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/sci/ - Science & Math

 Name Options Subject Comment Verification 4chan Pass users can bypass this verification. [Learn More] [Login] File Please read the Rules and FAQ before posting.Use TeX with $tags for inline and [eqn] tags for block equations.Right-click equations to view the source.  05/04/17 New trial board added: /bant/ - International/Random 10/04/16 New board for 4chan Pass users: /vip/ - Very Important Posts 06/20/16 New 4chan Banner Contest with a chance to win a 4chan Pass! See the contest page for details. [Hide] [Show All] #### Janitor acceptance emails will be sent out over the coming weeks Make sure to check your spam box! [Catalog] [Archive] it's been a month since i've lost my motivation to study. I'm a 5th year student (from EU, so it's the last year before university). I really love what i study, e.g. maths or IT, but i've totally lost motivation. I spend the most of the day doing nothing in front of the pc. I just wanna do nothing. I do not want to go outside instead of studying. Just want to laze around and to sleep. What can I do? I'm lost and I do not want it. No, the "just do it" thing does not work >> >>10498587 You’re probably depressed. If you have a school counsellor or some other support through your school, I’d talk to them. For me personally, I find the only thing that helps my motivation is planning. Have a set amount of things for the day, from easy to hard, and do them. Yes, just do it is vague as fuck but the encouragement to do shit helps. So plan out what is important, have a cup of coffee, and get to work. I believe you can do it if you set your mind to it. >> Yeah. You are probably depressed. That lack of motivation is not only trying to study, It seems to be around all your regular activities. With that said, you don't have a study motivational problem as a particular thing. Motivation is not something that you have as it was air, blood or neurotransmitters, motivation is a result of your desire of something. In my case I study all day, I read and do my researches. I'm preparing myself for a PhD right now. I been studying 7 years more that you and I want to study for 5 more years. if you ask me "Why" the answer is really simple. It is because I love my knowledge field. And it is not something I discover since high school, I started being interested in this field one year before I did my master degree. Beside this, I like art, music, I paint for money and I play with my mates in those lowlife bars. I have a strong desire of doing things, I love the feeling of improve myself and to discover new things. I do not like traveling for example, so it is not every new thing I like to discover. I have personal preference about what kind of activities I like to do and discover. You just need to discover yourself first. Motivation does not work on thing you do not enjoy. If I was forced to travel I will start hating my life, no mater how much I enjoy discovering "new things". That does not work that way. Motivation is a result of your desire. If you don't know and accept yourself you will feel that lack of drive and fire inside you. The only thing I can suggest to you is to find something you will love to discover, to do or research. To discover the feeling of improvement, for example I have that sensation when I make some progress playing guitar, when I finish an album or when a learnt how to build in fortnite (I am a little bit obsessed with that game). Your problem is not about motivation, is a bout finding something to burn you from the inside. >> File: rYRn49a.jpg (269 KB, 1920x1080) 269 KB JPG >>10498587 talk to someone i just started seeing a counselor to see if i can get out of the "no motivation" boat. >> >>10498587 Just have routine and have a good breakfast in the morning Wake up at the same time every morning and have a good breakfast Thank me later >> >>10500002 thanks reddit Eyesight is one of the most important things to have for survival so why can't 40% of the population see shit? Shouldn't natural selection have eliminated such a big issue? 13 replies omitted. Click here to view. >> If evolution is true, than what's the evolutionary advantage of bad eyesight >> Just get lasik bro >> >>10499130 >myopia becomes more and more prevalent Is this because of better diagnosis, or an actual increase in myopic individuals? >> >>10499807 leave >> >>10500001 fuck too slow.... File: day_22-problem.png (33 KB, 1411x170) 33 KB PNG [math] \text{For each positive integer }n\text{, write the sum }\sum_{m=1}^n 1/m\text{ in the form }p_n/q_n\text{, where } \\ p_n\text{ and }q_n\text{ are relatively prime positive integers. Determine all }n\text{ such that 5} \\ \text{does not divide }q_n\text{.}$
>>
>>10497705

looks like it's just n=1,2,3,4. bump in case it comes to me later. for n=5 it's 137/60.

