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/sci/ - Science & Math


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9633554 No.9633554 [Reply] [Original]

This thread is for questions that don't deserve their own thread.
>give context
>describe your thought process if you're stuck
>try wolframalpha.com and stackexchange.com
>How To Ask Questions The Smart Way http://www.catb.org/~esr/faqs/smart-questions.html
Previous thread >>9622645

>> No.9633557

What is the biggest animal that can live off inside my body?

>> No.9633571

>>9633557
Probably a tapeworm if you count by length; otherwise a lot of bugs are known to sometimes crawl through a person's ear.

>> No.9633908

>>9633554
What state variables define a thermodynamic system completly?

>> No.9633932
File: 299 KB, 1412x1756, CONST.png [View same] [iqdb] [saucenao] [google]
9633932

>>9633554
Is this a good proof for the Fourier Transform of a constant?
The only part I'm kind of iffy about is the line towards the middle:
"We have 0/0, which is an indeterminate form, which means we have a nonzero value"

I can't really think of any other way to motivate the fact that the FT of a constant is an impulse

>> No.9633940

>>9633554
I understand that when you smell something, you are actually detecting airborne particles of that something. Does this mean that everything you can "smell", wood, metal, cloth, everything that has a detectable odor, is spontaneously just being vaporized? Obviously it's a tiny tiny amount but is everything that is able to be smelled spontaneously losing a very small amount of mass?

>> No.9633947

>>9633940
Yes, but is not always literally the molecule of the thing you are smelling, for example in metals you are actually smelling the oxidation reaction with the air.

>> No.9633959

>>9633932
1) Prove the Fourier transform is its own inverse (upto a constant factor and time reversal)
2) Prove the Fourier transform of an impulse is constant

>> No.9634019
File: 405 KB, 793x642, 1522379345309.png [View same] [iqdb] [saucenao] [google]
9634019

>>9633554
How do you solve this
[math]tan\frac{x}{2}=-2 [/math]

>> No.9634035

>>9634019
x/2 = arctan(-2)
x = 2*arctan(-2)

>> No.9634142

>>9634019
you'll need a calculator for that one

>> No.9634149

>>9634019
When does tanx=-2
Just double that x.

>> No.9634334

how can I understand lagrange equations with two constraints? intuitively

>> No.9634350

>>9634334
Multiplier*

>> No.9634411

>>9634334
you minimize with respect to the intersection of both constraints

>> No.9634416

>work in lab
>Work under pH.d from Russia.
>Claims he went to a school that's the Russian equivalent of MIT plus Stanford.
>He's asked to find the slope on a graph by his supervisors
>He comes to me and asks"what is a slope?"

>> No.9634504

>>9634416
He probably knows it as gradient.

>> No.9634528

>>9634416
probably translation error, or pronunciation

>> No.9634595
File: 8 KB, 815x55, 2018-03-31-091021_815x55_scrot.png [View same] [iqdb] [saucenao] [google]
9634595

Can someone explain the step in pic related from the wiki page on AM-GM proof?

>https://en.wikipedia.org/wiki/Inequality_of_arithmetic_and_geometric_means#Proof_by_induction_#1

How can you multiply the LHS by n+1, yet on the right hand side remove denominator n and add x_n+1?

I'll likely have more questions, so if you'd like to just walk a brainlet through it I'd be very appreciative.

>> No.9634600

>>9634595
fuck nevermind, the denominator is n+1 to begin with and you simply multiply it out

this always happens right after I post

>> No.9634626
File: 192 KB, 602x338, main-qimg-5e7b7796d6bfaf5172c66b5c2ac39b7e.png [View same] [iqdb] [saucenao] [google]
9634626

What are the most employable fields of physics?

>> No.9634747

>>9634411
Yeh, I get that. Donno how it works tho

>> No.9634758
File: 392 KB, 2508x1672, images.duckduckgo.com.jpg [View same] [iqdb] [saucenao] [google]
9634758

>>9634626
mechanics

>> No.9635305

Mg+O2->MgO
If theres 24.3g of Mg and 32g of O2 would the theoretical yield be 50% and unreacted be 16g O?

>> No.9635952

In an infinite horizon ramsey problem (macroeconomics) how do I proceed after I know the solution of the system of difference equations given by the Euler Equation and the Resource Feasibility Constraint?
I know that I should use the Transversality Condition to ensure that the present value of the capital stock goes to 0 and t goes to infinity but I do not know how to do it in practice.
My understanding is that since only initial k is given and initial consumption is not, I need the transversality condition to get a specific trajectory solving the problem. My guess would be to check which solution of the 2-eq system satisfies the TC but my problem is the B^t always goes to 0 as t goes to infinity since it is less than 1 and higher than 0.
So basicly the TC tells me nothing and I am sure I am wrong.

>> No.9636087

>>9635952
Nevermind, I managed to do it. Why is it that every time I decide to post my question here (after some thinking on my own) I get the answer by myself?

>> No.9636095

None of you have proof that numbers exist in the physical world. Prove me wrong.

>> No.9636104

>>9636095
1 God

>> No.9636113

>>9636104
Dope. Thanks man. I'm going to link some dude to your post, so you can argue numbers and stuff with him. I don't feel like it.

>> No.9636115

>>9636087
Half of the answer is a correctly formulated question

>> No.9636352

How do you prove [math] tan(x)+csc(x) = (tan(x)+csc(x)-1)/(cot(x)-csc(x)+1) [/math]

>> No.9636578

>>9636095
>None of you have proof that numbers exist in the physical world.
Nothing exists in the physical world.

>> No.9636632

>1920: There will be flying cars in the future
>2018: We don't have flying cars but we have _______
What fills the blank here?

>> No.9636647

>>9636632
Pepe

>> No.9636650

>>9636352
Try multiplying on both sides by [math]\cot\,x \,-\, \csc\,x \,+\, 1[/math].

>> No.9636653

>>9636632
Millions of people discussing the same meaningless shit and posting images of a sad frog on the greatest technology which has ever been created by mankind.

>> No.9636671

>>9636650
I thought it wasn't allowed to do something on both sides when proving and that you should only pick one side to work with

>> No.9636682

>>9636671
Of course it is a=b <=> a*c=b*c, if c=/=0.

>> No.9636685

>>9636352
https://www.wolframalpha.com/input/?i=tan(x)+%2B+csc(x)+%3D+(tan(x)+%2B+csc(x)+-+1)%2F(cot(x)+-+csc(x)+%2B+1)

>> No.9636865

Let S and T be finite sets and [math] F_{S,T} [/math] be the set of all functions from S to T.
Is [math]\Phi\colon F_{s,t}\to \prod_{s\in S} T\,;\ \Phi\colon f\mapsto (f(s))_{s\in S}[/math] a bijection and how do i prove it?

>> No.9636872

>>9636865
>Is Φ:Fs,t→∏s∈ST; Φ:f↦(f(s))s∈S a bijection and how do i prove it?
What have you tried?

>> No.9636894

>>9636671
so you multiply the righy side with this term both in numerator and denominator. like multiplying it by 1

>> No.9636910

>>9635305
Yes

>> No.9636915
File: 33 KB, 720x720, BEA82C4C-A40D-4C8C-B4A5-F66A002A50EF.jpg [View same] [iqdb] [saucenao] [google]
9636915

>>9633908
Number of particles, chemical potential, Volume and temperature.

>>9634626
Quantum field theory

>> No.9636935

>>9636671
>>9636682
You should always separate the both sides of an equation when proving equality, otherwise you are just starting from a statement and deducing a true conclusion, but a true conclusion can be deduced from a false statement take for example
[eqn] \quad ~~~1=0 \qquad \leftarrow \textrm{false} \\
\quad ~~~ 0=1 \\
1+0 = 0+1 \\
\quad ~~~1=1 \qquad \leftarrow\textrm{true} [/eqn]
this doesn't mean that we aren't allowed to manipulate both sides of the equation in proofs, but we need to be very careful in how we do it.

>> No.9637194

Hello. Knowing this and only this property about numbers:
[math]a + (b + c) = (a + b) + c[/math]
How do you prove that
[math]a + b + c + d = (a + b) + (c + d)[/math]
?

>> No.9637214

>>9637194
https://en.wikipedia.org/wiki/Associative_property

>> No.9637233

>>9637214
Dude I know the associative property but how do you prove these
1. ((ab)c)d
2. (ab)(cd)
3. (a(bc))d
4. a((bc)d)
and this 5. a(b(cd))

are all the same??

>> No.9637251

>>9637194
could you just replace d with (d + 0) and then use substitution to do the rest?

>> No.9637255

>>9637251
Nope. You have to do it with no knowledge of 0 i think

>> No.9637266

>>9637194
You have to define what a+b+c+d means in the first place.

