/SQT/ - Stupid Question Thread

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bump limit is 305 posts btw, best to just have one thread going at a time

>>8858743
No one really asks questions at past 250-270 posts out of fear of autosage.

>>8858830
I do, but then again I'm a no one, so I suppose you're right

>>8858725
If space is permitted by particle/anti particle annilations would that limit the speed of light

How do they go from the 2nd to the 3rd line in this proof?

http://www.ams.org/journals/proc/1967-018-04/S0002-9939-1967-0212477-6/S0002-9939-1967-0212477-6.pdf

can someone tell me how gpa works? do i need a 100 average in every class at the end of the semester for a 4.0 or will all A's give me a 4.0 which means i only need a 90 in every class?

>>8858956
It works with grades, so A, B, C etc. That's why it's called grade point average, not points point average

What to do after graduation?

I'm graduating uni in a month and i feel like I haven't learned anything and have no clue what to do next. Is this normal?

>>8858964
ok thanks. so does it give more points for an A+ over an A- or do all A's give the same amount of points?

>>8858974
depends on uni

>>8858966
Apply for a shItty job whIle you look for a good one. If not go to grad school or something.

>>8858966
>What to do after graduation?
Move out of your dorm. Go live with mommy and daddy again, or rent an apartment if you can afford it.
Send job applications. Go to job interviews. If they won't hire you, try to get a paid internship or something.
>I'm graduating uni in a month and i feel like I haven't learned anything
>Is this normal?
Yes, if you studied a meme degree.

Can someone give me some examples of mutations that have actually added information to a species? So far whenever I ask my teacher he just gets dodgy because he obviously isn't getting paid enough to actually care about the course.

>>8859040
what do you mean by information?

>>8858725

I am generally a bright and logical person; I have strong verbal intelligence some might say; However, like a lot of people I have math issues; It's not that it goes over my head I just can't seem to stand it; I don't know if I hate maths or just really find it really boring; Is there some way to approach math that is not so tedious; Something to do with understanding mathematical algorithms through verbal logic maybe ?

should i do cs or ee? planning on working in rural mississippi since all my family and friends and here and i'm not sure which one would be better for finding a job and making more money

>>8859045
Well, there is literally a sub-field of mathematics called Logic.
https://www.youtube.com/watch?v=OLGVhszBlq4

What are good math books for highschool students? I want to do math regularly but I chose social as program so we don't use anything other than arithmetics

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Can some MATLAB/Octave expert here tell me why this function isn't being plotted? It's just an empty graph

For reference, the function is:
[math]r(u,v)=<u^2 +1, v^3 +1, u+v>[/math]
where u and v and both bounded by [math]-1 \geq u and v \geq 1 [/math]

>>8859125
fucked up the inequality signs, but anyway pls halp

>>8859072
book of proof, you'll glide through other stuff if you get through that. so much of math is just being mathematically mature enough to grasp the material readily, and proofs help that imo

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>>8858725
What did he mean by this?

>>8859125
I think this is because I wasn't using period, like this page: http://www.poritz.net/jonathan/past_classes/spring14/ml/parametric.html

still trying to figure it out via trial and error, so if any anon has insight pls share

How would I go about solving the following differential equation?

[math]
m\frac{dv}{dt} = g - kv^2
[/math]

I've tried the integrating factor method several times but it doesn't seem to be working

>>8859171
Not really sure what you're trying to plot, but what you're really plotting is:

z(u,v) = u.^2 + v.^3 + 2;

but you're plotting versus "x" and "y" not "u" or "v", did you mean that?
(yes, using the dot carat is the notation you'd like to use here)

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Getting from 3 to 4?

>>8859252
from 4, how do you get to [math]z^2 > 4 - z^2 \to z > sqrt(2)[/math]

>>8859257
Which part of that is confusing you?

Best in your opinion introduction to logic?

also textbook/class on propositional calculus

>>8859262
turning 4-z^2 into sqrt2

>>8859339
z^2 > 4 - z^2
2z^2 > 4
z^2 > 2
z > sqrt(2) (since we know already know z is positive)

>>8859281
>>8859281
TrevTutor has a good series using Discrete and Combinatorial Mathematics - An Applied Introduction

personally, I find the path of least resistance is often the best approach, at least initially, and he makes it pretty easy

>>8859347
ahh, duh.. thanks anon

>>8859189
>How would I go about solving the following differential equation?
The integral is direct
[math]\int{\frac{dx}{a^2+b^2*x^2}}=\frac{\arctan (bx/a)}{ab}[/math]
[math]\int{\frac{dx}{a^2-b^2*x^2}}=\frac{\arctanh (bx/a)}{ab}[/math]
So
[math]v=\sqrt{\frac{g}{k}}\tanh (\sqrt{gk}t/m)[/math]

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made this a few months ago and i dont know why its wrong

/scared/

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If humans did manage to build bases on the moon how would we solve the super abrasive regolith problem that can chew through multiple layers of kevlar moonboots? also what stops a smallish astoroid from obliterating the base?

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What are the 'pre-reqs' to studying particle physics?

What's a good source to start studying particle physics?

>>8859769
The two series you've written in the second line do not converge

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>>8858725
IF two standard normal variables X and Y are dependent and are corellated, is (X, Y) bivariate normal?

>>8859769
Riemann proved that any alternating series (it goes + - + - ...) where the negatives and the postive parts go to infinity can be rearranged to be equal to any number you want.

In other words: If you change around more then finitely many elements of your infinite series its value can change.

>>8859898

https://www.youtube.com/watch?v=2eFvVzNF24g

His lectures are pretty good.

>>8858974
What >>8858976 said. Check your university's site on this info. At mine there are no A+s. Only A- and A.

>>8859975
BUMPin

>>8860011

They're not bad, but I'd like something a bit heavier on the mathematics.

Hey guys, I have a Lab Report due to tomorrow and I need some help. It's fairly simple redox reaction stuff. We mixed copper metal with an aqueous solution of copper(II) sulfate. What exactly would occur? Another experiment was Zinc in the same solution and that was a simple single-displacement reaction, but this other thing is bugging me. I also need to answer the question "why did we add NaCl into the solution". What I'm thinking is that it increased electric conductivity in the solution so the redox reaction happened faster. Does this make NaCl a catalyst? Where can I find more information on this? Another thing our teacher showed us as a clue is a copper plate that was blackened by just staying exposed to air. I think it might be the same thing as rust but for copper (oxygen reacting with outer layer of copper, etc.).

tl;dr:
$$ Cu + CuSO_4 \rightarrow ? $$
NaCl in the solution above acting as a catalyst? Why?

>>8860517
Annnnd my TeX fucked up. Didn't know how to use it

tl;dr*:
[eqn] Cu + CuSO_4 \rightarrow ? [/eqn]
NaCl in the solution above acting as a catalyst? Why?

>>8860517
>>8860522
Cu + CuSO4 → nothing happens.

>Another experiment was Zinc in the same solution and that was a simple single-displacement reaction, but this other thing is bugging me.
What is bugging you? When you add Zn to the Cu solution, then something happens. It's the redox
Zn(0) + Cu(II) --> Zn(II) + Cu(0)

>Does this make NaCl a catalyst?
If everything happens in the same beaker, for example, then NaCl should be useless. Otherwise you need it to compensate the charge.

