/sci/ - Science & Math

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/sqt/ - Stupid Question Thread: Coffee Edition Mr. Christie Tue Jun 27 07:20:11 2017 No.8999352 [Reply] [Original]

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: http://www.catb.org/~esr/faqs/smart-questions.html

Previous thread: >>8986316

>>	Anonymous Tue Jun 27 07:27:36 2017 No.8999360 Why do you still eat dead animal flesh.

>>	Anonymous Tue Jun 27 07:28:43 2017 No.8999361 >>8999360 it's tasty

>>	Anonymous Tue Jun 27 07:36:47 2017 No.8999373 Bachelors -> Masters -> PhD Or Bachelors -> PhD With the first option I could apply to a european school (dream school), but would it cost much more money? Are TA and RA positions and fellowships easy enough to get to cover all costs for masters?

>>	Anonymous Tue Jun 27 08:42:07 2017 No.8999458 Is Kahn Academy's advanced physics section good for understanding topics like relativity and quantum mechanics?

>>	Anonymous Tue Jun 27 08:51:42 2017 No.8999464 >>8999458 Anything in Khan Academy is a very basic introduction for beginners. It's a good introduction. But far away from a deep study on the subject.

Anonymous Tue Jun 27 09:02:34 2017 No.8999479

>>8999373
I'm also curious.
Here in Australia you don't have to do the Masters to go into the PhD, you just need to do an honours year which is just a year of research.
Is it worth doing the extra 2 years in the Masters, which might be a bit harder to support myself as a then 22 year old?

>>	None !AtRUMPi5R2 Tue Jun 27 09:03:30 2017 No.8999480 >>8999373 do your studies in europe

>>	Anonymous Tue Jun 27 09:35:57 2017 No.8999502 I don't know if i'm phrasing this correctly, but are quantum systems technically defined over a lie group? This leads to me asking: Is a system utilizing lagrangian mechanics technically defined over a lie group as well?

>>	Anonymous Tue Jun 27 10:38:53 2017 No.8999587 >>8999480 I am a US student, would a masters in the US be fine for europe phd, or should i try to do the masters at the school i want to pursue a phd?

>>	Anonymous Tue Jun 27 10:53:22 2017 No.8999613 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

>>	Anonymous Tue Jun 27 11:01:55 2017 No.8999620 >>8999587 Universidad de Sevilla best university

>>	Anonymous Tue Jun 27 11:01:55 2017 No.8999621 >>8999613 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.

>>	Anonymous Tue Jun 27 12:09:15 2017 No.8999688 >>8999352 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?

>>	Anonymous Tue Jun 27 12:21:53 2017 No.8999713 What area of math should I study if I want to get into the procedural generation of text (ie the library of Babel)?

>>	Anonymous Tue Jun 27 13:03:28 2017 No.8999788 >>8999360 social norms i dont find it to be morally wrong because i wasnt raised to think so by my parents or my society

Anonymous Tue Jun 27 14:09:34 2017 No.8999906
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>>8999352

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.

Anonymous Tue Jun 27 15:56:53 2017 No.9000088
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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

>>	Anonymous Tue Jun 27 16:23:32 2017 No.9000154 File: 54 KB, 628x314, n-CHINA-CHILDREN-628x314.jpg [View same] [iqdb] [saucenao] [google] >>8999352 Isn't it inbreeding when 2 people from the same race breed because they are from the same race?

>>	Anonymous Tue Jun 27 16:27:00 2017 No.9000163 >>9000154 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

>>	Anonymous Tue Jun 27 17:07:33 2017 No.9000227 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?

Anonymous Tue Jun 27 18:16:00 2017 No.9000402

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.

Anonymous Tue Jun 27 18:30:44 2017 No.9000431
File: 241 KB, 1729x1000, orbit_graphs_tmp.png [View same] [iqdb] [saucenao] [google]

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?

>>	Anonymous Tue Jun 27 19:05:54 2017 No.9000471 >>9000402 >Prove T is Lipschitz continuous Under what metric?

>>	Anonymous Tue Jun 27 19:10:31 2017 No.9000479 >>9000431 f(t)=(acost,bsint) where a is how much you stretch in the horizontal direction, and b is for the vertical direction

Anonymous Tue Jun 27 19:10:36 2017 No.9000480
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>>9000088
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.

Anonymous Tue Jun 27 19:12:55 2017 No.9000483
File: 34 KB, 660x495, aHR0cDovL3d3dy5saXZlc2NpZW5jZS5jb20vaW1hZ2VzL2kvMDAwLzA3Ni8wMzcvb3JpZ2luYWwvd2hhbGUtZXZvbHV0aW9uLmpwZw==.jpg [View same] [iqdb] [saucenao] [google]

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

>>	Anonymous Tue Jun 27 19:16:25 2017 No.9000489 >>8999620 literally who? I am applying to a swiss and german universities

>>	Anonymous Tue Jun 27 19:19:26 2017 No.9000492 >>9000471 Assume max norm always

>>	Anonymous Tue Jun 27 19:20:52 2017 No.9000494 >>9000483 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.

>>	Anonymous Tue Jun 27 19:28:49 2017 No.9000510 >>9000479 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.

>>	Anonymous Tue Jun 27 19:29:53 2017 No.9000513 >>9000483 They luck into the upgrades, and those that don't die faster than those that do. Lucky upgrades get passed down to future generations.

>>	Anonymous Tue Jun 27 19:35:21 2017 No.9000519 >>9000402 shouldn't the arrow be [math]\mapsto[/math]

>>	Anonymous Tue Jun 27 19:40:11 2017 No.9000530 >>9000519 Yes but I dont know the LaTeX code for that symbol by heart.

>>	Anonymous Tue Jun 27 19:49:01 2017 No.9000545 >>9000530 \mapsto pretty intuitive

Anonymous Tue Jun 27 19:49:48 2017 No.9000546

>>9000510
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...

>>	Anonymous Tue Jun 27 19:51:14 2017 No.9000549 >>9000545 Okay, but that still doesn't help me solve this problem :/

Anonymous Tue Jun 27 20:11:26 2017 No.9000593

>>9000483
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

Anonymous Tue Jun 27 20:33:01 2017 No.9000623

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?

Anonymous Tue Jun 27 21:00:13 2017 No.9000663

>>9000431
[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.

Anonymous Tue Jun 27 21:08:01 2017 No.9000670

>>9000663
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.

Anonymous Tue Jun 27 21:17:23 2017 No.9000695

>>9000670
>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.

>>	Anonymous Tue Jun 27 21:26:01 2017 No.9000710 >>9000695 Well, yeah, the shape of the ellipse (including its radius/semi-major) is constant, so that'd make this doable right?

Anonymous Tue Jun 27 21:37:43 2017 No.9000729

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.

Anonymous Tue Jun 27 21:39:59 2017 No.9000738
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>>9000710
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.

>>	Anonymous Tue Jun 27 21:50:31 2017 No.9000760 EPFL or UIUC for MS if end goal is PhD at ETH Zurich?

>>	Anonymous Tue Jun 27 21:57:48 2017 No.9000776 >>9000729 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

Anonymous Tue Jun 27 22:03:01 2017 No.9000787
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>>9000738
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?

Anonymous Tue Jun 27 22:06:03 2017 No.9000796

>>8999352
Hey /sci/. 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.

>>	Anonymous Tue Jun 27 22:30:33 2017 No.9000843 File: 9 KB, 427x296, parallelprojection1.jpg [View same] [iqdb] [saucenao] [google] >>8999352 Linear algebra: Is the length of the vector projection of vector $v$ with vector $u$ supposed to be $\sqrt{x \dot u}$?

>>	Anonymous Tue Jun 27 22:31:40 2017 No.9000846 If you live around people of < 80 IQ, how do you develop verbal IQ?

>>	Anonymous Tue Jun 27 22:32:39 2017 No.9000848 >>9000843 >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]?

>>	Anonymous Tue Jun 27 22:44:03 2017 No.9000864 >>9000848 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

>>	Anonymous Tue Jun 27 22:45:09 2017 No.9000868 >>9000864 you're in the wrong thread nigger

>>	Anonymous Tue Jun 27 22:50:02 2017 No.9000879 >>9000868 >>9000864 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?

>>	Anonymous Tue Jun 27 22:50:47 2017 No.9000880 Is the following true? [math]\displaystyle z \in \mathbb{C}, \lim_{\|z\| \to \infty} \left\|\frac{z^2}{z^2 + 1}\right\| = 1 [/math] ?

>>	Anonymous Tue Jun 27 22:53:49 2017 No.9000886 >>9000760 Someone answer this before I attack

Anonymous Tue Jun 27 23:07:10 2017 No.9000896

>>9000879
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.

>>	Anonymous Tue Jun 27 23:08:12 2017 No.9000897 >>9000896 Crap formatting, I haven't used LaTeX in a while.

>>	Anonymous Tue Jun 27 23:13:57 2017 No.9000901 >>9000880 No

>>	Anonymous Tue Jun 27 23:17:07 2017 No.9000906 >>9000880 Iirc my limit theorems correctly, yes. [inline]\frac{1}{1+\frac{1}{z^2}}[/inline]

>>	Anonymous Tue Jun 27 23:18:19 2017 No.9000909 >>9000906 [eqn]\frac{1}{1+\frac{1}{z^2}}[/eqn]

>>	Anonymous Tue Jun 27 23:19:52 2017 No.9000911 File: 909 B, 96x85, ss-000211.png [View same] [iqdb] [saucenao] [google] >>9000906 >>9000909

>>	Anonymous Tue Jun 27 23:20:29 2017 No.9000914 >>9000897 click [math]T_{E}X[/math]

>>	Anonymous Tue Jun 27 23:24:43 2017 No.9000920 File: 23 KB, 640x559, pillow laughter.jpg [View same] [iqdb] [saucenao] [google] >>9000914 >holy shit

Anonymous Tue Jun 27 23:28:30 2017 No.9000924

>>9000896
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.