>> No.9637267

Why do physicists suck the cock of Bell’s theorem like it’s gospel? >Hurrrrrr I can’t see the details as to why quantum shit happens therefore it just does hurrrrrr.
>Hurrrrr we can change the state of electrons by looking at them therefore conscious creates fucking existence hurrrrrr.
I think it’s incredibly arrogant to believe that you know everything just because you’ve deemed certain aspects of reality unknowable. Will we ever find these hidden variables?

>> No.9637279

>>9637255
that doesn't really make sense to me, I mean we could always just define zero can't we?
for instance suppose e is some number s.t. for all numbers a, a + e = a

if not then I don't think it's possible, you have to have some starting point in order to apply that property such as a + b + c = a + (b + c)

>> No.9637302

>>9637194
>>9637233
Let's rewrite the first line as
[eqn]x + (y + z) = (x + y) + z[/eqn] to make it clearer
Then for the second equation, we can choose x = a, y = b, z = (c + d), this is exactly the right hand side of the equation, from that directly follows
[eqn](a + b) + (c + d) = a + (b + (c + d))[/eqn]. Now, by applying the same process again (and choosing x = b, y = c, z = d, this time going fro left to right), [eqn]a + (b + (c + d)) = a + ((b + c) + d)[/eqn]
This proves that 2. = 5. = 4., and obviously you can go from 2. in the other direction as well to prove that 2. = 1. and 1. = 3.

>> No.9637307

>>9637279
well you can prove
((a + b) + c) + d = (a + (b + c)) + d
knowing that
a + (b + c) = (a + b) + c

>> No.9637309

>>9637279
>>9637307
The variable a, b and c in the different equations are independent

>> No.9637312

>>9637302
Thank you kind sir!!

>> No.9637361

Why did the board became so fast all out of a sudden?

>> No.9637391

>>9637361
stephen hawking died and everyone flocked here to pay respects

>> No.9637440

>>9637267
They dont, thats just what popscientists promote to sell books and lectures

>> No.9637602

Two disguinshable particles trapped in a 1D potential well of length [math]a[/math]have the following wavefunction:

[math] \psi_{nm}(x_1, x_2) = \frac{2}{a} \sin \left( \frac{n \pi}{a} x_1 \right) \sin \left( \frac{m \pi}{a} x_2 \right) [/math]

Now, two undisguishable bosons would have the following wavefunction:

[math] \psi_{nm}(x_1, x_2) = \frac{2}{a} \sin \left( \frac{n \pi}{a} x_1 \right) \sin \left( \frac{m \pi}{a} x_2 \right) + \frac{2}{a} \sin \left( \frac{n \pi}{a} x_2 \right) \sin \left( \frac{m \pi}{a} x_1 \right)[/math]

Shouldn't the ground state of the latter be:

[math]\psi_{11} (x_1, x_2) = \frac{4}{a} \sin \left( \frac{\pi}{a} x_2 \right) \sin \left( \frac{\pi}{a} x_1 \right) [/math]

Why does Griffiths' QM textbook says it's [math] \frac{2}{a} [/math] instead of [math] \frac{4}{a} [/math] ? I don't get where I'm going wrong.

>> No.9637629
File: 19 KB, 400x400, 1500770420591.jpg [View same] [iqdb] [saucenao] [google]
9637629

Any New York fags here? Do any of the SUNYs have a good undergrad math program? And for math people in general what kind of curriculum should I look for? Should I expect to have hack professors?

>> No.9637635

Is there any point to getting both a math and physics masters?

>> No.9637698
File: 3 KB, 211x239, brainlet6.png [View same] [iqdb] [saucenao] [google]
9637698

>tfw trying to show that if t ~ t(n) then t^2 ~F(1,n)
>tfw get a factor of 1/2 from the jacobian that I cant get rid of

>> No.9637717

>>9637698
disregard this
t. stopped being a retard for 5 seconds

>> No.9637732

>>9637440
Brainlet here, why do physicists say that observation creates existence just because they can change the wave-particle state of electrons? Are there any other particles they can “change” by looking at them?

>> No.9637743
File: 84 KB, 379x350, 1508633430244.jpg [View same] [iqdb] [saucenao] [google]
9637743

>>9633554
>Be born male
>Get most of intelligence genes from mother
>Mom is mulatto and dad is white
>Sister has more of dad's intelligence genes as she's female
>Somehow smarter than my sister

Does anyone know what this means?
My sister is about as smart as a white guy I met back in school, but I know a smart girl that manipulated that guy and used him like a tool, but I don't know how smart that girl was. She's in college, but a lot of people go to college that don't belong there.

He's currently 21 and married, and I think he's more successful than I can ever hope to be despite not being as smart as me.

I'm 21 and don't know how to drive.
My sister learned how to drive at 18 even though she can't hope to win against me in a game of chess.

What's going on here?

>> No.9637748

>>9637743
How the fuck do you know where your "intelligence genes" came from?

>> No.9637765

I'm fully aware that an accelerating body cannot be the frame of reference, but how does length contraction/time dilation work if two bodies are travelling towards each other when they're already at relativistic speeds? Do they both experience length contraction?

>> No.9637768

>>9637748
I keep seeing it throughout history and various people saying your mother's IQ has a higher influence over your general intelligence than anything else.

Arthur Schopenhauer straight up said this, so I think he might've observed something I haven't because I'm not socialized.

Then they took rats and injected them with their mother's chromosomes and they wound-up with swollen heads and brains.

Then they took rats and injected them with their father's chromosomes and they wound-up with little heads and big bodies.

Then I look at a roach and I see that we're both perfectly symmetrical despite being two totally different types of animal, and I can't help but think I'm not too far off from a rat or a cat.

https://psychology-spot.com/did-you-know-that-intelligence-is/

Then I see studies with mixed-raced kids that are smarter because their mom's are white.

>> No.9637813

>>9637732
>why do physicists say that observation creates existence
They don't

>> No.9637852
File: 280 KB, 750x1334, 182D6ECA-B79F-41AF-ABCF-184954A548EA.png [View same] [iqdb] [saucenao] [google]
9637852

>>9637813
What is this pseudo philosophical nonsense? I demand answers!

>> No.9637879

>>9637743
>>9637768
most people are raised by their mothers. if your mothers intelligent, then you might be raised to read a lot and study. if not, then maybe you won't do a lot of stuff thats conducive to intelligence.

this might be interesting: https://en.wikipedia.org/wiki/L%C3%A1szl%C3%B3_Polg%C3%A1r

>> No.9638150

>>9637879
>Jewish family

Opinion discarded

Those kids had WAY more "genius" at their fingertips.

>> No.9638418

>>9636865
clear from the definitions

left as an exercise

>> No.9638439

>>9636865
Suppose any two functions are mapped to the same target. In particular, the image of s coincides for both functions for all s. This means by definition that the functions are equal. Hence injective.

Now let (t_1,t_2,...t_n) be any element in the codomain. Since n is the same as the cardinality of S, then define a function f:S -> T that takes the first element of S, s_1, to t_1, the element s_2 to t_2, ... , s_n to t_n. This obviously is a function between finite sets hence belongs to F_S,T and is clearly mapped to (t_1,...,t_n). This proves surjectivity

>> No.9638587

>>9638439
>wasting your time proving surjectivity instead of noting the sets have the same cardinality

>> No.9638872
File: 480 KB, 1200x1600, 1521059730593.jpg [View same] [iqdb] [saucenao] [google]
9638872

alright so my right triangle looks like pic related.
Ive integrated my function and the answer I get is:
>lnIsec(1/2)+tan(1/2)I.
Itd be easy to just replace sec and and tan by the sides I get in my triangle except the (1/2) inside are bothering me.
Does anyone know how I go?
-Maybe replace them when they are on their form sec(theta) and tan(theta) and then multiply what I get by 1/2?

>> No.9638874
File: 11 KB, 1022x1100, x.png [View same] [iqdb] [saucenao] [google]
9638874

>>9638872
Whoopsie daisy, more like pic related.

>> No.9638889

>>9638872
>>9638874
kek
>team mini

>> No.9638982

Do we know.of any information that transcends the boundaries of time? More specifically. My coworker and I were discussing reincarnation. Her question was: "If time is continuous, and reincarnation is real. Is it possible we die and are reincarnated the next day, or could we be reincarnated in the past/ future?" Basically, would our "spiritual information" be continuous as well, or could it jump space time?

>> No.9639117

>linear algebra
I still don't get source and target. Mainly how to identify them. Given some linear system that yields a matrix of size m×n, the source is F^n correct? The target I don't understand.

>> No.9639236

Is IV faster at brain drug delivery than inhalation?

All the research ive read says iv is faster, or that its essentially the same rate as inhaled.

