/SQT/ - Stupid Question Thread

depends on uni

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

>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.

what do you mean by information?

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

Well, there is literally a sub-field of mathematics called Logic.
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

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)=[/math]
where u and v and both bounded by [math]-1 \geq u and v \geq 1 [/math]

fucked up the inequality signs, but anyway pls halp

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

What did he mean by this?

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

still trying to figure it out via trial and error, so if any user 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

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)

Getting from 3 to 4?

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

Which part of that is confusing you?

Best in your opinion introduction to logic?

also textbook/class on propositional calculus

turning 4-z^2 into sqrt2

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

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

ahh, duh.. thanks user

>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]

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

/scared/

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?

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

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

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

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

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.

youtube.com/watch?v=2eFvVzNF24g

His lectures are pretty good.

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

BUMPin

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?

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?

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.

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

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.

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.

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.

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.

There is literally NOTHING wrong with his writing.

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?

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

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

no

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

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

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

I'll rewrite it and post a better version.

>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!

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

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?

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

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.

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.

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

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.

ok, thanks.

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.

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 Veeky Forums wiki's opinion on it.

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?

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.

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.

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

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

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. Veeky Forums likes to spend hours plotting curriculums instead of reading but book choice doesn't really matter very much.

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.

oh if y is prime then yeah then they're the same and f(x,y)=x/gcd(x,y) works

shouod be this

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?

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

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

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.

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.

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.

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

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?

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

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

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

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

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?

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?

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.