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

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# /sqt/ stupid questions thread

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What did I do wrong here?

can i get some general pros and cons concerning the following majors? please no bullying.

aerospace engineering

biomedical engineering

physics

I've got a glass of roughly 25% vodka, 70% SunnyD and 5% water. Will the mixture keep the vodka from evaporating as fast? I imagine putting it in the fridge will help retain the vodka right?

This is my, well... I'm not quite sure how many I've had, but I'm probably not gonna finish this one tonight but I don't want to waste precious booze.

Pros:

Interesting

Cons:

Over saturated job market

Applies equally to all 3.

imagine putting it in the fridge will help retain the vodka right?

Yes.

Nothing. But you were probably expected to use implicit differentiation.

How do we know that inductive reasoning is valid? If you say "because it has worked in the past", doesn't that require using inductive reasoning to be valid? From a Bayesian perspective, there is some prior that says "induction works", and instances of induction working would be Bayesian evidence that induction works, but it still wouldn't be valid if the prior probability of induction working is small enough.

So assuming space can bend

Can it intersect itself?

Why does alcohol make me constantly hungry, but weed can make me forget about food for a day or two?

the instructions only told me to find the second derivative

Implicit differentiation is pointless when y can be solved for explicitly.

How many points was this worth?

You didn't prove [math]x\ \neq\ 0[/math] before dividing by it and that [math]y[/math] was of class [math]\mathscr D^2[/math]. Also, you should write [math]y\left(x\right)[/math]. A function isn't a number.

10, my professor is an engineer

Your professor is a retard for designing a question with a much simpler solution than whatever he expects you to do

You are an autist boy.

No, I just did two years of math in a civilized college.

I did last time and got marked wrong because my solution was different from my professor's

pic unrelated

I know it's extra-stupid, but could I get an answer to this: ?

Is it because alcohol takes energy to metabolize? Do the active compounds in cannabis not require as much energy to process? What gives?

ask the person that market it brainlet.

Oh right, you're probably too much of an autist to think about making conversation with another person.

Hey people of /sqt/, I'm just curious on whats the best way to use khan academy?

As in should I go though math by subject or math by grade?

Hey guys I'm a real brainlet when it comes to maths and am having some trouble trying to solve this problem I have. I want to find the coordinates of B and D in pic related. I have the coordinates of A and C currently and have calculated the length of each edge and the diagonal length.

The problem is it's a 3 dimensional object and it's on a reasonable angle such that A is much deeper than C.

If anyone could point me in the right direction of what they'd do next that would be super appreciated.

I know this is a very easy question but I don't know much math so I don't know where to look this up.

Anyways let's say you have a deck of cards with an N amount of cards in total. There are only two types of cards: R red and black.

You shuffle the deck and draw 3 cards in a row.

What are the odds of drawing 0, 1, 2 or 3 red cards? How would the formula look like with the variables N (number of cards in the deck) and R (number of red cards in the deck)?

I am supposed to calculate the angle of deflection for a proton crossing the magnetic field of a dipol magnet. The proton is moving perpendicular to the magnetic field. The formula for the angle [\latex] $\alpha$ [\latex] is given by [latex] sin(\alpha )=L/R [\latex] what happens if my radius is smaller than the lenght L of my dipol ?

R choose 0/N choose 3

R choose 1/N choose 3

R choose 2/N choose 3

R choose 3/N choose 3

Best place to download free scholarly articles/material?

if my unit vector ends up being 1.019, have I fucked up? Should it always be exactly equal to one?

I ended up getting:

sqrt(-9.7631/26.5998 + -26.052/26.5998 + 8.15321/26.5998)

= 1.019

i thought unit vector was (1/||v||) * v

Is it theoretically possible to engineer an electrical mechanical master key/device to magnetically unlock any common house lock?

I do:

vi/||v|| + vj||v|| + vk||v||

Not sure if that's the same as you said.

Keep your limit notation until the point where you substitute in the variable.

vi/||v|| + vj/||v|| + vk/||v||

Those have all been over the magnitude, miss typed that.

but lim as x->c of f(x) =/= f(x)

Exactly, that's why you need to keep your limit notation in there.

I did, I was chewed out for declaring f(x)

he didn't even define dy/dx in his solution baka

baka

s.m.h.

anyone?

It's theoretically possible but practically impossible, you'd still need to know the configuration of the pins to unlock it. You can use some kind of magnetic inductor to melt the lock if you want

Why not just pick it?

How do I calculate the vector of two points on a cube?

Have a device do it for you

question doesn't make sense

Isn't a vector a line/direction in space? So I want to calculate the vector that is between two points on a cube

Pythagorean theorem?

depends on which point is the origin

AC is just point C - point A, right?

only if A and C line up horizontally and C > A

How do you work it out if they don't line up horizontally? C is > A in this situation.

AC = sqrt(A^2 + C^2)

How old are you?

What is the deal with women who take math/engineering classes?

Probably older than you.

Comp sci student with one subject left, my first years maths class that i've been putting off forever because I hate maths. I understand the beauty of maths but I really struggle with it and thus completely loathe it.

Let [math]\epsilon>0[/math]. How do I prove that the set [math]\{ x\in [0,1] : f(x)\geq \frac{\epsilon}{2} \} [/math] is finite, for [math]f(x)[/math] being Thomae's function?

by the way it's called the distance between points, not vector

I don't want the distance between the points though. I've already calculated that. I want the vector that is the center of two points.

Where I've circled in this picture. Because I want to rotate it 90 degrees right and left to get the location of B and D

the center's coordinates O(x_0,y_0) are (|x_a-x_c|/2, y_a - |y_c|/2)

I should have said the center to point A. Center (C) being: {37.62465, 21.677315, 12.501505} which is what you were saying, which isn't the vector CA

(x_c + |x_a-x_c|/2, y_c + |y_a - y_c|/2)*

Yes I have the coordinates, I want the vector of Center -> A so that I can rotate it 90 degrees either way and get the coordinates of B and D which are at Z index: 12.501505

This can't be right because the X coordinate it gives is less than the X coordinate of C

If you have the coordinates of the center C and any of the vertices, for example A, then coordinates of the vector from C to A are just the coordinates of A-C. You can rotate this and then add it to C to get the coordinates of the other vertices.