But my reasoning is that IV drugs go to the lungs anyway becauae it is not in oxygenated blood.

For inhaled drugs
The lungs aborb the drug and oxegenate your blood, and send both to your arteries


What am i missing?

>> No.9639319

>>9638872
>>9638874
what the question?

>> No.9639360

Hi guys, I'm learning about networks and how signals are sent along wires.

I have to determine the Nyquist maximum data transfer rate for a 8000hz Modem, it is using QPSK.

Is the number of Discrete levels being measured 4? As in V = 4, in -D = 2B * log2 * V.

>> No.9639437

What's beyond the universe? If it exists, and is finite, then surely something is containing it

>> No.9639440

>>9639437
>If it exists, and is finite, then surely something is containing it
[citation needed]

>> No.9639519

>>9639440
It isn't?

>> No.9639576
File: 35 KB, 445x604, 1473397097370.jpg [View same] [iqdb] [saucenao] [google]
9639576

WHY IS THE EDUCATION QUALITY AT UNIVERSITIES SO FUCKING SHIT I WENT TO A CC FOR 2 YEARS BEFORE TRANSFERRING AND THE TEACHERS THERE HAD THE DECENCY TO USE PROPER GRAMMAR AND WORD THINGS THAT MAKE SENSE. EVERY PROF HERE HAS THEIR SHIT WRITTEN IN BROKEN ENGLISH AND THEY AREN'T EVEN PAJEET, CODE FULL OF BUGS LITERALLY INCORRECT INFO IN LECTURES VAGUE NON ANSWERES WHEN PEOPLE ASK SHIT ON THE CLASS FORUMS, SHIT DUE ON EASTER I JUST SPENT 4 HOURS FIXING THE BUGS TO GET THIS FUCKING PROGRAM TO WORK IM SO FUCKING MAD DUDES I HAVE SO MUCH TO DO TODAYAND IM OUT OF ADDERALL I JUST WANT TO SLEEP

>> No.9639625

>>9639576
Ones who teach at cc usually do so because they enjoy it. Ones who teach at uni do so because it's how they get slaves for their research.

>> No.9639635
File: 41 KB, 600x800, 1513362896594.jpg [View same] [iqdb] [saucenao] [google]
9639635

as I said before this is the answer >lnIsec(1/2)+tan(1/2)I.
Now if it was lnIsec(θ)+tan(θ)l, I could replace them with the side of my right triangle (>>9638874), which would give me. ln ISqrt(1+x^2)+xI. and that would be the end of my solution but I cant replace them bc of the (1/2) inside sec and tan.

>> No.9639636

if
[math]
x^2 - y ^2 = (x-y)(x+y)
[/math]
and
[math]
(x+y)^2 = 2xy+x^2+y^2
[/math]

how can we simplify
[math]
x^2+y^2
[/math]
?

>> No.9639646

How long on average do you have to hold a chloroform-soaked cloth against a person's face before she passes out? Asking for a friend.

>> No.9639648

>>9639646
until SHE inhales at least twice

>> No.9639651

>>9639625
I guess that makes sense, its a big CS/Math research Uni. I wish they'd at least try though, I spend 70% of my time here trying to decypher assignments and slides rather than actually doing the work. What I'd give to have my old discrete math prof teaching these actually difficult courses.

>> No.9639652

>>9639636
If you like complex numbers, you can do x^2+y^2 = (x-iy)(x+iy)

>> No.9639659

>>9639636
as >>9639652 said, it is impossible without the use of complex numbers

>> No.9639661

>>9639652
>>9639659
thank

>> No.9639666
File: 942 KB, 2007x1804, image.jpg [View same] [iqdb] [saucenao] [google]
9639666

I highly doubt that pic related is a valid proof that exp(z+w) = exp(z)*exp(w). I understand that zw/n approaches 0, but limits usually don't work that way, do they? Because following this way of thinking, the whole fraction (z+w+zw/n)/n would approach 0 and the whole thing would be equal to exp(1). So is this proof wrong or am i missing something?

>> No.9639678

>>9639666 here
>would be equal to exp(1)
sry, i meant it would be equal to exp(0)

>> No.9639702

>>9639666
>and the whole thing would be equal to exp(1)
Why?

>> No.9639716
File: 813 B, 270x18, e01b2bdf7935d9f1ef39c418545af61.png [View same] [iqdb] [saucenao] [google]
9639716

Can someone explain this recursion formula

>> No.9639719

What is this "fundamental lemma"?

>> No.9639725

>>9639702
see >>9639678
because (z+w+zw/n)/n approaches 0 as n becomes really large, so theres only lim n->inf 1^n left, which is 1. i know that this is not correct, but it seems to me that the book uses exactly that logic and simply throws away the zw/n part.

>> No.9639727

> this recursion formula

Look up "Fibonacci sequence".

>> No.9639742

>>9639716
>Can someone explain this recursion formula
What do you not understand?

>> No.9639743

>>9639636
Funnily enough, this question but for higher powers is exactly what motivated almost all algebra/ring theory/number theory since the 1800s

>> No.9639748

>>9639742
Explain it to me like I'm a five year old. How would I go about finding A(n) up to A(10). I found by trial and error and finding the pattern that way but I'd like to know the actual way to solve these.

>> No.9639756

>>9639719
are you reffering to >>9639666 ?
this "fundamental lemma" says that lim n->inf (1+z/n) is equal to the power series for exp(z).

>> No.9639787

>>9639748
>How would I go about finding A(n) up to A(10).

You already know what A(1) and A(2) is, then A(3)=A(2)+A(1)=2+1=3, similarly you find A(4).

>> No.9639846

>>9639636
[math]x^2+y^2 = (x+y)^2 - 2xy[/math]

>> No.9639957
File: 23 KB, 681x481, asas.png [View same] [iqdb] [saucenao] [google]
9639957

How the fuck do you solve this? I'm getting 12.3077 when I try to do it.

>> No.9639977

>>9636935
>true conclusion can be deduced from a false statement
-2=2
(-2)^2 = 2^2

>> No.9639997

>>9639716
easy
a_2=2
a_1=1
a_0=1
a_-1=0
a_-2=1
a_-3=-1
a_-4=2
a_-5=-3
a_-6=5
a_-7=-8
a_-8=13

and so on

>> No.9640015

pls send help

[math]
\frac{2a \sqrt{2}}{9} = (a + \frac{2 \sqrt{2}}{3}) (\sqrt{(4a^2 - 2a (\frac{2 \sqrt{2}}{3})})
[/math]

how do I [math]a[/math]

>> No.9640030

>>9640015
Ask a CAS or some numerics software.

If you are desperate to do it by hand, maybe square both sides?
But be careful with that, unless you know that a is positive.

>> No.9640042
File: 57 KB, 560x658, 1504043337301.png [View same] [iqdb] [saucenao] [google]
9640042

>>9640030
>If you are desperate to do it by hand

Well I'm supposed to find it by hand by I believe

>> No.9640063

>>9633554
For you biofags, what am I eating when I eat lobster tail? I had an assorted feast of seafood this weekend where we had to peel and break everything to eat it, but the lobster tail was the only thing that perplexed me as I tore it apart.
Like, it's not a muscle is it? Not like crab meat which has tendons anyway. There weren't any traces of digestion making it's way anywhere. To me, it's seems to be a large mass of useless tissue. I don't even understand how it moves, or if it moves. I know it needs a purpose, but that's why I'm here asking anyone who might know. Google searches kept coming up with recipes.
You know what it really reminds me of? The emporers new groove, where they're eating at the restaurant and the llama is dressed in disguise as a woman, and the fat guy orders a giant rolly poly bug and cracks it open and it's just warm steamy insect mush.

>> No.9640067

Does the EM Drive work?

>> No.9640068

>>9640063
It's muscle.

>> No.9640093

>>9640068
This is the dumbest muscle I've ever seen. It's huge, and no where near the power of the claw muscles. Plus the tiny legs at the bottom are only connected by tiny stubs of flesh, so what gives. But thanks, I really felt weird eating what I didn't know.

>> No.9640099

>>9640093
That's probably why it's a delicacy. A little-used muscle makes the best meat. Think of the gluteus maximus (your ass) in humans. It's the largest muscle in our bodies, yet we don't use it much, directly at least.

>> No.9640109

>>9640042
I have to say that it is a pretty ugly Problem, I don't really see a "nice" solution.

But since you know that a>0 you could square both sides of your equation and calculate the roots of a polynomial with degree 4.
That is what I would call "ugly".

>> No.9640114

>>9640109
>you could square both sides
you mean pow2 both sides?

>> No.9640122

>>9640114
Yes, that will make the square root disappear and give you a polynomial of degree 4, where you need to find the roots.

>> No.9640146

Is it true that hairy chest indicates high intelligence?

