/sqt/ - Stupid Question Thread: Coffee Edition

I have shit head arithmetic and freeze up when I'm asked to do simple arithmetic in public
Where can I practice that shit
Is khan the best choice

Universidad de Sevilla best university

why the fuck are you being asked to do simple arithmetic in public in the first place?
anyways just get some book teaching mental arithmetic - there are plenty of those.

Nice coffee.

Anyway, what's the difference in career oportunity between majoring in stats vs majoring in pure but taking stats electives?

Also, can any math jobs work from home / set own schedule?

What area of math should I study if I want to get into the procedural generation of text (ie the library of Babel)?

social norms
i dont find it to be morally wrong because i wasnt raised to think so by my parents or my society

How is the sum in this situation equal to:

(the amount of ways a necklace of m beads and n colors can be uniquely arranged)
TIMES
the length of the necklace?

How does it get that conclusion from this sum, which is:

The number of times a given shift is equal to the arrangement for all shifts of all arrangements.

This post was in response to me admitting about anxiety fits caused by my idea of what an universal phase transition would entail (unpredictable death at any possible second)

Since I'm not interested in the conspiracy theories or the occult beyond curiosity, can anybody clarify why this view is incorrect? What is partial about my view of this? I'd love to be corrected if it meant I'd stop being so fucking spooked

help pls

Isn't it inbreeding when 2 people from the same race breed because they are from the same race?

only if they're genetically similar enough to cause defects

it basically is inbreeding if you do this with purebred dogs which is why so many breeds have shitty genetic disorders that don't show up in their mutt children

I have a set of 3D points, i need to fit the smallest circumscribed geometric shape on them. The geometric shape is a cylinder with cones on the end.

Can anyone recommend anything on this?

So my exam had this question I cannot prove for some reason.

[eqn]T:A \rightarrow A^q[/eqn]
where A is a [math]n \times n[/math] matrix with real coefficients.

Prove T is Lipschitz continuous and determine a Lipschitz constant.
(Using Gronwalls lemma)
(Hint: Seperate into 2 different functions)

If anyone has any idea, or even a smart idea how to seperate T into 2 useful functions I'd love to hear it.

Preface: I'm handicapped when it comes to maths. Sorry.

I'm trying to create a function from which I can deduce, for any given moment in time, the position of a body in its orbit. This position would be defined as the position on the orbital ellipse, whether that be in degrees, radians, or 0 to 1.
Of course, for elliptical orbits, this position doesn't change linearly over time. It changes faster when closer to the focus point we're orbiting around, and slower when farther away.

Ideally, I'd be able to pass in the eccentricity of the orbit ellipse (or a similar attribute) and get graphs like pic related. The best I've been able to get so far is the graphs on the right, but these aren't steep enough for very eccentric ellipses. How do I fix that? Or are there better functions to use?

>Prove T is Lipschitz continuous
Under what metric?

f(t)=(a*cost,b*sint)
where a is how much you stretch in the horizontal direction, and b is for the vertical direction

You miss the point.

Your mind is limited, you can't always see what's wrong with an idea. But you can get used to the idea of knowing that you're probably wrong, without knowing how or why. This is why you can benefit from looking at how other people are scared about nonsense.

An analogy: when someone performs a magic trick in front of you, claiming he's a real wizard, do you believe him? No, you know it's a trick, even though you don't know how it works. You know your perception of what he did is wrong. This is because you are familiar with the concept of magic tricks.

I don't have to know what you mean by "universal phase transition" to know it's probably nothing. I had worries about quantum immortality at some point. I never disproved it, but I did stop worrying about it, because I realized it's just a scary idea that was designed by someone, just like many other things, like the concept of hell (which was never disproved either).

So, instead of looking for disproofs of one particular worry, look at the bigger picture.

Dumbfag here. Can someone explain how evolution actually works? Like, how do species just will upgrades to themselves into being over generations?

literally who? I am applying to a swiss and german universities

Assume max norm always

you save up enough xp in life, and when you go to heaven u can buy upgrades for your offspring. Of course, options are limited, so it's not like you can buy the acid claws without first having bought forearms.

I already know that's how I get coordinates from a given angle on the ellipse. What I'm trying to figure out is how to increase that angle over time so that it increases faster when closer to one of the foci.