A straight direction down is not equal to it's diagonal direction.

you're trying to get the location of B and D right?

D's x coordinate is the x coordinate of C + short side + long side, its y coordinate is y coordinate of C + long side

B's x coordinate is the x coordinate of C + long side - short side, its y coordinate is y coordinate of C + long side + short side

D's x coordinate is the x coordinate of C + short side + long side, its y coordinate is y coordinate of C + long side - short side*

Why the hell do people in major in Mathematics education? Is it literally because they're too dumb to major in Math? What's the benefit of majoring in the former. Can't you still land a teaching job with a math degree?

so long side is Yo - Yc?

Wouldn't the correct way to do this be to get the vertice that is center to A and then rotate it either direction to determine B and D?

no, that would be the retarded way

newX = centerX + (point2x-centerX)*Math.cos(x) - (point2y-centerY)*Math.sin(x);

newY = centerY + (point2x-centerX)*Math.sin(x) + (point2y-centerY)*Math.cos(x);

I already have the Z coordinate. This is the right way.

What you've done I can't prove to be true.

Does anyone know if its possible to use k-means clustering to identify confounding groups (like the ones in the graph) for regression analysis?

(accidentally posted this in the previous thread)

I hate picking symbols

Let:

ö := the distance between any vertex of the square and the center

s := the length of the sides of the square

Prove that D(x_d,y_d), x_d = x_c + r + p and y_d = y_c + r - p (what I just said in my previous post)

(r + p)^2 + (r - p)^2 = s^2 and r^2 + p^2 = ö^2 implies that for D(x_d,y_d), x_d = x_c + r + p and y_d = y_c + r - p

s^2 = 2ö^2

(r + p)^2 + (r - p)^2 = 2r^2 +2 p^2

r^2 +(2rp) + p^2 + r^2 -(2rp) + p^2 = 2r^2 +2 p^2

r^2 + p^2 + r^2 + p^2 = 2r^2 +2 p^2

2r^2 +2 p^2 = 2r^2 +2 p^2

∴D(x_d,y_d), x_d = x_c + r + p and y_d = y_c + r - p

q.e.f.d

I forgot to include that the vertical distance from D to O is equal to the horizontal distance from C to O and that the horizontal distance from O to D is equal to the vertical distance from C to O

actually, nevermind

A straight direction down is not equal to it's diagonal direction.

No it is not but you can use rule of triangle and find CO via two other vectors

what are you trying to find even?

Is the sum of all points a given distance from a central point equal to infinity?

well there are uncountably many points being summed in that "series", none of which approaches 0, so...

How do you pronounce [math] \LaTeX [/math]?

didn't prove x!= 0

x is a variable, every point at which it is well defined it is also differentiable, no problem

you're second point is beyond the scope of the question

while its true that he should express y as a function it's beyond the scope of the question.

abuse of notation aside he didn't exactly do anything wrong.

the lines without the limit notation aren't directly following from the above lines, he's declaring f(x), working with it to reduce then substituting it back into the original equation.

the only thing you did wrong was forget the 1 in the limit, but you should probably make it clear by writing "consider:" before declaring f(x) or something

Lah-tekh

just say layteks and listen to the autists ree

Isn't this an integral over a surface?

reasoning for why the soil of a plant i've been growing (for a project) contracted a saprophytic fungi? this particular plant was also grown with a .15% NaCl watering solution

If you have a time varying magnetic field, does this mean that a paritcle of charge q will be pulled in one direction for time t before the magnetic field switches?

lateh

What would be the most documentable, reliable and fair way to conduct a prize draw within a sample of ~2000 survey respondents? One respondent will receive a prize.

Anything in R? I already found one solution but decided to ask here anyway.

of course we have random.org but meh

Yes. Conisder it as a sin wave.

How the FUCK do I do this?

My stat mech professor just yanked the value of this out of his ass. It's (pi^2)/3, but I don't know how to get that.

Trig substitution.

I've got a weird question - do you have any assigned textbooks or do your teachers/professors just recommend a couple books and expect you to go through all of them? mine usually recommend around 8-10 books each and I'm not sure how I'm supposed to go through all of this simultaneously

Most people don't read them. Take a look at perhaps 2 of them, the ones you think will be most helpful

Trying with hyperbolics but there seems to be some weird divergences in the integration by parts which is odd because the integral is definitely convergent; it's doubly exponential in the denominator

Is pineapple a good pizza topping?

If kernel density estimation is supposed to help you figure out the distribution of a dataset without making any assumptions as to what the true distribution actually is, doesn't choosing a kernel function kind of render that moot? Won't the choice of kernel function affect how the overall estimated distribution comes out?

that's what I've been doing so far but I can't help but wonder if the professors actually expect me to read them all back to back or just pick a couple and supplement with some additional information from others

You didn't define the metric space.

Wait nevermind, it was an error. It can be done easily by the gamma function.

As the name says, it's an estimation. There's some ways of getting a good guess on the kernel falloff, but you can obviously get very different answers.

It's not a one-size-fits-all solution to the problem.

Gotcha, thanks for the answer.

Since we're on the topic, do you kmow what exactly is meant by efficiency in the context of what makes one kernel function more efficient than the other? Does it mean that efficient functions converge onto the true distribution more quickly?

Can you give a quick rundown of the steps I'd do? How exactly do I implement the gamma function when I only have the negative part of the integral in the right form?

what are the evidences for affirming the existence of the gnathostomata?

what the fuck does he want me to say? does he wants to me describe the evolution of the jaws? synapomorphies? all the differences between agnathans and gnathostomata?

such a vague question

I threw away the paper already, sorry. I'm trying to cram for a biology test. I'm getting absolutely fucked by taxonomy. Probably the hardest course I've taken in college.

It went sort of like multiplying by exp(-x) to put it in a more functional form, then substituting the 1+exp(x), you will then recognize a product of linear factors in the bottom that can partial fraction-ed which at that point you just u sub the lnx to get into gamma forms. I kept changing the bounds as I went along so I might've avoided some symmetry that you could've used to get the half infinite interval that a gamma uses.