>>	Anonymous Tue Jun 27 23:28:31 2017 No.9000925 Why is >I want to be an engineer because I like to build things is a meme?

>>	Anonymous Wed Jun 28 01:05:18 2017 No.9001012 >>9000897 >>9000896 >You can't help I'm gonna help you so hard you fucking nigger, tomorrow morning I'm gonna wreck your mathematically illiterate ass

Anonymous Wed Jun 28 01:22:31 2017 No.9001023

>>8999352
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?

Anonymous Wed Jun 28 01:49:09 2017 No.9001059
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>>8999352
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

Anonymous Wed Jun 28 01:58:28 2017 No.9001065

>>8999352

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.

Anonymous Wed Jun 28 02:15:24 2017 No.9001086

>>9001065
[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.

>>	Anonymous Wed Jun 28 03:44:03 2017 No.9001160 >>9001059 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.

>>	Anonymous Wed Jun 28 05:44:45 2017 No.9001249 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?

>>	Anonymous Wed Jun 28 05:47:45 2017 No.9001252 >>9001086 Thanks! Ive spent this whole time trying to figure it out and I came to the same answer

>>	Anonymous Wed Jun 28 06:33:34 2017 No.9001292 Is the art of problem solving book series legit?

>>	Anonymous Wed Jun 28 06:39:18 2017 No.9001296 File: 113 KB, 866x1300, 14195241-Portrait-of-a-young-man-skeptical-Stock-Photo.jpg [View same] [iqdb] [saucenao] [google] >>9001292 Why don't you read it and find out?

>>	Anonymous Wed Jun 28 06:46:06 2017 No.9001306 >>8999502 >defined over a lie group? What does that even mean?

Anonymous Wed Jun 28 08:17:52 2017 No.9001380

>>8999479

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.

>>	Anonymous Wed Jun 28 08:24:01 2017 No.9001387 >>9000483 It went from attractive and aesthetic looking in the first one to Bogdanoff/JUST fuck my face up tier in the third

Anonymous Wed Jun 28 08:25:48 2017 No.9001389

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

Anonymous Wed Jun 28 08:28:47 2017 No.9001395
File: 28 KB, 280x297, Principle_branch_of_arg_on_Riemann_(small).png [View same] [iqdb] [saucenao] [google]

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?

>>	Anonymous Wed Jun 28 08:31:35 2017 No.9001397 >>9001395 Correction: "simply evaluate [math]\cos0 = 1[/math]" should be "simply evaluate [math]2\pi \cos0 = 2\pi"[/math]. The confusion remains.

>>	Anonymous Wed Jun 28 08:39:22 2017 No.9001403 >>9001395 How did you compute the integral and get 2pi cos(0)=2pi? Any reason why you're not just using the residue theorem?

>>	Anonymous Wed Jun 28 08:45:50 2017 No.9001409 What's the best torrent for MATLAB?

>>	Anonymous Wed Jun 28 08:49:53 2017 No.9001410 >>9001395 >centered in origo

>>	Anonymous Wed Jun 28 08:52:45 2017 No.9001413 >>9001409 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.

>>	Anonymous Wed Jun 28 08:56:16 2017 No.9001416 >>9001409 Just get the latest version from piratebay. Do not fall for the Octave meme if you are a student.

>>	Anonymous Wed Jun 28 08:57:26 2017 No.9001418 >>9001416 Why not? It works fine.

>>	Anonymous Wed Jun 28 08:59:26 2017 No.9001420 File: 398 KB, 1453x1312, IMG_20170628_155733.jpg [View same] [iqdb] [saucenao] [google] I don't know anything about math. How do I solve this?

>>	Anonymous Wed Jun 28 09:01:38 2017 No.9001423 >>9001395 The cosine function is an entire function. The integral of it around any closed curve is 0.

>>	Anonymous Wed Jun 28 09:03:59 2017 No.9001424 >>9001420 Isolate x or y in one of the formulas, then replace the variable in the other formula with the other side of the equations

Anonymous Wed Jun 28 09:05:21 2017 No.9001425

>>8999788
>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 /sci/ is not the board for you

>>	Anonymous Wed Jun 28 09:05:35 2017 No.9001426 >>9001420 u = 1/x, v = 1/y

>>	Anonymous Wed Jun 28 09:06:40 2017 No.9001428 >>9001395 Go look at the conditions that f needs to satisfy to apply the mean-value theorem

Anonymous Wed Jun 28 09:06:47 2017 No.9001429

>>9001403
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 :).

>>9001410
What about it?

>>	Anonymous Wed Jun 28 09:16:56 2017 No.9001439 >>9001429 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

>>	Anonymous Wed Jun 28 09:18:04 2017 No.9001442 >>9001160 Interesting,I'll try that thank you

>>	Anonymous Wed Jun 28 09:19:35 2017 No.9001444 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.

Anonymous Wed Jun 28 09:20:05 2017 No.9001445 [DELETED]

>>9001423
You are right, that's why it is zero. This post >9001428 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!

>>	Anonymous Wed Jun 28 09:20:47 2017 No.9001446 >>9001444 Yes, they tape a ounce of weed to the back of the rovers

Anonymous Wed Jun 28 09:21:08 2017 No.9001448

>>9001423
You are right, that's why it is zero. This post >>9001428 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!

Anonymous Wed Jun 28 09:34:19 2017 No.9001459

I need help with analysis. Suppose that I have a curve, but this curve is not described by a function.

Now suppose I have a sequence of curves that at the limit converges to the curve previously mentioned.

How do I prove that indeed my sequence of curves converges to the curve? I am looking at the definition of uniform convergence but there it talks about functions and I don't have functions, I have curves that can't be represented as functions.

>>	Anonymous Wed Jun 28 09:35:21 2017 No.9001462 >>9001380 Thanks, and I'm in chemistry. The goal university is the best here in Aus, so being stuck there for a while wouldn't be the worst thing.

Anonymous Wed Jun 28 10:03:03 2017 No.9001480
File: 181 KB, 600x350, mold_20green.jpg [View same] [iqdb] [saucenao] [google]

Mold/fungus is warm to the touch because it has an active metabolism.

Why are trees and plants not warm to the touch, then? Is their metabolism less active? Or is it like aluminum foil, where the heat passes quickly?

Anonymous Wed Jun 28 11:29:30 2017 No.9001581

>>9001389
Mathematics is very prerequisites-heavy. Things build upon another a lot. If you don't understand one thing, you will have a lot of trouble understanding the next thing, and the next, etc. But the school system demands that they do move on (for a number of reasons).

>3. Calculator based, not problem solving based
>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
These are just the symptoms. Once you're too far behind, you will lack the space necessary to really understand things. You will start employing short-term strategies to pass the next test. By then, mathematics has become so associated with stress, you will avoid it, until you're forced to again. Almost all people are in this situation.

It's a kind of debt. (Similar to when a poor person can only afford shoes that last 1 year, spending more money in a 10 year period than the cost of shoes that last 10 years.)

>>	Anonymous Wed Jun 28 11:30:23 2017 No.9001583 >>9001448 Wait. what makes you think the integral of cos(z) around that circle is cos(z0)? It is the integral of cos(ζ)/(ζ-z0) dζ that is equal to 2πi cos(ζ0). (That integral is the one you wrote at the bottom).

>>	Anonymous Wed Jun 28 11:31:59 2017 No.9001588 >>9001459 You're wrong. Look up the definition of function and the definition of curve.

>>	Anonymous Wed Jun 28 11:33:59 2017 No.9001589 >>9001459 Curves ARE functions from a closed interval of R to R^n.

Anonymous Wed Jun 28 11:46:24 2017 No.9001601 [DELETED]

>>9001583
>Wait. what makes you think the integral of cos(z) around that circle is cos(z0)?
The circumferential mean-value theorem (but I understand now that I can not apply this theorem to cos(z), still dont know _why_ I can't apply it though).

>It is the integral of cos(ζ)/(ζ-z0) dζ that is equal to 2πi cos(ζ0). (That integral is the one you wrote at the bottom).
I'm not sure what you mean by this. I never talked about any integral [math]\int_0^{2\pi} \frac{\cos(\zeta)}{\zeta-z_0}d\zeta = 2\pi i \cos(z_0)[math] (via the cauchy integral formula).

Anonymous Wed Jun 28 11:47:39 2017 No.9001603

>Wait. what makes you think the integral of cos(z) around that circle is cos(z0)?
The circumferential mean-value theorem (but I understand now that I can not apply this theorem to cos(z), still dont know _why_ I can't apply it though).

>It is the integral of cos(ζ)/(ζ-z0) dζ that is equal to 2πi cos(ζ0). (That integral is the one you wrote at the bottom).
I'm not sure what you mean by this. I never talked about any integral [math]\int_0^{2\pi} \frac{\cos(\zeta)}{\zeta-z_0}d\zeta = 2\pi i \cos(z_0)[/math] (via the cauchy integral formula).

Anonymous Wed Jun 28 11:47:55 2017 No.9001605

>>9000483
The luck other anons told you about is further helped with the perception of success: animals mate with those mates, which seem the most succesful for some reason. This is why we want to fuck rich, popular and happy people.
It's because the most succesful are by definition the ones bearing the best genes.
This process works better with better perception and higher computational power of the brain of the animal.

Anonymous Wed Jun 28 11:48:58 2017 No.9001607

>>9001389
>reason 4.
there are primary school teachers in north america that barely know simple algebra or how to add fractions. i would chalk up a lot of it to that. also, there is a whole culture of "when am i going to need this?" when it comes to math. hell, even kids' parents reinforce it a lot of the time with the attitudes of "i never took precalculus and i turned out just fine".

in public education, other subjects are easier to justify to the students as to why they should study them. beyond simple arithmetic and accounting-style math, many people see no practicality in studying it. when the fuck am i gonna need to know how to sketch a parabola amirite? xD

if you wanna feel really depressed, go on twitter and search #ihatemath

>>	Anonymous Wed Jun 28 11:49:03 2017 No.9001608 >>9001603 Correction: I obviously integrate over some closed curve with z_0 an interior point of the curve, not from 0 to 2pi.

