/sqt/ - Stupid Questions Thread

This thread is for questions that don't deserve their own thread.

Tips!
>give context
>describe your thought process if you're stuck
>try wolframalpha.com and stackexchange.com
>How To Ask Questions The Smart Way: catb.org/~esr/faqs/smart-questions.html

Previous thread:

Other urls found in this thread:

tutorial.math.lamar.edu/Classes/CalcII/ArcLength.aspx
ecetutorials
academics.wellesley.edu/Physics/brown/pubs/effalgV92P2698-P2701.pdf
pastebin.com/kqG69fYJ
programming.dojo.net.nz/study/truth-table-generator/index
twitter.com/NSFWRedditGif

What is the significance of C-Squared and how does it relate to the energy-mass equivalence?

Why is the total energy of a system equal to its mass + the speed of light squared?

And why does total energy/c squared equal the total mass of a system?

How does light pass through a prism and what slows down it's speed to an outside observer?

Don't you dare say it's scattering or absorption, because, if that's the case, then explain why the light stays in a straight line. No bullshit.

Thank your very much ! Alpha = 60°

Once upon a time I ran across a website that had a bunch of mathematical questions ranging from "Easy" to "Hard". Where most if not all of them needed some knowledge of programming in order to find the answers to them.

My question is does anyone know of which website it is and what is the website?

Can someone clear up additive vs nonadditive genes for me? I'm getting multiple sources contradicting each other. From my understanding it's:
Additive---------
-works with other genes to build up trait (polygenetic)
-both forms of the allele (AA or aa) most be there (not can be dominate)

Nonadditive---
-can have a epistatic affect
-when the dominant allele over takes the recessive allele (dominate)

Does fecal matter?

Which grows faster, n^x or nCr?

Put nCr in terms of the gamma function

sounds like project euler

When our ancestors started losing their fur, why were they still mated with? Wouldn't the furless homos have been outcasts?

I don't get what you mean. n Cr what?

n^x will grow indefinitely as x increases. n Cr x will decrease when x starts approaching n.

Alright, so every time I think I have a handle on how linear algebra concepts work, some problem comes along that destroys that perception. Here this problem that first asks to show why Ax=b does not have a solution for every possible b. Easy enough, row reduce the augmented matrix associated with this equation and point out the inconsistency.

What I don't understand is the second part, "describe the set of b for which Ax=b does have a solution". What I ended up getting (for the row reduced matrix) was :
[ 1 1/3 b1/3
0 0 3b1 + b2]
The solution says "the set of b for which the equation is consistent is a line through the origin - the set of all points (b1,b2) satisfying b2 = -3b1".
I'm not understanding this answer. I know 3b1 + b2 has to be 0, but I don't know why we are solving for b2.

Do you mean what grows faster,
[math]n^{x}[/math]
or
[math]\frac{x!}{(x−n)!n!}[/math]
when n is kept constant and x varies?

How do you find the length from one point to a nother in a parabola Not from one point to another from a straight line but across the parabola?
Is there an equation for it?

Nevermind. I figured it out. Although, I'm surprised no one replied.

it's called arc length and is usually covered in Calc 2 courses. Have a read if you're ready for it:

tutorial.math.lamar.edu/Classes/CalcII/ArcLength.aspx

It's the speed of light squared, and it relates the energy mass has simply by existing i.e. all possible energy than can be extracted from purely mass

it's not.

it doesn't.

Correct.

Let n >> x then

looks like n^x grows way faster.

Why are we spending so much money and effort to fix global warming.
It is a self correcting problem
Humans make to much co2
Earth can't support the human population
Human population declines
Humans generate less co2

Because humans don't want to die?

The evidence dose not support you

what the fuck does it mean to "prove analytically"?
i've never done a proof before pls help

how do I get good at control theory?

>differential equations
This is probably simple, but I just can't figure out why the highlighted expressions are equal.

is the photoelectric effect a cause of ionization? this seems to say so ecetutorials . com/photo-electric-effect-and-photo-ionization/

how?

isn't it the case that the electron being hit stays in the atom, just at a higher energy level? and then emits a photon with caracteristic energy to descend back?

am i missing something?

