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# /sci/ - Science & Math

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File: 125 KB, 1440x432, Krapina Neanderthal Museum 2.jpg [View same] [iqdb] [saucenao] [google] [report]

 >> Anonymous Thu Nov 2 12:51:20 2017 No.9271476 File: 107 KB, 572x772, 1506497765516.jpg [View same] [iqdb] [saucenao] [google] [report] >>9271297Is this a "black culture" exhibit?
 >> Anonymous Thu Nov 2 13:41:22 2017 No.9271541 Resposting my chem question from before.TL:DR; I was halfassing organic chemistry in the backyard to make green fire for halloween and the commonly googled "methanol+borax=green fire" bit was getting me orange flames.Is there a specific ratio of methanol to sodium tetroborate that gets green fire, or is it just a fool's errand?
 >> Anonymous Thu Nov 2 14:25:14 2017 No.9271599 I'm taking calculus using baby Rudin as textbook and we just got to the topology of $\mathbb{R}$. However, my professor defined a neighbourhood of x as a superset of an open set that contains x, while baby Rudin defines it as an open interval around x. I tried to prove a double implication between them (as I normally do when given conflicting definitions by the professor and the book) but these are not the same thing at all. For starters, a neighbourhood, as defined by Rudin, has to be an open set. Why the conflicting definitions and what book should I use for this part of the course?
 >> Anonymous Thu Nov 2 14:33:15 2017 No.9271607 >>9271599Some people do as your professor and call open intervals "open neighborhoods." They're not equivalent, but it's not hard to switch back and forth.
 >> Anonymous Thu Nov 2 14:45:37 2017 No.9271632 >>9271599It depends on how you define it. I personally use you professors definition, cause it simply makes more sense linguistically.https://proofwiki.org/w/index.php?search=neighborhood&title=Special%3ASearch&profile=advanced&fulltext=1&ns102=1
 >> Anonymous Thu Nov 2 14:46:45 2017 No.9271636
 >> Anonymous Thu Nov 2 15:12:21 2017 No.9271686 >>9271297how do I learn organic chemistry, I don't want to memorize the reactions I want to see the reasoning behind themhelp
 >> Anonymous Thu Nov 2 15:24:12 2017 No.9271708 If you have a cone, you can cover it with a sheet of paper without folding it. You can't do this for a sphere. Is there a name for this property or these types of shapes? Mathematically, it seems to me that, for this to happen, the shape must be composed of nonintersecting, infinitesimally thin, straight strips, is that right?
 >> Anonymous Thu Nov 2 15:27:10 2017 No.9271712 >>9271607>>9271632So, is any open set on a metric space an open ball?
 >> Anonymous Thu Nov 2 15:34:20 2017 No.9271733 >>9271712That or a union(any union, even uncountable) of them. https://proofwiki.org/wiki/Definition:Topology_Induced_by_Metric/Definition_2
 >> Anonymous Thu Nov 2 15:35:54 2017 No.9271738
 >> Anonymous Thu Nov 2 15:38:07 2017 No.9271741 >>9271738btw there is an obvious error in the first directionit has an intersection instead of a union
 >> Anonymous Thu Nov 2 15:40:15 2017 No.9271745 >>9271741same for the other direction
 >> Anonymous Thu Nov 2 15:40:43 2017 No.9271748 >>9271686Most of it is just thinking about basic principles. You can relate most of the reactions you learn back to the 4 basic mechanisms - substitutions and eliminations. If you think about what's nucleophilic, what's electrophilic, what's acidic/basic and how end products look you will almost never have to memorize the mechanisms.You will have to memorize reagents no matter what, though.
 >> Anonymous Thu Nov 2 15:43:13 2017 No.9271749 >>9271733Thanks! It all makes sense now.
 >> Anonymous Thu Nov 2 15:48:06 2017 No.9271753 >>9271708Those types of shapes would be developable surfaces, I guess. Cones technically aren't developable (they're orbifolds), but you also can't really fold a piece of paper into a proper cone anyway.
 >> Anonymous Thu Nov 2 15:49:46 2017 No.9271754 >>9271748thanks pal, I just needed some reassurance
 >> Anonymous Thu Nov 2 15:52:08 2017 No.9271760 >>9271708https://en.wikipedia.org/wiki/Gaussian_curvatureFor the cone it is 0.
 >> Anonymous Thu Nov 2 16:21:24 2017 No.9271800 File: 14 KB, 300x170, 1509653631990.jpg [View same] [iqdb] [saucenao] [google] [report] why is the equilibrium constant of water pic related? Why isn't it divided by the moles of H2O - [H2O]?
 >> Anonymous Thu Nov 2 16:32:08 2017 No.9271822 >>9271753>>9271760Thank you, exactly what I was looking for.
 >> Anonymous Thu Nov 2 16:38:07 2017 No.9271833 solve this equation for 2 complex numbers:z^2 - 5z + 7 + i = 0rules - you CAN'T use a calculator or the quadratic formula, you need to be more sophisticated than that.
 >> Anonymous Thu Nov 2 17:33:15 2017 No.9271911 >grocery store, vegetables>I take a plastic bag off the roll>can't open it, foils stick together>wet your fingers with saliva, can separate them betterThat's because of van der Waal's forces, right?
 >> Anonymous Thu Nov 2 17:36:33 2017 No.9271916 >>9271599>using baby Rudin as textbookRudin is a meme.
 >> Anonymous Thu Nov 2 17:44:34 2017 No.9271928 >>9271800>why is the equilibrium constant of water pic related? It's not, it's the self-ionization constant. It even says so in your image.The equilibrium constant is K>K = [H3O+][OH-] / [H2O][H2O]If you switch it around you get[H3O+][OH-] = [H2O][H2O]KWhich you define as K_w, the self-ionization constant
 >> Anonymous Thu Nov 2 18:35:02 2017 No.9272011 >>9271928I can't take pic of my textbook but it's being confusing. I've worked out what they mean, they sorta have an unofficial definition of 'equilibrium constant' that means what you're talking about, Kw.Putting aside that confusion please explain this to me>"Ka is known as the dissociation constant of the acid. An expression analogous to this can be written for Kb, the dissociation constant of a base. Note that [H2O does not appear explicitly in the denominator, because the concentration of the solvent H2O is considered to be 1 mol/litre"What does that mean? the water would be around 55 mol/l, does this make any sense to you? It's not a specific example they're speaking generally for an acid dissociating.
 >> Anonymous Thu Nov 2 20:08:17 2017 No.9272152 I posted about this in a previous thread, but I think I may have been overthinking it something fierce. Basically, I need to make a java program that has two methods. One that adds 1 to a binary string, and another that subtracts 1 from a binary string.Now, I'm completely new to binary, and programming in general.The description for the assignment methods were "increase the value of binary string b by 1."It gives some examples like "1011" becomes "1100"When it says "binary string" does it literally just mean a string that has binary in it, like "1011"? Because I've been thinking it meant to find the binary value of a normal string that has words in it, and then add one to that.Have I just been grossly overthinking this for the past week?