They luck into the upgrades, and those that don't die faster than those that do. Lucky upgrades get passed down to future generations.

shouldn't the arrow be

[math]\mapsto[/math]

Yes but I dont know the LaTeX code for that symbol by heart.

\mapsto

pretty intuitive

Oh my bad.
Well, I guess it could work if we did it this way:

Say your point is (p,q).
The distance of it from a point in the ellipse f(t)=(a*cost,b*sint) is
sqrt((p - a cos(t))^2 + (q - b sin(t))^2)

Consider the quantity:
1 / ( (p - a cos(t))^2 + (q - b sin(t))^2 )
since we want to move slower when the distance is bigger (and squaring that shit doesn't really matter).

Then I don't know. Name that quantity s and solve for t? I am probably talking nonsense now...

Okay, but that still doesn't help me solve this problem :/

it's not will
random mutations can be caused by background radiation or (more commonly) fuckups when trying to copy dna

sometimes a random mutation is shitty and the animal with the mutation dies
sometimes a random mutations gives the animal an advantage over its buddies so it gets to fuck more sweet lady animals and have more babies than them. and its babies will have this positive mutation too

remember that this is a process that takes millions of years to accomplish shit. it's just a bunch of random luck plus time

Which sound would travel farther: a firecracker at the summit of a hill or at the bottom of a valley (assuming that pressure and temperature are constant)? I would assume that the firecracker on the summit would travel farther, but the firecracker in the valley would be more intense due to echoing. Or, does the valley channel the sound?

[eqn]\frac{d\theta}{dt}= \frac{L}{mr^2} [/eqn] Where [math]L = mr_{0}v_{0} = I\omega[/math] is the system's angular momentum. I suppose you already know the radius as a function of time you want, so for the angle you just solve the differential equation.

This doesn't fit well within the model I'm implementing though.
I want to be able to calculate positions for things at any given point in time, without any dependency on previous moments. I do not keep track of velocities, gravitational forces, etc. Just the ellipses that describe the orbit, and a time in which the orbit is completed.

Sorry, I probably should've specified this earlier, or kept my question strictly to generating the graphs I described.

>I want to be able to calculate positions for things at any given point in time, without any dependency on previous moments
You would need a closed form solution to the equation I posted above to do that and unless your radius is constant I don't think you'll be able to do that. Still, you could try, maybe you can approximate well with a series. Put the equation of the distance as a function of time in the variable r in the equation and try to solve it.

Well, yeah, the shape of the ellipse (including its radius/semi-major) is constant, so that'd make this doable right?

I took a single half derivate of e^x and got

[eqn]\sum_{n=\frac{1}{2}}^{\infty}\frac{ x^{n-\frac{1}{2}} }{\left( \frac{ 2(\frac{1}{2}(2n+1)!)}{2n+1} \right)} [/eqn]

but how can I prove this is correct? the graph of e^x and this certainly looks promising but it would be more satisfying to take the half derivative of this and get something that boils down to basic e^x again.

It certainly is, but it is by no means easy. The distance I refer to is the distance of a certain point on the ellipse to one of the foci, so it's actually a very complex integration you end up with. Just try to isolate d_1 or d_2 as a function of a, b and t and you'll see the mess you'll get. I suggest using the equation of the ellipse in polar coordinates instead of what you are using now. If you don't care about physical accuracy either, estimate the velocity on closest approach and on the farthest point and just build a nice smooth function that goes through them.

EPFL or UIUC for MS if end goal is PhD at ETH Zurich?

oh, and in general, where can i learn more about fractional calculus (>inb4 google)? I mean like a book or something of the sorts. I've been taking a pretty casual approach to it and i'm interested in learning more

I think I can probably do a reasonable approximation using bezier curves? Points more outward the more eccentric the ellipse of the orbit is. Seems about right?

Hey Veeky Forums. First time here, forgive me if I don't know your asking conventions. I'm doing some repetitive experiments with variables that I alter per batch, and within each batch for sub-sets

I'm wondering what naming conventions exist for such processes?

For example, i'm attempting now to write down the processes and inputs for one batch, which I have designated B07 HAC HA (13.06.03) 01.