>I think it might be the same thing as rust but for copper
This is correct, it's copper (II) oxide, CuO.

Anyway the experiment is not very clear, further explanation would help.

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>>8858725
Guys can you please help with this.
Is it correct?
T-t-thanks guys.

>>8860597
To clarify: by the same solution I mean copper(II) sulfate, but in a different beaker. By the other thing I meant [math] Cu + CuSO_4 \rightarrow ? [/math]

>If everything happens in the same beaker, for example, then NaCl should be useless. Otherwise you need it to compensate the charge.
Can you elaborate on this? What do you mean with "compensate the charge"?

For further clarification of the experiment (taken from the Procedure part of my Lab Report): The first experiment was performed by putting less than 10mL (around 7 mL) of copper(II) sulfate in a 50 mL beaker with a pipette. Then a small zinc pellet was dropped inside the beaker with a spatula spoon. After around 10 minutes, a pinch of NaCl was sprinkled into the beaker. The second experiment followed a similar structure. The same amount of copper(II) sulfate was placed in a different 50 mL beaker with a pipette. The difference is that a short and thin copper wire was placed in the solution rather than a zinc pellet. The solution was also sprinkled with a pinch of NaCl.

> nothing happens.
The copper wire started losing its color and becoming some weird metallic gray thing. Something apparently did happen and my teacher wants us to write about it.

>>8860630
In the first experiment the redox reaction between Cu and Zn occurs, as said before. NaCl does, or at least should, do nothing.

In the second experiment the only thing I can think is the formation of CuCl2, which might precipitate onto the copper wire, but since CuCl2 is soluble, I doubt.
NaCl might also helps the oxidation of the copper wire, but then again it's not something observable in a short time, I think.
Are you sure you did not use anything with silver? The reaction between a copper wire and AgNO3 is a pretty common experiment where Ag(0) deposit onto the copper wire.

The conclusion of your experiments should likely be that NaCl in one case does nothing, while in the second case does something. Still, I can't come up with that something, sorry.
I searched on the internet, but I did not find anything useful, other than people saying that nothing happens.

>What do you mean with "compensate the charge"?
That's what happen when you have a cell, but it's not the case. You can search for salt bridge, if you are curious.

>>8860624

can you at least not write like a fucking retard? Jesus, I'd give you fucking NO marks if you passed that in like that.

>>8860724
Thanks for your effort, it's greatly appreciated. I also did my fair bit of research and found zilch.

>Are you sure you did not use anything with silver?
Nothing with silver. My teacher clearly stated what the reactants are.

The thing is I talked to my teacher today and he said that the questions of the lab are: what happens with the [math]Cu + CuSO_4[/math] and with the [math]Zn + CuSO_4[/math]. He also faintly hinted that NaCl helps the electrons move in the redox reaction. The thing I didn't talk a lot about is the copper plate that reacts with the air. He basically said that this is some sort of hint to help us realize what's happening in the main reactions.

Anyways, if you think of something or this copper plate thing helps you in any way, feel free to post here. I'll keep the thread open. I'm sorry if I took a lot of your time and I'm really grateful.

>>8860736
There is literally NOTHING wrong with his writing.

>>8860736
I'm not going to pass it in like that, I just wrote it out as quick as possible to post it on here. I will fix the notation, etc when I write out the actual answer. Is it correct mate?

>>8860742

there's clear ambiguity in what's written. Is that a 2 or a 1? I don't fucking know and they don't pay me to figure out chicken scratchings

>>8860744

if you didn't get the hint I can't fucking read your drivel. have some decency and at least LaTeX it.

>>8859975
no

https://stats.stackexchange.com/questions/30159/is-it-possible-to-have-a-pair-of-gaussian-random-variables-for-which-the-joint-d

>>8860751
I have turned in WAY worse looking things and not even once got a complaint about it.

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>>8860624
This is the question I'm trying to answer.
Part (a) right now.

>>8860751
I'll rewrite it and post a better version.

>>8860741
>the questions of the lab are: what happens with the Cu + CuSO4 and with the Zn + CuSO4
Well, if those are the questions, then in the first case nothing and in the second case a redox.

NaCl may help to solubilize the Cu(II) and the Zn(II), but I doubt you can say that it catalyze the reaction in any way, though.
The "hint" might just refer to an oxidation. Pretty meh as hint, if you ask me.

Anyway I'm curious about this experiment, so keep me updated on the answers!

>>8860776
Will do. If no better info comes up I'll write what you gave me. Thanks!

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alright lads
I need some degree advice

I'm stuck between getting a CompE degree or EE degree
I've technically been in the CompE program, but I'm only now getting to the point where CompE and EE classes start diverging
which is better
CompE + math minor
or
EE + CS minor + math minor
for grad school and/or jobs

The time difference between all of them isn't very significant with how my schedule is looking, and if I didn't take the extra classes for the minors I would be wasting potential grant and scholarship money, but would finish pretty early.

also what kind of math electives would you guys recommend, I've got all the typical math classes already taken, and I need two more classes for my minor.

How do LL(1) Grammars work?
So if you have the input word
[math]aab[/math]
Does the parser look at the first a in an LL(1) method or the second a?

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>>8860751
I rewrote it and it seems the first one was definitely wrong since I multiplied by 2 instead of -2.
Hope this is more readable.
The question is here
>>8860768

After this term I'm going to be done with my school's calc series, which has taken me up to vector and multi-variable calc, with a sprinkle of differential equations. Next term I'm likely taking both Linear Algebra and Diff Eq.

Other than a cumulative review, what might be some good areas to explore in my own time? I'd really like to get into differential geometry. But also, making pretty graphs for Vector Calc in Octave is fun, so I thought topology might be nice.

>>8859782
We cover the base with lunar rocks and regolith to protect it from radiation anyways, so abrasion is hardly a concern. There is as much of a concern of asteroid impacts of that magnitude here on earth as there is on the moon. We'd have plenty of time to evacuate the base.

>>8860943
Oh, also I've considered diving into real analysis or advanced calculus too.

>>8860943
If you want to learn differential geometry, then do that. By the way, point set topology a la Munkres won't involve pretty pictures. You'd be better going the differential geometry route for that.

>>8860964
ok, thanks.

>>8860943
>>8860961
Differential geometry is easily the most fun thing on that list but keep in mind you're going to need to learn lots of linear algebra if you haven't already had a good course on it.
Do analysis before you try topology. Analysis examples make topology way easier.
Advanced calculus isn't really a subject so much as a relic of a course name from the 1960s; if you flip through one of these books you'll find it looks like a blend of vector calculus and real analysis in some proportion.

>>8861006
Ok, thank you. I was reading about the pre-reqs for differential geometry and linear algebra came up quite a bit. Is there anything else you'd recommend? Perhaps some of Euclid's Elements, or even non-Euclidean geometry (whatever that means)?

If linear algebra is going to help, do you have a book you'd personally recommend? I was thinking Strang's until I read the /sci/ wiki's opinion on it.

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dumbest question of the thread incoming:
If we assume the two trusses marked in red are of the exact same dimensions in the exact same orientations, do they just both take half the force each? Meaning around 2000N each?

>>8860883
G-g-guys.
Please help.

Is there a function that means "remove all instances of a factor y from a value x"? In other words, divide x by the highest power of y that divides evenly.