 >> Anonymous Thu Nov 2 20:48:36 2017 No.9272207 >>9272152Yeah it literally just means a binary string, i.e just a combination of 1's and 0's.Their meaning doesn't seem to matter in this problem, so the easiest way to do what you need is simply convert to base 10, add or subtract 1, and then convert back to binary
 >> Anonymous Thu Nov 2 21:06:50 2017 No.9272231 File: 11 KB, 580x510, binary.png [View same] [iqdb] [saucenao] [google] [report] >>9272207He has specifically forbade us from doing that.We're only allowed to use the string class in this program, and specifically no converting to int or anything other that stuff from string class.I seem to have gotten it working for the first one, but it's giving it to me backwards. Trying to figure out why it's coming up backwards.
 >> Anonymous Thu Nov 2 21:07:31 2017 No.9272234 how do i insert novel genes in a plant?
 >> Anonymous Thu Nov 2 21:53:41 2017 No.9272316 File: 9 KB, 662x76, 034a3110c55c474ed98d5f72114a03d0.png [View same] [iqdb] [saucenao] [google] [report] Lads, how do I set up the bounds for my integrals when the region is an inequality?
 >> Anonymous Thu Nov 2 22:33:06 2017 No.9272362 File: 12 KB, 569x627, binary2.png [View same] [iqdb] [saucenao] [google] [report] Okay, I think I fixed the reverse problem; I just made a little do while to switch it the right way.But now I have a different problem. It keeps returning 1000 +1 as 0011 and I can't figure out why. I keep going back over it but I can't find where it's going wrong.
 >> Anonymous Thu Nov 2 22:46:43 2017 No.9272389 File: 7 KB, 225x225, hzCGWXU.jpg [View same] [iqdb] [saucenao] [google] [report] Need a perfect set and a compact set such that their intersection is NOT compact.This is impossible, the intersection of two closed sets is closed (RIGHT???) and one of them (the compact one) must be bounded. So the intersection must be closed and bounded, methinks
 >> Anonymous Thu Nov 2 23:00:06 2017 No.9272405 >>9272362you put a b2 when it should be a b1also you could just use b1 = '1' + b1, instead of b1 += '1'
 >> Anonymous Thu Nov 2 23:03:39 2017 No.9272414 >>9272405Thanks, man. You don't know how grateful I am.You know those times where you look over something a hundred times but you just can't find that one tiny mistake that's bringing it all down? That was one of those times. Best to get another pair of fresh eyes to look at it.
 >> Anonymous Thu Nov 2 23:07:00 2017 No.9272424 File: 16 KB, 800x600, Snell's law.png [View same] [iqdb] [saucenao] [google] [report] How can I use Snell's law to find the fastest path between two points across varying terrains such as in pic related?Assuming I also know the width of each different slice of terrain.
 >> Anonymous Thu Nov 2 23:42:34 2017 No.9272504 File: 8 KB, 663x46, uniform.png [View same] [iqdb] [saucenao] [google] [report] How do I show the uniform part?
 >> Anonymous Fri Nov 3 00:17:27 2017 No.9272557 Help I'm a tard. (babby real analysis)Why doessqrt(n + 1) - sqrt(n)converge to 0? Need to prove. I'm fuckin with it algebraically but getting nowhere.
 >> Anonymous Fri Nov 3 00:21:22 2017 No.9272566 >>9272504sin(y) <= y
 >> Anonymous Fri Nov 3 00:55:20 2017 No.9272619 We have the matrix$A=\frac{1}{\sqrt{2}}\begin{bmatrix}I&B^T \\ -B&I\end{bmatrix}$ I want to find the conditions on B that would make A orthogonal and then the conditions for A being nonsingular. For A being orthogonal I found that B needs to be orthogonal (after multiplying A by its transpose I found that both $BB^T$ and $B^TB$ need to be I), but I'm unsure on proving singularity. I was thinking that it could be anything, since if we say:$\begin{bmatrix}I&B^T\\-B&I \end{bmatrix}x=0$the only solution for that would be x=0 since the only solution of Ix=0 is x=0, but I wasn't so sure.
 >> Anonymous Fri Nov 3 01:02:35 2017 No.9272630 >>9272619Your thinking is flawed on singularity. You would have $X+B^Tx$, which isn't guaranteed to have x=0 be the only solution
 >> Anonymous Fri Nov 3 02:02:35 2017 No.9272732 >>9272619[eqn]x+B^Tx=0[/eqn]From second line,[eqn]-Bx+x=0[/eqn][eqn]Bx=x[/eqn][eqn]B=I[/eqn]Plug back into the first equation,[eqn]x+x=0[/eqn][eqn]2x=0[/eqn]Only solution for this is x=0, thus A is always nonsingular.
 >> Anonymous Fri Nov 3 02:12:03 2017 No.9272739 How do i test my aptitude for math or coding? I feel like im not enjoying this stuff but maybe im just not smart enough? How can I find out if its worth it or I should go into some brainlet field like finance or something
 >> Anonymous Fri Nov 3 02:18:29 2017 No.9272743 >>9272732uhm, it's better to split x into (x1,x2) (vectors) and you get(x1,0) + (0,B^Tx2)=(0,0) ==> x1=0 , B^Tx2=0(-Bx1,0) + (0,x2)=(0,0) ==> -Bx1= , x2=0==> x=(x1,x2)=0
 >> Anonymous Fri Nov 3 02:34:33 2017 No.9272758 >>9272619The determinant of A/sqrt(2) is $\det(I) ( \det(I-(-B)I^{-1}B^T ) = \det(I+BB^T)$ which is always greater than 0 since BB^T is positive semidefinite (I assume B is a real matrix) and I is positive definite, making I+BB^T positive definite.
 >> Anonymous Fri Nov 3 02:51:52 2017 No.9272790
 >> Anonymous Fri Nov 3 03:05:08 2017 No.9272811 What's a good way to think about Fourier series to get an idea what they do/are? Prof is just deriving all the formulae without explaining anything and I've been busy with other courses so I haven't had time to take a look at the series/transforms stuff yet.
 >> Anonymous Fri Nov 3 03:11:12 2017 No.9272820 >>9272732jesus christ this so wrong. you cannot cancel out VECTORS, only invertible matrices. the implication Bx = x -> B = I is a nonsense.
