/sqt/ stupid questions thread

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/sqt/ stupid questions thread Anonymous Thu Jun 18 01:19:12 2015 No.7337217 [Reply] [Original]

What do you call a non-commutative field like quaternions?
What do you call a field that has a conjugate defined like the complex field?
In abstract algebra how do you define a conjugate?

>>	Anonymous Thu Jun 18 01:26:52 2015 No.7337220 >What do you call a non-commutative field like quaternions? One term that I have heard is "inversion algebra". But if you work with non-commutative fields regularly you can just call them fields or non-commutative fields.

>>	Anonymous Thu Jun 18 02:45:34 2015 No.7337312 My registration for college is tomorrow and two of my classes are already full. Assuming I can get into the wait list at 5 or under, what are the chances of getting in? This is for physics I and chemistry 101.

>>	Anonymous Thu Jun 18 02:48:41 2015 No.7337316 Re-asking this question cause i need to know If I jump in a pool filled with a low density liquid like propane R290 (494 kg/m^3) will the force of the impact be as strong as if I had jumped in water (1000 kg/m^3) ?

Anonymous Thu Jun 18 04:53:00 2015 No.7337435

>>7337217
>What do you call a non-commutative field like quaternions?
Division Ring
>What do you call a field that has a conjugate defined like the complex field?
*-field
>In abstract algebra how do you define a conjugate?
It's an automorphism that is also an involution.

>>	Anonymous Thu Jun 18 04:59:12 2015 No.7337442 >>7337435 >*-field got a wikipedia article on it?

>>	Anonymous Thu Jun 18 05:00:56 2015 No.7337444 >>7337442 https://en.wikipedia.org/wiki/*-algebra

>>	Anonymous Thu Jun 18 05:03:21 2015 No.7337447 >>7337444 perfect. thank you.

>>	Anonymous Thu Jun 18 05:12:23 2015 No.7337457 >>7337316 Density is not so important as surface tension (for breaking the surface) and viscosity (for deceleration after that).

>>	Anonymous Thu Jun 18 05:17:07 2015 No.7337468 >>7337457 what about the momentum of the water you need to move out of the way?

>>	Anonymous Thu Jun 18 06:11:35 2015 No.7337529 >>7337468 That's accounted for in viscosity.

>>	Anonymous Thu Jun 18 07:10:15 2015 No.7337597 Could anybody help me with this? Find the matrix for proju(v) where u = (1, 5, 3)T?

>>	Anonymous Thu Jun 18 10:18:19 2015 No.7337778 Are there are britfags studying physics here? Any advice on what topics I should learn/go over over summer before I start Uni? I was thinking of teaching myself further maths if I don't get any better suggestions, since I didn't do it at A level

>>	Anonymous Thu Jun 18 10:19:49 2015 No.7337779 Quaternions are a noncummutative division ring.

>>	Anonymous Thu Jun 18 10:25:05 2015 No.7337793 >>7337312 That's a question you should ask the professors of those classes, not us. My guess is they let you in if you ask them directly. Just be polite and explain yourself.

>>	Anonymous Thu Jun 18 10:31:39 2015 No.7337800 Not really stupid so much as doesn't merit its own thread, but are there any forensic anthropologists here? Thinking about going into the field and I'm wondering what it's like. >inb4 some troll says "just watch Bones"

>>	Anonymous Thu Jun 18 10:50:00 2015 No.7337826 >>7337800 just watch Bones

Anonymous Thu Jun 18 11:54:53 2015 No.7337892
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>be me
>community college
>fall semester classes

Today is my registration appointment, but half the good teachers are now gone. What are the chances of getting into the class if I go in the waitlist?

>>	Anonymous Thu Jun 18 12:00:01 2015 No.7337898 >>7337892 The red arrow signifies that I'm doing it in the summer, but not sure if I'll pass.

Anonymous Thu Jun 18 12:24:45 2015 No.7337940

>>7337892

I was waitlisted for several classes in college and got in to every last one - there's always someone on the list who drops out. Then again, I was doing a part-time foundation year. If you can see your ranking on the list and you're in the top five, I suggest attending the class and informing the professor of your situation in case someone drops it within the first couple of weeks.

Anonymous Thu Jun 18 12:26:31 2015 No.7337944
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Finally got around to doing college statistics class but a good chunk of it is terrible at explaining things. I'm already bad at math in general so that doesn't help.

Not sure if anyone would bother helping, but it's work on finding p-values from a Student's t distribution. This crap is basically saying "n = 29, t=1.921, this is p-value," but it's not showing or explaining how the fuck it got that p-value, just "Calculate it. It shows it's between 0.025 and 0.05 on the table, so it's this exact p-value."

So what in the hell am I missing here? Driving me crazy since nothing is actually explaining and showing how to do it.

>>	Anonymous Thu Jun 18 13:22:56 2015 No.7338029 how can i image the earth like a mri / sonargraph? why is it not possible? if you can tell me 1 way to image the through the earth plz also tell what equipment i would need and how much it would cost. thx!

>>	Anonymous Thu Jun 18 13:26:56 2015 No.7338032 >>7337312 There are 3 possibilities. You will either get in one class, get in both of the classes, or get in neither of the classes. Therefore the chance of getting in both is 1/3

>>	Anonymous Thu Jun 18 16:29:48 2015 No.7338326 >>7337217 Is having access to good drugs a good enough reason to become a doctor?

Anonymous Thu Jun 18 16:40:30 2015 No.7338339
File: 111 KB, 637x814, serre_dies.jpg [View same] [iqdb] [saucenao] [google]

If the local mean at k for a function f is defined as

 \langle f(k) \rangle := \int_{k}^{k+1} f(k') dk' [/spoiler]

what's a simple rational approximation for

 \sum_{k=0}^\infty ( k \, z^k - \langle k \, z^k \rangle ) [/spoiler]

when z = 0.99999 [/spoiler]?

Anonymous Thu Jun 18 16:46:25 2015 No.7338352

I'm going to apply to physics REUs for experimental physics in the winter, but I really don't know what I'm interested in. Where can I find a brief overview of things like gravitational wave, dark matter, particle stuff, accelerator physics, high energy physics(same as accelerator and particle?), condensed matter etc to see what kind of research I'd be interested in? Inb4 wikipedia, I really just want to know what to expect from the REUs.

>>	Anonymous Thu Jun 18 17:06:00 2015 No.7338400 If force is mass times acceleration, does this mean that a billiard ball does not apply a force, but rather it just changes the momentum of both balls? Does it apply a negative force? What is the meaning of negative force?

Anonymous Thu Jun 18 17:07:02 2015 No.7338405

>>7338352
The idea behind REUs is to let undergrads get a taste for these kinds of things. You should expect professors from each area to give talks about what they do during the program.
Most REUs should also give detailed project descriptions so you can see what you'll be working on.

>>	Anonymous Thu Jun 18 17:09:18 2015 No.7338412 >>7338400 Force isn't mass times acceleration, but rather change in momentum. Force isn't a number, but a vector, which you should think of as a size and direction. Do negative would imply same size, but opposite direction.

>>	Anonymous Thu Jun 18 17:11:16 2015 No.7338417 >>7338400 >If force is mass times acceleration, does this mean that a billiard ball does not apply a force, Why would it mean that?

>>	Anonymous Thu Jun 18 17:12:02 2015 No.7338419 >>7338417 Because the cue ball is slowing down before it hits the other ball, meaning it has negative acceleration.

>>	Anonymous Thu Jun 18 17:20:04 2015 No.7338437 >>7338412 >but rather change in momentum. I thought that was impulse.

Anonymous Thu Jun 18 20:44:11 2015 No.7338772

http://web1.assist.org/web-assist/report.do?agreement=aa&reportPath=REPORT_2&reportScript=Rep2.pl&event=19&dir=1&sia=MIRACSTA&ria=UCI&ia=MIRACSTA&oia=UCI&aay=14-15&ay=15-16&dora=SOFT+ENG

What's the difference between computer engineering, software engineering, and computer science? If I want a software engineering degree, all I need is Java I and II.

>>	Anonymous Thu Jun 18 20:52:53 2015 No.7338791 >>7338772 > computer engineering low level hardware and software. > computer science all software > software engineering project leaders

>>	Anonymous Thu Jun 18 20:55:26 2015 No.7338795 How can I learn C++, or any other language for good measure? I know Python at the introductory level but I don't know what to do know. I know I could take a class on Data Structures, but I only need programming for scientific purposes (physics).

>>	Anonymous Thu Jun 18 20:57:41 2015 No.7338800 >>7338795 Just keep coding different projects. Also switching languages introduces you to new paradigms and makes you a better coder overall.

>>	Anonymous Thu Jun 18 21:00:04 2015 No.7338803 >>7338800 Can you recommend any sites or something? I've been thinking about some stuff, but I need some ideas.

>>	Anonymous Thu Jun 18 21:21:16 2015 No.7338841 What can I do with a mechanical engineering degree? What are some good california universities for M.E.?

>>	Anonymous Thu Jun 18 21:22:32 2015 No.7338843 >>7338841 sex machines

Anonymous Thu Jun 18 21:31:20 2015 No.7338859

>>7338803
for physics? not really.
Just write scripts for whatever you do in class.
for random CS:
http://www.reddit.com/r/dailyprogrammer/
https://projecteuler.net/
for a real challenge:
www.pythonchallenge.com
>>7338841

> What can I do with a mechanical engineering degree?
All sorts of stuff. build engines, train, planes, and automobiles, robotics, improve steel manufacturing or heat exchangers...
> What are some good california universities for M.E.?
I think the only one I applied to was CalTech

>>	Anonymous Thu Jun 18 21:48:15 2015 No.7338881 >>7338032 1/4

>>	Anonymous Thu Jun 18 21:59:45 2015 No.7338899 >>7338412 >Force isn't mass times acceleration, but rather change in momentum Billiard balls have constant mass so they are equal in this case

Anonymous Thu Jun 18 22:32:08 2015 No.7338950

>>7338339
Just worked through it m8, way too much algebra for me to post here but this is the lowdown:

- The integral is analytic, get wolfram to do it for you.
- Sub in the limits and tidy the expression up.
- Write z=(1-a) where a <<1
- Only keep first order terms in a
- End up with sum of a geometric progression.

>>	Anonymous Fri Jun 19 00:34:52 2015 No.7339149 File: 39 KB, 1158x312, Untitled.png [View same] [iqdb] [saucenao] [google] How fucked am I?

>>	Anonymous Fri Jun 19 00:35:54 2015 No.7339154 >>7339149 If I get into Chem then I'm dropping Physics.

>>	Anonymous Fri Jun 19 00:38:52 2015 No.7339157 >>7339149 >biology >chemistry If you're not fucked then you are bored for sure.

>>	Anonymous Fri Jun 19 00:47:19 2015 No.7339174 >>7339149 e z p z

>>	Anonymous Fri Jun 19 05:47:10 2015 No.7339562 I fail to understand this... if a ≡ b (7) and a ≡ b (19) why a ≡ b (7*19)

>>	Anonymous Fri Jun 19 07:54:05 2015 No.7339686 >>7339562 Just use definitions: <span class="math">7 \mid a - b /math] and <span class="math"> 19 \mid a - b[/spoiler]. Since both are prime, you can conclude the result.[/spoiler]

>>	Anonymous Fri Jun 19 07:55:58 2015 No.7339688 >>7339686 Well fuck. That's 7 \| (a - b) and 19 \| (a - b). Since both are prime, 7 * 19 \| (a - b).