>> No.9640158

>>9640015
>he didn't think of squaring both sides
Must be tough being old enough to be legally allowed to browse 4chan while still being in middle school.

>> No.9640167

Why do nurses think they deserve the same level of respect as doctors?

>> No.9640195

>>9640099
Fair point

>> No.9640197
File: 9 KB, 563x503, Untitled.png [View same] [iqdb] [saucenao] [google]
9640197

I feel like a retard for not being able to do elementary geometry. How do I prove beta=theta/2?

>> No.9640220

>>9640197
Halve the angle at the center of the circle, which is formed by the black horizontal line and the red line.

>> No.9640222

for polar coordinates why do we integrate r first and then theta?

>> No.9640229

>>9640197
well, you know y and you know that Oy = r
so I assume you use tan/sin whatever here. Shouldnt be an issue to find n:

n^2 = r^2 - y^2

>> No.9640230

>>9640222
Does it really make any difference?

>> No.9640237

>>9640167
As my sister would say it, she does all the real work while the doctor just comes in and gives a diagnosis based on information she procured. I will give nurses this tho- there is no other profession imo as dirty and both mentally and physically exhausting, and to put up with hours of bullshit with a forced smile on their face for mediocre pay is beyond me. A doctor can talk some sass back, but nurses are required to suck it up, and if you've ever seen some fatass get shitty with a cashier over no ice in their drink than you can imagine what they'd be like with their grandma's sore wrists. God help you if you have 3 of those people ringing for you at the same time.
It's not the same respect I have for doctors, but damn, it's there.

>> No.9640241

>>9640220
so theta/2=arctan(.5y/r)=arctan(y/2r)=beta
That seems like circular reasoning, does it not? I feel like I'm losing my mind.
How do I show theta/2=arctan(.5y/r)?

>> No.9640242

>>9639957
I'm pretty confused as well. I get 43.69 uM and don't know why.

A = 2 - Log(%T), so 0.69897. The rest should be pretty straightforward...

>> No.9640247

>>9640197
The line from the centre to the red dot (x, y) is of length r.
So the triangle with β is isoceles and has 2 angles of size β and one of size 180° − θ.
The interior angles of a triangle sum to 180° so we have 2β + 180° − θ = 180°, hence β = θ/2.

>> No.9640252

>>9640241
You don't need any arctan fuckery.
Just halve the angle, then you get two triangles:
the line you have drawn - red line towards the left - the horizontal line

the line you have drawn - red line to the right -red line to the left.

These triangles are the same, the missing angle is 90-beta, so the horizontal line seen from the center has an angle of 180 degrees and you know that:
180 = 90 -beta + 90 - beta + theta.

If you don't get it I could also draw you a picture.

>> No.9640256

>>9640247
Aha. I could not see that the upper triangle was isosceles. Thank you anon.

>> No.9640257

>>9640247
this guy is right and I've missed it

>> No.9640259

>>9640256
>Aha. I could not see that the upper triangle was isosceles.
because you are mongoiloid and did not use special geometry syntax to mark equal sides of a n-gon.

>> No.9640266

>>9640259
Why the hostility? I already admitted I'm a brainlet.

>> No.9640356

>>9640230
Yeh it does

>> No.9640363

Why does kelvin go from 0 to 273? what happens at 0 and 273?

>> No.9640366

>>9640356
What about fubini though?

>> No.9640389

>>9640366
That's only for rectangular. It doesn't work for polar

>> No.9640431

>>9640146
bump
Is your chest hairy /sci/?

>> No.9640575

>>9633554
why does dad hit me and mommy?

>> No.9640578

>>9640363
nigga kelvin goes all the way to infinity. It's just that 273 kelvin is equal to 0 degrees centigrade

>> No.9640625

>>9640578
kelvin is retarded scale imo

>> No.9640708
File: 30 KB, 1024x238, 5FDvItRW.jpg [View same] [iqdb] [saucenao] [google]
9640708

Can anyone help me solve this system of equations? My algebra skills are incredibly shit.
How do I solve for the currents?

>> No.9640734

>>9640708
If, for example, you have I_2, and want to get I_1, then, starting from the second equation (the one starting with "-I_1...."), you add I_1*R_1 to both sides of the equation, then divide by R_1.

But I think you need at least 1 "I" to solve this, at least with the signs being the way they are. Are you sure those equations are correct?

>> No.9640737

>>9640734
Yeah, they're correct. My teacher gave us the equations and the known parameters. Everything except I is known.

>> No.9640775

>>9638439
thanks. i got the injective bit, but i was just a bit unsure about about proving surjectivity
i just showed it had an inverse in the end.

>> No.9640801

>>9640708
first put your system int matrix form
[eqn] \begin{bmatrix}
-R_1 & R_2 & 0\\
0 & -R_2 & -R_3\\
1 & 1 & -1
\end{bmatrix}
\times
\begin{bmatrix}
I_1\\
I_2\\
I_3
\end{bmatrix}
=
\begin{bmatrix}
V_2-V_1\\
-V_2\\
0
\end{bmatrix} [/eqn]
then solve however you want, either by reducing the matrix to row echelon form or by left multiplying the solution vector by the inverse matrix

>> No.9640807

>>9640167
Because nurses do most of the work.

>> No.9640811

>>9640363
0° Kelvin is the lower limit for temperature, temperature can never go below that (and 0° Kelvin cannot be actually measured either, because "measuring" would involve physical processes which produce heat)

>> No.9640820

>>9640811
It's just 0 though, without the " ° ".

>> No.9640821

What's the relationship between ideals of a ring and the linear span in a vector space?
Is one more general than the other? Is a linear span an ideal?

>> No.9640897

>>9640821
The span is just the ideal generated by the vectors in your span

>> No.9640939
File: 80 KB, 908x551, Screenshot 2018-04-02 at 5.38.36 PM.png [View same] [iqdb] [saucenao] [google]
9640939

I'm not in STEM, can some on explain the joke.

>> No.9640947

>>9640939
Someone on /sci/ decided to shitpost. That's the joke.

>> No.9640968

>>9640939
Just an exaggeration of the sort of assumptions different fields are more willing to take.

>> No.9640978

hardest math problem?

>> No.9641050

>>9640897
>The span is just the ideal generated by the vectors in your span
There are no ideals in a vector space since there is no ring structure.

>> No.9641051

>>9640978
>hardest math problem?
Riemann hypothesis

>> No.9641057

>>9640821
>What's the relationship between ideals of a ring and the linear span in a vector space?
Nothing.

>> No.9641062
File: 16 KB, 251x245, 1513227606329.jpg [View same] [iqdb] [saucenao] [google]
9641062

i have a presentation in 10 minutes that i am 100% not prepared for. should i just skip it and email the professor later? it's a large class and the presentations are being done over multiple days

i feel like huge fucking shit fuck fuck FUCK

>> No.9641110

How does horizontal centripetal motion interact with the force of gravity on a mass? For example if I were to spin a tennis ball on a rope how is the Y component of the net force 0?

>> No.9641127

Why does [math] \limsup_{n \to \infty} \sqrt[n]{|a_n|} = \frac{1}{\sqrt{2}} [/math] for the series [math] \sum_{n=1}^{\infty} \frac{2^n+3^n}{6^n} [/math]? The upper limit of a sequence is defined by Rudin to be the supremum of the set of numbers that the subsequences of that sequence converge to.

>> No.9641141

>>9641127
[math] lim_\limits{n \rightarrow +\infty} \frac{2^n+3^n}{6^n} = lim_\limits{n \rightarrow +\infty} \frac{2^n}{6^n} = lim_\limits{n \rightarrow +\infty} \frac{1}{2^n} [/math] so [math]\limsup_{n \to \infty} \sqrt[n]{|\frac{2^n+3^n}{6^n}|} = \frac{1}{\sqrt{2}} [/math]

>> No.9641150

>>9641141
ups meant
[math] \lim\limits_{n \rightarrow +\infty} \frac{2^n+3^n}{6^n} = \lim\limits_{n \rightarrow +\infty} \frac{2^n}{6^n} = \lim\limits_{n \rightarrow +\infty} \frac{1}{2^n} [/math] so [math] \limsup_{n \to \infty} \sqrt[n]{|\frac{2^n+3^n}{6^n}|} = \frac{1}{\sqrt{2}} [/math]

>> No.9641156

>>9640978
>A sky island above the north pole is populated by genetically engineered cat girls.
>At least one of the Nekos has a white collar.
>The rest have red collars.
>Each Neko knows the color of every other Neko's collar, but no Neko knows the color of their own collar.
>The Nekos can understand English, but they never speak or write, and there are no mirrors or reflective surfaces in reach, so they can never determine the color of their own collar.
>Although the Nekos spend most of the day asleep, they maintain lucidity and awareness of external sounds at all times.
>Once an hour a clock tower bell rings, and every Neko hears the bell.
>The Nekos were genetically programmed so that if one learns she has a white collar, she'll wait for the next hourly clock tower bell and then jump off the island.
>The deductive reasoning skill of each Neko is infallible.
>On one occasion only, instead of an hourly bell, every Neko hears a loudspeaker shout "AT LEAST ONE CAT GIRL IS WEARING A WHITE COLLAR!"