 >> Anonymous Fri Nov 3 03:17:32 2017 No.9272826 >>9272743This is bullshit and can be used to show any square matrix is nonsingular, fuck off
 >> Anonymous Fri Nov 3 03:24:03 2017 No.9272830 >>9272820I don't think that's necessarily what they're doing, they're saying that if we assume x is non-zero, the only matrix B satisfying Bx=x is identity, which I'm not sure is true. I don't really know how you would show this without determinants
 >> Anonymous Fri Nov 3 03:26:48 2017 No.9272832 >>9272826yeah I noticed it after and wrote this >>9272758block multiplication always confused me
 >> Anonymous Fri Nov 3 03:28:09 2017 No.9272834 >>9272832Ah I see I thought you were the original poster of the question posting something wrong to try to bait people into correcting him. My apologies for the hostility
 >> Anonymous Fri Nov 3 03:29:26 2017 No.9272837 >>9272830If x has linearly dependent rows then B=I isn't the only solution
 >> Anonymous Fri Nov 3 03:46:00 2017 No.9272855 >>9272830Without determinants:Multiply A by [x1; x2]x1+B^Tx2=0-Bx1+x2=0x2=Bx1x1+B^TBx1=0Multiply by x1^Tx1^Tx1+x1^TB^TBx1=0Since B^TB is positive semi definite, the right term is at least zero and the right term is also non negative. The only way for it be completely zero therefore is if x1=0 and it follows x2=0I'm a dumb Amerifat though so don't take my word for it
 >> Anonymous Fri Nov 3 03:57:10 2017 No.9272862   >>9272743>>9272834It's ok.Fixed it(x1+B^Tx2 , -Bx1 + x2) = (0 , 0) <==> x1=-B^Tx2 , x2=Bx1 ==> B^TBx1=-x1 0 <= = = =-<=0 ==> x1=0 ==> x2=0
 >> Anonymous Fri Nov 3 04:07:18 2017 No.9272876 >>9272834It's ok. Fixed it.(x1+B^Tx2 , -Bx1 + x2) = (0 , 0) <==> x1=-B^Tx2 , x2=Bx1 ==> x1=-B^TBx10 <= = =-<=0 ==> =0 ==> x1=0 ==>x2=0
 >> Anonymous Fri Nov 3 04:09:09 2017 No.9272877 This >>9272130 is wrong.Where does it go wrong though?
 >> Anonymous Fri Nov 3 04:22:03 2017 No.9272886 >>9272557|sqrt(n+1)-sqrt(n)| = |n+1-n|/|sqrt(n+1)+sqrt(n)| = 1/(sqrt(n+1)+sqrt(n)) <1/(sqrt(n)+sqrt(n)) = 1/(2sqrt(n)) 1/(4epsilon^2)
 >> Anonymous Fri Nov 3 04:29:06 2017 No.9272892 >>9272886>|sqrt(n+1)-sqrt(n)| = >|n+1-n|/|sqrt(n+1)+sqrt(n)|How?I get that you can write it as (n+1)/sqrt(n+1) - n/sqrt(n) , but what after it?
 >> Anonymous Fri Nov 3 04:46:37 2017 No.9272904 >>9272892>How?(sqrt(n+1)-sqrt(n))(sqrt(n+1)+sqrt(n)) = sqrt(n+1)^2 - sqrt(n)^2
 >> Anonymous Fri Nov 3 04:48:28 2017 No.9272906 >>9272904Oh I am retarded.Thanks!
 >> Anonymous Fri Nov 3 06:37:31 2017 No.9273009 Someone FUCKING explain something to me. In a world where there are only elastic collisions, if I drop a ball, it rebounds with the same velocity that it collided at. BUT, according to the equation vf=vi+at, the ball would just bounce higher and higher every time:Let's say the ball hits the ground at 80 m/s. That means it rebounds at 80 m/s; vi=80. To find the velocity say 10 seconds after collision, that's vf=80+(9.8)*10 = 178. 178 m/s is obviously faster than 80 m/s; how did the ball reach a higher speed on its rebound? that can't happen. Furthermore, it didn't even take 10 seconds for the ball to drop in freefall to get to 80 m/s: 80=0+9.8*t, t=8.2, meaning the ball is in the air for a longer time every time it collides with the floor. can someone please tell me what the fuck I'm overlooking?
 >> Anonymous Fri Nov 3 06:38:52 2017 No.9273012 So is gravity a "force"? As in, I guess, a Newtonian force? Or is it all just curved spacetime mumbo jumbo? Is gravity actually "real"?When you're standing in a box on a train and the train is accelerating, why is that a noninertial frame of reference while accelerating 9.8 m/s$^{2}$ towards Earth in free fall isn't? Does it have to do with the object in free fall going along a geodesic line in spacetime? If it wasn't going along a geodesic, it would then be a noninertial frame right?
 >> Anonymous Fri Nov 3 06:48:11 2017 No.9273023 Years ago, I was sitting in my apartment out in the boonies of my small town. I hear a loud popping explosion out in the distance and all power goes out. I decide to step out and smoke a cigarette. I go outside and everything is illuminated in red. It must have been a full moon out because I could see relatively well at 1:30 in the morning but instead of that dim silvery/blue like normal it was as if someone was holding a red filter over a stage light. It was strange. A tweeker staying @ the apartment above mine was seeing the same thing. We came to the conclusion a transformer (or whatever those big white things on telephone polls are) exploded and this caused the moon light to turn red.So my question is what would it take to shift the wavelength of light reflecting off the moon to appear red and does an exploding electrical transformer have what it takes.
 >> Anonymous Fri Nov 3 06:53:57 2017 No.9273026 >>9273009why did you come to /qa/ to post this? i may be wildly wrong, but if you drop a ball, wouldnt vi then be 0m/s?
 >> Anonymous Fri Nov 3 06:55:44 2017 No.9273029 >>9273009>if I drop a ball, it rebounds with the same velocity that it collided atsame speed sure, but opposite velocity, if the ball had the same velocity after it collided, then it never bounced rather it's now tunneling through the earth at 80 mps
 >> Anonymous Fri Nov 3 06:57:53 2017 No.9273030 >>9273009>>9273026also velocity is direction + magnitude. when you drop a ball it bounces in the opposite direction obviously, so wouldnt one of your values have to be negative since it would be moving in the opposite direction of the other?
 >> Anonymous Fri Nov 3 07:05:18 2017 No.9273032 File: 269 KB, 1200x1200, 1509552823751.png [View same] [iqdb] [saucenao] [google] [report] >>9273009fuck you cunt
 >> Anonymous Fri Nov 3 07:05:34 2017 No.9273033   >>9273026because it's the meta board and I was talking about a post, specifically mine. talking about posts is inherently meta discussion. anyway I don't think it would be 0 because I'm looking at the motion before and after the collision as different things, and I don't see any reason it would be wrong to do that. just imagine that you suddenly have an object and it has an initial velocity of 80 m/s upwards and gravity is 9.8 m/s^2 downwards. >>9273029yeah I know that but that doesn't change my question>>9273030the velocity would naturally be negative is what I thought. maybe I wrote it wrong at first. vf=-80+9.8*10=18 hol up that works fine actually I think shit okay I guess that solves it I still don't "get" it though
 >> Anonymous Fri Nov 3 07:09:16 2017 No.9273034 >>9272316>discThat's actually a solid cylinder. I'll assume they meant $(x-1)^2 + y^2 < 1$ and $z = 0$. So this is a disc in the x-y plane centered at $(1, 0, 0)$ with radius 1, we'll call it $D$. You're asked to find the area of the part of the surface $S = (x, y, 2 \sqrt{x^2 + y^2})$ which is directly above $D$. For all x and y in D, S lies above the xy plane, so what you need is the integral $\iint \limits_{D} \,dS$. If you parametrize $D$ by $x$ and $y$, $y$ varies from $- \sqrt{1 - (x - 1)^2}$ to $\sqrt{1 - (x - 1)^2}$ as $x$ varies from 0 to 2 - these will be the limits in the integral; and $\,dS$ is just $|\partial_x{S} \times \partial_y{S}| \,dx \,dy$. Now you can compute the integral.