If you put it in the integral calculator, you might get dilogathirms and something tells me you can use feynman's parametric or contour integration to do it.

Dude, fuck biology. Go away. There are some clades in Gnathostomata that were previously thought to be extinct. I already forgot the name but you can search something along that line. They're not fossils since they're still living today and satisfy all the apomorphies for gnathostomata.

Some fucking bony fishy shit.

But don't take my word for it. I'm a physics major.

No nigga, gnathostomata is everything with a fucking jaw, you're thinking of coelacanth which indeed is a gnathostomata but so are we homo sapiens

I have no idea what to do for this question. If anyone can help I would appreciate it. I think it has to do with one of the two equations I posted where the in phase and out of phase components are represented by the real and imaginary component of the polar coordinators.

5. During a phase-measuring EM survey, the resultant EM field was observed to have an amplitude 78% of that of the primary field, and lagged behind it with an angular phase difference of 22 degrees. Determine the amplitude of the secondary field of the subsurface conductor and of its real and imaginary components, all expressed as a percentage of the primary.

HELL NO

why would it be?

Fucking rip user. Thanks for your help. Stat mech is cool but just handwaving the integral is gay. Turns out it's a lot more complicated than I anticipated.

can someone explain second derivatives of chain rule multivariable functions to me cuz im a retard? i get everything up to actually taking the second derivative

can someone explain second derivatives of chain rule multivariable functions to me cuz im a retard? i

What do you not understand?

Basically this part. Can you explain why take the chain rule again for this dz/dx and dz/dy cuz my book doesn't explain it

this is 2 real...

I'm extremely slow at mental math, and if I don't use something to keep track like an abbicus or my fingers, I lose my train of thought. Should I kms?

What level are you at?

I wouldn't worry too much since calculators exist, but if you have to do the whole problem again instead of jumping back where you left off then I'd be worried.

This question is supposed to be solved without a calculator using only essential high school trig knowledge (no Taylor series approximation or whatever). As far as I can see, this requires a precise value for either cos60deg or sin40deg.

What is the student supposed to do here?

use trig identities, sum differnce and the other shit

cos60deg

60

?

what is being 60degress there? All angles are 50, 40 and 90

why do women get mad when you look at their cleavage? isn't it the point of it?

If there is an absolute zero in temperature because the movement of particles can't slow down any further, why isn't there an absolute "hot"?

Nothing can move faster than light so even the particles have a limit in speed, right?

Just practice. Most of the points I lost in differential equations I missed because I messed up adding/subtracting and making small algebra mistakes. You'll never get better if you use a calculator though, so just struggle through it.

temperature is more than just the average speed of the particles, it's the average kinetic energy and even though we can say that there is a limit to the speed that a particle can have we cannot say that there is a limit to the amount of kinetic energy that a particle can have, therefor there is no maximum limit for temperature.

asd

How do you take notes? I tend to write way too much so at the end of my semester I have about 100-120 pages per course alone. Makes reviewing kinda difficult.

Not sure but this is what I'd do:

Primary field = [math] A [/math]

Secondary field = [math] kA e ^ {i \theta } [/math]

Resultant = [math] 0.78A e^ {-i 22 \cdot \pi / 180} = A + kA e ^ {i \theta } [/math]

And then solve for k and theta.

One frequency is 32678Hz, the other is 32679Hz, what do you call the difference? 1KHz?

Mistyped, sorry. cos50, sin40.

[math](x^2)^3 = x^6[/math]

How do I properly write the transformation back? Given "x^2 = y" we need to find y^k of x^6

Now, I need to write it properly, how do we transform back? I cant do

[math](y)^k = x^6/x^2[/math] nor can I

[math](y)^k = 2sqrt={x^6}[/math]

What is the correct syntax?

[math](\frac{-9^2}{8})^4[/math]

can someone explain why isnt it the same as:

[math](-\frac{9^2}{8})^4[/math]

since we know the rules of negative fractions:

[math]-\frac{a}{b} = \frac{-a}{b} = -\frac{a}{-b}[/math]

I'm asking because if we simplify the farction we will get

[math]\frac{(-9^2)^4}{8^4} != \frac{(-(9^2))^4}{8^4}[/math]

!= in terms of logical operations, it wont matter with composite power but if it was prime shit would be bad

What? No, [math]-\frac{a}{b}=\frac{-a}{b}=\frac{a}{-b}[/math]

yes sorry that was extra - in the 3rd example

Well, the two fractions with 9 you provided are equal.

Yes, because we have composite power value

Swap it for any prime like -3 or -7 and thins get ugly and for some reason proper answer does not use fraction's negative sign rules

[math](\frac{-a}{b})^{k}=(-1)^k\frac{a^k}{b^k}[/math] for all integer values of k.

Maybe I don't understand what you're asking.

for example

[math]

(\frac{-3^3}{(-7)^3})^3 = (-1 * \frac{3^3}{(-7)^3})^3

[/math]

how do you solve this shit

I think the confusion lies with [math] -9^2 [/math] as this could mean [math] (-9)^2 [/math] or [math] -(9^2) [/math] which are not equivalent to eachother. The rule that you stated would only apply if you are assuming the latter interpretation

I think you mean even and odd? I don't really understand why you would say composite and prime, 9 is a composite number and as far as I understand would cause similar problems if you replaced the 4 or the 2 with a 9

negative integers are not generally considered prime

I think you mean even and odd?

yeah I forgot the words lol

I think the confusion lies with

it kinds is yeah

see

I think the confusion lies with −92−92 -9^2 as this could mean (−9)2(−9)2 (-9)^2 or −(92)−(92) -(9^2) which are not equivalent to eachother. The rule that you stated would only apply if you are assuming the latter interpretation

basically the question is:should be first power of 2 -9 in the nominator or should we first expand the -1 as multiplier of thayt fraction and THEN calculate the power of 2 for 9 (if we are to solve it directly without power rules)

(-7)^3=-(7^3) because 3 is odd

[math](\frac{-3^3}{(-7)^3})^3=(\frac{-3^3}{-7^3})^3=(\frac{-1}{-1}\cdot\frac{3^3}{7^3})^3=(\frac{-1}{-1})^3\cdot(\frac{3^3}{7^3})^3=1\cdot(\frac{3^3}{7^3})^3=\frac{(3^3)^3}{(7^3)^3}=\frac{3^{3\cdot3}}{7^{3\cdot3}}=\frac{3^9}{7^9}[/math], which by the way is just [math]\frac{3}{7}^9[/math]

what are the odds that the local university's geology professor would identify a rock for me? I'm not a student btw

you mean:

[math]

(\frac{3}{7})^9

[/math]

because without parenthesis it is kinda reads diferently

I didn't really understand any of that, but if your asking whether you should treat [math] -9^2 [/math] as [math] (-9)^2 [/math] or [math] -(9^2) [/math] I would say to assume the former, that is [math] -9^2=(-9)^2 \neq -(9^2) [/math], but again it could be either. This is a good example of why it is important to make your equations completely unambiguous.

