/sqt/ - Stupid Questions Thread

Is this monkey the average sci poster?

>calling blacks monkeys
That's pretty intolerant of you.

see

>Divide by G*4*m_a^2
why

Because F = G*4m_a*m_a \hat(r) / |r|^2
You want to isolate \hat(r) / |r|^2
Then you can isolated the unit vector \hat(r) to find direction and |r|^2 to get magnitude

Even though I suck at geometric proofs since I forgot everything, I am able to follow this one without drawing it. Zanks for the geometric proof.

[math]\displaystyle{x}^{4}+{32}{x}^{3}+{256}{x}^{2}-{289}={0}[/math]
Not math homework, how do I do this?
I got this quadratic from set
[math]\displaystyle{F}={\left\lbrace{x}{|}{\left({x}^{2}+{16}{x}\right)}^{2}={17}^{2}\right\rbrace}[/math]
Thanks

Anyone knows the answer to my μετά-post?

Oops
[math]\displaystyle{F}={\left\lbrace{x}{|}{\left({x}^{2}+{16}{x}\right)}^{2}={17}^{2}\right\rbrace}[/math]

My brother
Now you only need to take square roots, so get the solutions from
[math] {x}^{2}+{16}{x}={17} [/math] and [math] {x}^{2}+{16}{x}=-{17} [/math]

Holy cow, thanks! I am a moron.

[math] x^4 + 2^5 x^3 + 2^8 x^2 - 2^8 - 2^5 - 1 [/math]
x=1 is a solution by inspection

(x-1)(x^3 + 33 x^2 + 289 x + 289)
Try the factors of 289 = 17*17
x=-17 is a solution

(x-1)(x+17)(x^2+16x+17)
Solve the quadratic.

Can someone help me with gearing on my lathe?
I need as much gear reduction as possible from A to B.
The direction B turns in the end doesnt matter (You can reverse A direction accordingly) hard RPM numbers dont matter

>A is power from spindle with a non changing Duplex gear
>the "front" gear is 16 teeth and the "back" gear is 32
>S is a stud and bushing that stacks any 2 gears
>There are two studs and bushing sets even though only one in picture
>B is the screw that needs reduced, any gear goes on it. It has a spacer to choose "front" or "back" depending on how other gears end up
>the banjo the gear studs attach to moved up and down to accommodate different gear sizes.

Gears I have
20t
36t
40t (x3)
44t
46t (x2)
48t
52t (2)
54t (2)
56t (2)
64t (2)

There are supposed to be 3 studs, and im missing several small gears, and Im not supposed to have any duplicate gears. So im trying to make due with what I do have

The system is made to cut threads. It moves the cutting tool a certain amount per rotation to cut accurate threads.
When you slow it down enough it doesnt cut threads, it just becomes a feeding system to cut off the diameter which is what im looking for. Im missing gears for the stated feed in the manual, hoping to find something close enough

>Try the factors of 289 = 17*17
Why?
I know that x|289 is a necessary condition for rational solutions, but he didn't say that he was looking for rational solutions.

how does the Fiber Bragg Gradient system measure temperature? i understand how it produces strain measurements but research yields no results on temp.

How to actually take good notes when/after reading the textbook without spending much time?

I feel like I'm losing a pretty good amount of time when I write down notes

Just don't take notes.
Mark the important stuff on the textbook and comment when needed.

Could someone explain what exactly question 1 is asking. Is it about the intersection/unions of all the sets in the class or something else?

You are asked to show that the union of all the A's is contained in the union of all the B's when every A is also a B.

Just fill in missing steps in derivations and do the exercises.

{Ai} and {Bj} are collections of sets and {Ai} is a sub-collection of {Bj} therefore for a given Ax there exist a y such that By = Ax.

a∈∪Ai ⇔ ∃x a∈Ax ⇒ ∃y ∃x a∈Ax = By ⇒ ∃y a∈ By ⇔ a∈∪Bj
a∈∩Bj ⇔ ∀y a∈By ⇔ (∀x a∈Ax) AND (∀y st ∄x Ax = By AND a∈By) ⇒ ∀x a∈Ax ⇔ a∈∩Ai

Can someone help
Me understand this. I'm having trouble understanding the derivation of this parametric derivative. The F(x) represents the function of x, but how can the chain rule be applied to this. Can't some functions have multiple chain rules that need to be taken. For example, a function like x^2+2x, wouldn't you have to apply the chain rule twice for x^2 and also 2x which will have two dx/dt?

rotate your image mobilefag

>x^2 and also 2x which will have two dx/dt
Then you factor them out x^2 dx/dt + 2x dx/dt = (x^2+2x)dx/dt

I'm not sure I understand that. Wouldn't you have to use a chain rule on x^2 and also a different chain rule for 2x?

Any recommendations for a babbies first dynamic programming tutorial?

amazon.com/Dynamic-Programming-Dover-Computer-Science/dp/0486428095

You get 2x dx/dt+ 2dx/dt = (2x+2)dx/dt

Thanks I'm starting to get it a bit.