Oh wow, I understand it now. Product rule.

My physics is rusty, but I got this from a quick search:
>"Pulses of radiant energy, such as X-ray and gamma-ray photons, can eject electrons from atoms by the photoelectric effect to cause ionization."
>"In the photoelectric effect, light incident on the surface of a metal causes electrons to be ejected."
It's got something to do with the work function of the metal or something.

hmm. so then what's the difference between it and the Compton effect?

maybe just the energies involved?

or the energy of the outgoing photon in the case of the photoelectric effect is characteristic to the atom being ionized and in the case of the Compton effect it isn't?

[math]\lim_{x \to 1} \frac{x^2+x-2}{x-1} = 3 [/math]
I’ve been finding deltas in terms of epsilon for a little while, and all of them seemed obvious until I tried this one. I was getting (correct) answers of delta equaling some simple fraction of epsilon, so in this case I figured that they would equal each other. Apparently, though, delta is *less than or* equal to epsilon here. Does anyone know why the answer has that extra condition?

is this correct? if not plz help. ty

guys I feel like a complete and utter brainlet in basic probability... could you help me solve this for P(A)? please show the steps so I could figure out where I got lost (tried using set theory algebra but got stuck).
the problem is in pic related.
thanks in advance!

C^2 is there for the unit conversion
We know energy and mass are equivalent because when a body of mass for instance exerts radiant energy it also lose mass, and when a body of mass increases velocity it's kinetic energy increases and so it's mass does as well.

Light always moves in a straight line, it's angle however can change and that is waht happens when it scatters. The light beam enters the prism an than scatters into dofferent angles and thereby different wavelengths.

How can Neanderthal have reproduced with homo sapiens and/or cro-magnon if they were different species ?

By the way, can eskimos and aborigenes have fertile offspring ?

Why doesn't the minimal polynomial need to exist when T is a linear operator on an infinite vector space?
I couldn't understand the very few examples that I've seen on Google.

It means to prove with rigorous mathematical formulations of the concept, rather than construct a geometric interpretation. For example, a parabola with the origin as its center can be described as increasing on either side of the origin exponentially as x approaches infinity. Or you could just give an analytical solution that describes it and not bother with the geometry of the curve, and say y = x^2 and throw out any geometric description, it's completely described by variables and numbers.

can i use le hopital when the limits result in 1/0, and not in 0/0 or infinity/infinity?

...

What is the difference between the inner product and the dot product? How is the inner product a "generalization" of the dot product?

no, depending on whether 0 is being approached from the left or the right, it would be -∞ or ∞ respectively

Factor the quadratic user.

>What is the difference between the inner product and the dot product?
inner product is a map taking two vectors to a field element which satisfies certain axioms

dot product is a particular function that satisfies those axioms, so it's an inner product

thanks so much buddy

seriously nobody?

Can [math]\sqrt{5}[/math] be shown to exist?

Fuck you.

Excuse me?

It can be shown that [math]\sqrt{5} \not \in \mathbb{Q}[/math]. The existence of a set [math]A[/math] such that [math]\sqrt{5} \in A[/math] is currently an open problem.

[math]\sqrt{5} [\math] has [math]x^2 -5[\math] as its minimal polynomial over [math]\mathbb{Q} [\math]. This polynomials is irreducible, so [math]\sqrt{5} [\math] belongs to [math]\mathbb{Q}[x]/(x^2-5) [\math]

Brainlet. Quadratic reciprocity. The square root of 5 exists in many Z/nZ rings.

I see.
This doesn't look like a proof.
>The square root of 5 exists
Prove it.

Consider the field Z/11Z.
Here 4^2 = 5. Therefore the square root of 5 is 4.

Prove that it is a field, prove that 4^2 = 5.