 >> Anonymous Fri Nov 3 07:09:23 2017 No.9273035 >>9273026because it's the meta board and I was talking about a post, specifically mine. talking about posts is inherently meta discussion. anyway I don't think it would be 0 because I'm looking at the motion before and after the collision as different things, and I don't see any reason it would be wrong to do that. just imagine that you suddenly have an object and it has an initial velocity of 80 m/s upwards and gravity is 9.8 m/s^2 downwards. >>9273029yeah I know that but that doesn't change my question>>9273030the velocity would naturally be negative is what I thought. maybe I wrote it wrong at first. vf=-80+9.8*10=18 okay so that's obviously a lot different, but still that means at 10 seconds it's going pretty slow and at some point a few moments later it will be 0 and start turning around again and falling. AND IT WILL BE FALLING FROM A HIGHER POINT THAN IT DROPPED FROM ORIGINALLY. this will occur every time, so the ball bounces higher each time.
 >> Anonymous Fri Nov 3 07:12:17 2017 No.9273037 >>9273035>IT WILL BE FALLING FROM A HIGHER POINT THAN IT DROPPED FROM ORIGINALLYyou didn't drop it, you threw it at the ground
 >> Anonymous Fri Nov 3 07:13:50 2017 No.9273038 >>9273035I will add that, for absolute certain, the original freefall took around 8 seconds. If at 10 seconds the ball has some positive velocity, it means it's bouncing higher on the first rebound than it originally fell from, and this will keep happening.
 >> Anonymous Fri Nov 3 07:14:51 2017 No.9273040 >>9273037I did fucking drop it. it started with v=0 in freefall.
 >> Anonymous Fri Nov 3 07:20:39 2017 No.9273042 >>9273035>vf=-80+9.8*10=1818 is positive, but that is positive in the direction of gravity, meaning that it is falling at 18 mps
 >> Anonymous Fri Nov 3 07:21:47 2017 No.9273043 >>9273012↑ anyone? sorry it's such newfag questions
 >> Anonymous Fri Nov 3 08:07:21 2017 No.9273075 Can someone in this thread explain to me how Wham-O Superballs work?
 >> Anonymous Fri Nov 3 08:12:06 2017 No.9273079 https://youtu.be/m0_PjJBC8gUPlease explain.
 >> Anonymous Fri Nov 3 08:22:52 2017 No.9273086 >>9272830that's PRECISELY what they're doing and that's PRECISELY what you just said. for any matrix B with an eigenvalue 1 there exists a nonzero vector x such that Bx = x. so tell me, is every matrix with eigenvalue 1 an identity matrix ?
 >> Anonymous Fri Nov 3 08:27:20 2017 No.9273090 >>9273086>so tell me, is every matrix with eigenvalue 1 an identity matrix ?Consider $\begin{bmatrix} 1 & 0 \\ 0 & 0 \end{bmatrix}$
 >> Anonymous Fri Nov 3 09:04:34 2017 No.9273126 >>9272739Aptitude and enjoyment are different. If you don't enjoy it, do something else.
 >> Anonymous Fri Nov 3 09:11:27 2017 No.9273142 what would happen if all the artificial orbiting satellites deorbit.
 >> Anonymous Fri Nov 3 11:56:29 2017 No.9273388 What does a capacitor do? I'm studying circuitry and I really don't see what they perform in a circuit.
 >> Anonymous Fri Nov 3 12:06:16 2017 No.9273403 >>9273388From what I remember in my class, they store charge for electrical energy. I think it creates a voltage drop between their two plates so that one of the plates is more positively charged and the other is more negatively charged, creating a way to store electrical potential energy
 >> Anonymous Fri Nov 3 12:07:38 2017 No.9273405 >>9273142Deorbiting away from Earth: nothing specialDeorbiting towards Earth: burn in the atmosphere and look like a shooting star.
 >> Anonymous Fri Nov 3 12:11:07 2017 No.9273411 2+2 = 4 and minus one equals three.Does that make it quick maths?
 >> Anonymous Fri Nov 3 12:12:11 2017 No.9273414 >>9273411Only if trees are being smoked.
 >> Anonymous Fri Nov 3 12:13:01 2017 No.9273415 >>9273012↑ anyone?
 >> Anonymous Fri Nov 3 12:17:10 2017 No.9273422 >>9271297how did you get the idea to use a picture of a croatian museum as the thread pic?
 >> Anonymous Fri Nov 3 12:43:24 2017 No.9273482 >>9273414I believe I saw your lady in a park, very unsatisfactory to look at.
 >> Anonymous Fri Nov 3 12:55:33 2017 No.9273516 File: 67 KB, 791x388, simple_neural_network_header[1].jpg [View same] [iqdb] [saucenao] [google] [report] Nueral Networks and Machine Learning fascinate me, but I'm too brainlet to understand them.What is a good "track" for someone who wants to possibly get into machine learning? I know basic java, python, and C as far as technical skills and am currently on Calculus 2 as far as math. Book recommendations to eventually get me there?
 >> Anonymous Fri Nov 3 14:34:59 2017 No.9273697 >>9273516this
 >> Anonymous Fri Nov 3 14:45:34 2017 No.9273712 >>9271297Front to back:>/sci/>/his/>/g/>/lit/>/int/>/pol/
 >> Anonymous Fri Nov 3 15:06:46 2017 No.9273754 >>92735163blue1brown is doing a series on neural networksyou will need linear algebra and probably (multivariable) calculus soonif you can't into linear algebra then you're not entirely fucked, most CS people have no idea what they're actually doing, they just learn to use their libraries and import whenever they encounter something they can't figure out
 >> Anonymous Fri Nov 3 15:35:06 2017 No.9273790 >>9273388If you are talking more about application wise they are often used to reduce noise in a circuit and smooth waveforms. At high and low frequencies capacitors behave differently and this allows either ac or dc current to pass based on circuit configuration. In datasheets you will often see these added in a componet's circuit as a safety measure to help prevent a chip or other device from being fried by voltage spikes (normally due to switching). Sometimes these can be left out but other times they cannot.
 >> Anonymous Fri Nov 3 16:51:10 2017 No.9273875 Is Islam a science?Did science come from Islam?
 >> Anonymous Fri Nov 3 16:52:22 2017 No.9273877 >>9273754I mean, I'm willing to learn whatever math would be make better at the subject, I enjoy it.
 >> Anonymous Fri Nov 3 18:58:24 2017 No.9274044 File: 4 KB, 170x93, equal.png [View same] [iqdb] [saucenao] [google] [report] Does this sign mean "approx equal" or something?