>>	Anonymous Fri Jun 19 07:56:29 2015 No.7339691 >>7339562 a-b is divisible by 7 a-b is divisible by 19 7 and 19 are primes. they must both be in the prime factorization of a-b. thus 719 must divide a-b. thus a=b mod 719

>>	Anonymous Fri Jun 19 08:08:07 2015 No.7339701 >>7338339 >>7338950 f(k)=k z^k <f(k)> = \int_k^{k+1} t z^t dt = (z^k((k(z-1)+z)*log(z)-z+1))/(log^2(z)) \sum (k z^k - <f(k)>) =(-z^2+2 z+z log^2(z)-1)/((z-1)^2 log^2(z)) via Wolfram alpha. Basically you need \sum z^k and \sum k z^k formulas

>>	Anonymous Fri Jun 19 08:16:31 2015 No.7339706 >>7337778 Not britfag but physicsfag. I suggest Mechanics, Electromagnetism and some very basic quantum. Also math like basic differential calc, integrals/derivaties and differential eq.

Anonymous Fri Jun 19 08:43:40 2015 No.7339731

>>7337217
>What do you call a non-commutative field like quaternions?
Skew-fields.
>What do you call a field that has a conjugate defined like the complex field?
*-algebras
>In abstract algebra how do you define a conjugate?
Just as an involutive morphisms.

>>	Anonymous Fri Jun 19 08:53:57 2015 No.7339745 >>7339149 >Topics in Biology >C++ Level 1 >Critical Thinking and writing (kek) lol you'll be fine man lol I think you'll be fine man

>>	Anonymous Fri Jun 19 09:02:25 2015 No.7339754 >>7338339 >serre dies >fuck you very much for making me look, asshole

>>	Anonymous Fri Jun 19 10:29:28 2015 No.7339866 >>7337529 wait wut? So if I jump into a block of water thats falling at 10m/s it'll hurt as much as if it wasn't falling at all?

>>	Anonymous Fri Jun 19 13:21:47 2015 No.7340092 >>7339691 >>7339688 There's no prime factorization of "a-b" if a=b=0, rather they divide a-b.

>>	Anonymous Fri Jun 19 13:25:49 2015 No.7340102 >>7340092 Agreed. Although it doesn't really help OP to understand why 7*19 must divide a-b when 7 and 19 do.

>>	Anonymous Fri Jun 19 14:59:23 2015 No.7340253 How do you write only with symbols that a couple (x;y) is solution of a equation E ?

>>	Anonymous Fri Jun 19 16:13:13 2015 No.7340444 >>7340253 If (x,y) = (a,b) is a solution of the equation E then you write <div class="math">(x,y) = (a,b) \models E </div>

>>	Anonymous Fri Jun 19 16:23:14 2015 No.7340462 File: 92 KB, 504x420, Dolan.png [View same] [iqdb] [saucenao] [google] >>7339754 >mfw >>7339701 >not computing the limit z->1

>>	Anonymous Fri Jun 19 16:35:19 2015 No.7340477 >>7340253 You.. write down the equation E ?

>>	Anonymous Fri Jun 19 16:37:20 2015 No.7340484 Will I be able to get a job as a Mechanical Engineer from UC Riverside or UC Irvine compared to a school like UCLA, Berkley, and UC San Diego?

>>	Anonymous Fri Jun 19 17:34:31 2015 No.7340570 >>7339691 what I don't understand is why they "must" , I don't think I have seen any proofs of that

Anonymous Fri Jun 19 18:03:58 2015 No.7340639

>>7340570
>a-b is divisible by 7
This means there is a m \in \mathbb{N}[/spoiler] such that a-b=7 \cdot m[/spoiler].
>a-b is divisible by 19
This means there is a n \in \mathbb{N}[/spoiler] such that a-b=19 \cdot n[/spoiler].

Now we have that 7 \cdot m=19 \cdot n[/spoiler] which implies that 19[/spoiler] divides 7 \cdot m[/spoiler].
But 19[/spoiler] is a prime element so by the definition of a prime element 19[/spoiler] must either divide 7[/spoiler] or m[/spoiler]. Since 19[/spoiler] doesn't divide 7[/spoiler], we know that 19[/spoiler] divides m[/spoiler] which means there is a k \in \mathbb{N}[/spoiler] such that m = 19 \cdot k[/spoiler].

Therefore we get that a-b=7 \cdot m = 7 \cdot 19 \cdot k[/spoiler] which implies that 7 \cdot 19[/spoiler] divides a-b[/spoiler].

>>	Anonymous Fri Jun 19 18:20:39 2015 No.7340659 If I can prove that (1+a)^r > 1+ar for all positive a and rational r >1, how do I extend it to all reals greater than 1

>>	Anonymous Fri Jun 19 18:28:31 2015 No.7340671 for some reaosn i cannot post

Anonymous Fri Jun 19 18:46:36 2015 No.7340700

>>7340659
Let r>1[/spoiler] be any real number. The set of rational numbers greater than 1[/spoiler] is dense in the set of real numbers greater than 1[/spoiler] so there exists a sequence of rational numbers (r_n)[/spoiler] with r_n>1[/spoiler] for all n[/spoiler] such that \lim_{n \to \infty} r_n = r[/spoiler]. For those r_n[/spoiler] we have

<div class="math">(1+a)^{r_n} > 1 + a r_n</div>
Now take the limit as n goes to infinity to get
<div class="math">(1+a)^r \geq 1 + a r</div>

>>	Anonymous Fri Jun 19 18:59:11 2015 No.7340727 Why isn't momentum's unit a base unit? Could you construct an alternate unit system in which it was?

>>	Anonymous Fri Jun 19 20:07:44 2015 No.7340895 File: 113 KB, 506x159, Untitled.png [View same] [iqdb] [saucenao] [google] How do I do these type of problems, /sci/? The book doesn't make sense and the notes are unclear. Can someone do 11 for me so that I can do the rest?

>>	Anonymous Sat Jun 20 06:56:58 2015 No.7341788 why coffee make me want to sleep ?

>>	Anonymous Sat Jun 20 07:25:54 2015 No.7341805 >>7339866 You can't jump in a pool that falls with the same g as you. You would be hovering above it, ignoring air resistance and assuming the pool will remain the aame shape throughout the falling proces.

Anonymous Sat Jun 20 08:39:56 2015 No.7341875

>>7337217
>What do you call a non-commutative field like quaternions?
depends of your country and your definitions. Some people allow non-commutative fields in the cathegory of fields (like in france). If you're unsure why not use non-commutative field ?
>What do you call a field that has a conjugate defined like the complex field?
>In abstract algebra how do you define a conjugate?
both questions are linked and the answer is : it depends. In galois theory there is a definition for the conjugate of a number in an extansion of fields, look it up it's interesting.
An other definition of the conjugate which is even closer of the conjugate of a complex number is given by the real closed fields : https://en.wikipedia.org/wiki/Real_closed_field but it's only a particular case of the definition of a conuugate in galois theory.

Also the other answers of your questions by the other guys >>7337435 and >>7339731
are also valid answer, it's really depends on what you want, what definition you use etc.

>>	Anonymous Sat Jun 20 11:40:01 2015 No.7342094 >>7340570 Any prime that divides N must appear in the prime factorization of N. Otherwise the prime factorization wouldn't be unique.

Anonymous Sat Jun 20 12:52:12 2015 No.7342211

what is this volume of this person? i need in cubic feet

"they defined as a 30-year-old weighing 154 pounds, standing 5 feet 7 inches tall, and possessing a body surface area of 20 square feet."

20 square feet of surface area, 154 lbs, hwo the fuck, i need cubic feet ;/

Friend Sat Jun 20 12:59:09 2015 No.7342227

Hey everybody, my first post here, I'm really in need of some advice, opinions, experiences from you people.

My situation:
>be me, 20 y/o
>leave school as 3rd best student, had a scholarship in school
>want to work 2 years and then study pharmacy
>start university
>somehow end up in machine engineering
>get scholarship for university
>1 year and a lot of alcohol/drugs later decide to change my subject, 'cause I didn't pass any exam in 1 year of uni
>change to computer science
>stop drinking, stop smoking, still smoke pot a few times a week tho'
>1 year later (now)
>i have 3 exams at the end of the semester
>didn't pass any in the last
>am in great fear going into those exams
>feel like a failure
>don't know if i should switch subject again or push through my BA even, if i wasted this year too
>am 22 now

I talked with my father about my fear and that it may be better that I'd learn a profession for 2 years now, make a bit of cash, move out, and get a diploma AND THEN start university again for pharmacy/medicine, but he told me to push through and don't waver in my determination, 'cause that's what uni teaches, finishing something, even if it means finishing my BA not in 3, but in 4-5 years.

>>	Anonymous Sat Jun 20 13:02:13 2015 No.7342230 >>7342211 A person is roughly a cylinder. V=hr^2(pi)

Anonymous Sat Jun 20 13:21:05 2015 No.7342255

>>7342227
Go get a job, you are losing way too much money by not being in the economy right now and it's very hard to get a degree related job with an academic record like yours anyway. Also you can forget medschool, they don't want older candidates and especially not with your record.

No offense but your dad is retarded it's not the 60s anymore, getting your bachelors at 25 is a terrible idea and won't magically make your life better, it's not just that you aren't cut out for academics, it's that your life would be so much better doing something else, like earning money right now while spending your free time doing things you enjoy instead of wasting time and money on a degree that probably won't mean much to you in the end.

To be clear I'm not saying it will be impossible to get a pharma/health job after a few years of very hard work, I'm saying it won't be worth it.

>>	Anonymous Sat Jun 20 23:39:04 2015 No.7343341 File: 399 KB, 622x357, Untitled.png [View same] [iqdb] [saucenao] [google] How do I get to the answer?

>>	Anonymous Sat Jun 20 23:48:28 2015 No.7343356 >>7343341 with a calculator

>>	Anonymous Sat Jun 20 23:49:24 2015 No.7343357 >>7343341 exp(2t)+exp(-2t)+2 = 4 cosh^2(t)

Anonymous Sat Jun 20 23:52:57 2015 No.7343368

>>7342255
>, it's that your life would be so much better doing something else,

Not him, but what exactly can you get without a degree nowadays? Getting a job right away means going into a fast food place or retail. Do you really want him to work the rest of his life for 10-15 dollars an hour? I have a sister in law who has a GED only and all she does is work for 20 dollars an hour. The job market is moving forward where you'll need a bachelor's degree just for the basic jobs. Especially when minimum wage is raising to 15 dollars an hour.

>>	Anonymous Sun Jun 21 00:38:28 2015 No.7343431 >>7338795 If you're just doing work with physics, I'd recommend you don't bother with C++. Python is widely used for sciences, so I'm not sure why you'd want to jump ship.

>>	Anonymous Sun Jun 21 02:51:17 2015 No.7343601 How's UC San Diego for Business?

>>	Anonymous Sun Jun 21 02:51:23 2015 No.7343603 So I want to start learning Python, but after going to the website I'm unsure if I should get the 2.x version or the 3.x version. Advice?

Anonymous Sun Jun 21 02:59:07 2015 No.7343611

>>7343431
> Python is widely used for sciences
are you in an actual lab that uses python?
I love coding in it, but most labs use shitty outdated languages like fortran, matlab and labview.
>>7343603
doesn't look like numpy has updated to 3.x (it's been years) yet so I'd stick with 2.6/2.7 for now.
at the top of all your programs you should have
from __future__ import division

>>	Anonymous Sun Jun 21 03:04:26 2015 No.7343619 >>7341805 10m/s not 10m/s2. >>7339866 Anyway if you fell into a water falling down its equivalent to you falling into a stationary one at a slower velocity. How the fuck can you not know shit like this

>>	Anonymous Sun Jun 21 03:43:00 2015 No.7343656 Anyone know what college in california is good for business degree?