i tried an inductive proof and other things along that line but i can't see how you'd show that, after finding the LCD and adding (pn/qn + 1/(n+1)), the numerator would have fewer 5's in its prime factorization than the denominator.
>>
>>10499353
That's because it's wrong. A quick program shows this not to be the case
>>
>>10499475

>>
>>10499646
Smallest counterexample is 20: the sum yields 55835135/15519504.
Here is a python. You can check by varying the bound N that there does not seem to be a largest n:

def gcd(a,b):
if a < b:
return gcd(b,a);
else:
if b == 0:
return a;
else:
return gcd(b, a%b);
N = 100;
p, q, d = 1, 1, 1;
for n in range(1, N):
p, q = (n+1)*p + q, (n+1)*q;
d = gcd(p,q);
p, q = p/d, q/d;
if q%5 != 0:
print(n+1);
>>
>>10499673
>there does not seem to be a largest n

makes sense. though, the wording of the question made it seem like we were dealing with a finite set of n where 5 | qn, rather than trying to characterize an infinite set

File: official mg curriculum.png (1.37 MB, 1140x4777)
1.37 MB PNG
Official curriculum edition.
Previous: >>10460638
>>
>>10499676
>Library Genesis
Danke, I had forgotten aboot that.
Which one of the books in the wiki would you recommend?
>>
>>10499952
The textbook.
>>
>>10499965
XD
>>
>>10499952
Series proofs are 75% "are you actually retarded lim a+b=lim a+lim b is fucking obvious", 15% nice trick, 10% Bolzano-Weierstrass and similar results. Evaluations are mostly cancer.
It's not worth it.
>>10499984
He's serious.
>>
>>10499952
Absolutely this >>10499988 if you plan to study for evaluations. If you want a broader understanding, search different sources online for more stuff. Just dig on different places. Like this weird test that nobody talks about https://en.wikipedia.org/wiki/Cauchy_condensation_test

You can survive knowing the ratio test, the root test (you only have to use it in REALLY obvious cases), the test for divergence, and knowing how to "build" series. This is, if you want to prove that the series S = A+B is convergent, proving that A and B are convergent suffices, stuff like that.

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gravity or go fast?

antimatter can only propel a spacecraft to 96 percent C and i wanna go 99 percent and wouldnt you need some kind of forcefield to protecc from micrometeors and dust/gas?
>>
>>10499864
Gravity. Just go inside a blackhole. It's way more practical than trying to reach the speed of light.
>>
>>10499983
well you would only want to travel near one instead of "in" one but black holes are far away

are you implying a man made black hole?

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How was the process of getting accepted? What GPA and stuff did you have?
>>
>>10497248
>>
>>10497855
Not any of them, but my bet is overall GPA. What's your minor/other major?
>>
>>10498234
Classical music
>>
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>>10496759
>muh major gpa
graduate school is about reading papers, doing research, figuring out which questions to ask, thinking and reasoning accurately, expressing yourself clearly in writing, and giving effective presentations.
in other words all the shit you got a 3.1 in.
just go be a code monkey
>>
>>10498670
Wtf

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Which STEM field appears most impressive / polymathic to uninitiated normies?
>>
>>10498650
That picture gives the value for the reduced Planck constant as the value for the actual Planck constant
>>
>>10499195
to be fair chem papers look like schizo writings with all the symbols and shit
>>
>>10498678
As a mathematician i wouldnt even allow the most distinguished theoretical physicist to lick the dirt off of my shoes
>>
>>10499900
And with your salary you probably couldn't pay them to do so.
>>
>>10499900
you so smrt wow, I'm sure all those lemmas and axioms come in handy in your daily life.