>>8861063
Yes, everything being symmetrical, forces are symmetrical too.
If trusses were vertical, the force would be 2000N, but it is at an angle, so the force is much higher. Just image pulling on a rope, which has a weight hanging in the middle. In order to pull it horizontally, you will need enormous force. Just take a string, and hang something in the middle, you'll see that you will first break the string, beforce it becomes perfectrly horrizontal.

>>8861102
i think you described two different functions
>Is there a function that means "remove all instances of a factor y from a value x"?
this is f(x,y)=x/gcd(x,y)

so f(12,9)=12/gcd(12,9)=12/3=4

>In other words, divide x by the highest power of y that divides evenly.
i'm not sure how to write this one down but
if x=12 and y=9 then this function outputs 12 since the highest power of y dividing 12 is 9^0=1

>>8861123
>this is f(x,y)=x/gcd(x,y)
i take it back this is wrong

>>8861016
The elements are a historical document by this point. If you really want to learn synthetic geometry for some reason (although this is just what you did in high school geometry class) you should find a more modern book on it. Just search Amazon.
Stuff about non-Euclidean spaces is basically a subfield of differential geometry.

Axler's book is pretty well-suited to what you want, although you can pick almost anything. /sci/ likes to spend hours plotting curriculums instead of reading but book choice doesn't really matter very much.

>>8861123
What I'm saying is decompose x into prime factors, eliminate every prime factor that is equal to y, then recompose what is left. So y has to be prime.

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>>8860883

shouod be this

>>8861224
That's for part (b), not part (a) that he's answering.

I never had Chemistry in highschool, but i'll get it in university next year year so i wanna prepare.

Should I memorize the periodic table?

>>8861293
How are you getting into university, presumably to do a subject that involves some chemistry, without studying any chemistry?

>>8861298
All engineers get chemistry in the first semester of the first year.

>>8861310
Yes I know that, but you're usually expected to have done basic high school chemistry at least before that. At least in the UK.

>>8861354
Same here but I went to a vocational highschool so I got less science and math classes. You have to choose at the age of 12, that's just how our system works here.
It's not a bad system, but there occasionally people like me who made the wrong choice but by the time you realize it's already to late.

But rather than sulk about it id rather do something about it.

I'm not even bad at it. I'm doing Calc 1 and Physics atm and I don't think it's that hard at all.

>>8861293
No, that would be useless even for a chemist.
If you're curious, you can search some basic stuff on the internet, otherwise just wait for the lecture.

>>8861382
I'm not shitting on you mate, just curious.

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what did he mean by [math] A ^r [/math]

I love math but did not really care during high school and now I have gaps. Not on entire subjects, but only on really small details. How do I fill these without re-learning all the stuff that I already know 95% of.

How long could you eat only glucose (and maybe fructose)? Would there be any significant risks other than malnutrition?

>>8861473
Start taking calculus at a university. They'll fill in as you go

>>8861466
>>8861466
A raised to the r-th power...
A*A*A*...*A (r times)

>>8861466
It's just the matrix A raised to the exponent r

in the case of this theorem r is the length of the path

>>8860883
Just wondering guys what will happen to the interval of validity for the Taylor series for g(x). It will remain the same as f(x). Correct?

>>8861513
>>8861514

ayy, i thought its r dimension adjacent matrix or whatever.

also is there something wrong with this?

if [math] \sum _{n = 0} ^{k} {a ^n} = H[/math],

then [math] \sum _{n = 1} ^{k + 1} {a ^n} = aH[/math],

then [math] { a ^{k + 1} - 1} = aH - H[/math],

then [math]H = \frac{a^{k + 1} - 1} {a - 1}[/math]

my question is, how come

>A full m-ary tree with i internal nodes has n = mi +1 nodes, and y =( m −1) i +1 leaves.

because obviously its just H..right?

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I have a stupid question. Im jist getting into math in anyform seriously and I was fucking around with Arithmetic. And someone had to figure this out before hand when it comes to finding numbers that are divisible by a number.

Basically,
"For any odd number *n*(given n=/= 1), *n* will be divisible by atleast one natural number less than *m*

Given that *m* = (*n*-1)/2

*m* will also not be in the set of numbers divisible by *n*

Am I stupid? Someone had to have known this before me.

Are there any other professions for someone with a degree in pure mathematics? I really want to major in mathematics but I don't want to teach or work anywhere near a University.

>>8861615
What about prime numbers?

Why is it surprising that n will not divide m when n > m?

Let´s say we have a static magnetic field [math]\vec{B}[/math] then by Lorentz Law, if a charge is moving through the field we have. [math]\vec{F}=q\vec{v}\times \vec{B}[/math]. If it moves through a path [math]\vec{r(t)},t\in [a,b][/math] then the work done by the field would be the line integral, [math]W=\int_{a}^{b}(q\vec{r'(t)}\times\vec{B})\cdot\vec{r'(t)}dt=0[/math] for all paths. This would be also true for closed paths, but that would imply the force is conservative. But I read this force was not conservative and I really cannot think of a potential for the force so which hypothesis I'm missing.

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redpill me on trigonometric identities

so....a planar representation of a planar graph is just a isomorpism of planar graph, which is also planar?

>>8861702
Yeah, like 90% of math students don't go into academia. Most math PhDs don't teach or work in academia. Talk to someone who knows what they're talking about like a student advisor who can put you in touch with former students.

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If you have a dog and add a negative dog, what do you get?

>>8862021
>if i have one dog and subtract one dog, how many dogs are there?

1+-1 = 1-1

0 dog

>>8861720
m and n are not dividing into each other.

Lets say n = 5, a prime number.
To find 5's divisors we can look in the set we get when we subtract 1 from 5 and divide the result by 2.

(5-1) /2
(4)/2
2
m = 2 in this case.

Atleast one natural number less than 2 will be divisible by 5. In this case it's 1 (And since 5 is prime not surprising.)

Let's take 13, another prime.
(13-1)/2
12/2
6
n=13
m=6

To find any divisor of n it will be less than m

Which it is, 1.

>>8862002
Okay. Thank you anon.

>>8861102
google "p-adic absolute value"

What kind of educational background do people who work with, eg. genetically engineering crops have?

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Adding led light strips to get better light to trunk.
I plan to tap into the trunk light wires.
WHile examining trunk light, I notice a Diode installed in the Trunk Light holder.

What is this diode doing in this circuit? It lookes like its connectected in parralel to the circuit, but I'm not sure.

>>8862840
btw: its a honda, and this picture is off the internet.

CS with a minor in math or a minor in physics? Would like to be able to work on software (or a software/hardware mix) involved with natural systems so things like simulations, engineering statics/dynamics etc. Kind of leaning towards physics because of that, but at the same time I couldn't give any less of a shit about anything "quantum" and ever since the early 20th century that's been a big part of it.

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How do I improve the formatting of my LaTeX documents? I'm getting better at the syntax, I'm just having trouble making it look pretty (the lines look cluttered, spacing's kind of funky at times). Any tips/resources?

>>8862840
My first guess would be that its a zener diode thats ment to be used for TVS/general voltage regulation.

My second guess (although this is kind of retarded) is that its a flyback diode

>>8861746

u can get them from Euler's formula.

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Bear with me since i dont know jack about chemistry.