>>	Anonymous Wed Jun 28 11:50:17 2017 No.9001612 >>9000163 Makes sense. Thank you. Also I feel relieved that no one shitstormed on me for asking such a dumb question but that was a genuine question from me.

Anonymous Wed Jun 28 11:50:24 2017 No.9001613

>>9001603
>The circumferential mean-value theorem
You have to look up again what that theorem says.

>I'm not sure what you mean by this. I never talked about any integral ......
Yes, you did.
I told you. That integral is the formula you wrote for f(z0)., just with a different notation.

>>	Anonymous Wed Jun 28 11:50:33 2017 No.9001614 >>9000846 >verbal IQ what's that?

>>	Anonymous Wed Jun 28 11:54:53 2017 No.9001619 >>9001614 Speaking like an intelligent person

>>	Anonymous Wed Jun 28 11:55:10 2017 No.9001621 >>9001613 Like z=z0+exp(iRθ) dz=iR exp(iRθ) dθ = iR (z-z0) dθ therefore dθ = bla bla bla

Anonymous Wed Jun 28 11:55:25 2017 No.9001623

>>9001389
math is by far the most unnatural of all subjects. Your mind operates on heuristicss and other kinds of dirty computation, whilst math is 'pure' and requires computer-like thinking. Thus you have to develop ways of thinking unnatural for you, which is very hard.
Biology on the other hand is very intuitive

>>	Anonymous Wed Jun 28 11:58:22 2017 No.9001626 >>9001607 People think math is useless to feel better about their failure. It's only a dominant sentiment because SO MANY people are failing at math. I don't think it's there in the former Soviet Union, for example.

>>	Anonymous Wed Jun 28 12:02:36 2017 No.9001632 >>9001621 god dammit I messed up with the R

Anonymous Wed Jun 28 12:04:50 2017 No.9001635

>>9001626
>to feel better about their failure
i'm skeptical about that, because even a poor student in other subjects can surely see the value of say, being able to write. maybe it could be true in the context of "oh, everyone is failing this class, so it's fine if i do poorly too".

>>	Anonymous Wed Jun 28 12:09:36 2017 No.9001642 >>9001446 I can't find any sources. Is this true, anon?

Anonymous Wed Jun 28 12:10:37 2017 No.9001643

>>9001635
Yes that's what I mean. The sentiment is accepted by other people because they fail too.

(And the people who don't fail are mostly nerds; people actually prefer to disassociate themselves from them. It's like when climate change became a leftist issue, the Right became actually proud of their ignorance.)

>>	Anonymous Wed Jun 28 12:24:20 2017 No.9001663 >>9001589 My babby analysis book only defines convergence for functions from R to R Do you have source for a generalized definition?

>>	Anonymous Wed Jun 28 12:40:14 2017 No.9001683 >>9001632 Yeah I understand what you mean by "different notation" now. But my confusion remains. The issue must be with the first equality in >>9001429 since the last equality holds ([math]\int_0^{2\pi}cos(e^{i\theta})d\theta=2\pi[/math]).

>>	Anonymous Wed Jun 28 13:10:08 2017 No.9001713 >>8999688 bump

>>	Anonymous Wed Jun 28 13:27:10 2017 No.9001738 >>9001663 Yes, https://proofwiki.org/wiki/Definition:Uniform_Convergence/Metric_Space The metric in our case is the usual euclidean distance between points in R^n.

Anonymous Wed Jun 28 13:32:41 2017 No.9001746

>>9001683
You forgot to put the derivative inside the integral. It should be cos(7exp(iθ)) * ( 7exp(iθ) )'

In general, if you have a function f and you want to integrate it along a curve γ:[a,b]-->C , you do this:

Integral from a to b of f(γ(t)) γ'(t) dt

Anonymous Wed Jun 28 13:34:06 2017 No.9001750
File: 7 KB, 569x65, photo.jpg [View same] [iqdb] [saucenao] [google]

Reposting from math thread:
Need some help. Was checking out previous years' admission tests for a university I'm planning on applying to, and in the math section, pic related came up.
I'm supposed to find out the missing digit, a, and that I can do (some more information regarding the relation between A, B, and C is provided), but I don't understand what do the line over the top and the smaller digit at the bottom right mean. Not asking for a solution to the problem, just asking what do the symbols mean so I can get to study that.

Anonymous Wed Jun 28 13:35:22 2017 No.9001753

>>9001738
I see, but no. The problem I have is that you see that in the definition it compares the distance between f(x) and [math] f_n (x) [/math]. In other words, it checks the same x.

In my curves, the parametrization I am using for the sequence of curves is not the same parametrization I am using for the limit curve. And I have given it some thought and I do not take I can parametrize both in the same way.

Is there a way to just check that the set of points of the sequence of curves converges to the set of points of the limit curve? Regardless of parametrization?

Because you see, I care specifically about the shape of the curves and not really about how I parametrize them. I am ultimately using my curves for line integrals.

Anonymous Wed Jun 28 13:40:08 2017 No.9001762

>>9001663
Curve is a map [math]I \to \mathbb{R}^n[/math] where I is some interval, closed or open depends on the context. This is both the definition and the intuitive approach, because a curve represents a motion occuring in time. Convergence of a sequence of curves in this case is defined in the exact same way as in the case of real-valued functions, except the part with [math]|f(x)-f_n(x)|[/math] is replaced by a different metric, in our case the euclidean metric.

Anonymous Wed Jun 28 13:46:04 2017 No.9001773

>>9001762
>[math]|f(x)-f_n(x)|[/math]

This is exactly my problem. For a given x, [math]f_n (x) [/math] does not necessarily approach [math] f(x) [/math] because the parametrization for the sequence functions is different from the parametrization of the limit function (for practical and I think necessary reasons).

I do not want to show that for each x, the sequence functions approach the limit function. i want to show that the shape of the sequence functions approaches the shape of the limit function.

How do I prove that? Just that.

Anonymous Wed Jun 28 13:53:10 2017 No.9001786

>>9001773
Well the definition (which I am making up right now) is easy. Let [math]A_n[/math] be a sequence of sets. [math]A[/math] is the limit if for any open [math]U \supseteq A[/math] there is [math]n_0 \in \mathbb{N}[/math] such that [math]n \geq n_0[/math] implies [math]A_n \subseteq U[/math]. But good luck using that.

Anonymous Wed Jun 28 13:58:46 2017 No.9001794

>>9001773
By the way this really isn't the right way to think about curves. Even when computing line integrals, the result depends on the parametrization in some sense. I don't know what you're trying to prove, but if it's something like "if the curves converge, then the integrals converge", you will need parametrized curves still I'm afraid.

Anonymous Wed Jun 28 13:59:33 2017 No.9001796

>>9001786
Your definition sounds good and I think I could prove it using that, but if I don't use a well known and well established definition then I doubt doing a proof would help me.

That said, that definition does make a lot of sense. Are you sure there is no similar thing in topology textbooks? Perhaps with an already established theory so that I can use theorems and properties to aid my proof. (Even though I think I could do it directly, but I still want to use an accepted definition).

Anonymous Wed Jun 28 14:02:04 2017 No.9001804

>>9001794
>the result depends on the parametrization in some sense.

No, only the procedure depends on the parametrization. There is a theorem that says that line integrals are independent of parametrization and I am kinda exploiting that theorem in what I am trying to do. And if I want to have any chance of success then I need to keep exploiting that property, because as I said before, there is no way to give the same parametrization to the limit curve and the sequence curves.

>>	Anonymous Wed Jun 28 14:06:14 2017 No.9001812 >>9001804 So what are you trying to prove ?

Anonymous Wed Jun 28 14:07:59 2017 No.9001816

>>9001812
Right now, I am just trying to prove that the limit of my sequence of curves converges to the limit curve I already have.

But after I have that then I will do some manipulations with integrals, but that is completely independent from the first step. I just need to show that my sequence of sets converges to my limit set. I need a generalized "uniform convergence" definition that is also independent of parametrization.

>>	Anonymous Wed Jun 28 14:10:32 2017 No.9001818 >>9001425 All humans rely on other people to tell them what is right and wrong. Morality is a social construct, not an objective fact of reality.

Anonymous Wed Jun 28 14:10:52 2017 No.9001819

>>9001796
You can define the distance between a point x and a set B as d(x,B) := inf d(x,y) where y ranges over B.
I think you can then define the distance between sets two sets A, B as d(A,B) := sup d(x, B) where x ranges over A.

And use that to define convergence of sets (curves in this case).

Anonymous Wed Jun 28 14:19:00 2017 No.9001831

>>9001819
this isn't symmetric. consider [math]A_n[/math] such that for each [math]n[/math] we have some [math]x_n \in A_n[/math] such that [math]x_n \rightarrow x [/math]. then in this "metric" [math]A_n \rightarrow \{ x \}[/math] if we insist that we write [math]d(\{x\},A_n)[/math] instead of the other way around. this is not what he wants.

Anonymous Wed Jun 28 14:20:54 2017 No.9001833

Roughly how much math is required for a masters in computer science?

And building on that, how much math should I take during undergrad to increase my chances of acceptance of admission to top programs?

I am good at statistics and algebra (will be getting an A in linear algebra, taking a grad level stats class in the fall) but I really dislike calculus. I received a B in Vector (Multivariable) Calc and I am wondering how much farther I have to go.

>>	Anonymous Wed Jun 28 14:26:50 2017 No.9001839 >>9001831 Any chance to make it work? max{sup d(x,B) , sup d(A,y)} (No need to reply, I know it's probably a lost cause.)

Anonymous Wed Jun 28 14:53:39 2017 No.9001884

>>9001750
Bumping.
In case the picture's too blurry
A=1a1 (with a line over the top of the three digits and a 4 at the bottom right)
B=1101 (with an 'a' at the bottom right)
C=1a24a (with a line over the top of the five digits and a 5 at the bottom right).