If you haven't even studied Z/nZ rings then I recommend finishing 8th grade before you post opinions about math

>Z/nZ rings
Prove that Z/nZ is a ring for arbitrary n.
>before you post opinions about math
What are you even talking about? I asked a simple question. If you don't have the expertise to answer it, then just don't even reply.

I like the idea of burning things with sunlight and a large converging lens.
However, I don't like the fact that the burning point is a set distance away from the lens.

Is there any reason why I couldn't place a diverging lens just before the focal point or a converging lens just after it, and collimate the cone of sunlight into a "beam"?

Dude, all you are asking for is on google. Even wikipedia tells you all you need.

I don't use the websites you mentioned though.

Then get a book on elementary number theory

Which book do you recommend?

I have a question regarding evolution/genetics.

How is it that when a woman and a man have a kid, the 2 genes manage to mix so perfectly? Since the potential genes on the mother's side and the father's side can be so different, how can they come together so perfectly to form a healthy child? For example, when you take the combined genes for bone structure, why are there relatively few deformities?

Or take something like skull size and brain capacity, is it possible to get a slightly larger brain from one side of the family, and a skull incapable of adequately housing the brain from the other side?

I can notice in my hands that one hand resembles my mothers, and the other my fathers, and they work but theyre relatively crude parts of the body compared to extremely delicate things like eyes, ears, brain, heart, nerves, etc. work so well based on randomization?

My understanding of this subject is primitive and im studying in a completely different field, but can anyone give me some sort of normie answer?

tldr:
Why isnt everyone completely deformed based on the randomization of genetics?

Is it advantageous for an actuary to have a Master's degree or doctorate? If so, when (relative to accreditation as ASA and FSA)?

Is there a name for this sort of flawed reasoning?

Someone flips a coin 10 times, notes the results, and since the probability of this exact sequence coming up is 1/1024, the fact that this sequence came up should be regarded as an extremely unlikely occurrence. Obviously the error is that some sequence of coins had to come up, and the person flipping the coins would have made the same statement no matter what sequence came up.

where exactly is the flaw supposed to be?

I know I could just plug it into wolfram, but how would you figure this out by hand other than just multiplying it out?

My professor used Niven. It's pretty good. I learned all from my professor so I have never actually read a full elem. number theory book, I have just skimmed some, but if he says its good then its good

Binomial theorem.

I think that's simple statistics.
(b) and (c) should be obvious.

It's (1+x^3 + x^5) * (1+x^3 + x^5) * .... * (1+x^3 + x^5)
Which options are there to arrive at a*x^3?
1*1*...*1*x^3
1*1*...*x^3*1
...
1*x^3*...*1*1
x^3*1*...*1*1
In total 15
Similarly for (d)

Aw makes sense. So we are really just thinking about how it could be done and then counting the permutations. Interesting. Thanks!

I would describe that as a misinterpretation of a probabilistic event. It's not unlikely compared to the probability of any other sequence of coin-flip results. So if there isn't anything else involved but the flipping of coins, saying "wow that was really unlikely" isn't a meaningful statement.

Now, suppose someone predicted that exact sequence in advance, and it occurred. THEN you could say "wow that was really unlikely," and it would be a meaningful statement. Namely, given the null hypothesis that the actual outcome will have a 0 correlation with the predicted outcome, a correlation of 1 would be evidence that the predictive mechanism is real.

Alternately, suppose someone won the lottery. Because winning the lottery is significantly less probable than losing, then it would also be meaningful to say "wow that was really unlikely" both because of the comparative probability of a win to a loss, and because of the actual reward involved.

I want to get my hands on some quality lunar tools the astronauts used during the moon program, where could I go to get an exact replica?

Looking for something that is functional and as close to flight hardware as possible

I did...? That's how I got my original answer or delta = epsilon. I don't see how that explains it.

I did...? That's how I got my original answer of delta = epsilon. I don't see how that explains it.