How does a short carboxylic acid (say acetic acid CH3COOH) of high concentration (say 70%) react with long hydrocarbon molecules (~30 carbon atomes) at 20°C, sea level pressure (without contact to air if that makes any difference)?

Am I right in suspecting it does not react at all or in a slow "back and forth" reaction?

tl;dr can a container made of parafin wax contain high concentration acetic acid without leaking?

thx in advance

Hey everyone, brainlet here.

I'm trying to figure out how to calculate the mixture of 2 products that have different melting points, such that i can have the right temperature at the right weight.

Assume it's proportional.

I've got it down to a formula as follows:

t=y/x + (zx-z)/x

where t= the temperature I'm aiming for, y = the melting point of the first product, z = the melting point of the second product, and I would like x to be a multiplier for it all ( so I have a ratio). This works but I end up with a negative quantity of 1 item which obviously isn't the answer. Any help would be appreciated.

As an aside, would be interested in what that sort of problem is called.

>>8862956
>>8862959
relative amount of product B as part of whole mixture: b = (t - x) / (y - x)
relative amount of product A as part of whole mixture: a = 1 - b
t is the desired melting point of mixture
x is melting point of A
y is melting point of B

Hope i understood your problem correctly. It "feels" like linear equation stuff but idk really

>>8858725
Why are particles particles?

>>8862891
>How do I improve the formatting of my LaTeX documents?
\begin{align}
eq & eq \\
eq & eq \\
eq & eq
\end{align}
It align the multiple lines such that all the places with & are vertically align.

\, little space
\! little negative space

\left[ \right] (also valid with (, \{, \langle, \rangle,...)
Make the brackets (like the ones in your eq. 1) as big as the bigger element inside of them.

\text{....} to write text inside the math mode (it also keeps the spaces)


\DeclareMathOperator\sech{sech} In the preamble defines the comand \sech which will behave like other math operators (\lim, \sin, etc.)

>>8862930
>tl;dr can a container made of parafin wax contain high concentration acetic acid without leaking?

Yes, it should resist quite well.

>>8858725
Is it true that if X is normal and Y is normal then (X, Y ) is bivariate normal?

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>>8862893
>flyback diode


Its looking like a flyback diode. The wiki has an image of a simple circuit, that seems to fit the trunk light circuit.

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>>8858725
massive trick question?
Would it be:
a) p^4 (1-p)^2?
b) p^4 (1-p)^2?
c) 1-p?

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>>8863389
>>8862840
A further search of "flyback diode",and "trunk light" have gave me the confirmation (off the internet, however).

off a car forum:
>Officially, it is a 1N4004 diode. Rated at 1 Amp. When installed in this manner in parallel with a load, such as a lamp, it functions as what is known as a 'flyback' diode, which helps to reduce the voltage arc across the contacts of a relay by helping to dissipate the current that will try to flow across the contacts of the relay as they open or close. Suppressing this arc will improve relay contact life.

Since, my LED strips don't have any potential arc points, simply tap into the harness with some water prrof schlocky connectors, and I'm good to go.

Good, stuff this "internet".

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How do i get from 4.20 to 4.21?
first term is clear, then i guess i have to apply the product rule to the second term (to e^(beta_2t) and to the integral). But i have no idea how to get the resulting third term in 4.21

>>8863475
I think its from the Fundamental theorem of calculus when you take the derivative of the integral without any t terms inside.

>>8863451
In question (c), you need to use conditional probability to solve.
It is P(T | HHHHHHHHH...), not P(T).
Try to figure it out.

>>8863699
>>>8863451
> In question (c), you need to use conditional probability to solve.
> It is P(T | HHHHHHHHH...), not P(T).
> Try to figure it out.
That smells like Gambler's Fallacy....

Does anyone know of a way to project a surface from a (implicit_)3d plot onto the coordinate planes ({x=0}, {y = 0}, {z=0}) using SAGE ?

>>8863730
Oops, sorry, I'm retarded. Since each toss is independent to the previous, P(T | HHH...) = P(T).

>>8863642
Thank you! I guess you are right. So i use dominated convergence to pull the limit inside the integral (z is bounded) and apply the Fundamental theorem of calculus. How would i handle the dtau ? Does it cancel (after renaming) with the infinitesimal 1/dt coming from the derivative?

>>8862891
aside from what the other anon said
-write in sentences. for example "plugging into the equation [eqn] 'yields/gives/etc.' [eqn]" and "we now have: [eqn] 'and' [eqn], 'which means'...". Avoid having multiple seemingly random equations one after the other
-don't use inline math where you've just got an equation on one line, use display. I'd personally not use inline maths for any integral 2bh
Minor points:
-use \cdot instead of *
-ln should be typeset in roman
-punctuate after equations. If a sentence ends with an equation, use \,. after it
-use \exp\left(\int...\right) rather than e^\int. same goes for any other large operator or complex expression
-use \, between whatever you're integrating and the dx
-I'd also use roman for the d in dx, but most people don't care

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Would this work?

>>8863875
what's stopping it from going backwards instead of forwards?

>>8863887
Make one of the magnets stronger

Just heard the latest Waking Up podcast with Sam Harris and Charles Murray and it got me interested in the book The Bell Curve.

Is there a decent updated version of this book which adds interesting new discovery/research to complement the book itself in an introduction chapter or something?

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Which math electives would be most useful or interesting for an EE major, I'm not sure what my concentration is going to be atm, but I'm digging my signal processing class quite a bit, so I might try to go down that route

I need two electives for my math minor

here are my options:
>Introduction to Abstract Math
>Introduction to Analysis
>Introduction to Abstract Algebra
>Mathematical Modeling
>Introduction to Number Theory
>Differential Geometry and Topology
>Advanced Calculus I
>Advanced Calculus II
>Abstract Linear Algebra
>Group Theory
>Introduction to Complex Analysis
>Numerical Analysis
>Partial Differential Equations and Fourier Analysis
>Applied Probability and Stochastic Processes
>Applied Linear Algebra
>Mathematical Programming
>Probability and Statistics II (already took I)

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>>8858725
help me, bois

>>8864030
>>Mathematical Modeling
>>Numerical Analysis
>>Partial Differential Equations and Fourier Analysis
>>Applied Probability and Stochastic Processes
>>Mathematical Programming

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Can all math be represented geometrically?

Also, if anyone has pic related, please share.

Can someone post a boiled down pdf of all things notable in the study of calculus?

Things I may have forgotten, like L'Hospitals rule, Reinmann sums, etc.. But without explanations, or if there explanations, very brief. Like a cheat sheet.

>>8864120
nvm, found this http://web.mit.edu/asf/www/CheatSheetsIndex.html

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So, I sat this exam today and I'm wondering whether my answer to diii) was correct. I put f = 1, g = 0 and it just seems far too easy to be the right answer.

>>8864051
no matter, already solved it

>>8863756
I guess your suppose to treat it as t in this case, since once you evaluate the integral it becomes a function of t since there's a t in the interval

>>8864132
Your answer is correct, but maybe the prof. expected f and g to be nonconstant (as stated, what you did works), in which case f(z)=e^z and g(z)=e^{-z} would have done the trick.

>>8864148
I thought so. Probably forgot to put that in. Suits me, heh, because I had absolutely no idea of anything else at the time. Thanks for the alternative

>>8863253
already answered ITT
>>8860759

Let U be a vector space with basis (1,1).
Express U as a direct sum of vector subspaces V, W. Describe V, W.