 >> Anonymous Fri Nov 3 20:34:20 2017 No.9274193 can someone just give me a straight answer if there's no air resistance or literally anything else except gravity, will a perfectly elastic ball bounce just keep bouncing forever? like it bounces, and returns to its same height. all that happens when it collides with the ground is the velocity is reversed right? doesn't that necessarily mean it takes the exact same amount of time to get right back to the drop point as it did to drop from it?
 >> Anonymous Fri Nov 3 20:46:08 2017 No.9274210 File: 5 KB, 286x124, foof.png [View same] [iqdb] [saucenao] [google] [report] how do you solve pic related when n goes to infinity
 >> Anonymous Fri Nov 3 20:47:45 2017 No.9274214 >>9273012Free fall is a noninertial frame of reference. If you are the ball that is free falling toward the earth, you're in a nonintertial reference frame, just like if you're in an accelerating train.The definition of a noninertial reference frame is a frame of reference that is not accelerating. You can attach a reference frame (coordinate system, basically) to anything and do physics within it. You can even let it move at a constant velocity and do physics within it and everything's still good. But if your reference frame accelerates then the typical Newtonian's laws of physics break down. And that's not because of some crazy stuff with General Relativity. Newton knew his laws broke down in accelerating reference frames, we just have to do some extra modifications to fix the physics.Honestly, I recommend to just think of gravity as a force and don't worry about any of this General Relativity mumbo jumbo unless you ever go to grad school and study it.Study how to deal with noninertial reference frames. That's in introductory physics books and is mind boggling enough itself.
 >> Anonymous Fri Nov 3 20:49:29 2017 No.9274217 >>9274214sorry, the definition of an INERTIAL frame of reference is one that is not accelerating. Noninertial reference frames are accelerating frames.
 >> Anonymous Fri Nov 3 21:15:23 2017 No.9274288 >>9274193Yeah, assuming that this happens in an ideal environment with zero air resistance and the collision with the ground is perfectly elastic the ball would continue bouncing and return to the starting position. This is not possible even when performed in a vacuum though because the collision with the ground will never be perfectly elastic and some kinetic energy will be converted into internal energy. A decrease in kinetic energy causes a decrease in speed and the ball can no longer bounce back to the same height.
 >> Anonymous Fri Nov 3 21:16:32 2017 No.9274293 File: 502 KB, 564x644, 4b0.png [View same] [iqdb] [saucenao] [google] [report] >Asked my professor about jobs in his field>He said there's a research project at the university that I could get involved in>Tells me to email him about it>I email him>No response after 2 weeks>I email him again to check he got my previous email>Still no response after another week>My friend emailed him yesterday and got a reply within an hourIs he ignoring me?
 >> Anonymous Fri Nov 3 21:40:20 2017 No.9274348 Why does /sci/ hates computer science?I know the engineer meme, but not the compsci one
 >> Anonymous Fri Nov 3 23:16:16 2017 No.9274494 >>9274288ok thanks, I was really confused for a while nothing seems to make intuitive sense I hate this fucking class
 >> Anonymous Fri Nov 3 23:56:56 2017 No.9274542 File: 101 KB, 1122x584, Screenshot from 2017-11-03 23.53.49.png [View same] [iqdb] [saucenao] [google] [report] What is this book trying to say here?>The sets A and B have the same cardinality if and only if there is a one-to-one correspondencefrom A to B. When A and B have the same cardinality, we write |A| = |B|.This is not true, and they even say it is not true in the next definition. It needs to be a bijection and not just one-to-one, right? What point are they trying to make and why are they using a definition which is not true? Am I completely misunderstanding what is being said here?
 >> Anonymous Fri Nov 3 23:58:57 2017 No.9274545 >>9274542>one to one correspondence is the same as one to one function
 >> Anonymous Sat Nov 4 00:02:55 2017 No.9274548 >>9274545oh lol. Is a one-to-one correspondence a bijection?
 >> Anonymous Sat Nov 4 00:03:57 2017 No.9274549 >>9274548>In mathematics, a bijection, bijective function or one-to-one correspondence is a function between the elements of two sets, where each element of one set is paired with exactly one element of the other set, and each element of the other set is paired with exactly one element of the first set.
 >> Anonymous Sat Nov 4 00:10:09 2017 No.9274553 >>9274549Yeah, the word "correspondence" is kind of a giveaway. I guess I've been glazing over that word as I'm reading. Whoops
 >> Anonymous Sat Nov 4 01:01:49 2017 No.9274611 >>9273009>>9273035Define upward as your positive direction. So, acceleration due to gravity acts in the downward direction and is -9.81. You drop the ball. Let's say it hits the ground after 10s. The velocity when it hits is vf = 0 + -9.81*10 = -98.1 m/s. Negative because it's going in the negative downard direction.Elastic collision, so vi = 98.1 m/s in the positive upward direction now.after 10s, vf = 98.1 + -9.81*10 = 98.1 -98.1 = 0.so after 10s, the ball is back up to where you initially dropped it from and has a velocity of 0. Then you repeat forever and the ball keeps bouncing up and down forever. Of course in the real world that can't happen because there are no perfectly elastic collisions, you lose some energy due to heat and all that, and eventually even the bounciest of balls will stop someday.
 >> Anonymous Sat Nov 4 01:11:48 2017 No.9274629 >>9274542One to one correspondence means one to one and onto. It doesn't make much sense, but that's what it usually means.
 >> Anonymous Sat Nov 4 01:24:38 2017 No.9274641 >>9274210It's probably a riemannian sum and you solve it using the fundamental theorem of calculus.
 >> Anonymous Sat Nov 4 02:17:54 2017 No.9274703 File: 410 KB, 560x600, 1507254231677.png [View same] [iqdb] [saucenao] [google] [report] >>9274210>goes to infinityNo such thing.
 >> Anonymous Sat Nov 4 02:21:26 2017 No.9274710 >>9274629>one to one and ontoThe proper words are "injective" and "surjective".
 >> Anonymous Sat Nov 4 02:25:25 2017 No.9274716 >>9274710the proper words are whichever the fuck I deem proper
 >> Anonymous Sat Nov 4 02:27:38 2017 No.9274722 >>9274716Seriously now, enough.
 >> Anonymous Sat Nov 4 02:29:57 2017 No.9274724 >>9274722Enough of what?
 >> Anonymous Sat Nov 4 02:58:20 2017 No.9274751 Can an Atom of (for example) Carbon which atomic number is 6, have less than 6 neutrons?
 >> Anonymous Sat Nov 4 03:05:28 2017 No.9274757 >>9274751Helium-3 is stable, and technically protium fulfills that criterion. But generally the heavier an atom is, the more neutrons are needed for it to be stable.
 >> Anonymous Sat Nov 4 03:10:00 2017 No.9274760 >>9274757Thanks a lot
 >> Anonymous Sat Nov 4 03:25:50 2017 No.9274772 File: 13 KB, 613x533, 1354398921835.jpg [View same] [iqdb] [saucenao] [google] [report] In physics when I have an equation,X(t),the first derivative dx/dt,give me the velocity,the second derivative is acceleration. Now my question is: wnhen i write the dv/dt ad then instead of the (v) I put dx/dt. this comes out as d^2x/(dt)^2What does this mean? the "d^2x/(dt)^2" is it just a formality that this is a second derivative of X(t) function?
