic befor delet

>>9951543
I googled:
>draw derivative graph from original graph

I found stuff. I am disappointed in you. Polish your Search skills.

>>9951794
Should we begin starting secret societies again?
>No Officer. This is just a book club, not a What-did-you-call-it-again U-ni-veehr-ci-ty.

>>9951847
>gonna suck a lot more then the loss of those other industries
Why wouldn't loosing industries (and the knowledge not written down) suck?

>>9953036
No, Lang is trash

>>9953036
cyka blyat anon i went through the efford of translating it myself with russian online keyboard and google translate

top says "CZECH REPUBLIC"
bottom says "BEFORE" "AFTER"

>>9953208
i still don't know what the box at the box is and what the significance of it is damnit

>>9953208
top troll, it says ukraine.
t. hohol

>>9953282
lol it does say ukraine i must have typed the wrong character and then it translated from serbian
yкpaинa
now explain the box

>>9952143
Hey, someone else here.
Why is it not differentiable?

>>9940526
What limits should be for this shape (triple integral in cylindrical coordinates)? For r should it be sqrt(3)<=r<=sqrt(3z) ?

>>9954264
>For r should it be sqrt(3)<=r<=sqrt(3z) ?
think about what that means, your essentially saying that in the volume you are integrating over, there are no points with a distance from the z axis less than [math] \sqrt 3 [/math]