Batch 07
High Added Carbon
High Acidity
A nutrient list
First repetition of this subgroup.

I'm wondering what conventions you all would use for this batch/group.

Sorry again for not using the terminology you might expect; i'm not a scientist.

Linear algebra:

Is the length of the vector projection of vector $v$ with vector $u$ supposed to be $\sqrt{x \dot u}$?

If you live around people of < 80 IQ, how do you develop verbal IQ?

>Is the length of the vector projection of vector [math]v[/math] with vector [math]u[/math] supposed to be [math]\sqrt{x \cdot u}[/math]?

why are you even asking this? this isn't even linear algebra, it's much more rudimentary and any linear algebra student should know about vector projections

you're in the wrong thread nigger

haha, maybe, but I only say that to boost my non linear algebra ego. I mean really, why can't you just look up the formula for projections?

Is the following true?

[math]\displaystyle z \in \mathbb{C}, \lim_{|z| \to \infty} \left|\frac{z^2}{z^2 + 1}\right| = 1 [/math]
?

Someone answer this before I attack

Well, you can't help, but for the interest of those who can, I'm having trouble getting the correct length for an example.

[inline]u = \begin{bmatrix}
1 \\
3 \\
2 \\
\end{bmatrix},

v = \begin{bmatrix}
3 \\
2 \\
1 \\
\end{bmatrix} [/inline]

I get the vector projection by [math]u (u' u)^{-1}u'v[/math] and I get

[inline]\hat{v} = \begin{bmatrix}
11/14 \\
33/14 \\
11/7 \\
\end{bmatrix}

which has length 2.94. The square root of the inner product of [math]\sqrt{u \cdot v}[/math] meanwhile is 3.32.

Crap formatting, I haven't used LaTeX in a while.

No

Iirc my limit theorems correctly, yes.

[inline]\frac{1}{1+\frac{1}{z^2}}[/inline]

[eqn]\frac{1}{1+\frac{1}{z^2}}[/eqn]

...

>holy shit

I'm having trouble getting the correct length for an example.

[eqn]u = \begin{bmatrix}
1 \\
3 \\
2 \\
\end{bmatrix},
v = \begin{bmatrix}
3 \\
2 \\
1 \\
\end{bmatrix}[/eqn]

I get the vector projection by [math]u (u′u)^{-1} u′ v[/math] and I get

[eqn]u = \begin{bmatrix}
11/14 \\
33/14 \\
11/7 \\
\end{bmatrix}[/eqn]

which has length 2.94. The square root of the inner product of [math]\sqrt{u \cdot v}[/math] meanwhile is 3.32.

Why is >I want to be an engineer because I like to build things is a meme?

>You can't help
I'm gonna help you so hard you fucking nigger, tomorrow morning I'm gonna wreck your mathematically illiterate ass

I'm currently an undergrad majoring in mathematics + philosophy and this past semester I completed the introductory math courses which are essentially through calc 4 and linear algebra; now I'm wondering what I should study next? I would like to possibly continue this path with graduate work, but I'd appreciate any recommendations for topics/books that I should understand for higher level math, and especially around the intersection of math and philosophy (logic, number theory, etc.). My program seems to be very oriented toward actuarial science/applied mathematics so anything that strays from that area I'd appreciate as well.

tldr What mathematics concepts should I study as a 19 year old if I want to consider an academic future?

Heading into my 3rd year in Engineering without any research or related experience, and I cant seem to land an internship. My co-op office isnt helping me at all and idk what to do. Surely my problem isnt GPA since I'm above the 3.50 they usually ask for... advice pls

If I have two solutions; 80 mL lemon juice at an assumed 2.3 pH and 1000 mL water at a pH of 7 and I mixed the two; what method/formula would I use to determine the mixed liquid pH?

Thanks if anyone could tell me; and Thanks^2 for the answer if anyone could provide the end pH.

[math] - \log \lbrack H^{+} \rbrack = 2.3 [/math]
[math] \lbrack H^{+} \rbrack = 10^{-2.3} [/math]
[math] \frac{\text{mol H+}}{V} = 10^{-2.3} [/math]
[math] \text{mol H+} = 0.08 * 10^{-2.3} [/math]
so new molarity
[math] \frac{\text{mol H+}}{1.08} = \left 0.08* 10^{-2.3} + 1*10^{-7} \right / 1.08[/math]
new pH
[math]- \log \lbrack H+ \rbrack = 3.43 [/math]

I can't quite remember chemistry, so feel free to correct me.