>>	Anonymous Sun Jun 21 04:13:12 2015 No.7343699 How hard would a class on Time Series be for someone who's just finished Calc III and would be taking a proof-based Linear Algebra class alongside it?

Anonymous Sun Jun 21 04:43:45 2015 No.7343731

>>7343611
Numpy, and most scientific computing packages for Python, now support 3.x. moving between 2 and 3 is also not hard once you know how to program. You should only learn 2.x if you're some scientist or something working in a lab where they use 2.x packages and you have to learn how to program in order to use those packages

>>	Anonymous Sun Jun 21 04:43:51 2015 No.7343732 >drop differential equations >Physics I >drop engineering major >pick up business classes like economics and accounting >decide to go to SDSU or UC Irvine for Business undergrad Are those colleges worth a business degree?

>>	Anonymous Sun Jun 21 04:56:27 2015 No.7343740 >>7338437 german?

>>	Anonymous Sun Jun 21 04:57:15 2015 No.7343741 >>7343601 >>7343656 >>7343732 I take it you're the same person...seeing as no one here can apparently answer your question, have you tried >>>/biz/?

>>	Anonymous Sun Jun 21 04:57:23 2015 No.7343742 >>7339149 Drop whatever has a lab. Fuck long ass labs.

Anonymous Sun Jun 21 05:12:31 2015 No.7343750

>>7343368
>Not him, but what exactly can you get without a degree nowadays?
-Trades
-Technicians and technologists which is in more demand than any professional degree
-Military

Working retail is for women and I never told you to do that. It's because people aren't willing to leave their comfort zone and more around for a job.

>>	Anonymous Sun Jun 21 05:14:09 2015 No.7343752 >>7343611 Python is very similar to matlab and your department will like you more if you can use free software. No really uses fortran anymore except to maintain legacy code.

Anonymous Sun Jun 21 05:41:05 2015 No.7343765

>>7343752
> Python is very similar to matlab
They're both interpreted turing complete languages, but similarities stop there
> your department will like you more if you can use free software.
Both schools I went to every student had access to free MATLAB.
We have DoD grants anyway so they buy us all sorts of stuff.

Anonymous Sun Jun 21 06:00:28 2015 No.7343777

>>7343765
>They're both interpreted turing complete languages, but similarities stop there
No, the syntax is very similar.

>Both schools I went to every student had access to free MATLAB.
>We have DoD grants anyway so they buy us all sorts of stuff.

I don't mean free as free beer I mean free as in freedom. If you can publish open source software you get more citations because people want to directly use your code without having to rewrite it, not everyone on the planet wants to buy a matlab license and there's other issues with publishing executatbles.

Anonymous Sun Jun 21 06:25:22 2015 No.7343799

>>7343777
> No, the syntax is very similar.
These are my top two languages. They really aren't that similar compared to other normal languages (I guess they're close if you consider stuff like Malboge or Assembly)

> end statements
> significant whitespace
> 0 vs 1 indexing
> all those nice short statements in matlab
> namespaces
> lists aren't arrays
> etc etc

>If you can publish open source software you get more citations because people want to directly use your code without having to rewrite it, not everyone on the planet wants to buy a matlab license and there's other issues with publishing executatbles.
you're shifting goalposts.
Everyone in my department uses MATLAB because toolboxes, legacy code and it's free as in beer.
Everyone in my field doesn't give a shit about poorfags outside of universities.
All the books on theory are written for MATLAB.

>>	Anonymous Sun Jun 21 13:38:02 2015 No.7344312 File: 21 KB, 732x212, Untitled.png [View same] [iqdb] [saucenao] [google] How fucked am I this semester?

>>	Anonymous Sun Jun 21 13:50:14 2015 No.7344341 >>7344312 None of these classes are difficult, rather if you got anything below an A in any of them you should feel fucked for being a fuckup.

Anonymous Sun Jun 21 14:42:38 2015 No.7344461

This might not be all that stupid, but here goes
At some point I'll be running an SN2 reaction using a tosylate and KCN. The procedure I'm following uses an excess of KCN (~2.5eq). I know the salt will get trapped, but in case any of it hydrolyses (I know silica is slightly acidic), will HCN be forced through my in 10% MeOH/DCM column? Will I have to degass my fractions before concentrating them on the benchtop? There isn't an aqueous workup btw, it's just filter through celite, then column.

TL;DR Does HCN stick to silica and if not, should I care?

Anonymous Sun Jun 21 17:53:32 2015 No.7344834
File: 108 KB, 650x712, rigid_moment.png [View same] [iqdb] [saucenao] [google]

Posted a couple of statics problems in the last thread and you guys were able to help me out. Could someone maybe show me how to do #1 and I could work the rest from there. Examples in my text are a bit different than these and I would like some clarification.

Would #1 start off with 2(300)?

>>	Anonymous Sun Jun 21 18:05:12 2015 No.7344857 File: 2.09 MB, 240x180, 1407519739396.gif [View same] [iqdb] [saucenao] [google] A capacitor and a Battery are both voltage sources right? How do voltage sources in a series work vs in paralell?

Anonymous Sun Jun 21 18:07:37 2015 No.7344861

Super dumb question regarding boolean algebra and absorption law (preface y' means y prime):

z+xy'z = z

because z + xy'z = z(1+xy') and (1+xy') = 1 so z(1) = z

correct?

I know this is basic algebra but its making me lose some confidence with my answers.

Anonymous Sun Jun 21 18:18:51 2015 No.7344885

>>7344861
z or x, not y, and z is equivalent to z.
makes sense doesn't it?
make truth tables if you want to check it
>>7344857
> A capacitor and a Battery are both voltage sources right?
sorta. capacitors and batteries have different discharge curves so they aren't usually treated as the same.
> How do voltage sources in a series work vs in paralell?
In series ideal voltage sources (like batteries) the voltages add.
In parallel they take the maximum voltage difference (in practice it's not good for batteries if you don't use the same voltage), and total charge and maximum current doubles.

>>7344834
c'mon man. if you can't handle statics you're gonna be screwed in engineering.
Just work it all out the best you can and someone will check it if you post it.

>>	Anonymous Sun Jun 21 18:48:15 2015 No.7344946 >>7344834 OP here, #1 is ma = 2(0) + 3(300) + 5(300) + (400)4sin30 ?

>>	Anonymous Sun Jun 21 21:50:32 2015 No.7345291 File: 38 KB, 711x570, foo.png [View same] [iqdb] [saucenao] [google] Is there a software like pic related out there (for Windows and GNU+Linux), and if not what libraries do I need to make it myself?

>>	Anonymous Sun Jun 21 21:59:55 2015 No.7345307 >>7345291 LaTeX, nigga

>>	Anonymous Sun Jun 21 22:03:13 2015 No.7345310 >>7345307 You’re not helping. I want a way to preview formulae quickly.

Anonymous Sun Jun 21 22:13:56 2015 No.7345323

Is a double major in Geology and Mathematics a stupid idea for someone who wants to get a PhD? (If you want to read about my situation I will post a story below, you can answer without reading it.)

I am fairly close to a math degree and fairly close to a geology degree. I like Geology a lot and want to enjoy a research heavy career in a field closely related, but I feel that I am semi-mathematically talented (emphasis on semi) and love my math classes just as much as my Geology classes. There is a slight overlap in the degree plan, so I will be able to graduate in a good amount of time (I had a lot of dual credit hours and I bust my ass taking 19 hour course loads and no summers off). Getting a double degree would also give me more time to prepare for graduate school and improve my application profile, which I think might be a big deal because I am going to a no-name state-system university. On the other hand, I could drop my Geology degree, and then graduate next year (I would be 20 y.o.).

What do you think /sci/?

>>	Anonymous Sun Jun 21 22:16:25 2015 No.7345326 >>7345310 have u tried lyx?

>>	Anonymous Sun Jun 21 22:17:16 2015 No.7345329 >>7339149 Entirely depends on how terrible your labs are, definitely doable if you work hard but don't expect to party or go home early every day.

>>	Anonymous Sun Jun 21 22:19:12 2015 No.7345333 >>7345326 WYSIWYG is not really what I’m looking for.

>>	Anonymous Sun Jun 21 22:19:26 2015 No.7345334 >>7344312 Just go to class and do the homework, and it should be ezpz... Definitely is a lot of time in class though.

>>	Anonymous Sun Jun 21 22:30:47 2015 No.7345353 >>7345310 texnic center + sumatra pdf is pretty fast... I almost have a LaTeX document opened so it's a non-issue for me. Detexify is good for single symbols. There's plenty of online LaTeX preview apps.

>>	Anonymous Mon Jun 22 12:22:42 2015 No.7346404 Hypothetically would C variance cause huge miscalculations?

>>	Anonymous Mon Jun 22 13:12:57 2015 No.7346471 Is it possible to get a undergraduate degree at a CSU then getting a Master's degree at Stanford/MIT/etc?

>>	Anonymous Mon Jun 22 13:51:52 2015 No.7346553 >>7338032 nice b9

>>	Anonymous Mon Jun 22 16:45:57 2015 No.7346872 Is getting into precalc easy? I'm trying to do CS, but im a fucking idiot, and I want to try and prepare myself this summer.

>>	Anonymous Mon Jun 22 19:36:05 2015 No.7347151 Help me understand integration by substitution. Integral (a * b) = a * Int(b) - Int(Int(b) * Der(a)) and then keep doing this until there is no x in an integral. Is this correct?

>>	Anonymous Mon Jun 22 19:37:36 2015 No.7347153 Help me understand integration by parts. Integral (a * b) = a * Int(b) - Int(Int(b) * Der(a)) and then keep doing this until there is no x in an integral. Is this correct?

>>	Anonymous Mon Jun 22 19:49:09 2015 No.7347173 >>7337944 You can't calculate those p-values analytically, you have to do it numerically

>>	Anonymous Mon Jun 22 20:22:48 2015 No.7347237 How can I create a parasitic form of life that absorbs and re-purposes the biomass and is controlled by a hive-mind? I just want to be part of the Many.

>>	Anonymous Mon Jun 22 20:25:57 2015 No.7347245 >>7347237 Take estrogen.

>>	Anonymous Mon Jun 22 20:26:32 2015 No.7347246 >>7347245 Way ahead of you. I've already got my engineering degree. What's the next step?

>>	Anonymous Mon Jun 22 20:37:06 2015 No.7347261 I can type a superscript as ^X where X is the power to which I'm raising, and most programs will recognize it. Is there a similar way to denote a subscript such as is used in chemical formulas?

>>	Anonymous Mon Jun 22 20:37:26 2015 No.7347263 >>7347153 Integration by parts is the product rule integrated, basically. (ab)' = a' b + b' a ab = int a'b + int b' a more or less...

Anonymous Mon Jun 22 20:56:57 2015 No.7347299

I was thinking of geometric series a long time ago, and how they converge if the geometric thing is between 0 and 1 (exclusive on one obv). Has there ever been an attempt to use them in functions to describe probabilities?

Say you divided 1 by a geometric series. Between 0 and 1 it would have values, and could probably be normalized. Outside of 0 and 1 (let's say for the sake of argument, the negative side is absolute valued for each partial) the value would go to 0, because 1/infinity. In my mind this creates a hard interval where you could have a finite probability, thus could be used in say, QM. I'm sure they use something, probably even more convoluted for probability intervals, but I'd like to know if anyone has any experience with this.

>>	Anonymous Mon Jun 22 21:01:07 2015 No.7347307 The only question worth asking, physics or math?