What happens next?

>> No.9641160

>>9641150
and i also made a mistake here it's 3^n not 2^n on the numerator in the second limit

>> No.9641165

>>9641160
I appreciate you taking the time to type this out but I still don't understand why the first statement implies any of the others.

>> No.9641195
File: 36 KB, 1898x817, Untitled.png [View same] [iqdb] [saucenao] [google]
9641195

anyone have any experience with ltspice?
trying to figure out why i keep getting a different answer on paper than on here

so v(n002,n001) is the voltage drop on the resistor at t=4.452202

if i use voltage division with complex numbers i get [math]\displaystyle \dfrac {10e^{-j \frac{\pi} {4}}}
{2+2j} * 2 [/math], where 2+2j is Zeq
that's equivalent to [math]5\sqrt{2}e^{-j \frac{\pi} {2}}[/math], so that would mean [math]v_r(t)=5\sqrt{2}\cos{(0.5t-\frac {\pi} {2} )}[/math], and v_r(4.452202)=5.60638 which is off from the value ltspice gave
in fact most times i've tried stuff with other numbers it's been close but definitely not a rounding error or accuracy problem (if it were, that voltage wouldn't be correct, and it is)

i doubt that it's my math that's wrong since this is how the professor teaches it and how the book does it
also as you can see the current plotted at the top is weird, it should be decaying from a value rather than going from negative to positive like that, when it should be I(t)=I0(1-e^t/T)

so uh what am i doing wrong here

>> No.9641201

Rudin also writes [eqn] \limsup_{n \to \infty} \sqrt[n]{|a_n|}= \lim_{n \to \infty} \sqrt[2n]{\frac{1}{2^n}} = \frac{1}{\sqrt{2}} [/eqn] which I also don't understand. I thought that the upper limit should be the largest number that some subsequence converges to, in this case I would have assumed that the subsequence that converges to the largest number is the sequence itself and calculated [eqn] \lim_{n \to \infty} \sqrt[n]{{\frac{2^n+3^n}{6^n}}} < \frac{5}{6} [/eqn] by the binomial theorem, ergo the series converges. Why is this not the correct way of doing this?

>> No.9641204

>>9641201
This is in reference to
>>9641127

>> No.9641250
File: 19 KB, 906x176, Untitled.png [View same] [iqdb] [saucenao] [google]
9641250

Can someone explain how exactly this constitutes an abuse of notation?
and by the same token is [math]\nabla=\left(\frac{\partial}{\partial x_1},...,\frac{\partial}{\partial x_n}\right)[/math] also an abuse of notation?

>> No.9641254

>>9641201
the ratio test and the root test both exist to test the existence of some geometric series that over approximates the absolute series. While it is possible for these limit tests to fail to converge, that doesn't mean the strategy is not applicable.
If the least upper bound of the set of limits of sub sequences of the sequence of root (or ratio) test terms is less than 1, then you can still use that supremum to construct a geometric series to over approximate the absolute series (so the absolute series converges because its a monotonically increasing sequence of partial sums bounded above, and so the series converges because the [eqn]\frac{\left | a_{n} \right |+a_{n}}{2}[/eqn]

[eqn]\frac{\left | a_{n} \right |-a_{n}}{2}[/eqn]

sequences are monotonically increasing, and bounded above by the absolute series.
The limit that you are computing has nothing to do with this; you just divide the numerator and denominator by [eqn]3^{n}[/eqn], and take the limits of the numerator and denominator. Because the numerator is always bigger than 1, its roots will shrink, so the sequence of upper bounds [eqn]\left ( \frac{2}{3}\right )^{n} + 1[/eqn] will converge to 1, so the limit is just 0.5.

>> No.9641265

>>9641250
This is abuse of notation because you can't multiply a 1x1 matrix with a nx1 matrix or a vector.
>>9641254
Thanks for clearing things up for me, I think I understand now.

>> No.9641268

>>9641265
unless those are just normal brackets in which case it seems fine.

>> No.9641271

>>9641250
it looks like it would be to the average student, but it's actually just an operation
del F is defined like an operation

if you define each term as if it were a 1x1 matrix, then it wouldn't make sense to apply that operand to a function because of those basis vectors, so instead it's defined like a mapping

>> No.9641316

>>9641195
i-it's not like i wanted an answer or anything b-baka

>> No.9641359
File: 48 KB, 458x389, z.png [View same] [iqdb] [saucenao] [google]
9641359

can you guys suggest me an approach to calculate both these values? the only information being that this is an equilateral triangle and P is its barycenter

>> No.9641371

>>9641359
assuming the bottom left is the origin, x^2=p_x^2+p_y^2 or if you prefer x=p_x*sqrt(3)/3, and h=2p_x

if p is the origin, then you have no way to calculate it since you know no measurements

>> No.9641517

Having a brainlet algebra moment:
How do I get from
[math]8^{k+1}-3(8^k)+3(8^k)-3^{k+1}[/math]
To
[math]8^k(5)+3(5^k)[/math]
swear to god I'm gonna have to re-learn this shit

>> No.9641537

>>9641517
>How do I get from
>8k+1−3(8k)+3(8k)−3k+1
>To
>8k(5)+3(5k)
You can't.

>> No.9641556
File: 260 KB, 2048x1433, IMG_6718.jpg [View same] [iqdb] [saucenao] [google]
9641556

>>9641537
Surely I'm reading pic related wrong then?

>> No.9641564

>>9641556
>Surely I'm reading pic related wrong then?
Yes, since it does not say "8^k(5)+3(5^k)" anywhere.

>> No.9641648

>>9639957
The biology TA's who wrote this question don't know what they're doing. 43.7 micromolar is the correct answer. You can tell that the tool who wrote this is retarded by only providing two possible answers, and three other answers only a 4 year old might consider.

Biologists are notoriously bad at chemistry, and I know this from personal experience.

>> No.9641768

>>9641359
let it be ABC - clockwise by vertices
Do we know value of h? If so, then we calculate half-area, then we have full area, then we prove that triangle APC = CPB = APB thus area of APC = full area/3

now, since we have area and it is equilateral, we can find P-to-AC cathetus and we know that 2nd cathetus will be half of h

So we can use Pith. theorem to find x.

>> No.9641785

How much damage would one milliliter of nitroglycerin do if set off on a weightlifters chest?

>> No.9641812
File: 97 KB, 787x787, 1521534566404.jpg [View same] [iqdb] [saucenao] [google]
9641812

is taking some kind of precalculus course/self study important for studying calculus, or can i hop straight into it? i've got a few months before i start back in school and i want to get a head start so i want to start learning it on my own.

while i'm at it, is khanacademy a good place to self study, or are there other/better places?

please don't bully me.

>> No.9641882

>>9641156
If there are two or more white collars, nothing will happen. If there is only a single white collar, it will jump of the island when the bell rings again in an hour

>> No.9641897
File: 9 KB, 184x80, 5.jpg [View same] [iqdb] [saucenao] [google]
9641897

Can anyone check my work here? Question is to identify singularities of the function and classify it as removable, a pole, or essential.
I have a removable singularity at 0 and essential singularities at pi*n, for nonzero integers n

>> No.9641915

>>9641812
please respond

>> No.9641916

>>9641882
Second sentence is correct. First is wrong.

>> No.9641928

>>9641897
double checked my work, the singularities at pi*n should be poles, not essential singularities

>> No.9641931

>>9641812

Brush up on trigonometry and equation solving. Khan academy is good and you should use it as a companion with a book of your choice (see the wiki).

>> No.9641957

>>9641812
You need to understand trigonometry. Not necessarily finding sides or angles of non-right triangles (law of sines/cosines and other crap) but you need to know the geometric meaning of the sine and cosine functions. An intuitive understanding of the tangent function is helpful too. Learn to use radians instead of degrees, degrees are useless for calculus. You must also be able to reduce equations algebraically (properties of exponents, FOIL, etc), and know properties of logarithms. Being good at factoring is important too and you may need to do polynomial long division once or twice. Understand how a function relates to its inverse, and inverse operations in general. Some of this stuff can be learned as you go but it helps if you've at least had exposure to it beforehand. Calculus is not hard, it's the algebra that trips students up. Use a good textbook for rigor and definitions, and use khan academy for practice problems and when you get stuck. Some pre-calc books have a section on limits, doing that would give you a head start. You can skip the section on matrices but doing it would be helpful if you take linear algebra later. It also makes solving systems of linear equations easier once your good at it. Paul's math notes is also a really good resource.