I've found that some companies that don't advertise have internships if you ask . Send a lot of emails to companies related to your field and you might get a response.

Not sure if this is the right place to ask, but are totality and decidability essentially the same thing from a computer science/constructive mathematics perspective?

Thanks! Ive spent this whole time trying to figure it out and I came to the same answer

Is the art of problem solving book series legit?

Why don't you read it and find out?

>defined over a lie group?

What does that even mean?

It depends on the field you're in. If you want to focus on a certain field from your honours project, then it's okay to do the phd. But masters is usually recommended for maths, some sciences, etc.

Unless you want to be pigeonholed into the university that you are going to.

It went from attractive and aesthetic looking in the first one to Bogdanoff/JUST fuck my face up tier in the third

Why does the average person find mathematics difficult? and then attempt to justify it.

I can sum it to the following topics:

1. Bad childhood teachers
2. They were lazy students
3. Calculator based, not problem solving based
4. Most teachers aren't primarily employed to teach mathematics
5. Most people get to symbolic representation and then lose it from there
6. Expectations when solving. i.e. doing trigonometry but getting stuck on algebra

I am computing the complex line integral: [eqn]\int_{|z|=7}\cos(z)dz[/eqn] using the Circumferential mean-value theorem: [eqn]f(z_0)=\frac{1}{2\pi} \int_0^{2\pi} f(z_0 + re^{i\theta})d\theta[/eqn] Since [math]|z|=7[/math] is the circle of radius 7 centered in origo, I use [math]z_0=0[/math] and simply evaluate [math]\cos0=1[/math] but according to the solutions manual it should be [math]0[/math]. Where did I go wrong?

Correction: "simply evaluate [math]\cos0 = 1[/math]" should be "simply evaluate [math]2\pi \cos0 = 2\pi"[/math]. The confusion remains.

How did you compute the integral and get 2pi cos(0)=2pi?

Any reason why you're not just using the residue theorem?

What's the best torrent for MATLAB?

>centered in origo

Just install octave if you are doing prototyping, it's unlikely you'll notice the speed difference. The code is the same and if you ever need to work the company will have Matlab.

Just get the latest version from piratebay. Do not fall for the Octave meme if you are a student.

Why not? It works fine.

I don't know anything about math. How do I solve this?

The cosine function is an entire function. The integral of it around any closed curve is 0.

Isolate x or y in one of the formulas, then replace the variable in the other formula with the other side of the equations

>i dont find it to be morally wrong because i wasnt raised to think so by my parents or my society
So you need other people to tell you what's right and wrong? You do not use your brain to think for yourself? Maybe Veeky Forums is not the board for you

u = 1/x, v = 1/y

Go look at the conditions that f needs to satisfy to apply the mean-value theorem

I applied the Circumferential mean-value theorem with [math]f=cos, z_0 = 0, r=7[/math] and multiplied both sides by [math]2\pi[/math], like so:

[eqn]\int_{|z|=7} \cos(z)dz = \int_0^{2\pi} \cos(7e^{i\theta})d\theta=2\pi \cos(z_0)[/eqn]

I'm still learning Complex Analysis and haven't gotten to the residue theorem yet :).

What about it?

The answer should be 0 so you must not be able to apply this theorem to cos(z), there's probably some hypothesis on f that cos(z) doesn't satisfy

Interesting,I'll try that thank you

Is it true that when NASA sends probes to other planets and moons, they also send gift offerings in case they come across intelligent life? I've heard this from somewhere before but I can't remember where.

Yes, they tape a ounce of weed to the back of the rovers

You are right, that's why it is zero. This post states why I can't apply the circumferential theorem to my integral. I still haven't found what conditions f needs to satisfy but I havent figured it out yet (the author actually poses the question "Question: Why is the integral theorem not always zero by the Cauchy Integral Theorem? (Look closely!)" but I can't figure it out.. But ill probably manage in time. Thanks for the help!