Any help with this? Would the following be correct?
>U: (1,1)
>W: (2,2)

I can't think of anything else. I'm not sure if I am allowed to have a vector space consisting solely of (0, 0), which would allow me to trivially set U to be (1,1) and W to (0,0)

>>8864210
If it wasn't specified that V/W must not be the same, why don't you just set both to (1,1)

>>8864251
direct sum requires the intersection of V and U to be empty I think

>>8864257
That's impossible, all vector spaces include the zero vector

>>8864210
A vector space that's a direct sum of two disjoint nonzero vector spaces implies that it's at least 2-dimensional. Your question makes no sense.

Can you post the original question?

>>8864275
transcribed it from a classmate, it just said U = (1, 1) and to express it as a direct sum of V,W

>>8864107
You're gonna have to clarify what you mean by that. What counts as a geometric representation to you?

>>8864287
Maybe V,W don't have to be subspaces of U?

>>8864335
right, they probably don't.

>>8864306
I'm not sure, I suppose something that could represented physically. Maybe you could describe what you mean, and why I would need to define 'geometric representation'?

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c in both cases will just be the minimum of f right?

>>8864632
I believe so, the minimum in a x2 is also the vertice of the parabola. Since the inverse of x2, sqrt(x) requires you to restrict the function exactly at the vertice(since 0 is the vertice of the point).

>>8864632

yes but you're being indoctrinated in set theory. you don't need any of that to prove minimums. use your brain.

Would a double major in Electrical Engineering and Mathematics be worth it? Would it increase my job prospects or is it just a waste of time?

>>8864755
>increase my job prospects
as opposed to what?

>>8864777
As opposed to only having a degree in EE.

>>8864140
Thank you kind sir

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The material point moves along the x-axis by law x (t) x coordinates change from time t. For which of the cases of a point rate increases with time?

WHAT THE FUCK LAST TWO BOTH WORK FFS WTF???!!!

Question about citation.
I am currently attending a "ring lecture" (several professors take turns talking about their research projects), and i am expected to write a paper about one topic of my choosing. Basically, i have to summarize what the professor said with my own words to show that i understand it; and i may have to fill some gaps that the professor left due to time limitations during the lecture.
Now, how am i expected to cite what the professor said? Do i write "Ring lecture from April 25 2017"?

>>8864107
bump, really need this book

>>8865107
what the fuck did you try to say? english please

What part of the collatz conjecture exactly makes it so hard to prove? Is it because addition and multiplication aren't properly connected, so we can't track how a number's factors change as you add to it?

>>8865141

POSITION BASED ON TIME IS GIVEN. WHERE IS THE SPEED INCREASES WITH TIME FFS?!

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Does anyone know of any good R course?
The coursera one is fucking awful.
I mostly will use it for generating random samples of most distributions, and density plots

>>8865107
brainlet

>>8865145
>What part of the collatz conjecture exactly makes it so hard to prove?
unsolved problems are usually hard because the mathematical technology needed to solve it hasn't been developed

>Is it because addition and multiplication aren't properly connected, so we can't track how a number's factors change as you add to it?
there's some results along this line (i.e. abc conjecture), but nothing that helps solve collatz

Is this correct?
[math] \lim_{x\to0} \frac{t^2 - t^6}{t^4} = \lim_{x\to0} \frac{t^2}{t^4} - \frac{t^6}{t^4} = \lim_{x\to0} \frac{1}{t^2} - t^2 = +\infty [/math]

I ask because some people flip their shit whenever you separate fractions like this inside limits instead of dealing with the whole fraction at once. By the way, I know the result is right because Wolfram but is the procedure rigorous?

>>8865361
>Is this correct?
yes

Just got rekt on my algebra test.

Let [math]F[/math] be a field. Let [/math] [math]\phi: F\rightarrow F[/math] be a ring homomorphism. Prove that [math]\forall a\in F, phi (x)=0 \vee \forall x,y\in F, \phi (x)=\phi(y)\Rightarrow x=y[/math]

>>8865586
Excuse my gross Latex. I'm asking to prove that: all of F is in the kernel OR phi is one to one.

fa/tg/uy here, what kind of (concentration of) acids/bases would be strong enough to quickly melt metal, like a lock on a door or bars in a jail cell?

Ideally it should be obtainable in a pre-industrial setting

>>8865591
Pretty simple. The kernel of a ring homomorphism is an ideal. A field only has two ideals, 0 and the field itself.

>>8865600
>A field only has two ideals, 0 and the field itself.
proofs?

>>8865606
I would be very surprised if an algebra course did not cover the proof as soon as it started talking about fields. Google it if you don't know.

>>8865606
its trivial brainlet

>>8865606
just follow your nose dude. Did you even try?

>>8865606
Suppose F is a field and J ideal of F. Pick arbitrary x in J. By definition of ideal, r*x in J for all r in F. But by definition of a field, either x unit or x=0. x unit then x^-1 * x in J and therefore 1 in J. If 1 in J then r*1 in J for all r and thus J=F. If x=0 then either J as above or J=<0>.

>>8865606
>field is binary
Actually, the field exists as a spectrum

>>8865754
Actually because of this fact about ideals, SpecF={<0>} for every field F.

Opinions about Euler Elements of Algebra? Is it good for self-study?

any compsci majors here

how can a compsci brainlet grow into a 6 feet brain and do cool important shit that'll be interesting to talk about instead of just ending on some tedious programming job doing some stupid fucking website or retarded GUI java application

>>8859053
As a CS major I'd go with EE.

What are the best skills after C to learn to become an embedded devices programmer/reverse engineer?

>>8865838
I would start doing those things.
This might be helpful: https://beginners.re/

>>8863875
Absolutely not.

>>8864799
Nobody willing to hire a fresh EE out of college will be considering the number of degrees you have as a competitive point. It would be much better to have a recommendation from somebody already working. If you're competing against someone that has this, they'll get the job over you even if you have better grades, more degrees, etc.

tl;dr - don't double major. Do internships. Get people that already work there to like you and vouch for you.

>>8865119
The "ring" part seems unnecessary. That's not something I've heard in undergrad or grad school and it sounds like it's something they've coined as part of their professor click and use among themselves. Of course, it would give them a little dick tugging if you used their terminology..

>>8865838
C, C++, then start reading on up on Xilinx ISE and interesting modules. Pick out an FPGA of your choice and read the datasheets to start you dive.

>>8865598
If you search "metal chemical resistance" there are several and pretty long tables with different ratings, with more substances than just acids and bases.

Nevertheless, even if the rating is low, the reaction with a metal is not always very fast. You also have to consider that jail bars are usually pretty thick and in a difficult position. A lock might be more doable, but still not fast.
Also, depending on what you are using, might not be so safety to use it open air and smell the chemical fumes, but here depends on the accuracy that you need/want.

If you need any explanation, feel free to ask.

>>8865838
why reverse engineer? what's good about that

what's good about embedded devices programmer in general, what cool things can u accomplish

>>8865969
You can make devices and hide them in a box with little legs.

>>8865869
Thank you anon.

too lazy to read notes.

help me understand fourier series.

>>8864021
Kys Nazi scum

>>8866594
Rude.

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WHY THE FUCK IT'S THE LAST ONE AND NOT PRE LAST ONE?!!!