>> No.9641960

>>9641050
>>9640821
well it is the submodule. Rings and vector spaces are both modules, one as [math]\mathbb Z[/math] module and the latter as a module over a field, and an ideal is the submodule generated by some elements, just as the span is.

>> No.9641961

>>9641957
Oh and understand the difference between even and odd functions, and know the basic graphs of logarithmic equations, exponential equations, polynomials, etc. You don't need to know graphs involving more than one of these in the same function, one of the things you'll be learning in calc is how to graph these without a calculator. Often problems in calculus will come down to simplifying a complicated problem into parts that can be easily understood, like these basic graphs.

>> No.9641963

There is typically no multiplication in a module. A module is first and foremost a group that only satisfies addition.

The ring provides an action, but that's different. Generally you can't multiply vectors but you can multiply by a scalar, that's the difference between having a ring and an action.

Though if you have a module under R I'm fairly certain they work as modules under ideals of R as well - not quotients though I believe.

>> No.9641964
File: 346 KB, 2048x1536, _145RvfR.jpg [View same] [iqdb] [saucenao] [google]
9641964

Can someone help me with this?
Sorry for the crappy quality.

>> No.9641967

>>9641963
Meant to link
>>9641960
Also rings are modules in a really trivial way.

>> No.9641972

>>9641964
Find the volume of the orange juice, then find the depth of another rectangle contained within the flipped over carton that has the same volume

>> No.9641981

>>9641972
Ah, that makes sense now. Thanks.

>> No.9641986

>>9641916
Ok, then I'll try again. If there are N white collars, they will all jump the Nth time the bell rings again

>> No.9641993

>>9641127
You have two different ways of attack. You can either bound the sequence from above and then show there exists a subsequence that attains that value, or you can just show that the sequence actually converges to that number, and hence the limsup is trivially it.
[eqn] \frac{2^n+3^n}{6^n}\leq \frac{2\cdot 3^n}{6^n}=2\frac{1}{2^n}=\frac1{2^{n-1}}\implies\lim \sqrt[n]{\frac{2^n+3^n}{6^n}}\leq\lim \sqrt[n]{\frac{1}{2^{n-1}}}=\lim \sqrt[n]{\frac{1}{2^{n}}}=\sqrt{\frac1{2}}[/eqn]
Ok, so now you know your sequence is bounded above by [math]\frac{1}{\sqrt2}[/math]. This sequence is quite obviously decreasing and always positive, so i sense it must converge, and hence we have case 2. Now:
[eqn]\frac{2^n+3^n}{6^n}\geq \frac{3^n}{6^n}=\frac{1}{2^n}\implies\lim \sqrt[n]{\frac{2^n+3^n}{6^n}}\geq\lim\sqrt[n]{ \frac{1}{2^n}}=\sqrt{\frac1{2}} [/eqn]
so it is also bounded below by it, hence [math]\limsup=\liminf=\lim=\sqrt{\frac1{2}}[/math]

>> No.9642009

What he fucks a {m,n}-graph in basic graph theory? My textbook doesnt have this notation but there's a question in my assignment asking for you to show that if a {m_1,n1}-graph and {m_2,n_2}-graph are isomorphic, then m_1 = m_2 and n_1 = n_2.

Is it a graph of order m and size n, or the graph K_{m,n}? I dont know.

>> No.9642019

>>9641967
I don't see what your problem is. Yes, rings are Z-modules trivially, and vector spaces are F-modules by definition, where F is a field. The span of a set of vectors in a vector space is precisely the submodule generated by them, just as an ideal generated by elements in a ring is an ideal and hence a submodule of the ring. The multiplication in a ring is captured in the fact that it is also a Z-algebra, but that doesn't add anything to what i said

>> No.9642020

>>9642009
prolly nodes and edges

>> No.9642048

>>9633571
What about by Weight?

>> No.9642057

>>9642009
>What he fucks a {m,n}-graph in basic graph theory? My textbook doesnt have this notation but there's a question in my assignment
Email your instructor.

>> No.9642060

>>9641812
>is taking some kind of precalculus course/self study important for studying calculus, or can i hop straight into it?
Try and see.

>> No.9642068
File: 38 KB, 877x546, 1499695340131.png [View same] [iqdb] [saucenao] [google]
9642068

>>9642057
I cant be bothered to deal with that retard for this. Ill just assume its >>9642020

Pic related is part of the assignment, and is exactly what I expect from him. Look at the Hs. look at the first part of question d. I hate my university.

>> No.9642078 [DELETED] 

>>9641960
>well it is the submodule. Rings and vector spaces are both modules, one as Z module and the latter as a module over a field, and an ideal is the submodule generated by some elements, just as the span is.
It is true that for a commutative ring, the set of submodules is equal to the set of ideals, but vector spaces are not commutative rings, in fact not rings at all, and so there are no ideals one could speak of when discussing a vector space aside from the trivial ones in the field of scalars.

>> No.9642086
File: 31 KB, 485x443, 1512666625659.png [View same] [iqdb] [saucenao] [google]
9642086

what the fuck is a surface integral? i can't for the life of me see this conceptually

>> No.9642097
File: 8 KB, 766x386, 755.png [View same] [iqdb] [saucenao] [google]
9642097

>>9642086
a surface is made of an infinite number of infinitely small little squares of dx*dy size
When you're integrating a surface you're summing all of them, which gives the size of the surface in it's entirety

>> No.9642100

>>9642086
a line integral, but instead, over a surface instead of a line.

>> No.9642106

>>9642097
>muuh infinitely small little squares
such a dumb brainlet explanation. did you copy that straight from your hs teacher?

>> No.9642112

>>9642106
then show us how you would explain it Einstein

>> No.9642115

>>9642097
isnt that just square cm/m/km?

>> No.9642121

>>9642115
What do you mean?

>> No.9642122 [DELETED] 

Is there a way to solve
3e^{25t} – e^{10t} = 1
Without using the quadratic formula?

>> No.9642123

>>9642112
a surface integral is an integral along a surface

>> No.9642125

Is there a way to solve,
[math]3e^{25t} – e^{10t} = 1 [/math]
Without the quadratic formula?

>> No.9642127

>>9642121
square cenetimeter (just using SI unit) is used to calculate area (surface). To do so, we divide the existing x-gon by x squares each 1x1 unit

https://proofwiki.org/wiki/Area_of_Square

Unless what you've drawn isnt accurate and dx/dy not equal

>> No.9642133

>>9642123
>a surface integral is an integral along a surface
such a dumb brainlet explanation. did you copy that straight from your hs teacher?

>> No.9642135

>>9642125
>Is there a way to solve,
>3e25t–e10t=1
>Without the quadratic formula?
Is there a way to solve it with the quadratic formula?

>> No.9642137

>>9642125
>>9642122
insert it into a computational solver such as wolframalpha

>>9642133
lol someones very butthurt

>> No.9642153

>>9642125
cant you

[math]
e^{10t}(3e^{15t} - 1) = 1
[/math]

>> No.9642156
File: 8 KB, 385x217, 471741.png [View same] [iqdb] [saucenao] [google]
9642156

>>9642127
in calculus they are actually infinitely small instead of just being of a very small size, to the point of being able to make curves with them since the difference is negligible

>> No.9642158

>>9642156
in Geometry too, you have mm^2, nm^2 etc
if cm^2 does not fit the shape you crack it down so smaller units if needed

>> No.9642159

>>9642153
That doesn't tell you what t is.

>> No.9642161

>>9642158
so you do understand the concept

>> No.9642184

how do I show [math]\nabla \cdot \nabla \times \mathbf{F} =0[/math] without iterated partial differential operators and regardless of coordinate system?

>> No.9642215

>>9642184
einstein notation

>> No.9642254

>>9642019
There are complications with that view. You can guarantee things about the size of bases in vector spaces, you cant in finitely generated rings. Ideals may be infinitely generated in a ring which is finitely generated and so forth.

>> No.9642325

>>9642254
I never claimed anything about how many elements you needed to generate it. Obviously, modules over a field are better behaved that modules over a ring, and given that finite dimensional vector spaces are by definition noetherian, every submodule is going to be obviously also finitely generated.

>> No.9642392
File: 8 KB, 229x250, 1564578.jpg [View same] [iqdb] [saucenao] [google]
9642392

So lets say a "friend" throws a ball at my face at 10m/s, would this hurt more if I was running towards the ball at some velocity (lets say 5m/s), or if I were stationary?