>>	Anonymous Tue Jun 23 00:39:38 2015 No.7347700 >>7347307 Business Administration with an emphasis in finance.

>>	Anonymous Tue Jun 23 01:37:35 2015 No.7347821 If I can pass Calculus III and Linear algebra, what are my chances in majoring in EE/CE/ME and Finance/Accounting?

Anonymous Tue Jun 23 03:20:17 2015 No.7348014

>>7347261
Most wrappers like LaTeX and jsMath (which 4chan uses) allow you to denote subscript by x_y where y is the subscript.
If you use LaTeX, make sure that if you have more than one character in the subscript, use brackets so the program doesn't get confused, like this x_{stuff}
<div class="math">x^{superscript} x_{subscript}</div>
If you right click (I think) that equation, it will show you what I typed to get it.

>>	Anonymous Tue Jun 23 03:21:48 2015 No.7348018 >>7348014 It's double click actually.

Anonymous Tue Jun 23 03:26:17 2015 No.7348024

Why can't you calculate n-body astrodynamics? I was playing some KSP recently and wondering why they used spheres of influence rather than multibody physics. A google search revealed that it is impossible to calculate for multiple celestial bodies, unless you use an approximation.
My question is: is there a proof or reason for this, or is it something that nobody has solved yet?

>>	Anonymous Tue Jun 23 07:40:56 2015 No.7348260 how can i image the earth like a sonagraph or mri? why is it not possible? plz also tell what equipment i would need and how much it would cost. thx!

Anonymous Tue Jun 23 07:42:07 2015 No.7348263

any1 can give me a good estimate on the volume of this person?

(or any person with their weight, height along with the volume also)

"they defined as a 30-year-old weighing 154 pounds, standing 5 feet 7 inches tall, and a body surface area of 20 square feet."

Anonymous Tue Jun 23 08:04:47 2015 No.7348279

>>7348263
>any1 can give me a good estimate on the volume of this person?

Humans are very close to the density of water, so you can get a good estimate of volume with nothing but weight. You can make minor adjustments based on body type (muscle is denser than water, fat is less dense than water), but that probably isn't necessary, depending on your application.

154 pounds / (density of water) = ~70 liters

>>	Anonymous Tue Jun 23 14:05:48 2015 No.7348827 So a body m that's accelerating at 1 mm/s^2 will give me a greater impact that a body M traveling at a constant velocity of 1000 km/s?

>>	Anonymous Tue Jun 23 14:06:48 2015 No.7348829 File: 15 KB, 500x500, e.jpg [View same] [iqdb] [saucenao] [google] >>7348827 I forgot the picture.

>>	Anonymous Tue Jun 23 14:10:13 2015 No.7348834 are there any modern theories relating time to motion in a fundamental way?

Anonymous Tue Jun 23 14:30:25 2015 No.7348860

>>7348827

The accelerating object may have more force, but force isn't what fucks you up, it's impulse.

The greater the momentum (or kinetic energy, whichever way you'd like to think about it) of an object hitting you, the worse your day is going to be.

Anonymous Tue Jun 23 15:52:05 2015 No.7349010
File: 13 KB, 220x249, 220px-Clrs3..jpg [View same] [iqdb] [saucenao] [google]

well, guys, im taking an algorithm analysis class next semester. and there will be lots of proofs.

how should i prepare myself for the proofs?

this is teh book we will be studying from

>>	Anonymous Tue Jun 23 16:07:47 2015 No.7349039 What le fug would an aleph number to the power of something be? What about an aleph number to the power of an aleph number? Also wtf are ordinals and ordinality?

>>	Anonymous Tue Jun 23 16:12:35 2015 No.7349044 >>7348827 Well you see, the trick is that when the body M crashes to the ground its velocity goes to zero very quickly, thus the acceleration.

Anonymous Tue Jun 23 16:21:24 2015 No.7349054

>>7348829
If you are falling at terminal velocity, v, and decelerate in 2 different ways:

1) Land on a crash mat
2) Hit solid concrete

Delta V in your picture is the same for both (it's just 0-v=-v). Delta T is larger for 1) and very small for 2). Thus the force and acceleration applied to you during impact are much smaller in the first case.

>>	Anonymous Tue Jun 23 17:12:40 2015 No.7349118 >>7349010 If you can't follow the trivial as fuck shit in CLRS then you should kill yourself

Anonymous Tue Jun 23 17:33:53 2015 No.7349143

>>7349118
The content of CLRS is easy (ie. selection sort, merge sort, heap sort, heaps, hash tables, efficiency, they're all basic as fuck) but the proofs are difficult if it's OP's first heavy proof course.

>>7349010
http://math.byu.edu/home/sites/default/files/u107/proofs_crash_course.pdf
This might help you.

Anonymous Tue Jun 23 18:03:48 2015 No.7349187

>>7344834
Dude just read the material, you are going to get fucked in strength of materials and structural mechanics.
List of shit you need to know to not fuck up on further courses:
>Vector and matrix operations, use of moment
>Moment of inertia
>Centres of Gravity
>Basic classical mechanics
>Virtual work
Have fun m8
#1 >>7344946
#2 Mb=2(400)+3(300+400)+5(300)+0+0
#3 Mc=3(300+400)+2(400)+4(300)cos30º+0(4)sen30+5(0)
With #3 you should figure out the rest, as I wrote everything.

Guys I feel like I have forgotten something very important about basic calculus, I'm doing diff eq all day and something doesn't feel right. Where should I systematically check if I know my shit? khan is being a waste of time.

>>	Anonymous Tue Jun 23 20:18:11 2015 No.7349405 If I want to learn a lot of math but do physics is going for a math bs, or even ms, then a physics phd a decent idea? Would a good p gre score be enough to show physics knowledge or is undergrad research and coursework necessary

>>	Anonymous Tue Jun 23 21:11:17 2015 No.7349491 I'm trying to pass an online math 101 class. I am terrible at math and I need to pass this class. What's the best way to get better at math? How can I better myself?

Anonymous Tue Jun 23 22:28:19 2015 No.7349642

>>7349405
You're better off as physics undergrad. Research as an undergrad is crucial and it's hard to get if you're not a major. As a physicist aiming for PhD, you should take,
Calc 1-3
ODE
PDE
Linear Algebra
Complex Variables (NOT Complex Analysis unless you take Real Analysis and do well in there)
Possibly statistics and a CS class or two. Then Differential Geometry and Abstract Algebra if you're going into theory instead of experiment.

>>7349491
Read the book. Read from multiple sources on the subject. Watch video lectures from multiple sources. Master the basics. Do as many problems relevant to the class as you can, try tackling every problem in your textbook. Do this little by little every day instead of cramming. If you get stuck, zoom out mentally and consider the big picture of what the problem is getting at.

>>	Anonymous Tue Jun 23 22:32:16 2015 No.7349650 >>7348260 To start, a solenoid of inner radius 13e6 meters. Cost - infinity $$$. You're fucked,.

>>	Anonymous Tue Jun 23 22:33:52 2015 No.7349655 >>7347821 Double major, 10%. Single major, 80% for engineering 90% for moneystuff

>>	Anonymous Tue Jun 23 22:35:56 2015 No.7349658 >>7347307 Physics. >>7347700 lel

>>	Anonymous Tue Jun 23 22:37:10 2015 No.7349660 Does C get used a lot in science research?

>>	Anonymous Tue Jun 23 22:38:46 2015 No.7349664 >>7349660 Yeah. I've also encountered Fortran, Matlab and Cuda being used for research.

>>	Anonymous Tue Jun 23 22:46:21 2015 No.7349673 >>7349650 inner diameter, mb but radius works too

>>	Anonymous Wed Jun 24 05:44:20 2015 No.7350175 >>7349187 help pl0x

>>	Anonymous Wed Jun 24 08:25:41 2015 No.7350300 I haven't done any maths study since high school, but I'd like to start studying it again. What textbooks would you recommend that go over year 11 and 12 for revision before I start anything else?

Anonymous Wed Jun 24 13:12:57 2015 No.7350746 [DELETED]

File: 52 KB, 500x309, neural-network.png [View same] [iqdb] [saucenao] [google]

How long would it take one to learn about artificial neural networks with no machine learning experience to have enough skills to be able to make a basic programm from scratch?

>>	Anonymous Wed Jun 24 14:04:26 2015 No.7350820 If I don't "network" with people, how fucked am I?

>>	Anonymous Wed Jun 24 14:10:41 2015 No.7350826 >>7350820 Very fucked

Anonymous Wed Jun 24 14:32:17 2015 No.7350857

Can someone help me with thsi chemiatry problem
The temperature of 5.5 g of stainless steel is increased from 20 degrees Celsius to 100 degrees Celsius what is the change in the entropy of the stainless steel? The specific heat capacityof stainless steel is 0.51 jkg

>>	Anonymous Wed Jun 24 15:43:00 2015 No.7350948 >>7346471 With a 4.0 or close

>>	Anonymous Wed Jun 24 16:18:02 2015 No.7351019 >>7350857 dS=dQ/T where Q=reversible heat Relate the heat capacity to T and Q Use this to eliminate Q from the first expression Evaluate the integral from T_0 to T_1

>>	Anonymous Wed Jun 24 16:31:54 2015 No.7351043 >>7349650 thx m8

Anonymous Wed Jun 24 19:15:35 2015 No.7351291

>>7346872
I am but a lowly Calc III student right now, but imo the hardest math class I ever had to take was pre-calc. I can't even remember exactly what pre-calc entails, but if you work at that hard enough and get those concepts in your head Calc I will be the easiest math class you've ever taken, and Calc II shouldn't be too much worse, most people really only trip up around series by that point,

>>	Anonymous Wed Jun 24 20:57:14 2015 No.7351429 >>7348829 I feel this joke would work better without the lefthand equation. It's not the Vi + at, it's the m dV/dT.

Anonymous Wed Jun 24 21:15:49 2015 No.7351468

What would be a better degree in the business world, /sci/. Math with economics or Business with an emphasis in accounting or finance?

http://web1.assist.org/web-assist/report.do?agreement=aa&reportPath=REPORT_2&reportScript=Rep2.pl&event=19&dir=1&sia=MTSJC&ria=UCSD&ia=MTSJC&oia=UCSD&aay=14-15&ay=15-16&dora=MATH-JOINT

http://web1.assist.org/web-assist/report.do?agreement=aa&reportPath=REPORT_2&reportScript=Rep2.pl&event=19&dir=1&sia=MTSJC&ria=SDSU&ia=MTSJC&oia=SDSU&aay=14-15&ay=15-16&dora=BA+ACCT

I basically just need differential equations and Calculus III and I'll be done with the Maths. Or would it be better to try to get a minor in Math with the business degree? I've never done Proofs in my life.

Anonymous Wed Jun 24 21:30:20 2015 No.7351500

>>7351468
Epsilon and delta don't mean shit in a business environment. Take some statistics, probability, differential equations, programming class or two, and make sure you know how to do simulations. After that, Econ vs Business probably wont matter but Business will be easier.

>>	Anonymous Wed Jun 24 21:59:57 2015 No.7351536 File: 370 KB, 2082x1527, tesla.jpg [View same] [iqdb] [saucenao] [google] If I waved my hand through the ?(lightning shit) what would happen?

>>	Anonymous Wed Jun 24 22:23:16 2015 No.7351573 >>7351536 You would have failed the moron test

Anonymous Wed Jun 24 23:26:29 2015 No.7351684

My stupid question:
How the fuck can bar code scanners scan codes on convex objects like cylindrical cans? The light can't be reflecting it back properly but it works every time! Also is the programming required to interpret the information as complex as I think it could be?