WHAT

THE

FUCKING

FUCK

?

!

>>8866648
>WHY THE FUCK IT'S THE LAST ONE AND NOT PRE LAST ONE?!!!
All of them are rewritings of expression they give you, but because most of us cannot read Russian, we don't understand what they are asking for.

>>8866665

WHICH OF THE EQUATIONS IS EQUIVALENT TO THE GIVEN ONE (FUCKING OBVIOUS COME ON)

CLEARLY IT'S FUCKING PRELAST, CLEA-FUCKING-RLY. WTF?!!!!

>>8866674
>CLEARLY IT'S FUCKING PRELAST, CLEA-FUCKING-RLY. WTF?!!!!
(4sin^2-2*sin*cos+7*cos^2)/cos^2=4tg^2-2tg+7
Why not the second one?
(4sin^2-2*sin*cos+7*cos^2)/sin^2=4-2ctg+7ctg^2
Why not the first one?

I was asking you because the original expression and the five answers are all equivalent.

>>8866682

I fucked up haha it actually asks which one is NOT equivalent.

But then how do you get B anyway?

And why is the last one WRONG?

I plug in 90 and 0 degrees and it works. And how can first 3 be equivalent if I can't fucking plug 90 and 0 degrees in them? WTF?!

>>8866698
>I fucked up haha it actually asks which one is NOT equivalent.
I only checked the first three because they can be obtained by dividing the original by sin^2, cos^2 and sin*cos respectively.

Let's see the last one. If you use cos^2=1-sin^2 you get
-3sin^2-2sin*cos+7=0
If you now use that sin(2x)=2*sin(x)*cos(x) you get
-3sin^2(x)-sin(2x)+7=0
Instead of the fifth result (which has as extra 2 in front of sin(2x)). Then that is the one that is NOT equivalent.

The next time read the problem more carefully.

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What did they mean by this? Kinda stuck up on the equivalent part.

>>8866711
>Kinda stuck up on the equivalent part.
Each polynomial ax+b can be written as an element in Q[x] and vice-versa.

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>>8866714
>Each polynomial ax+b can be written as an element in Q[x] and vice-versa.
>implying x^2+1 in Q[x] can be written as ax+b
???

>>8866674
brainlet

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>>8866714
Do I like show there's a bijection between those sets or something? Shieeet

>>8866721
>Do I like show there's a bijection between those sets or something?
Yes, sorry.

>>8866717
>>Each polynomial ax+b can be written as an element in Q[x] and vice-versa.
>>implying x^2+1 in Q[x] can be written as ax+b
>???
I think the same, but that's what the problem says..."Equivalent to a polynomial of degree less or equal 1".

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Which one is equivalent?

> якщo = if

WHY THE FUCK IT'S NOT PRELAST FFS?!

>>8866732
>I think the same, but that's what the problem says..."Equivalent to a polynomial of degree less or equal 1".
what is the equivalence?

>>8866737
brainlet

I have an object mounted on a force torque sensor.
When the object is still, the force I am measuring is the mass * gravitational acceleration.

When the object is moving, lets just say it is moving down, the force I am measuring gets smaller, which makes sense as there is a force pushing the object down, meaning the gravity is having less of an effect.

But the force remains lower after the after the movement is stopped, and moving it back to the original position brings the measurements back to what they where originally.

Does anyone know why?
Is it just sensor drifting or is there a physical explanation for this?

>>8866737
>WHY THE FUCK IT'S NOT PRELAST FFS?!
1+cos(2*x)=2*cos(x)^2
Apply that two times.

>>8866752

Well here's the fucking thing about that. The answer IS NOT 2sqrt(2)cosx, it's actually the third one.

SO HOW THE FUCK DO YOU GET THE THIRD ONE AND NOT THE SECOND ONE FFS?!

I know I said prelast but I meant to say postfirst.

>>8866766
>SO HOW THE FUCK DO YOU GET THE THIRD ONE AND NOT THE SECOND ONE FFS?!
Because for 0<alpha<pi/4, cos(4alpha) is positive, while for pi/4<alpha<pi/2 it's negative, so you have to use 1-cos(2*x)=2*sin(x)^2 in that region.

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WTF DOES PRELAST NOT FUCKING WORK FFS?!

>>8866797

POSITION OF TIME IS GIVEN, WHERE DOES THE SPEED FUCKING INCREASE WITH TIME FFS?

>>8866797
>WTF DOES PRELAST NOT FUCKING WORK FFS?!
This is already the third or fourth question.... This is my last answer for you:
Because prelast is not always increasing, for negative values of t it decreases.

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WTF IT'S FUCKING -1.5 THIS MAKES NO FUCKING SENSE. IT'S FUCKING -1.

IT WOULD BE FUCKNIG -1.5 IF IT WAS "WHAT'S THE BIGGEST ___ABSOLUTE___ FUCKING ROOT" BUT THAT'S NOT WHAT IT FUCKING SAYS.

SO -PI/3 IS BIGGER THAN -PI/2 FFS.

THESE RETARDS MADE A FUCKING TYPO I JUST WANT TO CONFIRM FUCKING FAGGOTS.

>>8866843
>THESE RETARDS MADE A FUCKING TYPO I JUST WANT TO CONFIRM FUCKING FAGGOTS.
If all the previous ones weren't typos but your brainletness, what make you think this one is a typo?

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Brainlet from other boards here.

Can someone explain to me the process of how to get rocket fuel from water, BUT THEN when you burn the fuel, you get water once more + a spare Oxygen atom. How can you bind the spare Oxygen atoms together to get breathable O2?


Does any of this even make sense? sorry it's really late here.

>>8866629
>>8866797
Speed is the absolute value of the velocity.

s(t) = |x'(t)| = |4t - 1|

It decreases for t between 0 and 1/4.

>>8866886

WHERE THE FUCK DID YOU GET 4T - 1? IT'S FUCKING 12T +2 ON THE _______sECOND________ FUCKIG DERIVATIVE FFS.

Anyway I already got it, you're just fucking confusing me with your bullshit.

>>8866870
Because you're a fucking scum and gonna be banned shortly. At least two people report your posts, so enjoy your month-long vacation from sci, faggot.

>>8866843

PLS HELP THIS IS A FUCKING TYPO THESE RETARDS FUCKED UP BIG TIME AND THEY WANT ME TO PAY THE PRICE.

FFS

>>8866843
>SO -PI/3 IS BIGGER THAN -PI/2 FFS.
but that's wrong brainlet

>>8866871
>Does any of this even make sense?
Sort of.

If you mean a liquid oxygen - liquid hydrogen propellant, then there's only one reaction.

2 H2O --> 2 H2 + O2

to get the fuel. Then, at very low temperatures, you can achieve liquid hydrogen and oxygen. And when you burn them together you get

2 H2 + O2 --> 2 H2O

which is the same reaction, but the other way around.

There are no spare oxygen, obviously. You probably forgot to balance the reaction.