Very rarely do I see someone intend [math] -9^2 [/math] to mean [math] -(9^2) [/math] usually when someone means to express [math] -(9^2) [/math] they will write it out explicitly and only use [math] -9^2 [/math] to mean [math] (-9)^2 [/math]. Given the context in your first post, this does not seem to be an exception

I plan on switching to a math major but have some holes in my math (due to not caring about math in middle school) I've gotten all As in my calc course and diff EQ but I know I still have to fix my gaps so that I can better understand what I'm doing (although I don't even know if this shit will matter in the higher level courses). Would this be a good book to give me a solid foundation before I apply for the major?

So how would you proceed here:

[math]

(\frac{-9^2}{8})^4

[/math]

Would you consider [math]-9^2[/math] as [math](-9)^2[/math] then thus completely disregarding the - and just doing the equation with positive fraction?

yes, that is the way that I would do it and the way that I believe most people would do it.

what's a good introductory book to linear algebra (I study chemistry)

I am interested in x-ray physics

Forget it. I answered my own question by reading the preface and the forward. I'm such a lazy piece of shit.

32679-32678=1 Hz

1 kHz = 1000 Hz

If im looking at charts in intervals of 24 mins, is the moving average of the past 60 intervals the same as a 1 day moving average?

Please someone post a random non-linear function in terms of not x and y, but for example idk for c amount of cookies you gain f amount of fat. It can be whatever and the function can be made up. Appreciate!

I'm trying to solve the following problem: find how many microstates exist of two quantum harmonic oscillators with frequencies [math]\omega[\math] and [math]2 \omega[\math].

This is basically the same as finding out how many solutions does [math] n + 2m = p [\math] has with [math] n, m, p \in \N [\math].

I can do it with N oscillators of frequency [math] \omega [\math]. It's just simple "stars and bars", but I can't get a simple formula for this problem.

[math] \omega [\math]

[math \omega [math]

$ \omega $

[equation] \omega [\equation]

What's the value of h in this picture?

I've never seen someone write -9^2 to mean (-9)^2, just write 9^2 then.

c^2 = a^2 + b^2

if h = a then

a^2 = c^2 - b^2 = sqrt(c^2-b^2)

if you have only angle then you cant do jack shit I believe you need the hypotenuse and opposite edge lenght so

sin(b) = h/hypotenuse

[math]tan(a)=\frac{x}{h}\rightarrow h\cdot tan(a)=x[/math]

[math]tan(b)=\frac{x+1}{h}\rightarrow h\cdot tan(b)-1=x[/math]

[math]h\cdot tan(a)=h\cdot tan(b)-1[/math]

[math]h=\frac{1}{tan(b)-tan(a)}[/math]

Probably dumb question: how to write tex like that?

not him but use [math] tag and google TeX syntax

oh I'm retarded

I actually googled and realized that knowing the "a" we can find all the angles in the small triangle thus we can find the smaller hypotenuse via 2 angles and one side (1) of the smaller triangle.

Why didn't it work up here, though?

Veeky Forums tags start with "[tag]" and end with "[/tag]"

but TeX uses different special slash - "\"

it'sa mess

Thanks a lot.

Test:

[math] \hbar \omega_0 [/math]

Bump

why does directional derivatives have to have a unit vector(magnitude of 1)

Do you understand what a directional derivative is?

Yes, integrals are linear in boundaries, and the product of the two divisors is exactly the length of the whole interval.

It should be

h = tan(b)/(tan(a)-tan(b))

Elaborate

Why has nobody made a gamma radiation camera using a CCD mounted parallel to the direction of the radiation, instead of perpendicular? It should have a much easier time detecting the photons with gamma rays' higher penetration.

Products after exponents. -x is the same as -1 * x, and -x^e is the same as -1 * x^e. It's not ambiguous at all. If you want (-x)^e you need brackets

Sorry, I messed up. It should be

h = tan(a)*tan(b)/(tan(a)-tan(b))

A solution to finding the square root of -1 (mod 193) reads

[math]31^2 \equiv −4 (mod 193)[/math]

multiplying by [math]2^−1[/math] gives

[math](31 \times 2^−1 )^2 \equiv −1 (mod 193)[/math]

How? I can only see [math]31\times 2^-1)^2 \equiv \frac{189}{2} (mod 193)[/math]

31^2 = -4 mod 193

implies 31^2 = (-1) * 2^2 mod 193

implies 31^2 * (2^(-1))^2 = (-1) * 2^2 (2^(-1))^2 mod 193

implies (31 * (2^(1))^2 = -1 mod 193

n/m, 2^-1 should be 2^-2.

I'm completely lost on this desu. So the methanol gets less efficient when a higher volume is injected? Someone please explain this shit to me.

Explain the following figure, Fig.1, for reversed phase chromatography eluted with 30:70 methanol :water, in which the number of theoretical plates is plotted against the injection volume for separate injections of the same sample (10 pg caffeine) dissolved in two different solvents water (dotted line) and methanol (solid line).

Can someone please explain this image to me like I'm retarded? Does more keV mean more intensity (photon abundance) with diminishing returns at higher levels, or would doing a really high keV give you less then a medium level? What the fuck do the discrete peaks mean and why are they there?

Oh wait I think I get it. The peaks are due to discrete energies from electron shells, while the continuous bit is from energy due to decelerations. Right?