It feels like it should hurt more, but the damage to your face comes from the sudden deceleration due to the impact, and whether I am running towards the ball or not, the ball will always have the same amount of force with which it can decelerate my face, if the ball can apply 5m/s of acceleration to my face, it shouldn't matter if I'm going from +5m/s (running towards it) to 0m/s or from 0m/s to -5m/s. Which one is it?

>> No.9642403

>>9642392
>would this hurt more if I was running towards the ball at some velocity (lets say 5m/s)
Yes. The ball would effectively hit you at 15m/s.

>> No.9642404

>>9642392
Yes, see newton's law

>> No.9642416

>>9642392
>5m/s of acceleration
M/s is a measure of velocity, not acceleration. And technically the ball applies force, which is a function of acceleration *and mass*.

>> No.9642472

A body was moving withing 4 hours. In first 1 hou it moved x kms, in second hour, it moved 0.5 less than previous hour.

How would I go about making a nice math model to calculate its travel path for given amount of hours?
t = 4
l(4) = x + (x-0.5) + (x-1) + (x-1.5) = 4x-3

l(t) = x + ((t-1)(x-1)) does not work properly. Recursion needed?

>> No.9642482

>>9642472
d is distance, s the initial speed
d = s * 1h + (s - 0.5 km/h) * 1h + (s - 1 km/h) * 1h + (s - 1.5 km/h) * 1h
d = 4s * 1h + 3 km
d - 3 km = 4s * 1h
(d - 3 km) / 4h = s

Now just put in whatever the total distance traveled is and you get the initial speed. If you actually want to calculate a travel path you need more information

>> No.9642484

>>9642482
dont necessarily need [to express via] speed, just how to express distance traveled knowing the give

>> No.9642490

>>9642482
oh ok you read it wrong,
for the first hour it traveled X km
for the next hour it traveled 0.5km less against the previous

it isn ot 0.5km/s or km/h, it is distance here

>> No.9642501

>>9642472
baby math
Just get the equation of a line using the two given points

>> No.9642506

>>9642490
I made a sign error in the second line, but the formula basically stays the same.
Total distance travelled:
d = 4s - 3 km
Distance travelled in the first hour:
s = (d + 3 km) / 4

With s being the distance covered in the first hour instead of speed

>> No.9642508

>>9642501
you mean linear equation y= kx+b?
how would it work here if the motion[supposedly] not a linear constant?

>> No.9642514

>>9642506
not working, try to calculate distance traveled in first 2 hours

should be 2x-0.5 but with your formula if we replace d we will get wrong result

>> No.9642517

>>9642508
in that case literally impossible to calculate anything with such small amount of information

>> No.9642526

>>9642517
There is no need for speed at all.
The question sounds like this:

The tourist was walking from A to B within 4hours. In the first hour, the traveled `x` kilometers. In the next hour he traveled 0.5 kilometers LESS than in previous hour.

then there are subquestions: a,b,c,d find his distance in first 2 hrs, all 4 hours, last 2 hrs etc etc

Now, it is a very simple task that is not supposed to be solved via complex formulas, it just a polynomial example, but I was curious if a function/equation could be made to express l(t) (l - distance)

>> No.9642529

>>9642514
Ok, lets say it's 2 hours, and the d = 5 km. Then we get (5km + 0.5km) / 2 = 2.75 km = s. 2.75 km + (2.75 km - 0.5 km) = 5 km, so the math checks out. If instead of d we are for example given s = 2.5 km, we get a total distance of d = 2s - 0.5km = 4.5 km

>> No.9642537

>>9642526
nothing can be done sorry
id like to see you try to prove me wrong though

>> No.9642541

>>9642472
l(t) = t * x - (t - 1) * t / 4

>> No.9642553

>>9642325
I don't get your point, then. You understand that rings are trivially modules and that subrings are therefore submodules. This isn't really news.

>> No.9642555

>>9642541
ok, this one works

>>9642529
nah see >>9642541


of course there has to be some limitations for
[math]
\frac{t(t - 1)}{4}
[/math]
so we wont end upo with negative distance

>> No.9642564

>>9633554
Can I model my jerkoff sessions with a fourier series if my thrusts into my fleshlight are periodic?

>> No.9642565

>>9642555
for t=0 or t=1, t*(t-1)/4 = 0
for t>1, t*(t-1)/4 > 0

No limitations needed

>> No.9642568

>>9642565
> "In the next hour he traveled 0.5 kilometers LESS than in previous hour."

Imagine he was walking like a madman 100hrs and x kilometers in first hours was 5

There isnt that many times you can reduce 5 by 0.5 until it goes negative

Therefore x must be >= (t - 1) * t / 4

>> No.9642579

>>9642568
Oh, you mean limitations for x. Those should be obvious: x >= 0.5h - 0.5, where h is the maximum number of hours travelled. If you just take x >= (t-1) * t / 4, then the distance travelled in the later hours can still be negative

>> No.9642581

>>9642579
yeah I realized later I was talking about the sum, my bad

>> No.9642593

>>9642579
>>9642565
>>9642541
what was your through process behind it? I know it is baby stuff but as a brainlet I'm curious. were you familiar with this approach or just bruteforced the original limited function?

>> No.9642630

>>9642593
The first step was recognizing the general formula: [math]l(t) = t * x - \sum\limits_{n=0}^{t-1}\frac n 2 = t * x -\frac 1 2 \sum\limits_{n=0}^{t-1} n[/math]
And any mathematician (or in my case computer scientist) knows the closed form for [math]\sum\limits_{k=0}^{n} k = \frac {n (n + 1)} 2 [/math], which is just the sum above shifted by 1, so you shift it back and get the formula

>> No.9642637

>>9642630
ok, I see you know japenese, that's cool

>> No.9642644

>>9642637
What are you talking about?

>> No.9642675

>>9642644
Your summation notation confused him.

>> No.9642688

>>9642675
I've never seen a different one

>> No.9642700

>>9642688
Well I've never seen one to being with

>> No.9642725

>>9642700
It's just a sum of the expression to the right of the upper case sigma (the strange "E") for the variables/lower bound below it to the upper bound specified above it
E.g.:
[math]\sum\limits_{n=1}^{3}n = 1 +2 +3 [/math]
[math]\sum\limits_{n=1}^{4}\frac 1 n = \frac 1 1 +\frac 1 2 +\frac 1 3 +\frac 1 4 [/math]
[math]\sum\limits_{n=1}^{5}1 = 1 + 1 + 1 + 1 +1 [/math]

>> No.9642729

>>9642725
oh I see

>> No.9642776

Any book recommendations for using R? Resources are also welcome

>> No.9643064

>>9641986
Correct. It takes N−1 bells for each white collar to conclude that she is wearing a white collar.

>> No.9643078

How do you solve
[math]\frac{36t}{5} + 21.581 = 9ln(5x-12) - ln(15x-4)[/math]
for x(t)?

>> No.9643174
File: 98 KB, 627x380, binomialquestion.jpg [View same] [iqdb] [saucenao] [google]
9643174

can someone explain why the fuck did he come up with the shit about the coefficient of x^18 to be the required answer?

>> No.9643185

Hey sci, how do I compute nth roots manually? Google on the wikiHow seems tedious and hard, is that how people really did it before?

>> No.9643189

>>9636352
My favorite way to tackle those types of problems back in high school was to split every trig function back into base components.
>csc(x) = 1/sin(x)
>tan(x) = sin(x)/cos(x)
Etc. Then just do algebra on what remains. Typically these types of problems involve combining fractions and factoring out common terms.

>> No.9643188

>>9643174
>can someone explain why the fuck did he come up with the shit about the coefficient of x^18 to be the required answer?
Because it works.

>> No.9643275
File: 806 KB, 1001x823, 1511588667781.png [View same] [iqdb] [saucenao] [google]
9643275

>>9641931
>>9641957
>>9641961
thank you, brehs. i think i'm gonna make it after all.

anyone else with tips on self studying calculus/how important precalculus is for understanding calculus is welcome to jump in as well.

>> No.9643514

>>9643174
The [math] x^{18} [/math] term will be the product of eight [math] x^{\text{odd number}} [/math] terms, that is [math] x^{\text{odd number 1}+\cdots+\text{odd number 8}} [/math]. The coefficient is the number of times this happens, i.e. the number of ways 8 odd numbers add to 18.
No idea how he came up with it, it's clever though. What book is it from?

>> No.9643527
File: 190 KB, 2000x1026, wavePolarization[1].png [View same] [iqdb] [saucenao] [google]
9643527

Can the polarity of light be changed by influencing it's magnetic field? I know most people just run unpolarized light through a physical filter, but could you expose light to some magnetic field and change the direction of the electric field?

Intuitively, I'd say yes this is possible but I'm not actually sure. I ask because I saw that study about the birds and magnetoreception.

>> No.9643673

How come math is stupid and only certain rules apply to certain formulas but not others?