>>	Anonymous Wed Jun 28 14:54:18 2017 No.9001885 >>9001753 Wanna tell us the curves we are talking about?

>>	Anonymous Wed Jun 28 15:02:46 2017 No.9001901 >>9001425 >implying morality is some set of objective facts that is accessible by thinking real hard you are the one who is not using their brain, friendo

Anonymous Wed Jun 28 15:07:47 2017 No.9001908

>>9001885
I may be being petty but no, my curves are secret. I am researching something and even though this undergrad research may not even get to arxiv, I want to keep it to myself just in case. The only person I have given the curves has been my analysis professor. I basically did all I wanted to do but without proving anything and just showed him that it works but then he told me to prove that my curves converge uniformly, and I haven't been able to.

>>	Anonymous Wed Jun 28 15:20:28 2017 No.9001936 >>9001908 np man, hope you find something good! good luck!

>>	Anonymous Wed Jun 28 15:31:34 2017 No.9001954 >>9000494 Fpbp

Anonymous Wed Jun 28 15:45:17 2017 No.9001975

>>8999352

> Show that if p mod 4 = 3, there is no integer n such that p divides n^2+1.
> hint: use Fermat's little theorem

> if [math]n^2 \equiv -1\ (mod\ p)[/math]
> then [math](n^{2})^{\frac{p-1}{2}} \equiv -1\ (mod\ p)[/math]
> but according to fermat's little theorem it should be congruent to +1

what the fuck... where did they get the (p-1)/2

>>	Anonymous Wed Jun 28 15:48:39 2017 No.9001982 File: 77 KB, 500x665, 1480875992321.jpg [View same] [iqdb] [saucenao] [google] >>9001975 heres some jap bitch so I get replies

>>	Anonymous Wed Jun 28 15:52:00 2017 No.9001990 How do I decide which Linear Algebra book to use? I've never studied it and hear names like Strang, Lang, Spence, Axler, Friedberg thrown around often. Is there a super meme book like Spivak's Calculus but for LA?

>>	Anonymous Wed Jun 28 15:55:00 2017 No.9001997 >>9001990 Strang's book is shit, just watch his lectures and supplement with literally anything

>>	Anonymous Wed Jun 28 16:09:09 2017 No.9002019 How to show that the pre-image of an affine subspace on a linear transformation is either empty or itself an affine subspace All I know is that affine subspace is the set sum of a subspace and some vector b.

>>	Anonymous Wed Jun 28 16:13:20 2017 No.9002027 >>9001990 >Strang Engineering tier mathematics. Don't read that shit if you are serious. Axler is good, but not sure if for an indtroductory one. Haven't read the rest.

>>	Anonymous Wed Jun 28 16:24:03 2017 No.9002049 >>9002019 Let [math]u,v \in f^{-1}(A)[/math]. Then [math]f( \lambda u + (1-\lambda)v) = \lambda f(u) + (1-\lambda)f(v) \in A[/math], because A is affine subspace. So [math]\lambda u + (1-\lambda)v \in f^{-1}(A)[/math].

>>	Anonymous Wed Jun 28 16:36:19 2017 No.9002080 >>9002049 Thats the same answer on stack exchange but I dont know how to show affine subspaces are closed under affine combinations from the definition I posted. In fact thats an exercise after this one so I would think there is another way

Anonymous Wed Jun 28 16:42:44 2017 No.9002088
File: 15 KB, 260x328, 41D23ONX3fL._SX258_BO1,204,203,200_.jpg [View same] [iqdb] [saucenao] [google]

>>9001990 >>9002027
Strang is for Brainlets.

Axler is a good introductory book (for math Majors)
Lax Linear algebra is a good intermediate book.
Hoffman is a good advanced book for Grad School

Anonymous Wed Jun 28 16:54:45 2017 No.9002106

>>9002080
Let's see that those definitions are equivalent.

Suppose we have [math]A = b + V[/math], where [math]V[/math] is a vector subspace. Take [math]b+u,b+v \in A [/math]. Compute
[eqn]\lambda(b+u) + (1-\lambda)(b+v) = b + \lambda u + (1-\lambda)v [/eqn]and conclude that this lies in [math]A[/math] because it's in the form [math]b + [/math]something in [math]V[/math].

On the other hand, suppose [math]A[/math] is a set closed under affine combinations. Let [math]b \in A[/math]. Then I claim that [math]A-b[/math] is a vector space. I leave this to you, it's similar to the previous argument. Then [math]A = b + (A-b)[/math].

>>	Anonymous Wed Jun 28 16:57:18 2017 No.9002112 I have a couple of bodies with a mass and I want to simulate how they pull each other with gravity. the resulting force for a body is simply the sum between the body and all other bodies, right?

Anonymous Wed Jun 28 16:58:01 2017 No.9002113

>>9001990
The ones I've read are Axler and Hoffman and Kunze. Both are good.

Axler is easier, and better if you haven't seen many proofs yet. The book intentionally ignores the determinant, which is good for a first approach because it's hard to intuitively understand the determinant, but bad because the determinant is in itself important, and it is helpful when approaching some topics. All in all, I think it's good as a first course in linear algebra.

Hoffman and Kunze is harder, but a lot more in depth. It's not afraid to take a more general and algebraic approach to topics, which often ends up being the best way to do things in linear algebra. This would be a good book for someone who has more experience with proofs (at the level of having completed a course in real analysis or abstract algebra), or as a second look at elementary linear algebra.

Anonymous Wed Jun 28 17:10:31 2017 No.9002135

>>9001997
Ok, thanks.

>>9002027
>>9002088
I'm adverse to Axler because he avoids determinants.
>>9002113
From your description I'm much more inclined to go with Hoffman and Kunze. I have some experience with proofs from Discrete Math and "How to Proof It".

>>	Anonymous Wed Jun 28 17:15:47 2017 No.9002145 >>9001975 They just take the first equation, and raise both sides to the (p-1)/2 power. The point is that (p-1)/2 is odd, so the right-hand side remains -1.

Anonymous Wed Jun 28 17:21:11 2017 No.9002162

>>9002106
Thanks for responding again. Since then I have written something for the other problem which seems similar to what you have written here. I would like to get it checked.
We say B is the affine space in the codomain whose inverse image we are interested in.
We note that if A is an affine space iff there is some vector in v such that A + v is a subspace. We take a_1, a_2, a_3 to be three arbitrary, not necessarily distinct, vectors in the supposedly nonempty preimage of the affine space in question. We consider -a_1 to be the v. We take a linear combination of a_2 - a_1 and a_3 - a_1 under the linear transformation T. We note that because B is an affine space, since T(a_1) is a member of B then the set B - T(a_1) should be a subspace. Therefore x_1*T(a_2 - a_1) + x_2*T(a_3 - a_1) should be in that subspace since B is affine. We have shown then that if A is defined as the inverse image of B under T, then the set A - a_1 is closed under linear combinations, since it maps to the subspace B - T(a_1). Therefore A is affine.

>>	Anonymous Wed Jun 28 17:23:54 2017 No.9002167 >>9002145 What says that (p-1)/2 is odd? what if p was a prime of the form 2^n + 1?

>>	Anonymous Wed Jun 28 17:25:39 2017 No.9002172 >>9002167 >p mod 4 = so p=4k+3 p-1=4k+2 (p-1)/2=2k+1 which is odd

Anonymous Wed Jun 28 17:47:14 2017 No.9002211

>>9002135
>I'm adverse to Axler because he avoids determinants.
I don't like the fact that he completely ignores them. But I guess that's essentially the point of the books. For an introductory book though I think you have to show proofs both with and without determinants. That's why I am not sure if it is good for an introductory one.

Anonymous Wed Jun 28 17:50:16 2017 No.9002220

>>9002135
I think trying H&K to begin with is probably a reasonable idea. If it doesn't gel well with you or you find it too difficult, you can just do Axler instead.

In case you don't already know, you can find both books (along with many others) on libgen. Good luck!

>>	Anonymous Wed Jun 28 18:29:02 2017 No.9002308 >>9000729 bump

Anonymous Wed Jun 28 19:27:59 2017 No.9002412

>>9001818
This is nonsense. If all people rely on others to tell them what is right and wrong, then no one would have any idea of what right and wrong are because no one would have told them. There has to have been at least one person to construct moral laws for the rest to follow. And if that person is capable of constructing moral laws, what restrains anyone else from doing so?
>>9001901
>implying he implied that
There is no implication there about objective morality, only that people can develop their own sense of morality. Should morality be subjective, then nothing stops a person from creating their own. Should morality be objective, then nothing stops a person from discovering it. I would personally argue for the former, but that's irrelevant.

>>	Anonymous Wed Jun 28 19:29:47 2017 No.9002417 File: 21 KB, 330x500, 4491e6c8e9d5586831882cc32a8db301-d.jpg [View same] [iqdb] [saucenao] [google] >>9002211 >>9002220 How do you two feel about pic related?

Anonymous Wed Jun 28 19:40:42 2017 No.9002432

>>9002417
Haven't read it. From skimming it and looking at the table of contents, it seems to hit all the standard topics, which is good. It seems to take a reasonably long digression into group theory, which is honestly more appropriate for an abstract algebra book. H&K tends to define the algebraic structure behind the object of study in linear algebra, but doesn't go into the theory of that structure beyond what is relevant to the immediate material. Here it seems like the author goes further than what is needed for understanding linear algebra.

Really though, you should probably just get PDFs of all these books, read a bit, and figure out what suites your needs best. Spend more time trying to learn math than figure out what book to pick.

Anonymous Wed Jun 28 19:46:41 2017 No.9002439

>>9002432
>just get PDFs of all these books, read a bit, and figure out what suites your needs best. Spend more time trying to learn math than figure out what book to pick.

I agree with this, thanks for your thoughts on the book though - I've started going through it and will likely pick up those others if/when I get bored of this one.

Anonymous Wed Jun 28 21:48:03 2017 No.9002585

>>8999352
Why are people convinced that by 1 test that required scrubbing data that the Higgs Bosson exists?