What the fuck is an illegal matrix?

illegal matrix operation means the sum or product is not well-defined

illegal - not lawful

the answer is B

is this loss?

I see it too, I feel like in that shitty jim carey horror film.

Addition and Subtraction are not well defined when the matrices are not the same size

Matrix multiplication is not well defined when the number of columns in the first matrix are not equal to the number of rows in the second matrix

A scout group is faced with the task of crossing from one corner of a rectangular patch of cane stubble to the diagonally opposite corner. The patch is 8km long and 3km wide and the scouts can move 1.3 times as fast around the outside as they can through the stubble.

1. What is the quickest way to get from one corner to the other?

2. Find an expression for the time this will take

what exactly do you need help with?

to solve this problem let point A be a point of distance x away from the goal along the long side of the rectangle, then find an expression for the distance that the scouts must travel through the patch to get to point A, in terms of x. Now find the expression for the amount of time it takes to reach the goal (distance divided by speed = time, and total time = time traveling through the patch + time traveling along the perimeter). Once you find an expression for the total time it takes to reach the goal in terms of x, find the minimum for the function as x varies from 0 to 8km, also remember to compare it to the time it takes to circumvent the patch altogether.

If you multiply tan(a)*tan(b)/(tan(a)-tan(b)) with cot(a)*cot(b)/(cot(a)*cot(b)) you can simplify the whole thing to

1/(cot(b)-cot(a))

lads

i would like to know more about contact stress. it's not something we really learned about in college.

before i took engineering, i understood that pressure = force/area, but that isn't mentioned in basic strength of materials. forces are simply forces, and we don't care about the shape of the objects.

basically, how does the shape (mutual contact area) of objects relate to the stress developed in them? any recommended texts?

Fuck, I see now, I typed tan but was thinking of cot, you're right, it's [math]\frac{1}{cot(b)-cot(a)}[/math].

Also I much prefer tg and ctg, I wonder why my country uses a different notation.

Any help with this? I'm not sure if I made the problem clear enough: it's just how many ways can I choose m and n so that n + 2n = p, where all the numbers are integers. I'm trying to find a closed formula such as in the case of [math]x_1+...+x_n=p[/math]. I this case, it's just simple stars and bars: [math] \frac{(p+n−1)!}{p!(n−1)!}[/math]. But this problem I can't do.

Age of Mythology. A villager produces 2 meats per second. For each 50 meats I can produce one more villager.

How can I know the amount of meat for each time?

[math]1 + {\lfloor\frac p 2\rfloor}[/math]

This line of reasoning is why some philosophers (Hume & Popper) consider induction in the real world invalid. You either have to believe it or don't

In math it's often part the axiomatic structure that it works, but that's different

Depends on what level you are. If you really are at a grade school level, do it my grade. If you are looking to learn calculus or something, do it by subject

[math] y^{3} = x^{6} [/math]

Not sure what else you need, it's just replacing x^2 with y

I have numerous independent survey data sets. In all but one, survey respondents self-rated their general health on a 5 point rating scale. In the other data set, one half answered to the usual 5 point scale and the other half to a 6 point scale (but with the same question).

My question is: How do I find out which scale is better? What kind of statistical analysis can I use?

Pic related contains two number sets above the line simplified by a process I invented by utility below the line. The process is as follows:

discover "like terms" (as in numbers which have the same base, I don't know if that's what like terms actually means) in each number set.

Reduce by subtraction like terms in the greater value number set by like terms in the lesser value number set

Cancel entirely terms in the lesser number set which were used for reduction in the previous step.

Leave all unlike terms in each number set alone

Context: the original number sets are prime factors of 1280 and 720. Using the output from the process outlined above, you get the ratio of these two numbers.

My question: is there an existing mathematical procedure or function which accomplishes the same task for number sets? What is it? How do I write it?

Young's modulus

Are you looping?

Using Matlab, how do I get the values for a f(x,y) using diferent values of x and y?

Having issues calculating square space of the trapezium.

I found out that h - height (perpendicular from B to CD) is equal to BD/2, angle B = 150°

This is where it all died. If I'm to find the surface via either trapezoid theorem or 2 triangles combined space I fucking need to know BD to find height.

Cant use sin/cos shit here, this is middle-school.

Formulas for reminde:

Strapez = h*(AB + CD)/2

Striangle = height*base/2, where base is the side to which height is perpendicular.

You can find BD with the law of cosines (AD2=AB2+BD2-2*AB*BD*cosB)

Brainlet here.

I'm having a lot of trouble with analytic trig. I do literally all of the homework assigned but cannot seem to develop the intuition needed for seeing the solutions to things like verifying trig expressions or solving trig equations. If anyone has a shit ton of practice problems or any other resources it would be much appreciated.

I was tasked with showing an example of a rational expression that is defined for all numbers, if there is one.

Given that rational expressions are not defined where the denominator is 0, I reasoned that there was none, since the assumption that there is would require for the denominator one of the following:

1) The factor sum cannot be 0 if the constant is 0.

2) The factor sum cannot be equal to -constant.

Since [math]0 = -0[/math], 1 follows from 2, so can be removed. We're left with:

[eqn] p\left(x\right) = a_0x^n+a_1x^{n-1}+\dots+a_{n-1}x+a_n, a_0 \ne 0\\\\

\exists p(x) \space\mathit{P}\left( \dfrac{p\left(y\right)}{p\left(x\right)} \ne \text{undefined} \right ) \iff \lnot\forall p\left(x\right)\exists x \space\mathit{P}\left( \sum_{k=0}^{n-1} a_kx^{n-k} = -a_n \right)\\[/eqn]

This obviously cannot be true; as long as [math]a_0 \ne 0[/math], we can make the sum whatever we want.

So I felt fairly confident in my answer; only then to be given [math]x^2 + 1[/math] as an example of such a denominator.

Where did I go wrong? Are [math]x = i, x = -i[/math] not valid solutions? Are polynomials not defined for [math]x \not\in \mathbb{R}[/math]?