>>	Anonymous Thu Jun 25 00:14:41 2015 No.7351755 File: 19 KB, 629x173, momentum brackets.jpg [View same] [iqdb] [saucenao] [google] Shouldn't the second line of {L1,L2} be {r2p3,r3p1} - {r3p2,r1p3} instead of {r2p3,r3p1} + {r3p2,r1p3}

Anonymous Thu Jun 25 00:19:00 2015 No.7351760

I need to make a point by analogy in an essay and would like to refer to the scenario in human biology where a virus cell takes over the organism by tricking natural cells either through imitation or some kind of influence. Ideally, to better make my point, it would concern neural processes. Thanks

>>	Anonymous Thu Jun 25 00:34:19 2015 No.7351780 >>7351760 So what is your question?

>>	Anonymous Thu Jun 25 00:42:42 2015 No.7351791 >>7351780 Name of a virus or process that does this, please.

>>	Anonymous Thu Jun 25 01:46:15 2015 No.7351857 >>7351684 it's black or white so it's reflected good enough no matter what

Anonymous Thu Jun 25 11:22:10 2015 No.7352620
File: 68 KB, 500x384, 1427903432450.jpg [View same] [iqdb] [saucenao] [google]

Ok so I have to explain a comparative method in my paper. I dedicate a whole subsection for it but how should I name the title for this subsection?
The method name was pretty long, and the title of the original paper is pretty vague (it's not descriptive about what their method do).
Can I just do
I. Abc Xyz et al. method
?
I'm sorry for this because I have never written a paper before.

>>	Anonymous Thu Jun 25 13:21:22 2015 No.7352809 >>7352620 Please help

>>	Anonymous Thu Jun 25 14:27:53 2015 No.7352935 In a quotient rule, that has (sinx2x)/(1+x)) do I have to derive sinx2x first to get (((cosx2x)+2xsinx)((1+x)) - sinx*2x(x))/(1+x)^2 then do the rest?

>>	Anonymous Thu Jun 25 22:06:13 2015 No.7353738 File: 362 KB, 531x800, diybioworkshop02-27-10-51.jpg [View same] [iqdb] [saucenao] [google] >>7337217 Does anyone have their own home lab setup? I'm thinking of starting my own setup.

>>	Anonymous Thu Jun 25 22:56:28 2015 No.7353860 http://www.payscale.com/college-salary-report/majors-that-pay-you-back/bachelors Can I make a living as a Finance or accounting Major? How accurate are these for someone who is starting out?

Anonymous Thu Jun 25 23:36:40 2015 No.7353939
File: 97 KB, 1007x561, Untitled.png [View same] [iqdb] [saucenao] [google]

How fucked am I? I want to transfer next year, and I'm pretty close to getting all the credits that I need. However, financial aid is now suspended. I have 6k saved up from previous financial aid, but not sure if that will be enough.

Anonymous Thu Jun 25 23:37:33 2015 No.7353942
File: 80 KB, 492x559, jacob barnett.jpg [View same] [iqdb] [saucenao] [google]

is there some software that will give me a list of equivalent representations of some mathematical object?

for instance, a group is equivalent to a groupoid with a single object, and it is also equivalent to a monoid with an inverse

>>	Anonymous Thu Jun 25 23:43:17 2015 No.7353957 >>7353939 i filed a SAP appeal cause i was taking care of my grandma and she got super fucked sick and i had to drop 3 classes gave them a months worth of medical bills adding up to (without insurance) $140,000 >DENIED

>>	Anonymous Fri Jun 26 07:17:07 2015 No.7354397 How can objects moving at SOL (speed of light) always be at SOL regardless of reference frame? What about their own reference frame?

>>	Anonymous Fri Jun 26 09:41:39 2015 No.7354504 I'm 20 and pulled an all nighter. I woke up at around 16:00. I don't plan on sleeping until around 20:00 today. How much am I fucking up my brain and cognition?

>>	Anonymous Fri Jun 26 09:43:41 2015 No.7354507 >>7354397 A reference frame traveling at the speed of light is not a valid reference frame

Anonymous Fri Jun 26 16:55:50 2015 No.7355035

>>7337217
>What do you call a non-commutative field like quaternions?
A ring in which all nonzero elements are units is called a division ring or a skew field.
https://en.wikipedia.org/wiki/Division_ring
>What do you call a field that has a conjugate defined like the complex field?
These are called *-algebras or "involutive algebras".
https://en.wikipedia.org/wiki/*-algebra
>In abstract algebra how do you define a conjugate?
The general notion is of an involution, i.e., a map that yields the identity when composed with itself. One often requires this to be compatible with the algebraic structure in some way (e.g., being an antiautomorphism).

>>	Anonymous Sat Jun 27 15:45:09 2015 No.7357173 Why do I hate you all?

>>	Anonymous Sat Jun 27 17:18:36 2015 No.7357304 >>7357173 Because you have the capacity to feel.

Anonymous Sat Jun 27 17:24:13 2015 No.7357316

In Chapter 1, 1.1 Example Rudin gives a proof for the fact that for every rational p[/spoiler] such that p^{2} < 2[/spoiler] there is a rational q[/spoiler] such that q > p[/spoiler] and q^{2} < 2[/spoiler].

Analogously, for every rational p[/spoiler] such that p^{2} > 2[/spoiler] there is a rational q[/spoiler] such that q < p[/spoiler] and q^{2} > 2[/spoiler].

Rudin constructs this number q[/spoiler]:

q = p - \frac{p^{2} - 2}{p + 2} = \frac{2p + 2}{p +2}[/spoiler].

Once we have this number, it's easy to verify that this indeed is the number that we wanted. However, I don't understand HOW one comes up with this number. I vaguely remember having done this in the past, but now I just can't think of how to come up with this number. I hope it's sleep deprivation, not a retardation.

Help would be appreciated.

Anonymous Sat Jun 27 18:05:47 2015 No.7357366

I'm stuck in an exercise from MacLane's Categories for the Working Mathematician.

"For a ring R[/spoiler], describe R-\mathbf{Mod}[/spoiler] as a full subcategory of the functor category \mathbf{Ab}^R[/spoiler]."

I think I already proved that it is a subcategory myself, but I can't figure out the "full" part. Isn't it asking me to prove that any morphism (i.e. natural transformation) in \mathbf{Ab}^R[/spoiler] is pretty much a group homomorphism over the corresponding module? (that doesn't sound right to me)

Anonymous Sat Jun 27 20:00:12 2015 No.7357546

>>7357316
Let's see if I can help:

Notice that if p[/spoiler] is "close" to 2, we can think of 2-p^{2}[/spoiler] as the "error" term which will hereafter be denoted \epsilon[/spoiler]

Intuitively, once we find p[/spoiler], we want to add a little more, p+ \delta[/spoiler], so that when squared is still less than two, and only depends on p[/spoiler] and moreover that this \delta[/spoiler] is expressed in terms of p[/spoiler].

We want to arrive at Rudin's answer p+\frac{\epsilon}{p+2}[/spoiler]. But why that denominator? Well, first let's try the most obvious thing, if q=p+\epsilon[/spoiler], squaring this will obviously overshoot. So lets introduce a "regulator term" L[/spoiler] so as not to overshoot. In other words, we want to find the right term so that

(p+\frac{\epsilon}{L})^2<2[/spoiler].

So just continue forward and square everything: p^{2}+\frac{2p\epsilon}{L}+\frac{\epsilon^{2}}{L^{2}} < 2[/spoiler], subtract p^2[/spoiler] from both sides and recall we can rewrite 2-p^2=\epsilon[/spoiler] to get \frac{2p\epsilon}{L}+\frac{\epsilon^{2}}{L^{2}} < \epsilon[/spoiler]. Now with some simple algebra we can rewrite this as a quadratic equation in L[/spoiler]:

\epsilonL^{2}-2p\epsilonL-\epsilon^2 > 0[/spoiler]. Now let's be a bit sloppy and solve for this quadratic exactly (=0 instead of >0), so that we then will select the bigger "solution" and let L[/spoiler] be larger.

Using the quadratic formula and rewriting all the \epsilon[/spoiler] in terms of p[/spoiler] (I just used Mathematica), we get that everything comes out nicely and the solution is p+\sqrt{2}[/spoiler] or p-\sqrt{2}[/spoiler].

Now we obviously want the larger, and so letting L[/spoiler] be the nearest integer (for convenience--could also choose a rational whose square >2) to p+\sqrt{2}[/spoiler] we get L=p+2[/spoiler], which is Rudin's term.

Tada. Rudin is filled with this type of horseshit.

Anonymous Sat Jun 27 20:05:38 2015 No.7357550

>>7357546
Hopefully this fixes the tex:

Notice that if p[/spoiler] is "close" to 2, we can think of 2-p^{2}[/spoiler] as the "error" term which will hereafter be denoted \epsilon[/spoiler]

Intuitively, once we find p[/spoiler], we want to add a little more, p+ \delta[/spoiler], so that when squared is still less than two, and only depends on p[/spoiler] and moreover that this \delta[/spoiler] is expressed in terms of p[/spoiler].

We want to arrive at Rudin's answer p+\frac{\epsilon}{p+2}[/spoiler]. But why that denominator? Well, first let's try the most obvious thing, if q=p+\epsilon[/spoiler], squaring this will obviously overshoot. So lets introduce a "regulator term" L[/spoiler] so as not to overshoot. In other words, we want to find the right term so that

(p+\frac{\epsilon}{L})^2<2[/spoiler].

So just continue forward and square everything: p^{2}+\frac{2p \epsilon}{L}+\frac{\epsilon^{2}}{L^{2}} < 2[/spoiler], subtract p^2[/spoiler] from both sides and recall we can rewrite 2-p^2=\epsilon[/spoiler] to get \frac{2p\epsilon}{L}+\frac{\epsilon^{2}}{L^{2}} < \epsilon[/spoiler]. Now with some simple algebra we can rewrite this as a quadratic equation in L[/spoiler]:

\epsilon L^{2}-2p\epsilon L-\epsilon^2 > 0[/spoiler]. Now let's be a bit sloppy and solve for this quadratic exactly (=0 instead of >0), so that we then will select the bigger "solution" and let L[/spoiler] be larger.

Using the quadratic formula and rewriting all the \epsilon[/spoiler] in terms of p[/spoiler] (I just used Mathematica), we get that everything comes out nicely and the solution is p+\sqrt{2}[/spoiler] or p-\sqrt{2}[/spoiler].

Now we obviously want the larger, and so letting L[/spoiler] be the nearest integer (for convenience--could also choose a rational whose square >2) to p+\sqrt{2}[/spoiler] we get L=p+2[/spoiler], which is Rudin's term.

Tada. Rudin is filled with this type of horseshit.

>>	Anonymous Sun Jun 28 00:10:32 2015 No.7357918 File: 25 KB, 1151x520, halp.png [View same] [iqdb] [saucenao] [google] Can I get some help with these real quick? I can't even find the right equations in my notes. The last one I just want to clarify that I have it written correctly.

Anonymous Sun Jun 28 00:36:54 2015 No.7357971

>>7357918
for a) i typed this into wolfram alpha 'd(ln(-x^3 + 3x^2 + 105x + 1))/dx' and it gives me a root at 7, so profit is maximized at 7000 units. plug x = 7 into P(x) and that gives 6.29157 or $6,291.57.

-(4c - 20)^2/320 + 450 for the next part... don't know what they really want here

Anonymous Sun Jun 28 00:49:35 2015 No.7357997

>>7357971
Thanks m8! I can't check the problem until its deadline (about an hour) but your answer makes more sense than mine did. I did get 7 for a) and 6.29157 for b) but just didn't carry the decimal over 3 spaces. It didn't make much sense for profit to be maxed at $6.