I'm not saying that it does not, but the scale and amount of extra noise found is clear indication that multiple other tests would be needed for any actual conclusions

Anonymous Wed Jun 28 22:29:31 2017 No.9002644
File: 50 KB, 611x499, Top kekule.jpg [View same] [iqdb] [saucenao] [google]

Why do most humans find the smell of benzene pleasant when it's a carcinogen and has toxic properties? My guess is the phenyl ring is found in a lot of plant compounds most find pleasant smelling (is so there's some sort of evolutionary conditioning going on), but I'm not totally sure of this

>>	Anonymous Wed Jun 28 22:34:55 2017 No.9002652 >>8999458 Download a PDF of a textbook online (see /sci/ sticky) and use YouTube and Khan Academy. MIT Opencourseware helps too.

>>	Anonymous Wed Jun 28 23:14:49 2017 No.9002710 >>9001607 Yes, being a teacher myself who teaches maths... A lot of students do have the idea "when will I ever need this" and obviously then brush it off and disengage from the classes topic.

>>	Anonymous Thu Jun 29 00:09:30 2017 No.9002747 File: 217 KB, 1124x747, IMG-20170628-WA0106.jpg [View same] [iqdb] [saucenao] [google] Why can't I simultaneously prescribe a dirichlet bc and a neumann bc on the same point/node in a heat transfer problem? Does it mean my model is ill posed?

>>	Anonymous Thu Jun 29 00:10:32 2017 No.9002748 Why is bird poop white?

>>	Anonymous Thu Jun 29 00:14:18 2017 No.9002752 Serious answers without descending into troll mode, please, because I feel like I'm being gaslighted by everyone here. What probability would you assign to the genetic contribution to the black-white IQ gap being >0%? How about >20%?

>>	Anonymous Thu Jun 29 01:08:58 2017 No.9002805 What the fuck is wrong with ETH zurich's EE masters required bachelors courses? Why are so many Analysis courses needed or a fucking mechanics course? Wanted to apply but no US uni covers that for EE reeeeeee

>>	Anonymous Thu Jun 29 01:16:15 2017 No.9002813 What did ancient people think airplanes were? Like ancient Greeks and Romans? Did they think they were terror birds or dragons or something?

Anonymous Thu Jun 29 01:20:00 2017 No.9002819

>>9001459
I am this guy. I don't know if anyone cares but I resolved this issue.

I thought a lot about it and even though I can prove that my sequence of curves converges to curve (in terms of sets) that would not be enough as what I then want to prove depends very hard on uniform converge.

What I did is that I came up with a parametrization from a fixed interval that is the same for both my sequence of curves and my limit curve. I thought this was impossible but actually not, but to achieve this I had to partition my sequence of curves at critical points (points where derivative is 0) and then construct a parametrization that preserves the parts of each partition along each function of the sequence. And this is important because as I increase n in my sequence of [math] f_n [/math], the points in each part of the partitions are very different, but in the end they represent the same thing, as long as the partition is exactly at the critical points.

And now I have separated the fixed interval into the parts that "contain" each partition and I can now prove that each part uniformly converges to its "equivalent" part of the limit function. And it works. I just tested it, but I must now start doing epsilons and deltas. But I'll do that tomorrow.

>>	Anonymous Thu Jun 29 01:24:09 2017 No.9002825 >>9002819 Oh, and I must add, to achieve this I now have a really messy and disgusting looking function instead of my clean function. But oh well, Wolfram alpha can do the limits for me ;^)

Anonymous Thu Jun 29 01:28:51 2017 No.9002836

>>9002710
Can confirm.

Wanted to do a meme degree: "game development" at some shitty college

Went there, spent three months, found out I liked programming, and got the fuck out once one of our teachers basically told us the course was a waste of our time in terms of finding reliable work

Now I want to do CS, but I did poorly as far back as grade 10 math, and I can't go back to grade 10 math at 19, so while doing pre-calc, and then calc I'm going to have to be re-learning (and in some cases learning for the first time) a lot of stuff I should have known years ago. Plus I never took pre-calc in high school 'cause I didn't think I'd need it.

>>	Anonymous Thu Jun 29 01:54:09 2017 No.9002862 >>8999587 Do your master at the university you want to do the PhD.

>>	Anonymous Thu Jun 29 02:17:50 2017 No.9002880 can i do this? $\int e^x = F(u^n)$

>>	Anonymous Thu Jun 29 02:26:01 2017 No.9002885 >>9002880 Or like this [math] \int e^x = F(u^n) [\math]

>>	Anonymous Thu Jun 29 04:47:44 2017 No.9002990 >>9002417 I don't know, I 've only read a Greek one, Axler's and some from Golan.

>>	Anonymous Thu Jun 29 05:03:02 2017 No.9003002 >>8999352 why is parallel impact velocity derived from sine and perpendicular derived from cosine? if I have a falling object of force A then shouldn't it's component parallel to the ground be it's x component?, i..e be Acos(θ) and not Asin(θ)?

Anonymous Thu Jun 29 05:07:19 2017 No.9003005

>>8999352
How would people keep track of time in a society spanning multiple planets?

Would you keep planetary time, and then one standard for space?

If x happened on the 30th June on Earth, how do people who live around alpha centauri know how long ago x happened?

Anonymous Thu Jun 29 05:51:07 2017 No.9003029

>>9003002
It depends upon whether θ is the angle relative to the tangent or the angle relative to the normal.

If θ is relative to the tangent, then the parallel component is cos(θ) and the perpendicular is sin(θ). If θ is relative to the normal, then it's the other way around.

>>	Anonymous Thu Jun 29 06:09:54 2017 No.9003041 dy/dt = (1-y)2 prove it is semistable with limits (diff eq)

>>	Anonymous Thu Jun 29 06:18:48 2017 No.9003050 >>9002644 Are you making fun of abos?

>>	Anonymous Thu Jun 29 07:14:08 2017 No.9003100 Please recommend a good book about set theory anons

>>	Anonymous Thu Jun 29 09:02:00 2017 No.9003202 >>9003100 for naive set theory: >Kaplanksy "Set theory and metric spaces" >Halmos "Naive Set theory" axiomatic: >Suppes "axiomatic set theory" >Nik weaver "forcing for mathematicians"

>>	Anonymous Thu Jun 29 10:37:14 2017 No.9003289 >>9002819 >>9002825 good job. I just realized that imho if the curve is smooth it can be approximated by a polygonal chain. maybe it's useful

Anonymous Thu Jun 29 10:39:19 2017 No.9003293
File: 3.45 MB, 1857x925, 1455498345592.jpg [View same] [iqdb] [saucenao] [google]

Studying calc. 2

having a little troule with this one.

using iteraten integration (double integration)
get the area of:
sqrt (x) + sqrt (y) = 2.
x = 0 , y = 0

book answer is 8/3

>>	Anonymous Thu Jun 29 10:47:29 2017 No.9003299 >>9003293 Integration over what interval?

>>	Anonymous Thu Jun 29 10:55:49 2017 No.9003310 >>9002752 At least some of the black-white IQ gap has to be due to genes. This isn't disputable. In terms of hard probabilities, I'd say 99.9% for the first claim and 90% for the second.

Anonymous Thu Jun 29 11:25:58 2017 No.9003344

My teachers constantly claim that a hash table reduces the complexity to find an element from [math]O(n)[/math] in a list to [math]O(1)[/math] in a hash table.

How can this be if there are [math]t[/math] buckets with evenly distributed number of elements? Clearly the complexity to find an element is [math]O(\frac{1}{t} \cdot n) \in O(n)[/math]? Thx.

>>	Anonymous Thu Jun 29 11:50:20 2017 No.9003371 >>9003299 that's a set in R^2

Anonymous Thu Jun 29 12:05:59 2017 No.9003386

I'm being told I have to take a course called "complex number linear algebra"

I've taken linear algebra and complex numbers were covered partially. I haven't taken ODE's though I understand they come up a lot in systems of ode's.

What should I be looking at to prepare for this class?

Anonymous Thu Jun 29 12:10:45 2017 No.9003393

So, came by this question in a test battery.
Three pairs of substances in pure crystalline state.
B and BF3
Na and NaCl
TiO2 and TCl4
Needing to indicate for each pair which has the highest fusion temperature.
According to it, answer's B, NaCl, and TiO2, but what's the underlying principle (also, how do I write the number indicating the number of atoms in small font)?

>>	Anonymous Thu Jun 29 12:14:42 2017 No.9003399 Allready asked this in the math general, but what should I read after finishing "forallχ" by PD Magnus?

Anonymous Thu Jun 29 12:32:00 2017 No.9003419

>>9003293
>Studying calc. 2
>having a little troule with this one.
>using iteraten integration (double integration)
>get the area of:
>sqrt (x) + sqrt (y) = 2.
>x = 0 , y = 0
>book answer is 8/3
Think of it as computing the area of the curve y=(2-Sqrt[x])^2. This is easy, isn't it?

Well, in this case you have to find the area of the figure bounded by sqrt (x) + sqrt (y) = 2. (or y=(2-Sqrt[x])^2), the X-axis (y=0) and the Y-axis (x=0). If you plot it, you will find that this is a closed area.

Then, by looking at the figure you have drawn, what you have to compute is
[math]\int_{0}^{\text{the point where sqrt(x)+sqrt(y)=2 and x=0 meet}}\int_0^{sqrt(x)+sqrt(y)=2}{dx dy} [/math]

Or, in a more formal way
[math] \int_0^4\int_0^{(2-\sqrt{x})^2}dxdy=\int_0^4(2-\sqrt{x})^2 dx=\frac{8}{3}[/math]

>>	Anonymous Thu Jun 29 13:26:06 2017 No.9003487 What are the chances of undiscovered elementary particles existing?

>>	Anonymous Thu Jun 29 13:53:57 2017 No.9003523 >>9002836 pre calc - do you understand what a limit is? then you know pre-calc calc - can you understand the concept of slope? then you can learn calc there's obviously more to it than that, but there's nothing too hard about those classes.