Basically a sapient distant hybrid between a Nemertean and a Bryozoan. It has an exoskeleton, four exoskeletal legs, warm brown blood, a lophophore with tentacles which it uses to manipulate objects, a rhynchocoel concealed proboscis with a stylet on the end which it uses to hunt, hooks on their feet which they use to climb and hunt and two pairs of red eyes on stalks. Also it has one central lung with it's breathing pore on it's back. It lives on a Super-Earth planet orbiting a k-type star in another galaxy. Their ancestors were seeded on the planet from Earth by an unknown alien race. What do you think /sci/?
>>
>>10499193
I'll have what this guys having
>>
>>10499290
Ah, each to their own!
>>
Jellyfish like creatures grow by inhaling organic molecule in jupiter's upper atmosphere. they towards lower layers as their mass increases and eventually fried/crushed by increasing heat and pressure. they reproduce before they are fried and eject their spore into updrafts to carry them up.

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How does science explain extra sensory perception?
>>
>>10498490
Hallucinations are normal and meaningless
>>
>>10499917
Get a chemistry degree and you will understand.
>>
>>10498490
Doesn't exist. Of course, anyone is free to try and provide evidence that it does and even win some hefty cash prizes for doing so.
>>
>>10498542
I have two invisible dicks, prove me wrong.
>>
>>10499957
Not him but I believe you. What now?

I suspect that I may have tetrachromacy. How would I go about getting this diagnosed? Are there any scientist interested in human tetrachromats?

I work with graphical design and have often commented on collegues work where they've only slightly adjusted hue/saturation on something and I pick up on it.

Also I've always thought I can make out a weird color beyond the violet band in rainbows.
>>
>>10498983
>>10498917
That color test is bullshit because a monitor can't render those colors.
>>
>>10498917
Top trole friend.
>>
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>>10498983
>>10499139
the actual image has only 12 colors, as stored in the actual image
I verified this with paint.net and the color picker tool, there are only 12 distinct colors in this image
it's a troll image
>>
File: color bullshit.png (177 KB, 793x793)
177 KB PNG
>>10499935
It's a troll image based on this pic
This one is of course also bullshit but lots of normalfags ate it up and now think they are tetrachromats
>>
>>10499940
wow that's stupid

ITT discuss witten’s monumental contributions to string theory, string cosmology, topological field theory, supergravity, dynamical supersymmetry breaking, holography and the AdS/CFT correspondence, kaluza-klein theories in 11D, the weinberg-witten theorem in QFT, the Weds-Zumino-Witten model, horava-witten domain walls, getting admitted to a Princeton physics PhD program with only a history major from brandeis, winning a Fields medal, being a really humble and friendly guy, playing tennis, preferring to figure out entire papers in your head without writing down any equations, his “alto” voice, and enviable forehead
>>
https://arxiv.org/pdf/hep-th/9407087.pdf
>brainlet.png
>>
>>10498756
how do I achieve this phentotype?

File: help.jpg (10 KB, 395x251)
10 KB JPG
any place where i can find the solution to problems like this?, i literally never learned this before, teacher is a dick who only teach you the theory and the basics in the class and then send you things like this without really teaching you how to do it
>>
>>10499843
Oof, you're right. In that case it is unsolvable unless you assume that part to the left of the bend is very small.
>>
>>10499863
The question isn't awful, dollars to doughnuts OP is just bad at reading/explaining.

The clue is in >>10499635
>but first i need to replace the forces to only one

This problem is one where you try to move all the forces and moments in a problem to one spot and have the moments cancel out so there is just a force.

>>10499680
had the correct equation with the wrong variable names
b should be there instead of D
>>
>>10499843
>>10499863
>>10499866
>No other sizes of this image found.
Well it's probably not a low-quality bait image if that's what you were thinking.

A key point I just noticed is that the 60Nm torque is in the opposite direction to the 300N force, but without knowing the distance of the short arm (I'd assume it's b) it's not possible to solve for the steady-state case.
>>
>>10499886
>No other sizes of this image found.
Weird Because I recognize this wrench. Maybe I can fish up my old statics textbooks.
>>
Actually if it's anchored at the centre point (the 60Nm torque would be the same around either origin, right?) then it is solvable, but then I'm not sure what b is supposed to be.