>> No.9643674

>>9643673
>How come math is stupid and only certain rules apply to certain formulas but not others?
Any rule can apply to any formula if you assume it as an axiom.

>> No.9643826
File: 648 KB, 2016x1089, It&#039;s a separable DE.jpg [View same] [iqdb] [saucenao] [google]
9643826

>>9643078
Alright, I'm gonna have to one-up myself here and post a pic of the entire problem instead of just the one step. I don't know what's going on; I did just fine on every exercise that came before and after this one. I keep going back to it, and I'm absolutely sure my calculations are solid number-wise, but the answer eludes me. This is fucking killer. I think I've already convinced myself it's impossible.

>> No.9643849

>>9633554
Is it true that if some problem in NP canot be solved in polynomial time, then non of NP-complete problems can be solved in poly time.

>> No.9643858

>>9643527
yes, it's called the faraday effect.

>> No.9643874

>>9643849
Yes, because by definition every problem in NP is reducible to any NP-complete problem in polynomial time. So if you have a polynomial time algorithm for an NP-complete problem, you also have a polynomial time algorithm for every problem in NP.

>> No.9643897

>>9643874
I am reading on wiki that NP problems are decision problems which have a nondeterministic TM which reaches an accepting state in polynomial time. Does that mean that this TM is only guaranteed to stop after polynomial time if the answer is yes, and can potentially run forever is the answer is no.

>> No.9644166

>>9633554
what matrix A operators on a 2x2 matrix to get a vector in R3

>> No.9644188

>>9644166
>what matrix A operators on a 2x2 matrix to get a vector in R3
None, since A must be mx2 for some m, and the product of an mx2 and a 2x2 is mx2.

>> No.9644198
File: 3 KB, 154x46, e83d59f49cc168d839793343ff5e87c1.png [View same] [iqdb] [saucenao] [google]
9644198

>>9644188
that's what i thought but this question in my applied lin algebra textbook specifically asks for a matrix A to represent pic related

>> No.9644212

>>9644198
Oh that kind of operator, just look how it acts on each of the four basis vectors of M_2(F).

i.e. [math] T(\begin{bmatrix} 1 & 0 \\ 0 & 0 \end{bmatrix}) = \begin{bmatrix} 1 \\ 0 \\ 0 \end{bmatrix} [/math]

[math] T(\begin{bmatrix} 0 & 1 \\ 0 & 0 \end{bmatrix}) = \begin{bmatrix} 1 \\ 1 \\ 0 \end{bmatrix} [/math]

[math] T(\begin{bmatrix} 0 & 0 \\ 1 & 0 \end{bmatrix}) = \begin{bmatrix} 0 \\ 1 \\ 1 \end{bmatrix} [/math]

[math] T(\begin{bmatrix} 0 & 0 \\ 0 & 1 \end{bmatrix}) = \begin{bmatrix} 0 \\ 0 \\ 1 \end{bmatrix} [/math]

so T can be written as [math] \begin{bmatrix} 1 & 1 & 0 & 0 \\ 0 & 1 & 1 & 0 \\ 0 & 0 & 1 & 1 \end{bmatrix} [/math]

>> No.9644219

>>9644212
so i pretty much ignore the fact i can't really check it and it doesn't make sense in terms of matrix multiplication
i was just going to ignore it and write the matrix i got which is actually the exact same as yours so it's right i guess. fucking stupid question wasting my time with a different basis

>> No.9644227

>>9639236
The time it takes to absorb the drug of interests via lungs takes longer than just the absorption is oxygen.

When you inject the drug, you just have to deliver it, if you inhale it, you have to absorb it and then deliver it, the "delivery" time is the same. The absorption times is what makes the difference.

*Citation needed*

>> No.9644246

>>9640625
You are retarded imo.

>> No.9644259

>>9641110
Never thought about this. I'll let you know tomorrow

>> No.9644261

can someone recommend me some good videos or books on electrodynamics/electromagnetics?
I have a midterm coming up and this stuff just doesn't click for me. Really don't want to retake this course.

>> No.9644322

>>9643185
x^(1/n) = 10^(log10(x)/n)
Use tables or a slide rule for log10(x) and 10^x.

If you need more accuracy than you can get from tables, then you'd use some form of successive approximation, as described in the wikihow article.

>> No.9644334

>>9643514
"A treatise on algebra" by charles smith its from the 1800s so its public domain and is easily available

>> No.9644429

>>9640821
>Is one more general than the other?
No, but both are special cases of submodule. A vector space V over a field F is just an F-module and the linear span of a set S is the submodule of V generated by S. Given a ring R, R is an R-module and an ideal of R is just an R-submodule of R.

>> No.9644443

>>9643897
No, the accepting state can mean both "yes" or "no"

>> No.9644460

>>9643275
Precalculus is basically algebra II and trig with the difficulty turned up. The extra trigonometry practice might help you later, but if you can pass a high school trig class, you’re pretty much good to go. As for self-study, everyone has their own method; I’m particularly fond of the Adderall method.

>> No.9644464

>>9633932
what does [math]x_3[/math] mean?

>> No.9644472

>>9644261
magnetic force is actually the electric force because einstein

>> No.9644479

>>9642392
different observers can disagree about speed of different objects, except for the speed of the light which is always constant to all observers

>> No.9644483

ok can you prove that [math]odd^{even}\%4=1[/math], for any odd number elevated by any even amount the remainder of the division by 4 is always 1?

(because I can't)

>> No.9644484

>>9639236
The whole how-blood-gets-to-the-brain concept, for starters.

>> No.9644493
File: 77 KB, 1280x720, 1420711922876.jpg [View same] [iqdb] [saucenao] [google]
9644493

Are there any online sites to test for IQ?
For free?

>> No.9644496

>>9644493
your iq just dropped by 20 by posting here

>> No.9644498

>>9644493

>>9636486

>> No.9644504

>>9644498
>Your IQ lies outside the area that the test is able to measure
I'm not sure how do I feel.
Are there different tests?

>> No.9644505

>>9644504
Thousands of them. And mensa is the most reliable one, so you're fucked

>> No.9644512

>>9644483
It basically reduces to showing that [math]1^{even} \equiv_4 1[/math] and [math]3^{even} \equiv_4 1[/math] (since 1 and 3 are the only odd numbers between 0 and 3). The first case is trivial. The second case is quite easy with the modular multiplication rules as well: [math]3^{even} = 3^2 \cdot. . . \cdot 3^2\equiv_4 1 \cdot 1\cdot. . . \cdot 1= 1[/math]

>> No.9644514

>>9644512
>between 0 and 3
>3 included
>0 isnt
???

>> No.9644518

>>9644514
Both are included, but 0 isn't odd. Are you stupid?

>> No.9644519

>>9644514
0 is even

>> No.9644526

>>9644512
so there is no general proof

>> No.9644527

>>9644518
looks like a very odd number to me

>> No.9644532

>>9644527
looks even to me

>> No.9644537

>>9644526
Firstly, I don't know what you mean with "general" proof. It is a proof for [math]odd^{even}\equiv_4 1[/math]. If you don't understand it, you revisit modular multiplication theory in your textbook

Secondly, even if 4chan could not present a proof for a particular problem to you, it would be retarded to assume that no proof exists just from that

>> No.9644546

>>9644537
how can I know that [math]5^{even}\equiv_4 [/math]1 by knowing that [math]3 & 1^{even}\equiv_4 1[/math]

>> No.9644551

>>9644546
Rules of modular multiplication. [math]5^{even}\equiv_4 1^ {even} \equiv_4 1[/math] since [math]5\equiv_4 1[/math]

>> No.9644657

>>9644493
>Are there any online sites to test for IQ?
No.

>> No.9644968

>>9644464

Just a constant

>> No.9645158

How would you do this and why:

[math]
18a^2 * \frac{a^2 - 3a^a + 1}{9}
[/math]

is it

[math]
\frac{18a^2 * a^2 - 3a^a + 1}{9}
[/math]

or

[math]
\frac{18a^2 * (a^2 - 3a^a + 1)}{9}
[/math]

and why?

>> No.9645177

>>9645158
The second one, because that's the convention

>> No.9645699

Why cant we draw [math]x_{(t)}[/math] graph for the motion if we dont know [math]x_0[/math] ? Since in physics vectors are free we can just use x0y i.e. centers of coordinates?

>> No.9645791

>>9644443
Tho I already found out, that if there exists a machine which either says yes in time p(n) or runs forever there is a machine which says yes in time p(n) or says no if it didn't manage to reach yes state in p(n) time.

>> No.9646160

>>9645699
motion has to start somewhere, unless you can somehow draw your curve in affine space.
This is the approach taken in differential geometry and high-level physics - you work in abstract manifolds and only use coordinates when absolutely necessary