>>	Anonymous Thu Jun 29 15:18:40 2017 No.9003648 File: 5 KB, 751x73, 2017-06-29-191709_751x73_scrot.png [View same] [iqdb] [saucenao] [google] What does the notation 1_s and 1_t mean? Is it just some arbitrary s in S and t in T?

>>	Anonymous Thu Jun 29 15:19:39 2017 No.9003652 >>9003648 What's the context?

>>	Anonymous Thu Jun 29 15:20:50 2017 No.9003656 I am working on a plot of electronic band structure with python. How would one insert a variable into a matrix / array, so i can calculate the eigenvalues of the matrix in general form ?

>>	Anonymous Thu Jun 29 15:46:12 2017 No.9003696 >>9003648 1_T means the identity map T -> T.

>>	Anonymous Thu Jun 29 16:10:13 2017 No.9003743 File: 3.02 MB, 4128x3096, 20170629_220651.jpg [View same] [iqdb] [saucenao] [google] If the thing on the left is my acceleration-time graph which in this case has a parabolic shape what will my velocity time graph look like?

>>	Anonymous Thu Jun 29 16:58:34 2017 No.9003849 >>9003743 reflect your a/t graph in the line y=x

>>	Anonymous Thu Jun 29 19:01:36 2017 No.9004060 Heard my bro's friend quit his job to be a Male nurse.Isn't that profession over-saturated in the US to drive down wages and have longer hours?I Also have a cousin who's gf quit working for a law firm to purse nursing...

>>	Anonymous Thu Jun 29 19:29:03 2017 No.9004093 >>9003743 velocity will be cubic in nature

Anonymous Thu Jun 29 20:00:48 2017 No.9004140

>>8999360
because it would be pretty brutal to eat it alive.

>>9001480
the plant metabolism is anaerobic most of the time, they consume CO2 and use sunlight to produce their energy. So they need an external source of energy, other than the chemical composition of their "food" making it an "endothermic" reaction in a very rudimentary way.

Fungus are from another kingdom of living things and they use Oxigen from the air and they gather their food from the ground they grow. so they genrate heat by an exothermic reaction.

they are not correctly classified as exothermic and endothermic, but you get the idea

>>9002112
no. Use the gravitational pull equation, is very similar to the magnetic pull equation, it depends on both the masses and the distance(quadratically). you cna do a free body diagram afterwards and check all the resulting forces of attraction.

>>9003393
most of them are from remmebering, but:
>Bf3 is a gas, you could have guessed this because fluoride is agas at room conditions.
>Na is an unstable alcaline metal and they usually have pretty low melting points, while NaCl is a crystaline salt.
>TiO2 is an Oxide, and oxides usually have high melting points, on the other hand, TiCl4 is a gas, so if you knew that that would have been it.

>>9003743
It will look LIKE your a/t diagram, just magnified by a cubic factor.

>>	Anonymous Thu Jun 29 20:02:56 2017 No.9004142 >>9004140 Alright, gotcha. Any other general rules regarding melting points?

>>	Anonymous Thu Jun 29 21:06:23 2017 No.9004198 >matrix has 3x3 size >it has 5 possible row echelon forms >matrix has 4x4 size >it has 7 is it wrong to assume that n-1 where n is the size of a matrix is the number of row echelon forms it can take?

>>	Anonymous Thu Jun 29 21:06:47 2017 No.9004200 Just HOW good do I need to be at basic mathematics (up to, say, calculus) before I attempt to learn "real" math? Is there a good way to tell if I have the necessary knowledge? Any good indicators?

>>	Anonymous Thu Jun 29 21:10:13 2017 No.9004205 >>9004198 a 4x4 matrix has more than 7 possible row echelon forms

>>	Anonymous Thu Jun 29 21:11:27 2017 No.9004207 >>9004200 >Is there a good way to tell if I have the necessary knowledge? Any good indicators? when you try learning "real" math and don't have foundational issues

>>	Anonymous Thu Jun 29 21:17:07 2017 No.9004220 >>9004205 you're right i forgot about the squiggly cases.

>>	Anonymous Thu Jun 29 21:28:51 2017 No.9004235 >>9003743 t=a^2 -> a=t^(1/2). Just integrate it.

>>	Anonymous Thu Jun 29 21:34:01 2017 No.9004243 >>9003041 Solve the equation, don't forget the constant. Pick a constant lower than one, take the limit as x->inf. Pick a constant greater than 1 and do the same.

Anonymous Thu Jun 29 21:50:07 2017 No.9004266
File: 33 KB, 500x375, 1470080329188.jpg [View same] [iqdb] [saucenao] [google]

>>8999352
So, I've posted about this before but I'm posting again. Basically, I failed a class last semester and it really fucked up my graduation plan. Currently taking summer classes, but it gives me a pretty full fucking plate if I want to graduate by summer of next year. But looking at my options for general tech electives in the summer, they all seem kinda shit and I wouldn't get a lot out of it. (mechanical engineering student here) Furthermore, I'd be busting my ass to try and graduate by summer or even the end of fall, and I feel like my GPA might suffer since I just got a job.

I was thinking of pushing my graduation back an extra year (Which would give me a grand total of 6 fucking years), and maybe pursuing a minor while I'm at it or just focusing on my current curriculum to make sure my GPA doesn't dip any further and I get "a little more" of the college experience. The only thing that kind of bites is money is getting tight since I got cucked by loans, but I'm also gonna start putting some money to pay those off. It ALSO gives me a chance to try and get in a good engineering project for senior design (I don't think ihave the resume for it this semester,) and really push for a summer internship. I just know I felt a lot of my life fall apart because of one project class and I'd be taking two to make up the slack next semester.

Does anybody have any advice on this? I kinda gather "What's an extra semester - year of my life and a few thousand dollars when I've invested this much time and money" but perhaps this is just my ignorance talking. I guess I just kinda figure "if I'm gonna be fucked when I graduate, does it make a difference?"

>>	Anonymous Thu Jun 29 21:52:40 2017 No.9004269 >>9004266 >>>/adv/

>>	Anonymous Thu Jun 29 22:42:48 2017 No.9004337 >>8999352 integral(sqrt(1+tan^2))dx from 0 to pi?

Anonymous Thu Jun 29 22:59:40 2017 No.9004350
File: 1.56 MB, 245x169, 1436468274856.gif [View same] [iqdb] [saucenao] [google]

>>8999352
>Live in South Louisiana
>Parish just said there's brain-eating amoeba in the water a couple hours ago
>Water king says it's okay to drink, just don't get any in your nose
Aren't your ears, nose, and mouth connected? If you drink it, does it not get in your nose? I don't know about all this...

Anonymous Thu Jun 29 23:09:20 2017 No.9004354

>>9004350
>Aren't your ears, nose, and mouth connected?
Ears are not connected to the nose and mouth. You think you can put something in your ear and get it to come out of your nose?
>If you drink it, does it not get in your nose?
Not unless you're retarded

>>	Anonymous Thu Jun 29 23:16:12 2017 No.9004361 >>9004354 >Ears are not connected to the nose and mouth. go see an ear doctor, have them put a little juice in there. know what they're gonna say? "don't worry, it'll drain down your throat after a few hours."

>>	Anonymous Thu Jun 29 23:37:12 2017 No.9004378 >>9004361 good luck getting a fluid through a fucking airtight eardrum

>>	Anonymous Thu Jun 29 23:47:30 2017 No.9004389 gearing up to take pchem in the fall, looking at McQuarrie and Simon right now and realizing I am quite mathematically deficient... what's the best way to get the necessary background? McQuarrie's Math, or Mortimer's, or Schaum, or? <3 ty guys

>>	Anonymous Thu Jun 29 23:54:22 2017 No.9004394 File: 11 KB, 371x202, Untitled.png [View same] [iqdb] [saucenao] [google] Scientifically speaking, is it safer to castle with a bishop in front of the king or not?

>>	Anonymous Fri Jun 30 00:27:13 2017 No.9004429 >>9004354 They´re connected. Trompa de Eustaquio.

>>	Anonymous Fri Jun 30 00:27:15 2017 No.9004430 >>9001420 just do a matrix........

>>	Anonymous Fri Jun 30 00:32:14 2017 No.9004435 Anyone know what this "blue substance" is? >http://rstl.royalsocietypublishing.org/content/58/181.full.pdf+html

Anonymous Fri Jun 30 00:40:51 2017 No.9004444

>>9004394
It's called a fianchettoed bishop.
Obviously it's safer but you're dedicating a piece for defense and they will likely force a bishop trade and you'll be left with an open pawn structure.

It's situational and it's more important to be able to see and understand your particular game and situation than ask kikey questions about "scientifically speaking blah blah".

>>	Anonymous Fri Jun 30 05:38:04 2017 No.9004729 >>9004378 >eardrum >airtight are you fucking retarded? did you even read what you wrote?

>>	Anonymous Fri Jun 30 11:18:37 2017 No.9005069 If I throw a rock straight up at 12.5m/s in Earth's a gravity ignoring air resistance will it fly 7.9m high?

>>	Anonymous Fri Jun 30 11:23:47 2017 No.9005078 >>9004200 When you don't have to think about it

>>	Anonymous Fri Jun 30 11:48:54 2017 No.9005106 File: 99 KB, 989x742, 27AgBdL.jpg [View same] [iqdb] [saucenao] [google] I'm taking QM 1 this fall, what should I get really good at doing/understanding before semester starts

>>	Anonymous Fri Jun 30 11:49:02 2017 No.9005107 Which [math]GNU[/math] [math]Octave[/math] should i use?

>>	Anonymous Fri Jun 30 12:05:57 2017 No.9005126 >>9004729 do you know how an ear works? Air can't get through an unperforated eardrum otherwise it wouldn't fucking work. The eardrum vibrates as soundwaves hit it. If it wasn't fucking airtight then how the fuck would you be able to hear anything?