>>8866732
Thanks.

is EnvE good? got offered this in uni and don't know what im in for

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FIND THE NUMBER OF EXTREMA ON THE INTERVAL


WHY THE FUCK IT'S 5 WHEN THE DERIVATIVE HAS 2 FUCKING ZEROS: AT PI/12 AND 5PI/12? WTF?!

what is the field with one element

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In which cases is the Gauss-Seidel method useful? It would be great to find an example of an applied problem in which it becomes necessary to solve such a system, that this method is better than the others.

hopefully the latex wont fuck up this time.
for the definition of [math] \lim_{x\to\infty}f(x)=\infty [/math] in pic related, why does K need to be restricted to positive numbers? im sure i was given a reason when being taught it. but the definition would be the same if it
said "for any [math] K\in\mathbb{R},...
[/math]" or even "any [math]K\in[a,\infty), a\in\mathbb{R} [/math]" wouldnt it?

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>>8867414
ffs

I need a good intro book on anatomy and the mechanical aspects of the human body, any suggestions?

I am a software engineer starting some projects in biomedical engineering and medical imaging for my master's.

so i have an algebra final in a few hours and i am so fucking lost, i'm pretty sure i'm going to flunk the class

the class size is small, the professor knows all of us and i don't think i can face him when i turn in my exam. Can I just fucking skip this thing??

>>8867414
>>8867419
If it is strictly positive, then the reciprocal exists and is strictly positive as well, which is sometimes convenient when it's easier to prove that [eqn]\lim_{x\to\infty} 1/f(x) = 0[/eqn]

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>>8867077
>sin(2x)+0.5cos(4x) from x=-1 to 3
Looks like 5 to me

>>8867108
>Because the identity condition is generally required to be different for addition and multiplication, every field must have at least two elements.

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what are good things to do in college to get "connections"? I'm going to be transferring to uni next fall, need to know what I have to do to make this investment worthwhile.

Good conferences to go to, workshops, summer camps, internships, etc..

I'm in Math/CS but might think physics and EE is cool too. Probably shooting for grad school down the road and want a nice resume / portfolio

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I was reading Simmons precalc when this pic made me wonder something

Are there any points B not on the circle for which the measure of the angle ABC is the same?

>>8864132
ha, you burned your prof. well done anon.

just gonna bump this out the way

If you have a task where you need to assign some unique value to something, and there is any number of functions that give you that value, can all of those functions necessarily be derived from each other? As in, you don't need to re-examine what the task actually is to come up with some of those functions.

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Part1:
I'm trying to figure out how the solution was determined in this problem.
Known values are
x component of AB = 700mm
alpha = 35 deg
beta = 25 deg
theta = 55 deg
BC = 400 mm
DG = 650 mm
They ask us to trace the ICR of ADG, BC and CD.
ADG and BC are obvious, however, without any equation, CD's ICR is G. How?

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>>8868266
Here is the provided solution. As stated, adg and BC are trivial to determine and it is also easy to determine that the system's ICR is where ICR ADG and ICR BC will meet, but how is it rapidly determined that point G is that meeting point? You can calculate it sure, but the point is to rapidly draw it out.

I don't know if this is the right place for this question but here goes. I got accepted for a Mech Eng undergrad program but I just realized that I would hate not doing chemistry. Should I jump ship to chem eng/chemistry instead?

Let [math]X,Y[/math] smooth varieties.

Suppose there exists [math]\mathcal{F} \in {\operatorname{D} ^b}\left( {X \times Y} \right)[/math] with proper support.

Why does this defines a functor [math]{\varphi _\mathcal{F}}:{\operatorname{D} ^b}\left( X \right) \to {\operatorname{D} ^b}\left( Y \right)[/math] given by [math]\mathcal{G} \mapsto {\mathbf{R}}{p_Y}_*\left( {{\mathbf{L}}{p_X}^*\left( \mathcal{G} \right)\mathop \otimes \limits^L \mathcal{F}} \right)[/math]?

>>8868404
its trivial

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Guys I'm in dire need of help here.
I'm not sure what I'm doing wrong here. Online solvers give my answer as

-128 - 128sqrt3i

And as you see from my pic, I'm not.

>>8868851
cos(-8pi/3) != cos(-pi/3)

>>8868851
cos((-8/3) pi)=cos((-2/3)pi)=-1/2

>>8868874
Please ignore that cos(8*(-pi/8)). I wrote 8 instead of 3 when writing it up to post on here, but the calculation for my final answer is done as cos(8*(-pi/3)).

>>8868894
i didnt say anything about cos(8(-pi/8))

the problem is that -8pi/3=-7pi/3-pi/3 doesn't imply
cos(-8pi/3)=cos(-pi/3)

>>8866750
You said it's a torque sensor? Is the moment arm the same at both positions (higher and lower)? I imagine it's not if it's on a fixed radius

>>8868899
So when I'm going wrong where I break down -8pi/3 to -7pi/3 - pi/3?

>>8868909
it's true that -8pi/3=-7pi/3-pi/3
but its not true that cos(-8pi/3)=cos(-pi/3)

>>8868911
So i'm unsure as to how to break it down, since as far I'm aware, it has to be broken down into the principal argument.

>>8868915
you don't have to break it down
cos(-8pi/3)= -1/2

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>>8868919
Okay. So I should just emit the part with the arrow entirely?

>>8867824
Consider reflecting the circle about the line AC.

>>8867771
>"connection
blamp

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>>8868919
I rewrote it and I t-t-think it is correct now. Thanks guys, greatly appreciated.

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>Axiom of regularity (also called the Axiom of foundation)
>Every non-empty set x contains a member y such that x and y are disjoint sets.
>This implies, for example, that no set is an element of itself
How does it imply that? Say that you have x = {x,1}. Then 1 is a member of x that isn't a set that has members in common with x. Doesn't that satisfy the axiom?

>>8869124
Thats why its called an axiom. The set you provided is not considered legitimate in this framework

>>8869127
But how does the axiom of foundation imply that it's not legitimate?

>>8869124
no it doesn't satisfy the axiom, because the element x is not disjoint from the set x.

>>8869147
It doesn't say every element has to be disjoint with the set. And in fact that doesn't make sense, because x = {a,{a}} is allowed.

>>8869129
Through a purely arbitrary convention that exists as part of a long historical development. These limitations are set to prevent more fundamental contradictions

>>8869155
That looks fine to me, here a and x are disjoint.

>>8869155
you're right; i misread your post

anyway you can just apply the axiom to x={x} to show that x can't be an element of itself

>>8869124
No set can be a member of itself under the axiom of foundation, because you can then write [math]x \ni x \ni x \ni x \ni \ldots [/math] and this violates the corollary that there is no set x with an infinite decreasing sequence of members [math]x \ni x_0 \ni x_1 \ni x_2 \ldots[/math].

To show that the axiom of foundation implies no infinite-decreasing sequences, suppose for a contradiction that such an x exists and let y = [math] \{x_n | n \in \mathbb{N} \}[/math] be the collection of infinitely-descending members. The axiom of foundation, applied to y, states that there is some [math]x_n[/math] that is disjoint from y, which is a contradiction since we know [math]x_n\cap y[/math] contains at least [math]x_{n+1}[/math].

>>8867759
>>8867108
https://ncatlab.org/nlab/show/field+with+one+element

i'm not too sure of the details myself but it seems like the algebraic geometer's version of analytic continuation - things make sense for patterns of fields with n elements and still make sense if n is 1, even if no such field exists

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this is either Co(edta)- or cis-[Co(IDA)2]-
which is it?