 >> Anonymous Sat Nov 4 03:31:00 2017 No.9274778 >>9274772Yeah, the second derivative of X(t) (position) is dv/dt or acceleration.
 >> Anonymous Sat Nov 4 03:47:39 2017 No.9274782 >>9274778Adding to this, i'm guessing your question is about Leibniz notation. This is just a general form of expressing derivatives. In physics quantities that are used often or represent a new concept are often renamed. For example, a Newton (N) = kg*m/s^2. Same with the derivatives of X(t). There is also a third derivative of X(t) called a jerk. This would be da/dt or the second derivative of v(t).
 >> Anonymous Sat Nov 4 04:19:09 2017 No.9274797 >>9274782>>9274778Many thanks.
 >> Anonymous Sat Nov 4 07:53:36 2017 No.9274967 >>9274044From wikipedia>≐ (U+2250, LaTeX \doteq), which can also be used to represent the approach of a variable to a limitI have never seen it used before though
 >> Anonymous Sat Nov 4 07:54:38 2017 No.9274969 >>9274348What is the engineering one?
 >> Anonymous Sat Nov 4 08:24:27 2017 No.9274993 >>9274293why would you ask a question and then answer it yourself ?
 >> Anonymous Sat Nov 4 10:04:29 2017 No.9275101 what is the technical term for square rooting (i.e. Multiplication, Addition, Subtraction, Division, Exponentiation...)? Radicalization? Radicization?
 >> Anonymous Sat Nov 4 10:12:45 2017 No.9275113 >>9271297How do you teleport.
 >> Anonymous Sat Nov 4 10:13:26 2017 No.9275119 >>9275101also, why is it that the square root of a negative number does not belong to the set of real numbers if I can square a negative number to reach the radicand?
 >> Anonymous Sat Nov 4 10:19:35 2017 No.9275126 >>9275119Positive times positive is positiveNegative times negative is positiveIt's always positive, you can't get a negative by multiplying a number by itself.>square a negative number to reach the radicand?What does that even mean?
 >> Anonymous Sat Nov 4 10:26:40 2017 No.9275137 >>9275126why are my calculators telling me -3^2 is -9 then? I'm not trying to be obstinate, I see what you're saying I just don't understand why it's evaluating to -9.>What does that even mean?I'm not very familiar with the terminology, forgive me.if I square 3, I get 9. 9 would then be the radicand of sqrt(9), which yields 3
 >> Anonymous Sat Nov 4 10:29:54 2017 No.9275148 >>9275137Obviously it's parsing it as -[3^2], not [-3]^2
 >> Anonymous Sat Nov 4 10:31:33 2017 No.9275153 >>9275148That's what I figured. And it's retarded that all 3 calculators would parse it that way.
 >> Anonymous Sat Nov 4 11:07:06 2017 No.9275208 >>9275137Sorry, I still don't really understand what you are saying.>>9275153All calculators/computers/whatever do that.Powers before multiplication
 >> Anonymous Sat Nov 4 11:43:19 2017 No.9275258 I'm second year engineering student and we've started doing signal analysis this semester.I'm heart I want to do electronics but this shit seems like obvious to me, could I in reality be a telecommunication engineer?How good is it compared to electronic engineering?
 >> Anonymous Sat Nov 4 12:01:44 2017 No.9275280 Lets say you have 10 people, 6 male 4 female, and you want to do a group of 5 people with at least 2 males, how many ways are there to do this?Why isnt it 6c2 * 8c3?
 >> Anonymous Sat Nov 4 12:08:35 2017 No.9275285 >>9275280You have 4 cases in each you choose from the group of guys and then from the group of girls, Where did you get that 8 from? "At least 2 males"Case 1. There are 2 males (and thus 3 females)6C2*4C3Case 2 There are 3 males (and thus 2 females)6C3*4C2Case 3 There are 4 males (and thus 1 female)6C4*4C1Case 4 There are 5 males (and thus 0 females)6C5*4C0Then you add up all 4 cases.
 >> Anonymous Sat Nov 4 12:13:45 2017 No.9275292
 >> Anonymous Sat Nov 4 12:21:05 2017 No.9275302 >>92752856c2 to get the number of needed males into the group, then out of the 10-2=8 people left to chose, you pick 3 to get to the 5 people.And just to be clear: i understand why you can solve it the way you did, i dont get why 6c2*8c3 doesnt work
 >> Anonymous Sat Nov 4 12:40:56 2017 No.9275326 >>9275302You might be overcounting some casesGuy A was chosen in 6C2, then Guy B was chosen in 8C2In another thingGuy B was chosen in 6C2, then Guy A was chosen in 8C2
 >> Anonymous Sat Nov 4 12:43:10 2017 No.9275329 https://en.wikipedia.org/wiki/Rule_of_productIt doesn't work because the same man might be in Set 1 as well as Set 2 which means you count (John , John).
 >> Anonymous Sat Nov 4 12:44:13 2017 No.9275331
 >> Anonymous Sat Nov 4 12:45:52 2017 No.9275332 >>9271297What is the square root of pi?
 >> Anonymous Sat Nov 4 12:47:09 2017 No.9275334 >>9275329wait nvm, you can't have (John,John), my badbut you can have what this guy said >>9275326(John,Bill) , (Bill,John).
 >> Anonymous Sat Nov 4 12:50:42 2017 No.9275338 >>9275332It's $\int_{-\infty}^{+\infty} e^{-t^2} dt$ .
 >> Anonymous Sat Nov 4 12:52:15 2017 No.9275341 >>9275338FANCY!
 >> Anonymous Sat Nov 4 13:05:25 2017 No.9275365 >>9275153It's not retarded. There's a good reason that every device does it.
 >> Anonymous Sat Nov 4 13:42:50 2017 No.9275407 >>9275326>>9275334>Guy A was chosen in 6C2, then Guy B was chosen in 8C2In another thingGuy B was chosen in 6C2, then Guy A was chosen in 8C2Thats why im only chosing people from 8 people on the second one, 6c2 is 2 males from all males, 8c3 is 3 people from the 8 people that are left after picking 2 males
 >> Anonymous Sat Nov 4 13:54:48 2017 No.9275414 File: 7 KB, 704x57, Untitled.png [View same] [iqdb] [saucenao] [google] [report] would evaluating this integral regularly i.e. (2x^2 + y^2) from its upper to lower bound be the same if I use the parameters for the curve? Path Integrals are confusing me a lot.
 >> Anonymous Sat Nov 4 14:15:12 2017 No.9275429 >>9272811https://www.youtube.com/watch?v=kP02nBNtjrUjust watch a ton of youtube videos about it, this ones ok
 >> Anonymous Sat Nov 4 15:12:47 2017 No.9275504 >>9275414>be the sameYou're basically asking if you can apply Stokes' theorem (a generalized version of the fundamental theorem of calculus). This is actually a rather sophisticated question and the answer is that yes you can, in this case. But there are situations where you can't do that. For example, the integral of $d\theta = \frac{-y\,dx + x\,dy}{x^2+y^2}$ around the unit circle gives $2 \pi$ and not 0 even though the starting and ending points are the same (roughly speaking, this is because $d \theta$ isn't defined at the origin, which happens to be in the region enclosed by the circle). You should probably just integrate parametrically at this point (as it always gives the correct answer) and wait until you learn Stokes' theorem before you apply it.