Guys what the fuck

Euler's formula says for any planar connected graph, the number of vertexes plus the number of faces minus the number of edges equals 2

v + f - e = 2

What about this? Am I literally retarded? It equals 1 here

Oops I found it out. The external of the graph counts as the "infinite face" lol so F=6 not 5...

what are you confused by? show f(a/b)=0 implies a divides c_0 and b divides c_n

If I have 2 linear trasnformations [math]A, B[/math] and a scalar product [math][/math] such that [math]=[/math] for all [math]x,y\in \mathbb{R}^n[/math] then is is true that the scalar product banishes everywhere?

How exactly would I show that this is true?

I mean isn't it just trivial. If you reduce a polynomial of power two or three you will always have a polynomial of power 1 which is always solvable for a rational number?

Is that enough proof?

use [math]\langle \ \rangle [/math]

What did he mean by this?

Gonna try here before I make a thread about it.

I'm doing to calculate the spectral kernels of a Constant Q Transform by calculating the temporal kernals, then doing an FFT as in this paper:
academics.wellesley.edu/Physics/brown/pubs/effalgV92P2698-P2701.pdf

My MATLAB code is at pastebin.com/kqG69fYJ

I'm stuck on the "calculating the temporal kernels" part. I'm trying to do it with the centered Hamming function and complex exponential as shown in Eq. 7, but my temporal kernels don't look anything like the authors, which increase in frequency and become less spread out in the time domain with increasing kernel number.

I noticed that with my current setup, every other complex exponential is simply 1. Is this part of the problem, or is there something else I've overlooked?

Thanks in advance.

Lost /x/fag here trying to not die.
Trying to refine Potassium Carbonate into Angel Water. The method I'm following says to use a glass dish but also mentions that the substance is corrosive enough to etch into the glass. Are there certain types of ceramic wear that it won't react with, or do I just stick with the glass.

not enough info

>Angel Water.
What's this?
If you're playing with chemicals just to make bullshit magical potions, then please kill yourself.

Angel water is a strong alkaline substance that you get from exposing potassium carbonate to ambient moisture.

Hi Veeky Forums,

Got a question here hopefully some of you guys can help to answer.

I'm currently working on university computing math and I'm told to proof (p ^ q) -> (p v q).

I more or less have it worked out, just need to sort out 1 tiny question.

In Logic, the commutative law states that (p v q) is logically equivalent to (q v p), however it does not state whether it applies for statements with more than 2 atomic propositions.

can you swap (~p v ~q) v (p v q) around so that it becomes (~p v p) v (~q v q) using the Commutative Law?

I know that they are logically equivalent, but what law can i use to swap the atomic propositions if I can't use commutative law?

>proof (p ^ q) -> (p v q).
Sorry that makes no sense

prove that? That is not a true proposition

Can anyone help me out as to how I would read these kinds of engineering drawings?

...

I know you would line them up but alot of it just seems like ADHD gibberish so many different section shots

Of course not. You can put an infinite amount of converging and diverging lenses together, but you'll lose some power as light changes between the glass and air. The only thing I'd say is you don't know where the rays from the diverging lens are going.

>If I have 2 linear trasnformations A,B and a scalar product such that = for all x,y∈Rn then is is true that the scalar product banishes everywhere?
no, consider A=B=identity

fugg I forgot to add a minus sign. I think I solved it though.

Are you kidding? It's literally a 3 liner constructively, which means it's valid classically as well.
Assuming "^" is "and", "v" is "or" and "->" is implication.

Let's say you started running a big software company, and many of your competitors are amoral assholes.
What kind of antidote/antipoison would you always keep at hand in case if some of the more coward competitors try to poison you?
Also, what other precautions would you take? What medical checkups are a must?

Asking here because this is somewhat med. science related.

Platintum (IV) Chloride Azanide

Why do the the hydrogens on the azanide group point toward the platinum atom?

It's a ring by definition, because it has group structure under addition and is closed under multiplication. the n can't be arbitrary though, must be integers. >=1 but Z/Z is isomorphic to the identity group so we just start with 2

input (p & q) -> (p | q)

at programming.dojo.net.nz/study/truth-table-generator/index