I'm dusty on my control theory and I want to revise some of the basics before next semester.

I'm looking for some slow KA/3B1B-type playlist that goes IN DETAIL over basics of control theory. More specifically, I want to gain a better intuition about the different meanings of the location of poles and zeros in the complex plane.

F.e. if I look at a root locus plot or at the location of the poles and zeros of a filter, I would like to have a better immediate understanding of the characteristics of the transfertfunction and/or which "device" (or model thereof) I'm looking at.

Anyone have a suggestion? All suggestions are welcome even if they don't fit the criteria exactly.

How did you get two [math]2^8[/math]?
How did you get a 5th term? Sorry, brainlet here..

what does [math]2^8[/math] equal?

So theoretically if I punch myself in the jaw it will get stronger?

...

*groans internally*

That's pretty easy and you didn't try any work yourself. Show work and I'll help you.

A^6=(A^2)^2*A^2=A^2*A=A*A=A
AB(A^tB)^t=ABB^tA=A*A=A
A-A=0

Please don't respond to homework posts unless user puts work in.

Why don't we just increase the capability of the inferior parietal region of the brain to be better at math? Einstein's was 15% bigger than the average person.

How do I use "wrapfig" with the "enumerate" functionality of LaTeX?
It seems like if I just keep typing stuff, it just moves the picture down, as opposed to keeping it in place and placing the text around the image. And the whole "picture below the text" is weird because I'm technically creating the image before I type the "a's" (see pic related)

Is science/math worth studying on your own if you never actually plan to get a degree or anything like that? I have an interest in studying but I want to do it on my own terms really.

pic not related

yes I wish I could do this myself
it's a good hobby like playing an instrument

You say you have an interest in it, so do it. What fields are you most interested in? Read some seminal textbooks, watch some OCW lectures, search libgen for articles.

LaTeX thinks it knows better than you on where to place the image and will do whatever the fuck it wants, bitch.

/g/ autism strikes again.

How are u supposed to evaluate the limit 3a

How do you figure out the radius from this, when you don't even know the angle?

l'hopital's rule, it's a doozy but doable with calc I techniques

It looks too much for series expansion and "normal" problem solving, so I guess you need to use l'Hôpital.
Good luck differentiating that shit.

Taylor series: sin(x) ~= x, tan(x) ~= x
x3x/(4x)^2 = 3/16

QED.

>How do you figure out the radius from this, when you don't even know the angle?

r*sin(x/2) = 4
r*x = 8.5

r~=7.08981...

Can anyone recommend me a Stochastic Processes book?
One with an intuitive approach and with applications?

You do not need to differentiate the whole fraction, but the numerator and denominator separately, so it shouldn't be too hard. Unless you need to apply l'hospital multiple times

Veeky Forums-science.wikia.com/wiki/Mathematics#Stochastic_Processes

I hate wasting brain cells over applying the quotient rule and I see tan^2, so it looks shit to me.

As I said, you do not need to differentiate the fraction, only both parts of it, so no quotient rule, only chain rule

Sorry if the question is too stupid.
Is it true that for any matrix norm [math] ||I|| = 1 [/math] , where I is the identity matrix?
And if not, what about multiplicative norms i.e. such that [math] ||AB|| \leq ||A|| \cdot ||B|| [/math] ?

Please tell me where to start.

Seems to me like all p-norm's values, of the unit matrix E, monotonously grows with the dimension d.
||E|| = d^(1/p)
I.e. no.

Did you make a list of possibly norms and plug in E before asking?

That's horrible notation and nomenclature - who wrote that?

In any case, you start by plugging in, into J, the formulas for the expressions given right before it. The only nasty part is taking the square of the square root etc.

If you feel uncomfortable, test all formulas with two concrete vectors of dimension 2. Then, after you understand how the expressions look for those two vectors, solve it abstractly.

>Is it true that for any matrix norm ||I||=1 , where I is the identity matrix?
No.
Let [math] \lVert \rVert_1 [/math] be a norm where [math] \lVert I \rVert_1 =1 [/math] (e.g. the supremum norm [math] \lVert \rVert _{\infty} [/math] ).
Define a new norm [math] \lVert \rVert_2 [/math] such that for any matrix A we have that [math] \lVert A \rVert_2 = c \lVert A \rVert_1 [/math] where c>0.
You can easily check that [math] \lVert \rVert_2 [/math] is indeed a norm and that [math] \lVert I \rVert_2 = c [/math] .