For the other equation I replaced p with the p(c) equation and ultimately got [-(16c^2 -160c +400)/320]+450. Again, I have to wait until the deadline to see which I got right and wrong.

>>	Anonymous Sun Jun 28 00:51:30 2015 No.7358001 >>7337217 can the diameter and the circumference of a circle both be rational numbers?

>>	Anonymous Sun Jun 28 00:53:58 2015 No.7358007 >>7358001 No. Won't give a proof, but rational * irrational = irrational.

>>	Anonymous Sun Jun 28 00:54:04 2015 No.7358009 What electives and humanities did you take throughout college? Chem major here but kinda a weeb so I am taking Japanese

>>	Anonymous Sun Jun 28 01:00:23 2015 No.7358021 >>7337217 Is a topological manifold uniquely (in the topological sense) determined by all of its homotopy groups? What about a general topological space?

>>	Anonymous Sun Jun 28 01:12:36 2015 No.7358045 >>7357316 The explanation that helped me https://archive.moe/sci/thread/6303981/#6311413

>>	Anonymous Sun Jun 28 01:26:22 2015 No.7358080 How do you find the fixed point(s) of an affine transformation? Do I just find the inverse and that's it or is it something else?

>>	Anonymous Sun Jun 28 01:31:32 2015 No.7358089 >>7358007 You mean an infinite sequence of digits multiplied by a finite or repeating pattern of digits is an unknowable infinite sequence of digits!? What is this madness!!!!!

>>	Anonymous Sun Jun 28 01:34:08 2015 No.7358093 >>7358089 underage b&

>>	Anonymous Sun Jun 28 04:24:18 2015 No.7358378 >>7357550 Thank you, this really helps.

>>	Anonymous Sun Jun 28 04:28:38 2015 No.7358381 >>7358378 Oh, and thank you too, >>7358045 , this also helps.

Anonymous Sun Jun 28 04:29:56 2015 No.7358382

All this talking all time and the air fills up, up, up, until there's nothing left to breathe.

And you think you feel most everything, and we know that our hearts are just made out of strings to be pulled. So you think you've figured out everything, but we know that our minds are just made out of strings to be pulled. Strings, to be pulled.

All this talking all the time and the air fills up, up, up, until there's nothing left to breathe. Up until there's nothing left to speak. Up until the better parts of space.

Anonymous Sun Jun 28 16:56:51 2015 No.7360215

If it takes 5 bakers, 250 minutes to make 500 cookies. How many minutes would it take for 2 bakers to make the same amount of cookies?

I'm stuck on this problem. Could I have a hint? I thought that it would be a function that I'd have to create, with 250 being the y and the number of bakers being the x, and insert the 2 into the x.

>>	Anonymous Sun Jun 28 16:59:55 2015 No.7360229 >>7360215 Here's a hint. Let y = cookies per minute for 1 baker

Anonymous Sun Jun 28 17:20:13 2015 No.7360281

>>7360229
Yes, that gives me 2/5 cookies per minute for 1 baker, which means that 4/5 cookies per minute are made for 2 bakers? Or should I give the 1 baker the 2/5 cpm, which means that I'm going to find the amount of time it takes to produce 250 cookies?

I'm really stuck on how to plug in this ratio

>>	Anonymous Sun Jun 28 18:47:21 2015 No.7360466 Should I do discrete math or differential equations? i honestly dont really know what theyre about

>>	Anonymous Sun Jun 28 18:50:56 2015 No.7360475 >>7360466 Depends on what you want to do afterwards.

>>	Anonymous Sun Jun 28 18:52:53 2015 No.7360482 lol it takes 1 minute to make 2 cookies so it takes 1 guy 5 minute to make 2, or 2 guys 5 min to make 4. 4 * 125 = 500 and 5 * 125 = 625 so it takes 625 min for 2 guys to make 500

Anonymous Sun Jun 28 18:54:46 2015 No.7360488

>>7360281
>Yes, that gives me 2/5 cookies per minute for 1 baker, which means that 4/5 cookies per minute are made for 2 bakers? Or should I give the 1 baker the 2/5 cpm, which means that I'm going to find the amount of time it takes to produce 250 cookies?

Jesus, you really want to be spoonfed, don't you?

>>	Anonymous Sun Jun 28 18:56:38 2015 No.7360494 >>7360475 I need 1 more class to graduate, and afterwards im going to the navy, so its not a real concern

>>	Anonymous Sun Jun 28 18:58:01 2015 No.7360498 >>7360494 diff eq

>>	Anonymous Sun Jun 28 19:16:18 2015 No.7360533 >>7358021 No. I believe that you can think up two simple topological spaces (subsets out R) which are not homeomorphic, but are both simply connected.

Anonymous Sun Jun 28 20:32:59 2015 No.7360659

>>7358021
Homotopy groups are homotopy invariants, so they certainly can't distinguish between homotopy-equivalent spaces (which can be very much non-homeomorphic — e.g., any contractible space is homotopy-equivalent to a point).

However, by Whitehead's theorem, if X and Y are connected topological spaces that are homotopy-equivalent to CW-complexes, and f: X \to Y[/spoiler] is a continuous map that induces isomorphisms of all their homotopy groups, then f is a homotopy-equivalence.

But be careful: that theorem only applies when a *single* map induces isomorphisms on all homotopy groups all at once. It's not enough for all the homotopy groups to be abstractly isomorphism; for example, as the Wikipedia article mentions, S^2 \times \mathbf{RP}^3[/spoiler] and S^3 \times \mathbf{RP}^2[/spoiler] have the same fundamental group and the same universal cover, so they have isomorphic homotopy groups. But some of their homology groups (another homotopy invariant) are different, so they're not homotopy-equivalent.

>>	Anonymous Sun Jun 28 20:42:14 2015 No.7360672 File: 156 KB, 549x349, 1435258170630.png [View same] [iqdb] [saucenao] [google] not a question but a request, anyone have pics, links, etc to the scum bag steve math professor pictures?

Anonymous Sun Jun 28 20:48:31 2015 No.7360684

>>7337778
Just finished first year. I also didn't do Fmaths but uh i'd suggest more differential equations stuff (A-level only covers separation of variables iirc so look at homogenous etc)
also do complex numbers, they're super easy but bread and butter stuff
once you're done with that, learn matrices/matrix operations, read up on things like vector spaces etc and maybe try out some multivariable calculus

>>	Anonymous Sun Jun 28 21:30:18 2015 No.7360767 >>7360498 whats it about

>>	Anonymous Sun Jun 28 21:45:17 2015 No.7360790 Is there a way to find a relationship or the correlation between three or more variables? I know how to find one between two but have no idea how to find one between three.

Anonymous Sun Jun 28 22:04:54 2015 No.7360821

>>7360790
https://en.wikipedia.org/wiki/Multivariate_interpolation

These sound homeworkish but I have no one to ask:
1.How many sequences of n digits with "69" in them are there?
My problem is that I start overcounting.
2. How many non-decreasing sequences are there?

>>	Anonymous Mon Jun 29 00:18:33 2015 No.7361095 >>7360767 It's basically an extension of the intro calc sequence. We study nature, the laws of physics in particular, by studying the universe's differential equations.

>>	Anonymous Mon Jun 29 03:49:57 2015 No.7361403 When people recommend engineering they always assume you're going to go into computer engineering or electrical engineering or mechanical engineering, but why not civil engineering?

Anonymous Mon Jun 29 09:50:06 2015 No.7361770

>>7357366
Figured it out:

I missed the fact that the components of a natural transformation are automatically (by definition) morphisms. That fixes the issue about any natural transformation working as a group morphism, thus there's a one-to-one correspondence of arrows in R-\mathbf{Mod}[/spoiler] and \mathbf{Ab}^R[/spoiler].

>>	Anonymous Mon Jun 29 09:54:12 2015 No.7361775 >>7361403 people on /sci/ think that building codes and HVAC are boring.

Anonymous Mon Jun 29 12:10:14 2015 No.7361929

How do I make my kernel make sense?
 f: V \to V [/spoiler]

 \ker (f(a)+f(b)) [/spoiler]
or should it be
 \ker (f+f) [/spoiler]
or
do I have to define another transform
 g: V\times V \to V [/spoiler]
 (a,b) \mapsto g(a,b)=f(a)+f(b) [/spoiler]
and then
 \ker g [/spoiler]

>>	Anonymous Mon Jun 29 12:15:21 2015 No.7361934 >>7361929 In your case <span class="math">\ker (f(a)+f(b)) = undefined[/spoiler] <span class="math">\ker (f+f) = \{x \in V \| 2f(x)=0\}[/spoiler] <span class="math">\ker (g) = \{(x,y) \in V \| f(x) + f(y) = 0\}[/spoiler]

>>	Anonymous Mon Jun 29 12:16:56 2015 No.7361939 >>7361934 perfect. thank you.

Anonymous Mon Jun 29 13:15:27 2015 No.7362049

>>7361934
https://en.wikipedia.org/wiki/Kernel_(algebra)
why is the monoid homomorphism so much different?
It should be
 \ker f = \{ m \in M: f(m)= e_N [/spoiler]
where e_N [/spoiler] is the identity element of monoid N [/spoiler].

There's plenty of structures including vector spaces that are also monoids. so doesn't this give two definitions for kernels on morphisms?
(pardon any language mistakes I'm still new)

>>	Anonymous Mon Jun 29 13:37:11 2015 No.7362096 >>7360659 What I meant to ask was, are two topological manifolds <span class="math">homeomorphic[/spoiler] if they have all of the same homotopy groups? And what about general topological spaces?

>>	Anonymous Mon Jun 29 13:44:48 2015 No.7362108 >>7362096 R and R^2 ?

>>	Anonymous Mon Jun 29 13:49:41 2015 No.7362118 >>7362049 This Is the exact definition of kernels of vector spaces , groups, etc.

>>	Anonymous Mon Jun 29 13:52:37 2015 No.7362125 >>7362108 Oh right, I'm stupid. I should have clarified that I meant topological manifolds of the same dimension.

>>	Anonymous Mon Jun 29 13:55:01 2015 No.7362132 >>7362118 but not homomorphisms on monoids. the wiki says it's <span class="math"> \ker f = \{ (m, m') \in M : f(m) = f(m') \} [/spoiler]

Anonymous Mon Jun 29 14:28:33 2015 No.7362181

>>7362125
Consider the closed disk D^2. What can you say about the 2-manifolds you get from removing either a closed or open disk from the middle of D^2?

>>7362132
Oh, I see what you're saying. There is a correspondence between the monoid kernel and the, say, group kernel when your monoid has inverses. If g is in the group kernel, then (g,g^{-1}) is in the monoid kernel and if (g,h) is in the monoid kernel, then so is (gh^{-1},g^{-1}h), so gh^{-1} is in the group kernel.

>>	Anonymous Mon Jun 29 14:32:23 2015 No.7362191 >>7362181 >same homotopy groups but not homeomorphic Ah yes, I should have figured that out earlier.

Anonymous Mon Jun 29 15:12:06 2015 No.7362268
File: 54 KB, 1271x351, writer2latex.png [View same] [iqdb] [saucenao] [google]

Hey /sci/, I have a bit of trouble converting my notes from LibreOffice-Writer to Latex.
I installed the writer2latex-plugin for libreoffice, exported my document, opened it in TeXstudio, compiled, and the result is pic related.
Writer2Latex doesn't recognize the formulas, it has to leave out, so Texstudio can compile them. Help is hugely appreciated.