 >> Anonymous Sat Nov 4 15:39:33 2017 No.9275536 if I can prove some field is conservative, does that mean that the path integral is also independent of path? >>9275504I ended up doing this with a lot of the problems and it turns out that the integrals didn't always come out to being equal.
 >> Anonymous Sat Nov 4 15:50:28 2017 No.9275551 >>9275536Then Stokes' theorem wasn't applicable in those cases. Also, the differential forms may not have been exact. https://en.wikipedia.org/wiki/Closed_and_exact_differential_forms> does that mean that the path integral is also independent of path?Yes, this is again an application of Stokes' theorem.
 >> Anonymous Sat Nov 4 19:20:03 2017 No.9275927 >>9274641just checked it out and it approaches [eqn]\int_{0}^{1}\frac{x}{(1+x)^2}~\mathrm{d}x = \log(2) + \frac{1}{2} [/eqn]
 >> Anonymous Sat Nov 4 19:33:33 2017 No.9275955 >>9274993t. brainletI didn't. Perhaps your post would work if it were>why would you answer a question and then ask it ?
 >> Anonymous Sat Nov 4 20:01:17 2017 No.9276018 how do you show the length of the sequenceI_k = {2^k, 2^k + 1,...,2^(k+1)-1}, k = 0,1,2...is 2^k ?aside from subbing in the k's, counting, then figuring out the pattern.t.brainlet
 >> Anonymous Sat Nov 4 20:05:35 2017 No.9276027 >>92760182^(k+1)-2^k = 2^k[2-1] = 2^k
 >> Anonymous Sat Nov 4 20:09:27 2017 No.9276037 I understand how there are more points on an infinite line than there are integers. Are there the same number of points on an infinite line as the number of points on an infinite plane?
 >> Anonymous Sat Nov 4 20:10:15 2017 No.9276040 >>9276027cheers. but what is the step before 2^(k+1)-2^k
 >> Anonymous Sat Nov 4 20:16:39 2017 No.9276054 >>9276040The number of integers n satisfying a <= n <= b is b-a+1.>>9276037>Are there the same number of points on an infinite line as the number of points on an infinite plane?Yes, but you should be using the term 'cardinality'.
 >> Anonymous Sat Nov 4 20:29:44 2017 No.9276077 How do i figure out the fitness of a particular population in an ecosystem?Like, there's 10 bacteria species in a petri dish and I want to figure out which one has the highest fitness. How do I do this?
 >> Anonymous Sat Nov 4 20:54:44 2017 No.9276135 >>9276054thanks mate
 >> Anonymous Sat Nov 4 21:33:09 2017 No.9276204 >>9276037It's misleading to say they have the same number of points. Infinite cardinalities can become confusing when you phrase it this way.
 >> Anonymous Sat Nov 4 22:30:34 2017 No.9276296 >A is an element of the power set of B if and only if A is a subset of BIs this true?
 >> Anonymous Sat Nov 4 22:31:43 2017 No.9276300 >>9276296>Is this true?by definition of power set, yes
 >> Anonymous Sat Nov 4 22:36:55 2017 No.9276309 >>9276300Thanks
 >> Anonymous Sun Nov 5 00:02:51 2017 No.9276427 I like doing math and solving problems and capable of finding answers in calc but my proofs are shit.How do I either get less shitty at proofs to not be a mathematics loser or what is the major where my solving equations but failure to explain why won't matter?
 >> Anonymous Sun Nov 5 00:12:04 2017 No.9276446 >>9271297If I smoke one cigarette a week will I become addicted and get lung cancer?
 >> Anonymous Sun Nov 5 00:17:42 2017 No.9276458 >>9275927log2-1/2 *
 >> Anonymous Sun Nov 5 00:18:15 2017 No.9276461 >>9271599Your professor's definition is one from topology—it can be used for any topological space. Rudin's definition of an open interval (or the more general consideration of a neighborhood as an open $\epsilon$ ball) can't be used when the topological space in question isn't metrizable.
 >> Anonymous Sun Nov 5 00:25:32 2017 No.9276471 >>9276446You won't be smoking one cigarette a week. So, don't do it.If you actually smoke just one a week, then it's nothing. It won't hurt you. But you won't be able to keep smoking only one.
 >> Anonymous Sun Nov 5 00:38:46 2017 No.9276483 File: 182 KB, 564x709, C0105F4D-2AA2-4DD0-8F44-2C3BC3A0E1AC.jpg [View same] [iqdb] [saucenao] [google] [report] Hi sci,I suck at math but acccidentally my way into geophysics research and now i am having trouble with math im applying in matlab to model inverted data from a soil conductivity sensorSo far this is how i understand my issue:I have to different functions A(x) and B(x)x represents the sensor readings, A(x) is the true depth that the reading indicates, and B(x) represents the value i get when i input my sensor readings into a partially inverted formula for the depth indicated by the readings. What is the math strategy i need to use to relate my B(x) values to the real depth values of A(x)?
 >> Anonymous Sun Nov 5 00:41:33 2017 No.9276486   >>9276483Wow thats a lot of spelling errorsBut I guess thats what i get for phoneposting at midnight
 >> Anonymous Sun Nov 5 00:47:50 2017 No.9276491 Here's a question:Why are the questions ITT less stupid than actual thread starters?
 >> Anonymous Sun Nov 5 00:49:05 2017 No.9276495 Best intro to differential geometry book? I want it to cover at least up to Theorema Egregium.
 >> Anonymous Sun Nov 5 00:50:13 2017 No.9276497 >>9276491Because stupid people think their stupid questions are difficult and there are too many dumb fucks around here.
 >> Anonymous Sun Nov 5 00:51:14 2017 No.9276499 >>9276491Only the ironic questions actually areMost people who ask questions in these threads are smart enough to not want to start an entire thread for their question, while the people who do start threads are too fucking stupid to ask in this thread first.
 >> Anonymous Sun Nov 5 00:52:07 2017 No.9276500 >>9276499That's actually a better answer than I deserved
 >> Anonymous Sun Nov 5 00:54:56 2017 No.9276502 File: 181 KB, 406x445, F4DE4DED-EF4E-4ADC-AF34-D9EBDA3567A0.jpg [View same] [iqdb] [saucenao] [google] [report] If you replaced all the nitrogen in a sample of air with CO2 but didn’t change anything else, could you still breath it?
 >> Anonymous Sun Nov 5 00:58:15 2017 No.9276506 >>9276037In general, if a set A is infinite then AxA has the same cardinality as A.