Cant use sin/cos shit here, this is middle-school.

it does depend on the domain of discourse

even if you *can* define polynomials over complex numbers it doesn't mean you're in the field of complex numbers

hi Veeky Forums

I have a stupid question, I am working on a project and it has 6 different points, each point is connected to every other point.

I am struggling to find a 3D shape or image which best describes it, perhaps an image of a chemical bond or a 3D hexagon with these lines neatly drawn?

Basic integration. This is the solution in the book.

I get most of it... But what happened with the -2x ?

Shit just disappears.

i'm a 1st year mechanical engineering student and it's very easy so far. i've gotten an A+ on every paper and at least a 98 on every test. i just got a 100 on an online assessment.

i know what you're going to say: "you're going to a shit uni then"

not true. i'm just able to memorize hundreds of things with relative ease. there were 178 terms and definitions that i had to memorize for a test two weeks ago, and i scored a 100(after the bonus question, so actually a 97, but i only lost partial credit on a few questions)

i really like theoretical physics, the link(s) between math and philosophy, cosmology, etc

should i switch majors to something more obscure? engineering is sorta lame. it interests me but i'm not enticed by the idea of being an engineer

Integration by substitution, -2x is the derivative of 25-x^2

25-x^2=u

-2xdx=du

So your equation becomes u^(1/2) du

integrating that you get (u^(3/2))/3/2 and then just substitute x back in.

For me the course started getting hard with heat transfer and fluid mechanics.However, if you're acing everything you'll likely do well for the rest of the course.

should i switch majors to something more obscure? engineering is sorta lame. it interests me but i'm not enticed by the idea of being an engineer

You should obviously work with something you like, but you should also consider how's the market situation in your country. If you can live with the standards you want by majoring in the courses you mentioned, then you should go for it.

i really like theoretical physics, the link(s) between math and philosophy, cosmology, etc

I have found that the simple memorization you can get by with in engineering will not serve you well in those subject (math). You might find like i did, that almost no memorization is required which makes them much harder.

Testing graphically shows that the limit as x approaches 1 of that polynomial is in fact 4. I think you got marked off for forgetting to keep your lim until all x's are gone, then you left your last lim incomplete.

4xy = 32

xy = 8

u = xy = 8

du/dy = y = 0

dy/dx = x = 0

KEK

i'd be happy with 60k/yr t-b-h

what exactly is hard about it

i'm thinking about using some of my elective credits to take a theory class

because you got the wrong answer OP:

Really stupid question guys, but lets suppose i have this situation, where 20N is the net force, how do i calculate the speed and acceleration of this ball?

I'm trying to find the probability density [math]p(x)[/math] for finding a random walk problem where the walker has a step of length [math]s[/math] randomly chosen from the following probability distribution:

[math] w(s) = \frac{a}{\pi} \frac{1}{a^2 + s^2} [/math]

So, p(x) should be given by:

[math] p(x) = \frac{1}{2\pi} \int_{-\infty}^{+\infty} [\hat{w}(k)]^N e^{-ikx} dk [/math]

where:

[math] \hat{w}(k) = \int_{-\infty}^{+\infty} w(s) e^{iks} ds [/math]

Anyway, I can do the first integral using the residues theorem and find that [math] \hat{w}(k) = e^{-ka} [/math] (taking the pole at [math]ia[/math] instead of the one at [math]-ia[/math]). But plugging [math] e^{-ka} [/math] into the above expression for [math]p(x)[/math] gives me an integral that diverges.

how do i calculate the speed

needs an initial condition and will vary with time

will take the form [math] |v| = |v_0 + at| [/math]

how do i calculate the acceleration

F=ma

I'm sorry, I meant the probability for finding a walker from a random walk problem between x and x+dx.

I should've also said that N is the number of steps taken. Choosing the pole at [math] -ia [/math] also makes p(x) diverge.

thanks, user, after calculating the acceleration i was able to solve my problem

Anyone?

i use khan academy

Thanks

so, not technically a math question, but I think this is the best place on Veeky Forums to talk about mind enhancing drugs. so...

Friend of mine showed me two pills, a white one and a red one, he peeled them off and they appeared to be layered in three colors

he said he takes them for his adhd, but i didnt believe him

So he gave me one pill of each type. Made my research and it's actually ritalin, quite high dosage, 58 mg I think

what I wanted to know is:

Can I take this and get shit done without dying?

what should I expect?

advice from someone that has already taken it?

What you have is Concerta 36mg (white) and 54mg (red). You should expect feelings of energy, focus and a heightened sense of self-esteem and confidence. You'll most likely feel like you need to take a shit and piss more often but it should help you focus and get shit done.

does it get noticed by people?

should I just swallow the 36 mg one or the 54?

Can I drink or be around in a party under the effects?

thanks in advance

I'm in thermodynamics and statistical methods, and I still really don't understand a lot of it. We're currently going over chemical thermodynamics (Helmholtz free energy, Gibb's free energy, etc.), and there are millions of equations that are all similar, but I don't get any of them. Does anyone know of any websites or books or anything that explain it nicely?

My mind goes completely blank when I take a test or try the hmwk. Help

I can read the chapter, take great notes, follow along in class. But when I go to actually do a problem, I just stare at the paper. How do I fix this?

Try to get a solution book for the subject and use it to learn the "recipe" for that sort of exercise (making sure you understand each step). After you get the hang of it, start answering them on your own.

I too would like the answer to this question

Am I fucked for grad school admissions if I have 0 research (or 1 semester of research)? Applying to optics/photonics/laser focuses at schools like URochester, UArizona, CUBoulder, and maybe some other ones. My GPA will be about 3.8/4.0 by the time I apply next fall and GRE is 165/168/5 (VQW) at an R1 school with alright rec letters. Should I be fine for MS admissions? Would prefer PhD, but understand that a MS first would be a good stepping stone for more research experience.

searching for textbook's solutions on the internet

every website with it wants money to view it

fucking jewish motherfuckers

iktfb, from my experience, if you go blank on a test, it's because:

1, the test is MADE to be hard, it's like they give you something that looks like the home work but it isn't, hw is basically teaching you how to use the tools and some thinking is involved, but when it is on the test, you're given a totally different problem but you should know how to solve it given the tools and some thinking. if that makes sense.