>>	Anonymous Mon Jun 29 16:09:45 2015 No.7362372 >>7337217 I have a stupid question about thermodynamics. I'm just starting to learn it. What is the difference between a reversible and an irreversible process?

>>	Anonymous Mon Jun 29 16:17:18 2015 No.7362383 >>7362372 A reversible process has constant entropy between states.

>>	Anonymous Mon Jun 29 16:52:18 2015 No.7362443 >>7339731 >>7355035 Finally got around to reading it: Why'd you guys say -algebra and not -ring? From what I understand the complex numbers are a *-algebra only trivially, like the rationals are a vector space.

>>	Anonymous Mon Jun 29 18:12:30 2015 No.7362604 Moron here Can someone explain ohms law? I read that the fatal current is in the miliamp range, but I work around 440 volt 200 ish ampere machines. If a hundred miliamps can kill you, why do you not burst into flames from a 120 volt socket?

Anonymous Mon Jun 29 18:19:20 2015 No.7362628

>>7362604

Well you're asking two questions. Ohm's law just says that the current that flows between any two points is equal to the voltage difference between those points divided by the electrical resistance between them, i.e. I=V/R

There isn't a set amount of current that will kill you - it depends on what path it is taking. It doesn't take much current to kill you if it is flowing through your heart.

>from a 120 volt socket

What do you mean "from" it? Like just being near it?

>>	Anonymous Mon Jun 29 18:22:03 2015 No.7362635 >>7362604 >why do you not burst into flames from a 120 volt socket? The air and the plastic has high resistance, so unless you stick a fork in the socket, it won't harm you.

>>	Anonymous Mon Jun 29 19:37:59 2015 No.7362825 To all physicist whats the general consensus on string theory? Is the whole string theory is pseudo science garbage a meme or is it actually as troubles as people make it out.

>>	Anonymous Mon Jun 29 19:44:07 2015 No.7362838 >>7362825 Nobody knows whether string theory is "true" or not. The physics community is deeply divided on this. However, no one can deny that string theory has revealed much about the union of general relativity and quantum field theory.

Anonymous Mon Jun 29 20:01:02 2015 No.7362890

i wanna see if I got the concept of action potential right

so i have a neuron, chilling at -70 mV, Na+ ions on the outside, K+ ions on the inside. Outside charge is positive, inside charge is negative due to the balance, and negative protein and whatever.

then i add an impulse, which is gonna depolarize the neuron to about -55-50mV, opening the voltage dependant Na+ channels, also creating the action potential. now that the voltage channels i open, i have a dickload of Na+ going into the cell, depolarizing it to around +40mV. this causes the Na+ channels to close, and the K+ channels to open. now the K+ is flowing in, and because the pumps close down slow, i end up hyperpolarizing the neuron. now diffusion and the Na+-K+ pump kick in bringing it all back to -70mV, and during the period of repolarization, a new action potential cant be made

anything i got wrong, or should add
not really going much into detail here i guess

>>	Anonymous Mon Jun 29 20:04:45 2015 No.7362901 I haven't studied mathematics in years and am looking to start from scratch. Any comprehensive resource suggestions, preferably ones which go into meaning as opposed to just methods of calculations.

>>	Anonymous Mon Jun 29 20:05:20 2015 No.7362904 How difficult are grad classes for undergraduates? Taking 2 next semester. Worried I'm going to wreck myself.

>>	Anonymous Mon Jun 29 20:07:03 2015 No.7362907 >>7362904 It depends on the subject and on the class, and on your own proficiency.

>>	Anonymous Mon Jun 29 20:11:03 2015 No.7362920 >>7362907 Algebra and Topology, Dummit&Foote and Munkres respectively. I've gotten As in every math class I've taken so far but this is my first algebra course and my first topology course.

Anonymous Mon Jun 29 20:13:04 2015 No.7362925

>>7362920
>first algebra course
Then why not take undergrad Intro to Abstract Algebra (or the equivalent) first?

>first topology course
On the other hand, topology doesn't really require any prerequisites (some people claim you need to do real analysis first, but that's bullshit), so go ahead.

Anonymous Mon Jun 29 20:21:11 2015 No.7362936

>>7362925
I was told it moved at a very slow pace. And many graduate classes past Topology 1 and Algebra 1 require Algebra 1 as a prerequisite. To prepare I'm working through Aluffi over this summer. And I'm quite fond of the professor teaching it the grad course.

>>	Anonymous Mon Jun 29 20:32:15 2015 No.7362946 >>7362890 No idea, but your writing style rustles my Jimmies big time.

>>	Anonymous Mon Jun 29 20:35:03 2015 No.7362952 >>7362383 >A reversible process has constant entropy between states PLS. GO. RRRRRRREEEEEEEEEEEEEEE.

>>	Anonymous Mon Jun 29 20:36:02 2015 No.7362955 >>7362952 what are you butthurt about now?

Anonymous Mon Jun 29 20:37:24 2015 No.7362959
File: 419 KB, 1600x1200, act_quickly_and_calmly_when_suffering_a_boiling_water_burn.jpg [View same] [iqdb] [saucenao] [google]

I'm making epsom salt (magnesium sulfate) deodorant and I wanted to crystalize the epsom salt into a block. I'm boiling epsom salt in water in the oven. I'm not gonna kill myself like this am I? It's not turning into like mustard case or something right? pls reply

>>	Anonymous Mon Jun 29 20:38:09 2015 No.7362960 >>7362946 its 3 am sorry

>>	Anonymous Mon Jun 29 20:44:27 2015 No.7362968 >>7362960 No anon, I'm sorry. I just got triggered by your anthropomorphisation and badass swearing. Sleep tight Eurobro.

>>	Anonymous Mon Jun 29 20:53:29 2015 No.7362981 >>7362959 Sorted.

>>	Anonymous Mon Jun 29 22:33:34 2015 No.7363160 A definite integral for a single variable function gives the area under the curve between the two given limits. Is there a similar significance to the definite integral of a vector function?

Anonymous Mon Jun 29 22:53:16 2015 No.7363182
File: 12 KB, 606x594, imanidiot.png [View same] [iqdb] [saucenao] [google]

Can somebody help me with this thing? I'm supposed to find m and x and I'm fucking retarded. It's not even for me, my younger brother asked me for help and I'm a chemfag that hasn't solved something like this in nearly two years.

Anonymous Mon Jun 29 22:58:12 2015 No.7363191

>>7363182
Triangles are similar.

\frac{x-3}{4}=frac{7}{x}[/spoiler]
(x-3)(x)=7 \cdot 4[/spoiler]
x^2-3x-28=0[/spoiler]
(x-7)(x+4)=0[/spoiler]
x=7[/spoiler]
x=m+4[/spoiler]
m=3[/spoiler]

>>	Anonymous Mon Jun 29 22:59:18 2015 No.7363196 >>7363191 First line should read: <span class="math">\frac{x-3}{4}=\frac{7}{x}[/spoiler]

>>	Anonymous Mon Jun 29 23:37:46 2015 No.7363262 >>7363191 >>7363196 Thanks, anon, I've forgotten a lot of stuff.

>>	Anonymous Mon Jun 29 23:45:34 2015 No.7363277 >>7363160 >definite integral of a vector function? Each component of the result is the definite integral of the corresponding component of the vector function.

Anonymous Mon Jun 29 23:55:52 2015 No.7363305

>>7363160
1) If f: \mathbb{R}\to \mathbb{R}[/spoiler] then \int_a^b f(x) \mathrm{d}x[/spoiler] is the area under the curve of f between a and b.

2) If f: \mathbb{R}^2\to \mathbb{R}[/spoiler] then \int_a^b \int_c^d f(x,y) \mathrm{d}y \mathrm{d}x[/spoiler] is the volume under the surface of f over the rectangle defined by points (x,y) where a<x\mathrm{R}^n[/spoiler] for some n>2, you can easily represent it in your brain as the domain being a hyperplane of something of dimension n+1 and the n+1-th dimension being the co-domain of the function, so it is harder to think about, but it works the exact same way as in the first two scenarios.

Now to answer your question.

4) If f: \mathbb{R}\to \mathbb{R}^2[/spoiler] then call f1 and f2 the canonical projections of f (basically, f1 and f2 are both functions from R to R, such that for all x, f(x)=(f1(x),f2(x)). Then \int_a^b f(x) \mathrm{d}x = (\int_a^b f_1(x) \mathrm{d}x , \int_a^b f_2(x) \mathrm{d}x)[/spoiler]. You know how to understand these two integrals using 1) since they are integrals of functions from R to R.

5) In the general case where f: \mathbb{R}^m\to \mathbb{R}^n[/spoiler], just combine the idea of 4) with that of 2-3).

>>	Anonymous Tue Jun 30 02:45:57 2015 No.7363636 File: 1.44 MB, 4208x3120, 1435593465675[1].jpg [View same] [iqdb] [saucenao] [google] What the hell is the answer to this riddle? What's the number on his hat? I am on the fence about whether the cap is 4 or 5. It may not even be any of those two.

>>	Anonymous Tue Jun 30 06:12:23 2015 No.7363916 >>7340727 If you can link it to some concept, without requiring another unit, sure. Just like they want to define Kg in terms of an amount of cesium-something atoms.

>>	Anonymous Tue Jun 30 06:22:05 2015 No.7363925 >>7363636 It's 7, you fucking retard.

>>	Anonymous Tue Jun 30 06:24:57 2015 No.7363930 >>7363636 2+5 = 7 Add the podium numbers to the side of the swimmer. Ex. To the far left: only got one podium adjacent: 8; hat 8: Next: two adjacent podiums: 3 + 2 = 5. The rest you can figure out yourself.

Anonymous Tue Jun 30 07:34:38 2015 No.7364003
File: 174 KB, 764x1024, 1430922197192.jpg [View same] [iqdb] [saucenao] [google]

>be dumb nigger
>summer is getting pretty intense
>my AC is broken
>using fans blowing on frozen saltwater solution
>have two different kinds of salt, iodine sea salt and non-iodine sea salt

Which one would cool better? Does it make a difference?

Anonymous Tue Jun 30 07:51:42 2015 No.7364016
File: 23 KB, 785x248, StupidQ.jpg [View same] [iqdb] [saucenao] [google]

I haven't taken a math course in years and this is my first online class and the reference material we're using is not the best. Anyways how do I go about finding the missing y-values. The current chater is about Quadratic Functions:Variable Rates of Change. I'm in Precalc btw.

Anonymous Tue Jun 30 14:07:21 2015 No.7364480

One of my students (I'm her MSc project advisor) keeps using emoticons in her e-mails to me. Mostly just :) and ;), but I've received the odd "Thank you :*" as well.

Should I tell her to stop doing it? I don't mind since she's cute but it is unprofessional.

>>	Anonymous Tue Jun 30 14:16:36 2015 No.7364491 >>7364480 My female professors have sent me :) and ;) fairly often in the past. It's unprofessional, but I don't think it's worth fighting.

>>	Anonymous Tue Jun 30 14:18:58 2015 No.7364494 >>7363930 Thank you.

>>	Anonymous Tue Jun 30 14:43:57 2015 No.7364528 >>7364480 > I don't mind since she's cute but it is unprofessional. Sounds like you're the unprofessional one m80 :)

>>	Anonymous Tue Jun 30 14:50:16 2015 No.7364536 >>7364480 if she's been doing it for a while, she will probably get pissed. i'd just ignore it and chalk it up to women not knowing how to be professional without using their sexual promiscuity to stay on top

Anonymous Tue Jun 30 14:58:19 2015 No.7364551

>>7364491
Well it's not like I'd be fighting for myself, since like I said I don't mind. I'm mostly wondering how to make sure she's aware that it's unprofessional and she shouldn't do it with people who might mind.