File: A1qVOTUAn4L.jpg (1.27 MB, 1604x2452)
1.27 MB JPG
Say you had 100 dollars american to gamble away quickly in vegas.
You have 10 minutes to do it once you get inside.
You have no interest in low to medium reward.
You want to walk out broke or a millionaire in 10 minutes.
>>
File: 1486354178485.jpg (104 KB, 900x1600)
104 KB JPG
>>10496841
you can't turn 100 into a million in 10 minutes with any kind of math betting system. there are mathematical systems that give you an edge, but they dont apply to any casino games.

You can gain an edge using math by playing blackjack or poker. You can also use math to profit from sports betting.

t. sports bettor
>>
File: allin1.jpg (853 KB, 1600x1200)
853 KB JPG
>>10496841
if you mean 10 minutes of actual play time, not counting the time to turn your money into chips and to walk between tables:
i'd say put it on 1 number on roulette, if you win you'll have 3,600.
then find the high limit area and put that on 1 number, if it hits you'll have 129,600.
now find even higher limit tables (e.g. caesar's spreads roulette that you can bet up to 50k on) and you have some options. one is to split your roll into 4 parts of 32,400 each, put them on 4 numbers. if any of them hit you'll have 1,166,400.
overall odds roughly 0.025*0.025*0.1 = 0.00006, which is 0.006% (it would take you an average of ~16,667 tries to win once)

if you mean 10 minutes from walking into the door (like a mob thug is on your ass and you need to come up with a million before he blows your kneecaps out), you really have no options. run to the jackpot slots and pray to hit a quick million. odds are like 1 in 10-50 million depending on the casino
>>
>>10499875
actually i noticed my calculator truncated the result. it should be 0.00625%, or 1 in 16000.
but the 2.5% and 10% odds i used were estimations anyway, so whatever.
>>
Single deck blackjack is your best odds, but 10 minutes functionally is not enough time. The absolute softest game in Blackjack has a -0.18289% house edge (so with perfect strategy you will beat that game over time), but I doubt any casino would offer that format especially at high stakes. Adding 1 (most cases more) deck, changing split rules, etc. all results in the house having an edge. IF the game is the softest possible, if they allow you to change table max every hand, the odds of you getting blackjack 14 times in a row are 0.00000294799.
>>
Anyone talking about the house edge missed the point of the thread.

File: 1553246536192.png (216 KB, 615x503)
216 KB PNG
could someone explain to me how 3D printers work?
>>
Designer here who dabbled in 3D printing. To really understand 3D printing you need to complete a specialized 4-year curriculum in 3D printing (or at best 2-year if all you want to do is tinker at home). Otherwise in the simplest possible terms, 3D printing is just layering of material to produce a 3D form. That's it.
>>
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>>10499774
>why doesn't it look sloppy
It depends on the layer height.
>>
>>10499784
>you need to complete a specialized 4-year curriculum
fuck off faggot, this guy just basically explained it in a crude picture! >>10499781
>>
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>>10499784
>>
>>10498418
make plastic hot
push it through a small nozzle
move the nozzle so it draws whatever form you want

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> applied mathematician
> Doesn't know difference between group and set

When did you realize that applied math is the Codemonkey studies of math
>>
>>10497749
What group operations? Addition mod 4? Multiplication mod 5?
>>
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>>10496761
>>10498485
So much this. "Group" has always meant a set with a binary operation since at least 1830. The denialists are either too stupid, or too dishonest, to engage with the facts on this topic. Either way, they are on the wrong side of history.
>>
>>10496761
The absolute state of pure math fags
>>
>>10498495
>even when being intentionally autistic, you're wrong
>>
>>10498485
>operations
>group
The operation can be checking answer, for instance.

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