2. you can't, you shouldn't even think about looking at an online solution. You get what you need from the homework by struggling. struggle, struggle, struggle, it sucks believe me im bad at math but i learned tons from my mistakes. ask questions or look up EXPLANATIONS, not answers online.

3. read the instructions carefully before starting the problem, then go back to an example and quickly skim it to get a general idea. then try the problem again.

4. try timing yourself on some of the hw problems, helps prepare for tests by getting you more comfortable with the pressure.

if this isn't bait, it's not an illegal matrix but an illegal matrix OPERATION. you can't divide 1/0, or add a 1 to a symbol. it's mathematically incorrect because the two are not alike, review the basic matrix laws, there should be a list of properties in your text. then see which one doesn't satisfy the list.

why can't I see these posts well? it's all lines of text and i feel it should be math looking. Do i install latex or some other program?

Veeky Forums x

it's loss

libgen

okay, after some time i finally figured out what the fuck you were asking.

So if im right you should see an explanation for a first order partial derivative. correct? using that equation in that example, you have to use that to find the second order partial derivative.

So you get something like d/dr times (2r dz/dx + 2s dz/dy)

then they apply the product rule to get

2 dz/dx + 2r d/dr(dz/dz)+ 2s d/dr(dz/dy), which should be a highlighted equation for later use in the explanation

now for your question, they use the fucking chain rule again because when you calculate dz/dx, because of the chain rule you have to calculate dx/dr.

So basically in your picture, what you get from those two partial derivatives of dz/dx and dz/dy is what you need to substitute back into the original equation i told you above, which should be equation 5 from your picture.

ALL of this is because you're trying to find the derivative of a composite function of several variables, 2 in your case. So in equation 5, you're just not fully done finding the second partial derivative, you have to calculate further. once you do that, you simplify THEN you have the second order partial derivative.

bitch....

Am I retarded?

b = 4, a = c/2, find c

[math]

c^2 = a^2 + b^2 = (\frac{c}{2})^2 + 16 = \frac{c^2}{4} + 16;

c^2 - \frac{c^2}{4} = 16; \frac{3c^2}{4} = 16; c^2 = \frac{64}{3};

c = \sqrt(\frac{64}{3}) = \frac{\sqrt(64)}{\sqrt(3)} = \frac{8}{\sqrt(3)};

[/math]

but proper answer is

[math]

\frac{8\sqrt(3)}{3};

[/math]

the fuck?

excel in middle school with good study habits.

highschool and my life spins out of control with depression and other circumstances ; grades dropped

here i am now in uni however i feel like im lost as to how to study effectively so i can achieve a high gpa.

any advice or suggestions as how i can git gud ?

function z = f(x, y) z = x^2 + y^2; end

f(0, 0)

ans = 0

f(0, 23)

ans = 529

Both are the same friendo

why would you be fucked?

are you a US student or foreign?

If youre US, you should be able to get in at arizona easily. Maybe not colorado but apply anyway. Youll def get in new mexico

So, here's a question. I'm not sure if computer science is accepted here, but I'm not really sure how to read a FAT file system. Where is the volume label located in this hexdump? I think it's 4c75 at 0x0b3, but I'm not entirely sure.

Both are the same friendo

how so?

1/sqrt(x) = sqrt(x)/x

Is it a proper way to write answer like that?

In my experience it doesn't matter which way you write it since they're just different ways of expressing the fraction. Although, I think some people don't like having a square root as a denominator so they rearrange it.

Yeah I am a US citizen and student, and just not sure on how important research really is for grad apps. URochester and UArizona are my main choices just because they are touted as the best in the field (Optics), at least for getting a job afterwards.

no takers?

reading comprehension

The task supposed to be solved by elementary school kids with simple geometry rules, without trigonometry stuff (sin/cos/tan etc). Which IS the reason I even ask about it.

i spent quite some time trying to figure it out but couldnt

Then how did Hume, Popper, etc. calculate probabilities of things being true for false for things that weren't immediately apparent to their senses?

Is it even possible?

Well, supposedly it is? I'd like to know, that was the thing from the school book so it should be doable.

Why is this -1?

any number to the power of zero equals 1. what do you not understand here?

where did "-" came from

25/4 is negative.

how so it will be a fraction in ^2

negative base in power of 2 alawys positive

Only 5/2 is squared

the way i put it in the picture should make it more clear

Ok, another question: how do you simplify this:

[math]

5*(-12)^3 *6 = 5 * -(12)^3 *6 = 5 * -(2^2 * 3)^3 * 6 = ???

[/math]

how do I open the negative parenthesis here? I assume

[math]

= 5 * -2^6 * 3^3 * 6

[/math]

but I'm not confident

why are you taking the negative out of parenthesis?

What do you mean? I cant do that?

(-12)^3 always will be - so with the same sucess I can write -(12^3)

what is 9999999999999999999999999999999999999 + 98768162763123?

does not answer my specific question

Here is full example:

[math]

\frac{4^2 * (-12)^3 * 9}{32 * (-3)^4} = \frac{2^4 * (-2^2 * 3)^3 * 3^2}{2^5 * (-3^4)}

[/math]

I believe I can just write [math](-3^4)[/math] as 3^4 because I can do the power and then revert back and it will be positive, but I'm unsure about the nominator

So what would be the different between

[math]

(-9^2)

and

-(9^2)

and

-(9)^2

[/math]

Would the biology of alien life actually be compatible enough with the biology of earths life so as that each could possibly "infect" each other wiping them out? Like how the microbes in the war of the worlds eventually killed the martians.

Didn't these microbes evolve along side and even specifically to target other earth biology?

if it is carbon-based I dont see why not

So I'm in physics I and the prof suggested some books that she likes.

-Berkeley Physics Course, Vol I: Mechanics by Kittel, Knight & .Co

-The Feynman Lectures on Physics, Volume I

-And some other book that's in spic language.

Any suggestions are welcome.

for example, a virus has to trick a cell into thinking it's harmless by using protein spikes to act as "key" to allow it access, once inside it's RNA is released and once inside the nucleus tricks the host DNA into making copies of it. AS All cells all use several types of RNA anyway the two are compatible allowing for exploitation.