>>	Anonymous Fri Jun 30 15:00:41 2017 No.9005380 >>9003344 Any practical hashtable implementation will increase the number of buckets in proportion to the number of elements, so the mean number of elements per bucket remains roughly constant.

>>	Anonymous Fri Jun 30 15:14:53 2017 No.9005397 >>9005069 I don't know LaTex so bear with me here v^2 = u^2 + 2as 0 = (12.5)^2 + (2 * - 9.80665 * h) 0 = 156.25 - (19.6133 x h) h = 156.25/19.6133 = 7.9665 m

>>	Anonymous Fri Jun 30 15:21:34 2017 No.9005404 Would changing most of my coursework to fit prereqs for a masters at ETHZ be worth it? At best I will still need to take 28 credits when I get there (am from US)

>>	Anonymous Fri Jun 30 15:25:05 2017 No.9005409 Our Time Our time apart will rend our hearts. Our time together will mend them together.

Anonymous Fri Jun 30 15:58:02 2017 No.9005458

http://www.ctc.cam.ac.uk/outreach/origins/cosmic_structures_one

https://phys.org/news/2013-12-collapse-universe-closer.html

https://www.sciencealert.com/physicists-have-finally-confirmed-a-decades-old-theory-that-explains-phase-transitions

I was one of the earlier posters of the thread. Basically, the idea of a first-order phase change occurring as described above and ending our surrounding reality spontaneously and inpredictably during my lifetime is giving me panic attacks.

Can any /sci/on reassure me?

Just tell me that this is unlikely, feed me some probabilities or tell me that it may probably not happen at all since our physical paradigm is incorrect/incomplete. I just want to stop worrying

>>	Anonymous Fri Jun 30 16:41:33 2017 No.9005514 >>9005397 thanks you just helped me out

>>	Anonymous Fri Jun 30 17:01:44 2017 No.9005536 >>9002412 People decide as groups what is right and wrong, no objective morals I'm afraid christfag.

>>	Anonymous Fri Jun 30 17:02:06 2017 No.9005537 >>9005404 not best time for EUs, but help if you can pls

>>	Anonymous Fri Jun 30 17:21:44 2017 No.9005564 >>9005514 No problem I'm glad I could help

>>	Anonymous Fri Jun 30 17:29:15 2017 No.9005577 How do you make meth?

>>	Anonymous Fri Jun 30 18:09:40 2017 No.9005664 What are the ultimate implications of godels theorem? Do we just accept that maths is fundamentally incomplete?

Anonymous Fri Jun 30 18:20:22 2017 No.9005702

>>9005458

I used to worry about this too, though if you're having panic attacks you may have an undiagnosed anxiety disorder and should see a therapist.

What I noticed that helped my worry was that the number of "scary ideas" (Fermi paradox, doomsday argument, quantum immortality, simulations, Roko's basilisk) is as boundless as peoples' imaginations, and that the scariest of these have a higher chance of reaching my sphere of awareness despite the fact that they can't all be true. I think you should accept the limits of human reason in sorting out nature of reality and also accept that our appetite for scary ideas will always outstrip their empirical value.

Anonymous Fri Jun 30 18:55:37 2017 No.9005776

>>9005536
That is simply not true. Morals have changed in the past (e.g. death penalty in civilised countries) and will change in the future - not because groups said "hey, yesterday the death penalty was totally ok, but today it ain't like that any more", but because a single person realized that for themselves, and could somehow get others to agree with them.

And yes, I agree, morals are subjective (otherwise, how could they change), exactly as the poster you replied to implied

>>	Anonymous Fri Jun 30 19:03:50 2017 No.9005788 >>9002752 >>9003310 >Measuring IQ differences in % of IQ That's like measuring temperature differences in % of °C or % of °F

Anonymous Fri Jun 30 21:39:48 2017 No.9006019
File: 56 KB, 648x749, Screenshot_2017-06-30_23-08-42.png [View same] [iqdb] [saucenao] [google]

why does this "oscillate" like a periodic function would when there's no components of the function that would indicate any nature of trigonometric functions? I'm not too well versed in the incomplete gamma function.

>>	Anonymous Fri Jun 30 21:41:15 2017 No.9006020 >>9006019 does it have something to do with [math]e^{ix} = \cos(x) + i\sin(x)[/math]?

>>	Anonymous Fri Jun 30 21:58:54 2017 No.9006045 File: 11 KB, 169x69, Proyección u sobre v.png [View same] [iqdb] [saucenao] [google] >>9000843 This is the length of the projection of u over v. If you divide this by [(vector v)/(length of vector v)], you get the projection vector.

Anonymous Fri Jun 30 22:01:48 2017 No.9006050

My insurance is shit and I don't have much cash to spare. I know you're not supposed to take medicine that wasn't prescribed for that purpose but I have about 20 leftover metronidazole 500mg and an obscenely painful ear infection. Is it likely to clear it up? If I do take it how long should I wait to see some relief before I just go to the doctor for something else?

>>	Anonymous Sat Jul 1 01:54:40 2017 No.9006322 Does anyone ever feel like intellectual growth is discrete? For example, I'll be struggling to understand something for days and not make any progress and then all of a sudden it all makes sense at once, kind of like leveling up in a video game.

>>	Anonymous Sat Jul 1 01:56:10 2017 No.9006323 File: 341 KB, 634x875, 1457459652101.jpg [View same] [iqdb] [saucenao] [google] Can a tree "feel" its branch break?

Anonymous Sat Jul 1 02:01:57 2017 No.9006329

>>9006020
It could also be that i^n follows a unit circle just like sin and cosine do (which is inherently related to Euler's formula). Interestingly, i is also cyclical when tetrated (that is to say, i^i^i^i^i...) But forget parsing out that equation to see which of those is causing it, my brain is too deep in summer mode.

>>	Anonymous Sat Jul 1 04:19:45 2017 No.9006489 >>9003344 Thx

Anonymous Sat Jul 1 05:58:26 2017 No.9006598

>>9006019
>why does this "oscillate" like a periodic function would when there's no components of the function that would indicate any nature of trigonometric functions? I'm not too well versed in the incomplete gamma function.
The incomplete gamma has the asymptotic behaviour
[math] \lim_{x\rightarrow 0} \Gamma (s,x)\rightarrow -x^s/s [/math]
as s=4i, you get those oscillations.

>>	Anonymous Sat Jul 1 06:01:24 2017 No.9006605 What are some good books about Statistics and Machine Learning? Is "AI: A modern approach" by Russel and Norwig still somewhat up-to-date?

Anonymous Sat Jul 1 06:18:34 2017 No.9006634

>>9006605
>Is "AI: A modern approach" by Russel and Norwig still somewhat up-to-date?
It's an introductory book that covers the fundamentals well and dispels the myths that people have about AI. That's why it gets recommended often here on /sci/.
It doesn't need to be up-to-date because the theory hasn't changed that much since it was written. If you're looking for the latest advanced techniques you'll need mathematical pre-requisites that Russell/Norvig don't assume you have, so you'll probably want a specialized book for that instead.

The equivalent of Russell/Norvig for statistics would probably be Bishop's "Pattern Recognition and Machine Learning". If you want a more solid grounding in the theory of machine learning you can look at Vapnik's classic "Statistical Learning Theory".

>>	Anonymous Sat Jul 1 06:26:32 2017 No.9006652 >>9006634 Ok, thanks, those books were already on my list

>>	Anonymous Sat Jul 1 08:04:35 2017 No.9006794 File: 13 KB, 358x193, 645654.png [View same] [iqdb] [saucenao] [google] Where can I imagine myself the 3 hidden hydrogen atoms on this skeletal formula for vitamin C? Am I doing it right?

>>	Anonymous Sat Jul 1 08:07:32 2017 No.9006798 >>9006794 >Where can I imagine myself the 3 hidden hydrogen atoms on this skeletal formula for vitamin C? >Am I doing it right? No, there is one hydrogen in the right red point and two hydrogens in the center point. The left point is not a carbon.

>>	Anonymous Sat Jul 1 08:20:00 2017 No.9006805 >>9006798 Okay, I see. Thanks!

>>	Anonymous Sat Jul 1 08:32:11 2017 No.9006819 How do I prove that 1+1 =/= 3?

>>	Anonymous Sat Jul 1 08:48:13 2017 No.9006846 >>9006819 Proof: 1 + 1 = 2. Therefore 1 + 1 =/= 3.

>>	Anonymous Sat Jul 1 08:51:26 2017 No.9006851 >>9005664 Yes.

>>	Anonymous Sat Jul 1 09:04:59 2017 No.9006861 >>9006846 No, you would still have to prove that 2 =/= 3 >>9006819 Assume 1+1 = 3 and derive a contradiction

>>	Anonymous Sat Jul 1 09:14:18 2017 No.9006881 File: 72 KB, 543x549, 1459619457253.jpg [View same] [iqdb] [saucenao] [google] What is a use case for a tangent line?

>>	Anonymous Sat Jul 1 09:19:35 2017 No.9006887 >>9006861 proving contradictions should not count as a valid type of proof go constructive or go home

>>	Anonymous Sat Jul 1 09:21:37 2017 No.9006892 >>9006887 >he thinks modus tollens is intuitionistically invalid

>>	Anonymous Sat Jul 1 10:15:39 2017 No.9006954 How do I know of an operator which properties it has? Is memorisation the only way? I keep being unsure about it or even mixing them up.

>>	Anonymous Sat Jul 1 10:20:47 2017 No.9006963 what are essential books to completely dominate Euclidean Geometry? thx

>>	Anonymous Sat Jul 1 10:57:48 2017 No.9007003 Is CERN useful or is it just smashing particles for fun? What useful technologies have resulted from there?

>>	Anonymous Sat Jul 1 11:10:57 2017 No.9007016 Why do I share 98% of my genes with a chimpanzee, but only 50% with my brother?