>And if not, what about multiplicative norms
No. Do the same as above but with c>1.
But, it is true that [math] \lVert I \rVert \geq 1 [/math] since [math] \lVert I \rVert = \lVert II \rVert \leq \lVert I \rVert \lVert I \rVert = \lVert I \rVert ^2 \implies \lVert I \rVert=0 \lor \lVert I \rVert \geq 1 [/math] and since the 0 operator is the only one with norm 0 we have that [math] \lVert I \rVert \geq 1 [/math]

So I'm just plugging in c_1 and c_2 into the first J so that I get the J at the bottom right?
I've been trying that and can't seem to get anything to make sense

Oh, and if the matrix norm is an induced norm (these are always submultiplicative), i.e. the infimum of the m's where m is such that ||Ax||

So I'm taking linear algebra at my community college, and the professor keeps doing this thing where she'll give us a problem, tell us to try and solve it, then after like 10 minutes back to lecture and explains why nothing we tried worked and that "this" is how it's done.
If I've already read the chapter, that time is just a waste, but if I don't, then I haven't been able to figure out the answer myself.
I guess I'm just wondering if this seems normal for math classes? Like, it doesn't necessarily seem too impossible yet, but once it's explained I feel like "well yeah no shit, of course that's how it works why did I try anything else"?

You need the right tools in your toolbox to accomplish a given task.
Sure, you could spend 10 minutes trying to drill a hole into a plank with the back of a hammer, but it's probably not going to work out too well.

Yes.
Especially at a bare minimum everyone should understand mathematical logic and the scientific method.

Also, number theory is always fun, but you should probably understand higher level courses first if you want to really grasp it.

If I sleep for four hours one night, will I need to sleep for 12 the next to make up the difference?

No. And sleeping more than 8-10 hours might make you more tired than just sleeping your normal 8

Brainlet here. I'm struggling with some basic math problem I was thinking about. Suppose you have a 50% chance (of winning the lottery or whatever) and you double that chance, what is the new probably?

a) 100% (0.5*2)
b) 75% (0.5+0.5*0.5)
c) 66.6% (going from a 1:1 ratio to a 2:1 ratio)

Feels like it should be b, but c seems to be true as well.

why cant we explore the deepest ocean floors for minerals n shit? its 2018 why do subs still suck

en.wikipedia.org/wiki/Sleep_debt

>double that chance
What do you mean by that?
Do you literally mean "double that chance"? If yes, then it's 2*50%=100%

>a) 100% (0.5*2)
double your chances
>b) 75% (0.5+0.5*0.5)
double your trials
>c) 66.6% (going from a 1:1 ratio to a 2:1 ratio)
double your odds

After thinking about it, you seem to be correct. My problem was what I answered 3 different questions:

a) doubling the chance of winning (1)
b) halving the chance of losing (0.75)
c) creating a scenario where I have twice as many wins as loses (2/3)

are there any non-flammable liquids/gasses one could practically use to create a continuously running cloud chamber? i had the idea that it would be neat to try to make a cloud chamber as a decoration piece but you obviously don't want to leave flammable gas/vapor in the chamber and have it be a fire hazard and it wouldn't defeat the purpose if you had to fill it when you wanted it to do anything

what's a cloud chamber?

There are multiple ways to interpret what you’re saying.
If you’re saying you play the same lottery twice, then your chance of winning once is still 50%.
This is called the Bernoulli trial, with p=0.5

lets you "see" the paths of ionizing radiation particles as they travel through it, due to the effect the particles have on the vapor inside the chamber

>but you obviously don't want to leave flammable gas/vapor in the chamber and have it be a fire hazard and it wouldn't defeat the purpose if you had to fill it when you wanted it to do anything

meant to say

>but you obviously don't want to leave flammable gas/vapor in the chamber and have it be a fire hazard and it _would_ defeat the purpose if you had to fill it when you wanted it to do anything

Oh shit, didn't see your post. Thanks for clearing it up while wording it more precisely then I did.

I just derped hard.
If you play the same lottery twice with p=0.5 your odds of winning once (and losing once) are 0.75.

nah you were right the first time, your chances of winning only once is 50%, but your chances of winning at least once is 75%

She's probably hoping for creative geniuses to come up with something clever so she can separate the wheat from the brainlets.

As long as you don't get punished with low marks, it's just an inefficient but fun way to find out who may be genius.

she wants you to try to think through different approaches to the problem so that when you learn the correct approach you'll have a better understanding of WHY it works and why other approaches don't

>inefficient

there's nothing inefficient about trying to work out a problem beforehand to gain a better understanding of it before learning the correct way to do it. you'll probably learn more/remember more through the process than just glossing over the correct approaches to problems as quickly as you can

*Warning* This thread might break.... First of all i am NOT a flatearther

The line integral [math] \displaystyle\int_C f\, \mathrm{d}S [/math] over the scalar field [math] f(\mathbf{r})=1 [/math] will give the length of the curve C.
Is there something equivalent for the line integral over a vector field?

they probably either drilled holes in the tires or made solid tires to put on the wheels

they could just underinflate the tires
since it doesn't have to drive anywhere or even support any weight they could just inflate them enough to give them some shape

>lol muh quirky intro!1!~
Get on with it

Actual brainlet question.
Where do i start with mathematics/physics and how do i progress from the simplistic things to quantum physics.
Never wanted to learn, grown up and realised my lack of knowledge is unacceptable as a human being. What books should i get etcetera