However an alien lifeforms genetic make up would be different, it likely wont use DNA or RNA, it would use a several different complex molecules, so the way DNA and RNA bind through adenine-thyamine/uracil and cystosine-guanine bonds would not be possible.

Though I guess it's possible for the them to bond in some way though it would likely damage the host and the "infector" meaning even if someone is infected with alien microbes and gets sick, it's likely there wont be a full on outbreak as both organism would die in the process and not be able to pass on it's genetic material.

How do I calculate how much force an exploding missile would impart on a ship in space?

made a 90 on my second calc 2 exam..feels bad being a brainlet

A projection maps from a compact set onto a convex, closed set. Is the image of this projection then compact?

Why?

If a = dy/dx, does that mean 1/a = dx/dy?

is the curl a vector or scalar?

A vector.

A pseudovector. See Boas.

A function.

why do so many chemical phenomena happen in a very narrow spectrum, around 100 degrees C, +- 100 degrees?

likewise, why are functions typically only interesting within a few units of the origin/axis of symmetry? They tend to be boring, tending towards +/- infinity for pretty much the entirety of the graph BUT around the origin. Why is that?

why do so many chemical phenomena happen in a very narrow spectrum, around 100 degrees C, +- 100 degrees?

An officer sees a drunk stumbling around the sidewalk around a lamp post. The cop comes up to the man and says, "Had a bit to drink tonight, sir? What are you doing here?" The drunk tells him, with some considerable slurring of words, "Looking for my officer, car keys." "Well sir, is this where you lost them?" The drunk says, "I don't know officer, but this is where I can see."

likewise, why are functions typically only interesting within a few units of the origin/axis of symmetry? They tend to be boring, tending towards +/- infinity for pretty much the entirety of the graph BUT around the origin. Why is that?

Part of it is the same joke. Another part is that to a large extent zero is the is a very unique point in a coordinate system (e.g. division by zero). Another part is that where you put zero is kind of arbitrary and you can translate things all around space (i.e. there's as much interesting shit elsewhere but it's just a translation of interesting shit around 0).

I know how to find the heteroscedastic standard error for βj in a linear regression (formula in the pic), but how do I find the heteroscedastic standard error for β0 (intercept) in a linear regression? I can't find an answer to my question in my textbook or the internet and this is driving me mad. I'm starting to think this is because the answer is obvious, so I'd rather spare my professor my brainletism and ask here.

How do I show <v,w> = <w,v> here? I don't know how to rearrange a^TAb to get b^TAa.

Studying so I can do the accuplacer placement test and hopefully get into precalculus. About a week ago finished up the section on Trigonometry, decided to look at some online exams. Got no idea how to go about this problem

(X.Y.Z)^T = Z^T.Y^T.X^T

=>

(a^TAb)^T = b^T.A^T.a

= b^T.A.a (It states that A is symmetric so A^T=A).

Just got accepted to my dream school for a MS with some funding (~half off tuition), but it will still be expensive as shit. Do I take out loans? Will FAFSA take care of it or no? I will need to pay tuition and afford housing + food, all together about $35k/yr, but can get RA/TA positions second year and will get paid about $30k and free tuition. I am going into an engineering field and this is a top 5 school for the subject so don't feel to worried about getting a job afterwards. I'm just not sure how these things are paid for as I got scholarships to pay for undergrad. I am a US citizen going to a US university if that matters.

Follow up from another question I asked. So I know I need to do something like

<v,w> = <sum(aivi),sum(bivi)> and then somehow rearrange this to get (1), but I have no idea how to do this.

He is making conversation with multiple people right now, what a pathetic loser you are.

Spent a while on it, it turns out that there's a formula for integral from 0 to infinity of x/(e^

(ax)+1)dx and you can differentiate it with respect to a, use the results for a=1 and -1, and then you get the answer which is pi^2/3.

Actually if anyone has a different online resource for learning trigonometry beyond the basics, please provide

is calc 3 really easier then calc 2 or am i getting meme'd on?

Is there anyway to be a researcher in Math without also being a professor? I am too autistic to teach and I don't want to make future math major's semester's miserable.

Contour integration. Choose x=iy, select -pi as the residue of (1+e^iy) and choose an appropriate contour to integrate over

yes it's easier

Someone please start a new thread so I can ask my question

A

If I swallow a fly will I feel it flying around in my stomach?

Could someone please tell me why the mass is being divided by the gravity constant here?

u = xy = 8

du/dy = y = 0

If the convex, closed set is bounded, then it is compact. Hope that's a helps in the slightest haha.

pounds are a measurement of weight, which is a force, but we need the mass so we apply F=ma with F being the given force and g being the gravitational constant to find the mass in slugs.

The reason most physics classes do this is to hammer in the fact that a measurement of weight is not a measurement of mass. In reality we can treat pounds as a measurement of mass for the most part (usually denoted lbm), but this can lead to a bit of confusion so it's generally better to only consider pounds as a unit of weight or force

This is probably the most stupid question to have ever been posted in one of these threads, but I'm curious.

As it stands now, it appears that the expansion of the universe will ultimately outpace gravity's effects. Is there a way (no matter how hypothetical unless it's just DUDE MAGIC LMAO) that the strength of gravity could somehow be artificially increased in order to compensate for this? I mean, I know we're talking about the fundamental forces of the universe here, but I figured maybe there's some weird esoteric field of physics that has eluded me thus far.

F=ma should be F=mg

How do i get a girlfrend?

This will be the stupidest question in this thread but how do i solve for t?

Put a rondom number in place of T untill you get closer and closer to answer.

Don't prank me bro

newton's binomial or something?

it looks like (a+b)^2 type of thing

new thread posted 3 hours ago**veekyforums.com**

no one links it

faggots

you don't have nerves in your stomach

you know how if you drink something hot you kinda feel it in your stomach? that's actually just your brain extrapolating

unless theres any clever numerical methods idk about, i think it's probably your best bet.

and if youve got something like 9.317 in a question you've probably got a calculator to hand so just type [math]\sqrt[4]{\frac{3}{2}\left(9.317+\texttt{Ans}^2-4\cdot\texttt{Ans}\right)}[/math] and press equals until you find a root