I might end up giving her a reference once she applies for positions elsewhere so I guess her unprofessionalism might reflect badly on me as well to some degree. I know people who dreaded giving their worst students any references because they didn't want to embarrass themselves, although that doesn't really apply in this case since the girl is quite competent.

>>7364528
How so?

Anonymous Tue Jun 30 20:51:00 2015 No.7365281

Hi. I was wondering, how can we remember a smell, or a taste ? How does the brain do that ?
For example, you feel like you're smelling something, but this something is not even around you. And I have a friend who once had a taste of vodka without drinking anything. This is weird, but interesting. So I wonder how it works.

Anonymous Wed Jul 1 07:30:51 2015 No.7366345
File: 24 KB, 753x234, ss (2015-07-01 at 09.29.15).png [View same] [iqdb] [saucenao] [google]

Can someone help point out how I'm fucking up/overcomplicating this? I can tell I am but I'm too tired to work out what it is I'm missing. Been going over this for the last 20min

>>	Anonymous Wed Jul 1 07:55:09 2015 No.7366362 is the permittivity of a metal infinite?

>>	Anonymous Wed Jul 1 08:07:09 2015 No.7366370 >>7366362 1

>>	Anonymous Wed Jul 1 08:34:18 2015 No.7366404 File: 36 KB, 752x459, ss (2015-07-01 at 10.34.12).png [View same] [iqdb] [saucenao] [google] >>7366345 Think I fixed it

>>	Anonymous Wed Jul 1 10:14:19 2015 No.7366539 >>7366370 fuck, I feel stupid

>>	Anonymous Wed Jul 1 12:13:28 2015 No.7366741 Is there a relation between the value of pi and the geometrical axioms? Does changing the axioms a bit yield a different value for "pi"? Or is this question nonsensical by nature?

Anonymous Wed Jul 1 13:06:29 2015 No.7366832
File: 9 KB, 349x136, eg.png [View same] [iqdb] [saucenao] [google]

How does one calculate this(and the ones in the picture) : sin 3x + cos 3x = √2 ? Is there any good online tutorial to learn this? I passed most of khan academy but I don't think I ever learned how to solve this kind of equations.

Anonymous Wed Jul 1 16:33:09 2015 No.7367147

Do you guys have problems with not giving yourself enough credit for doing well?

I just got an exam back today. I got a 96% percent which was by far the highest in the class, but my first thought was "What the fuck did you miss, you moron".

I feel like my standards have just gotten kind of out of control. I should be happy. I not only did really well, I did better than everyone else. I don't know. Just something I noticed today. Whenever I do really well, I write it off as having been really easy, and just think I should have done better, or done that work and then some. In reality, this shit isn't easy, and I worked hard to become proficient.

Anonymous Wed Jul 1 17:28:34 2015 No.7367262
File: 12 KB, 594x173, Capture.png [View same] [iqdb] [saucenao] [google]

can someone explain what happened between step 3 and step 4? the only way I can get the result is by cross multiplying the top fraction by h/h. Isn't that wrong? shouldn't I cross multiply by h/1, because (a/b) / (c/d) = (a/b) x (d/c). which means a (a/b) / (h) is (a/b) x (1/h).
division is multiplication of the inverse, and the inverse of h is 1/h.

Anonymous Wed Jul 1 17:35:31 2015 No.7367279

>>7367262
They did two steps at once.
The very top is 3-(3+h) = 3-3-h = -h
giving
<div class="math"> \frac{-h/(3+h)}{h} </div>
(a/b)/(c/d) = (a/b) *(d/c) so you'd be cross multiplying by 1/h. you kinda said both in that sentence.
which gives you step 4
<div class="math"> \frac{-h}{h(3+h)} </div>

Anonymous Wed Jul 1 17:42:34 2015 No.7367291

>>7366741
>Is there a relation between the value of pi and the geometrical axioms? Does changing the axioms a bit yield a different value for "pi"? Or is this question nonsensical by nature?
Well, how would you propose to change the axioms of geometry in a way that makes them logically inequivalent the current axioms but still internally consistent?
And even if you could do that, how would you then define the value of pi?

>inb4 muh Gödel, nothing is consistent

>>	Anonymous Wed Jul 1 17:54:44 2015 No.7367315 >>7367279 thanks, I forgot to do 3-(3+h) = 3-3-h = -h. that fixed everything.

Anonymous Wed Jul 1 18:09:48 2015 No.7367346

>>7362443
From what I learned : a ring is an abelian (additive) group together with a composition (multplication) law distributive with the addition. It has traditionally a unit for the multiplication. I never used a ring without unit, or it was called a non-unital algebra...

An algebra is kind of a generalization of a ring ; usually they're defined as a module over a ring together with a A x A -> operation... I was focused on C*-algebras on my studies, which are special Banach algebras: those are basically normed linear spaces together with a way of composing/multiplying elements. Spaces of Lebesgue-integrable functions with 1-norm and convolution product is a classic Banach algebra iirc.

Anonymous Wed Jul 1 20:23:32 2015 No.7367550

>>7362920
hello firendo. i'm currently finishing off the algebraic topology half of munkres. it is a great book. i'd say all you have to know is how to prove shit and basic definitions like what is a complex number. munkres is pretty self contained. except for the algebraic topology half when you may want to learn soome group theory before tackling it.

>>	Anonymous Wed Jul 1 23:44:13 2015 No.7367870 In my Calculus III class, there's this girl that keeps on smiling at me and shows teeth. I don't want to get her pregnant and destroy my future, so how do I avoid? I still have like 5 weeks of school left.

>>	Anonymous Wed Jul 1 23:45:37 2015 No.7367872 >>7364016 Can anyone help me? I still don't get it and whenever I use something like the average rate of change I'm still off.

Anonymous Wed Jul 1 23:49:41 2015 No.7367878

Is it possible when multiplying two polynomials that after the collection of all similar terms all vanish or have coefficients of 0, except for one?

Multiplying two monomials doesn't count, and polynomials with terms that already add to zero before the multiplication don't count.

I'm so shit at this. I can't believe Gelfand is kicking my ass.

>>	Anonymous Wed Jul 1 23:56:37 2015 No.7367888 >>7367872 Do you know what the words decreasing and concave down mean? It's not that hard.

>>	Anonymous Wed Jul 1 23:57:23 2015 No.7367889 >>7367878 Are they polynomials over a field? If so you might want to use unique factorization

>>	Anonymous Thu Jul 2 00:04:02 2015 No.7367901 >>7367888 If I knew how to do it I wouldn't be asking. But how does it being decreasing-concave down change the way I use the formula.

>>	Anonymous Thu Jul 2 00:19:42 2015 No.7367924 >>7364016 Insert the x-value into the equation and that's your y-value.

>>	Anonymous Thu Jul 2 00:21:26 2015 No.7367926 >>7367924 All I have is the table and the given information that the graph is decreasing-concave down.

>>	Anonymous Thu Jul 2 02:06:29 2015 No.7368106 >>7364016 Try y=-(x^2)+62

>>	Anonymous Thu Jul 2 04:23:21 2015 No.7368261 >>7367291 I don't know man. I just find it remarkable that by using the five geometrical axioms, you get this totally unique and irrational value. It's as if there should be a link between A and B.

>>	Anonymous Thu Jul 2 04:51:50 2015 No.7368293 >>7366832 Fuck this, finally managed to solve it using instructions from fucking Wikipedia. https://en.wikipedia.org/wiki/Nested_radical

Anonymous Thu Jul 2 14:40:57 2015 No.7368984

To any mathematics graduates is there any field of math that looks particularly promising or lucrative? I hear that machine learning and mathematical optimization are/will be big. Is there any field of pure math that looks promising too? No bully I'm just a stoopid undergrad

Anonymous Thu Jul 2 19:26:36 2015 No.7369497

Trying to not be a pleb anymore so I'm starting to refresh on algebra before moving up, but then this question arises

Evaluate 43x37
43x37 = (40 * 3)(40 * -3)
= 40^2 - 3^2
= 1600 - 9
= 1591

How did does it get to the first step?

Why would I ever want to do it that way?

Why don't I remember this from high school?

>>	Anonymous Thu Jul 2 20:12:16 2015 No.7369565 >>7369497 Anyone? Am I just stupid? Is that that "new math" thing I heard about one time?

Anonymous Thu Jul 2 20:28:14 2015 No.7369585

How the fuck do I solve (1/sqrt(x) - 3)^4 -1 = 0

My book gives no examples for solving something like this, but the section gives the options of peeling the onion, quadratic forumla and zero factor property. I suspect I have to use quadratic formula, but using the binomial theorem to expand the part in parentheses results in something crazy. I just don't see what I'm supposed to do here.

Pls help.

Anonymous Thu Jul 2 20:38:28 2015 No.7369600

During high school, I got pretty depressed and had no motivation to do schoolwork and my grades suffered. Now I'm about to enter college, and I know I'll still get depressed, but I don't want to suffer through it again. I used to really love learning. How can I get myself motivated?

Anonymous Thu Jul 2 20:40:08 2015 No.7369603

>>7369497
Unless you forgot the variables, this isn't algebra, just multiplication of two double digit numbers, a.k.a arithmetic.

https://www.khanacademy.org/math/cc-fourth-grade-math/cc-4th-mult-div-topic/cc-4th-multiplication/v/multiplying-2-digit-numbers

https://www.khanacademy.org/math/arithmetic/multiplication-division/multi_digit_multiplication/v/multiplication-5-2-digit-times-a-2-digit-number
___

>>	Anonymous Thu Jul 2 20:44:28 2015 No.7369612 >>7369603 The first line is what the book said "Evaluate 43x37" I was just wondering why did it should an overly complicated method to get the answer

Anonymous Thu Jul 2 21:01:49 2015 No.7369637

>>7369612
Hold on, I just realized that they used a different method to reach the correct answer. I've never seen it done that way either. I think it is just one of those mental math tricks where you break down numbers to make them easier to manage in your head

I understand it though and will explain (to the best of my ability) how they did this in the next post.

Anonymous Thu Jul 2 21:15:46 2015 No.7369664

>>7369612
Here's how I made sense of it:
Any value squared is the same number multiplied by itself.

Since both values have the same amount of digits, they have the same base (of 10).

43 and 37 are very close in value to each other, the difference is only 9. Subtract 3 from 43 and you get 40. That leaves an extra 3. Add 3 to 37 and you get 40. That leaves an extra -3.

You are left with 40 x 40, which is (40)^2 and that equals 1600. Then you have -3 x 3, which is -(3)^2, and that equals -9.

Take the difference of the two and you are left with 1591.

>>	Anonymous Thu Jul 2 21:17:24 2015 No.7369667 >>7369664 It still sounds retarded

Anonymous Thu Jul 2 21:25:59 2015 No.7369680

>>7369667
But does it at least make sense to you? It's retarded if you are doing the arithmetic on paper, but it is a very useful technique for when you need to do mental math. Try multiplying 37x43 in your head and see how hard it is to keep track of all the numbers (impossible at least for me). It's much easier to break it into chunks.

>>	Anonymous Thu Jul 2 21:27:14 2015 No.7369684 >>7369680 I can do it in my head fairly well already, but ya I think I get it. maybe. I doubt it'll ever come up again though

>>	Anonymous Thu Jul 2 21:35:09 2015 No.7369699 >>7369684 Props, I don't know how you do it in your head the regular way. I forget half the numbers and the ones I do remember are scrambled. But yeah, this will almost certainly never come up again.

>>	Anonymous Thu Jul 2 21:37:04 2015 No.7369701 >>7369699 I downloaded more RAM

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