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>>8869457
this is the other

File: curve fitting.png (350KB, 1620x943px) Image search: [Google]

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Trying to curve fit some solar radiation data. I'm trying to curve fit a cosine function to it in matlab and here's my code:
modelFun = @(p, theta)(p(1) + p(2) * cos(theta - p(3)));
p = nlinfit(x, radiation, modelFun, [1 1 0]);
yFit = modelFun(p, x);

but when I plot yFit on the graph it only has an amplitude of 1 and isn't doing the broad strokes like I want it too. Any help?

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Did they mess up this question? Because no matter what I try I get a different answer.

>>8869513

Nope, their answer is fine. Show us your working.

>>8869517
Ok, give me a sec while a retry it.

>>8869457
>>8869458
A couple of integrals would be useful, but given the nature of the ligands I'd say the first one is [Co(IDA)2] and the second one Co(EDTA).

The peak at around 4.5 it's the not-deuterated water from the solvent.

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>>8869519
Ok here.
My handwriting isn't the best though.

>>8869544
Wait a minute, I'm a fucking idiot. I just realized what I'm doing wrong.

>>8869544

But your answer IS correct. You can multiply both the numerator and denominator by -1 to get the required result.

>>8869557
Yeah, I just realized that, lol.

>>8869532
wasn't given sadly. nor was a IR or UV

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Why is it that when I differentiate the top equation, and then plug in (0, 1) into the derivative, I get the slope in the bottom equation? that's not a fucking tangent. This makes no sense.

>>8869508
I'm not familiar with user defined functions with the fitting toolset. While it may not be relevant, why is fitting a cosine to this absolutely necessary? What information do you get by fitting a cosine to the dataset?

>>8869858
[math]y=x^2-xy+y^2 \\ y'=2x-(y+xy')+2yy' \\
y'+xy'-2yy'=2x-y \\
y'(1+x-2y)=2x-y \\
y'=\frac{2x-y}{1+x-2y} \\
y'=\frac{2(0)-1}{1+0-2}=1 \\
y-y_0=m(x-x_0) \\
y-1=1(x-0) \\
y=x+1[/math]

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>>8869883
>>8869858
Updated graph

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>>8869883
I don't understand why you got that.
Ok so apparently the original equation in your post gives a different derivative than pic related?
I differentiated pic related and I'm 100% sure it's correct, maybe I'm graphing it wrong?

Also why y - y_0 = m(x - x_0) ?

>>8869936
>y - y_0 = m(x - x_0)
Reading his thing, when he reaches that step that "y" is not the same y as above.

Notice that he got the slope (which is 1) and has a point (0,1). Then he uses that formula which is for finding a line with a given slope and point. He should probably have used another letter.

>>8869955
No I mean why did he get a different derivative than me?

The derivative I got was (2x-y)/(x-2y) which gives me a slope of 1/2 at point (0, 1).

>>8869959
Well look at his procedure. It looks right. You made a mistake when differentiating.

>>8869961
I'm >>8869513, it's from the same question, the derivative I got is the same as in that image so I'm definitely sure it's correct since it matches.

>>8869970
putting a y instead of 3 makes a huge difference.

>>8869970
Bruh. You graphed the wrong thing.

>>8869974
>>8869977
Yeah, I don't understand why that is. I just wrote it in the y form to graph it on desmos, thinking it was the same, which is why I got confused.
I'm asked to find the tangent at the point (-1, 1). I just plug that into the derivative I have and that's the proper slope right?
Also how do I graph it properly on desmos?

>>8869980
[math] x^2 - xy + y^2 = 3 \iff y = \frac{3 - x^2 - y^2}{-x} [/math]

You have to know these things man. You are in calculus now.

>>8869983
I don't really understand what the 3 means though. Why can't I just substitute it with y?

>>8869991
What you have in >>8869936 is a cartesian expression of a curve.

That 3 is a part of the curve. If you change the 3 you chage the curve. For example, graph the same thing but instead of 3 put in 4.

Similarly, if you change the 3 for a y that also changes the curve. You saw that with your graph. Anything that you change about that expression will change the curve. Therefore: you shouldn't change anything.

Why don't we just shoot all of our garbage into the sun?

>>8870023
Because then there will be garbage rays in our sunlight.

If you have a graph, can every function that describes that graph be derived from every other function that describes that graph?

>>8870023
Because it costs Billions upon Billions to shoot things into space.

>>8870173
There is only one function which can describe an given graph.

If 2 different functions have the same graph, they are equal in all points and therefore equal in general.

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Which is the simplest form?

>>8870319
Neither. Depends on context.

1) is simpler if you want to factorize the polynomial and/or complete the square as having the coefficient of the z^2 term be 1 makes this job simple.

2) is simpler if you have a reason for wanting all coefficients be integers, and very often you want exactly that.

>>8870341
I'll go with the second option. Thanks.

[math]R_{eeeeeeeeeeeeeeeeeeeeeeee}[/math]

>>8870472
Here's a stupid question. Why doesn't 4chan see that as valid latex?

>>8870231
Related question: is there necessarily a relation between a function that creates a 2D graph, and a function that creates a 3D graph of which there is a slice of that matches the formerly mentioned 2D graph?

>>8870472
[math] R _ { eeeeeeeeeeeeeeeeeeeeeeee } [/math]

>>8870475
Because you are dumb lol

>>8870565
[math]R_e[/math]

>>8870472
>[math] R_{eeeeeeeeeeeeeeeeeeeeeeee} [/math]
the spaces between the content and tags maybe

>>8870572
[math] R_{eeeeeeee} [/math]
[math] R_eeeeeeee [/math]
[math]R_eeeeeeee[/math]
[math]R_{eeeeeeee}[/math]

Question about multiple regression that i am brain farting on

for a problem set, i am looking to determine housing values in different locations and an interaction term between income and bathrooms is significant, but has a negative coefficient. How do I interpret this. I know its simple.

When people say an expansion is "about" a point, what exactly do they mean?

>>8870560
Let's say you're functions are f(x) and g(x,y). Every vertical slice is just a plane that can be described with na equation relating x and y. For example if x+y=0 then plugging that back gets you f(t)=g(x,-x) with t being the distance from the center, in this case t=x*sqrt(2). In general if the slice isn't vertical it would be more complex but you could still find a relation.

why do dogs like cheese so much?

>>8870640
If you look at the general form of an expansion it has something like (x-x_0) in it. x_0 is the point that you're expanding about. Maybe "around" would be a better word.

>>8870663
I get that but how much "around" is it?

How do you sit your ass down and just work for 12 hours straight and actually focus?

>>8870703
discipline

>>8870713
How do you acquire discipline?

>>8870670
Not sure if I understand the question. It's (x-x_0) from the point obviously. If you're interested in where it's valid to do that look up radius of convergence of a series.

>>8870719
same way you got used to shitposting on 4chinz. practice and habit.

start by sitting down and working without distractions for as long you possibly can. next period, do a little longer, and so on

literally not magic, but it is difficult

how to join an edx course before stat date?

>>8870721
Thanks! That's what i was looking for

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>>8870584

in delta-epsilon proofs of limits, why cant delta depend on x?

>>8870737
really depends on what you're proving. if you're proving continuity at a point, then delta can depend on x. if you're proving uniform continuity, then it can't.

>>8870755
i mean as in proving that some function tends to a limit for example "show the function f tends to 2 as x approaches 4". idk what that counts as