>>	Anonymous Sat Jul 1 11:30:51 2017 No.9007051 >>9007016 because you are a chimpanzee and your brother is a kangaroo

>>	Anonymous Sat Jul 1 11:40:27 2017 No.9007065 >>9007016 You share all of your genes with your brother, what is different is the variant of the gene. An chimpanzee has actually different genes. (I'm not into genetics, so my semantics may be off)

>>	Anonymous Sat Jul 1 13:40:18 2017 No.9007239 >>9006887 GET THE FUCK OUT OF MY MATH, PHILOSOPHERFAGS REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

>>	Anonymous Sat Jul 1 13:41:47 2017 No.9007242 >>9006881 Literally nothing. Tangent lines are useless.

>>	Anonymous Sat Jul 1 18:18:44 2017 No.9007752 >>9006881 pls go back to studying three sided polygons

>>	Anonymous Sat Jul 1 18:19:59 2017 No.9007755 >>9006887 omfg, this is not the stupid statement thread man

>>	Anonymous Sat Jul 1 18:23:17 2017 No.9007763 senpai, recommend a book on Fuzzy Logic

Anonymous Sat Jul 1 21:45:48 2017 No.9008160

recommendations on
>books on math + philosophy + theology?
>books similar to euclid's elements, that is a classic, beautiful book
>books on math in relation to nature, with topics such as pi, theta or the golden ratio
>books with a bit of math + mysticism/numerology, but nothing too retarded/exotic
>basically books like the movie Pi (1998)

>>	Anonymous Sat Jul 1 21:48:46 2017 No.9008167 >>9008160 You're probably better off asking this stuff in /lit/ tb h. Too many fedoralords here.

Anonymous Sat Jul 1 21:56:17 2017 No.9008183

>>9008167
did ask. no answers.

what I have on my list:
>euclid's elements, which I am already reading, archimedes, apollonius and nichomachus, they are all in the same book
>a mathematician's apology
>introduction to mathematical philosophy by bertrand
>Gödel, Escher, Bach
>Geometry and the Imagination by hilbert
and
>Philosophy of Mathematics: Selected Readings

>>	Anonymous Sat Jul 1 21:59:23 2017 No.9008189 File: 52 KB, 485x844, where thje fuck did the 4 come from.png [View same] [iqdb] [saucenao] [google] Where the fuck did the four come from if it was already multiplied to 2x

>>	Anonymous Sat Jul 1 22:18:21 2017 No.9008222 >>9008189 Power rule on the outer function. Notice the exponent went down to 3.

Anonymous Sat Jul 1 22:19:33 2017 No.9008225

>>9008189
This seems fucked to me. The 4 is nonsense as far as I can tell, and also they take the derivative as though g(x) = sin(x^2)+1 but this is not the function.

The derivative of g(x) is 2sin(x)cos(x), and your final answer should be [math]8(sin^2(x)+1)^3sin(x)cos(x)[/math]

>>	Anonymous Sat Jul 1 22:19:42 2017 No.9008227 >>9008189 >>9008222 Oh, actually that's probably a mistake. nvm

Anonymous Sat Jul 1 23:44:01 2017 No.9008372

I'm an aerospace engineering student, and I'm far enough along that changing to mechanical engineering will cause me to stay in school an extra year. However, I also definitely do not want to be involved in designing weapons. Am I in a bad position, or are there enough civil aerospace companies for me to not have to worry? If the former, how much trouble would I have with getting a job in mechanical engineering?

Anonymous Sat Jul 1 23:55:59 2017 No.9008393

In a book i was reading it referred to the divergence of a vector function as "the exponential rate of growth of area in a small neighborhood of x" and also called it "the logarithmic derivative of the small area". What the fuck does this mean? I haven't seen an explanation of this anywhere.

>>	Anonymous Sun Jul 2 00:57:51 2017 No.9008504 >>9008225 That's what I got... The 4 just magically appeared....

Anonymous Sun Jul 2 05:05:20 2017 No.9008783

Let's say you timeslipped back to 1600 England, and assuming your accent wasn't a problem and you didn't immediately die of disease, what science experiments could you preform with easily obtainable materials that would revolutionize the science of the day?

>>	Anonymous Sun Jul 2 06:46:24 2017 No.9008890 Do hydrogen bridges always prove me that a chemical connection is therefore a dipole?

>>	Anonymous Sun Jul 2 06:49:55 2017 No.9008895 >>8999906 care to provide i cannot understand what is this author and book name i will

Anonymous Sun Jul 2 07:00:45 2017 No.9008913

>>9008783
>Let's say you timeslipped back to 1600 England, and assuming your accent wasn't a problem and you didn't immediately die of disease, what science experiments could you preform with easily obtainable materials that would revolutionize the science of the day?
Pressure cooking (a step toward the problem of food preserving), vaccination, and the use of lemons and limes against scurvy.
Easy and important.

Anonymous Sun Jul 2 07:11:22 2017 No.9008919

>>8999906
Author didn't not "get that conclusion from this sum"
Author showed you an example BRBR
where m = 4 and n = 2;
He showed you that shifting beads times(m = 4 times) the colors, doesn't change the identify of that necklace.
so there are beads times (here 4 times) every necklace that are similar to one that necklace. For example he showed
>BRBR
>RBRB
>BRBR
>RBRB
are identical.
He went from an example to formulate a sum. Not the other way around.
While doing science we go from intuitive evidence to formulate a mathematical model.
You can go reverse way but this is not what author showed.
And about the formulation he wrote. You can play with small examples m = 4 n =2 and find a pattern and then use variables to define a generic model. This is tough but once you learn it maths and science will be 4 times smoother and you will love Trump.

>>	Anonymous Sun Jul 2 07:31:26 2017 No.9008942 Is phrenology credible and how much do developmental social factors affect IQ compared to genetics?

Anonymous Sun Jul 2 07:43:56 2017 No.9008953

>>9000431
>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?
What about using directly the solution to the Kepler problem?
[math] \frac{1}{r}=-\frac{km}{L^2} (1+e\cos(\theta-\theta_0)) [/math]

Anonymous Sun Jul 2 07:47:35 2017 No.9008957

>>9008393
sauce on book. It is used in graphics programming.
Basically parametric form of vector function where x,y,z are functions wrt time.
divergence of vector function is same of divergence of any function. given a domain [t,t+T] he is saying the vectors diverges to infinite i.e one of x,y or z component of vector in question would tend to infinite, similar to how exponential function grow too fast too large.
To find rate of growth you need logarithmic derivative not normal dv/dt derivative. Your infinitesimal unit would be p = log(t) dp/dt = 1/t .
dp = dt/t, dt = tdp. Use tdp in place of dt.

>>	Anonymous Sun Jul 2 08:58:08 2017 No.9009040 >>8999360 kek >not eating sardines >claiming to be enlightened

>>	Anonymous Sun Jul 2 12:00:17 2017 No.9009290 >>9008895 The book is concrete mathematics by donald knuth and some others

>>	Anonymous Sun Jul 2 12:03:31 2017 No.9009296 >>9008890 yes

Anonymous Sun Jul 2 12:26:27 2017 No.9009338

This may be a brainlet question, but I'm sort of struggling with the semantics of orderings and equivalence relations.

Let's say I'm looking at sequences in a set X with a total order, and before defining an equivalence relation ~ or an ordering ≤, I'd like to list some properties I want these to have. Can an ordering exist without an equivalence relation? I don't think there's any reason I can't start defining an ordering on sequences even if I haven't defined equivalence, but then it seems like the anti-symmetry of an ordering gives rise to a notion of equivalence beyond equality of all elements.

To clarify, I have sequences a,b in X, and I never defined what it means for two sequences to be equivalent (beyond a=a since all terms are the same). One of the conditions I want to impose on an ordering ≤ is that a ≤ b if a(n) ≤ b(n) eventually. Doesn't anti-symmetry of an ordering imply automatically that a = b if a(n) = b(n) eventually? (a(n) = b(n) eventually implies a(n) ≤ b(n) eventually and b(n) ≤ a(n) eventually, which implies a ≤ b and b ≤ a and thus a = b) But this isn't equality in the trivial sense, some of the terms may differ. Shouldn't this be a ~ b then? Does an ordering assume there is already an existing notion of equality of equivalence classes?

>>	Anonymous Sun Jul 2 12:35:00 2017 No.9009357 >>9008919 >so there are beads times (here 4 times) every necklace that are similar to one that necklace what?

Anonymous Sun Jul 2 12:35:14 2017 No.9009359

>>9007016
This guy >>9007065 is correct.

Here's a simple model: Pretend humans have genes 1,2,3 ... 98,99,100. But, for a given number gene, you could have variants. If 1 is for Hair Color, you might have 1A for Brown or 1B for Blonde or 1C for Red ... etc.

Other species have different numbers (and you'll find they have different numbers of chromosomes, upon which these genes are found).

If we say the Chimp has 1,2,3...96,97,98 and that's it, that means whatever is 99 and 100 are only in humans, not in Chimps. 99 and 100 could have an alphabet of different versions, but the Chimp will have none of them. So, we could have 98% in common with chimps, in that we share broad genetics which impart the same functions on our cells.

When you compare two siblings, you're not doing that. If one of you is missing a gene, that's probably really bad. The 50% comparison would be of which specific variants you got from your parents, which are referred to alleles.

Anonymous Sun Jul 2 12:51:35 2017 No.9009392

Hello, can anyone give me a reference to a book or some other publication that states the problem in this math exchange question:
https://math.stackexchange.com/questions/2058905/limit-of-complex-line-integral-over-a-uniformly-convergent-sequence-of-curves

Perhaps someone who knows complex analysis and knows a lot about the literature? I need to find a precise statement, as the comments suggest that the asker did not express the problem correctly. but then they are vague as to what is missing and how to prove it. Please help, I've been looking for days.

>>	Anonymous Sun Jul 2 13:11:00 2017 No.9009419 >>9009418 >>9009418 >>9009418 NEW NEW NEW >>9009418 >>9009418 >>9009418

>>	Anonymous Sun Jul 2 15:42:09 2017 No.9009743 >>8999352 Is gravitational time dilation proportional to the acceleration of the gravitational field?

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