 >> Anonymous Sun Nov 5 00:58:53 2017 No.9276507 >>9276502Probably for a little bit but i feel like CO2 would act differently than N2 and it would result in different partial pressures or turn into carbon monoxide or some shit and be dangerous. Im not qualified to answer this question tho, thats just my two cents
 >> Anonymous Sun Nov 5 01:03:26 2017 No.9276515 >>9276502You would actually pass out faster than you would holding your breath. You'd also die pretty quickly.
 >> Anonymous Sun Nov 5 01:04:00 2017 No.9276516 >>9276502You can breathe 80% Helium, 20% Oxygen and be ok, I know that from experience.
 >> Anonymous Sun Nov 5 01:15:18 2017 No.9276532 >>9276515Why?
 >> Anonymous Sun Nov 5 01:41:08 2017 No.9276560 >>9276532Carbon dioxide is incredibly toxic at a fraction of the amount you are talking about, though concentrations like that occur so rarely that we actually don't have much information on the actual mechanism of death. Most cases involve CO2 being emitted from the ground near volcanoes, and surviving witnesses always describe the victims as appearing to fall unconscious or die instantly. It's thought to be exacerbated by the fact that CO2 is the one gas that triggers our suffocation reflex, so you hyperventilate more of it after you fall unconscious. There have been cases of people knocked down mid stride next to a leaking CO2 cylinder. Again - extremely rare.
 >> Anonymous Sun Nov 5 01:28:58 2017 No.9276614 >>9276560I'm almost certain you're talking about carbon monoxide, not carbon dioxide. You exhale carbon dioxide, carbonated beverages constantly emit carbon dioxide, etc. It's pretty much a biologically neutral compound, especially for oxygen-breathing animals like humans, so as long as there WAS oxygen, I don't know why it would be a problem.
 >> Anonymous Sun Nov 5 01:54:16 2017 No.9276634 >>9271297Why does the Moon's velocity away from us imply it's only 1.5 billion years old?
 >> Anonymous Sun Nov 5 02:07:39 2017 No.9276646 >>9276614No, there's loads of data on carbon monoxide poisoning. Also CO doesn't trigger a suffocation reflex.Bear in mind normal ambient CO2 level is less than 1/20th of a percent of dry air, vs 78% nitrogen. So we're talking about more than 1600 times normal concentration as I understood the formulation of the original question. And it is absolutely not biologically neutral.From NIH>Carbon dioxide does not only cause asphyxiation by hypoxia but also acts as a toxicant. At high concentrations, it has been showed to cause unconsciousness almost instantaneously and respiratory arrest within 1 min [6].>Carbon dioxide at low concentration has little, if any, toxicological effects. At higher concentrations (>5%), it causes the development of hypercapnia and respiratory acidosis. Severe acidosis increases the effects of parasympathetic nervous activity, possibly by interfering the hydrolysis of acetylcholine by acetylcholinesterase, resulting in a depression of the respiration and the circulation [6]. Concentrations of more than 10% carbon dioxide may cause convulsions, coma, and death [1, 15]. CO2 levels of more than 30% act rapidly leading to loss of consciousness in seconds. This would explain why victims of accidental intoxications often do not act to resolve the situation (open a door, etc.) [7, 10, 16].
 >> Anonymous Sun Nov 5 03:19:47 2017 No.9276711 I am almost 5/8 semesters done with EE but I am seriously thinking of switching to physics..would it be worth it ir matter at all for the 3 semesters? I could maybe stay another fall for 4 semesters total before my scholarship runs out. I plan on getting an MS at least and possibly a PhD if it seems right when the time comes. I plan to focus in photonics and related areas for EE and would follow similar optics/photonics focus for physics. Is it worth the gamble or no?
 >> Anonymous Sun Nov 5 06:15:49 2017 No.9276883 >>9271833Found answers of Z=(2+i) and Z=(3-i) by expanding with Z=(a+ib) but used wolfram alpha to avoid some algebra that resulted, so technically I didn't follow the rules. Is this the right way and I just have to slog through the algebra next time or is there a more elegant way?
 >> Anonymous Sun Nov 5 06:18:23 2017 No.9276886 >>9271833Does completing the square count as using the quadratic formula?
 >> Anonymous Sun Nov 5 06:19:51 2017 No.9276891 File: 424 KB, 680x880, 6cf.png [View same] [iqdb] [saucenao] [google] [report] When is that hack surgeon gonna decapitate that guy?
 >> Anonymous Sun Nov 5 08:35:39 2017 No.9277029 I need a good probability and statistics bookI know single variable calc and I'm learning multivariable now
 >> Anonymous Sun Nov 5 10:12:46 2017 No.9277161 >>92754076C2 Implies all the combinations of choosing 6 guys8C3 implies all the combinations of choosing the people that are not those 2 guysThat implies your overcounting. Since when you pick Guy A from 6C2, in some of your combinations You will pick Guy B in the 8C3 because 8C3 is ALL the combinations that don't include the first two guys (assume you don't pick Guy B in the first 2).When you pick Guy B in 6C2, you will inevitably choose Guy A in 8C3 (assuming you don't pick Guy A in the first 2) because again It's every combination that doesn't include Guy A or Guy C
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 10:55:47 2017 No.9277225 File: 43 KB, 974x1198, ButIXsx.jpg [View same] [iqdb] [saucenao] [google] [report] >>9271297n Secant = n Second?0Secant=0That doesn't look P=nP to me but it sure sounds like it. Just makes me feel like this song makes me feel cold after it warms me.http://lyricstranslate.com/en/%E5%AF%82%E5%AF%9E%E7%9A%84%E7%94%B7%E4%BA%BA-lonesome-man.html
 >> Anonymous Sun Nov 5 11:00:02 2017 No.9277234 >>9274293Check the email address, buddy.
 >> Anonymous Sun Nov 5 11:05:33 2017 No.9277246 >>9275113You can't teleport?
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 11:08:35 2017 No.9277257 >>9277246teleportlatin/greektele seeport go0xseegox0
 >> Anonymous Sun Nov 5 11:10:11 2017 No.9277260 Do you think someone who really sucks at studying could turn it around and become a good math student? good enough to get a math degree?
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 11:12:07 2017 No.9277265 >>9277260A degree in Integra Mathematica I make available to all who understand e/-1 upon second glance.
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 11:18:33 2017 No.9277279 >>9277265{XË例如Ĵ,XëëĴ克}轉換為盎司噸
 >> Anonymous Sun Nov 5 12:03:17 2017 No.9277360 >>9277029halp
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 12:19:49 2017 No.9277388 >>9277360Bae?
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 12:38:38 2017 No.9277423 >>9277360我愛你。
 >> Anonymous Sun Nov 5 12:41:03 2017 No.9277427 >>9277423Ching Chong to you too
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 12:42:26 2017 No.9277429 >>9277427性別4每+1 = 5. / 1秒
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 12:43:38 2017 No.9277432 >>9277427>>9277429青創也給你.Then maybe learn better English. Get a Degree of Simon-ism.
 >> Anonymous Sun Nov 5 12:44:51 2017 No.9277437 >>9277432I-I just want a statistic and probability book
 >> Anonymous Sun Nov 5 12:49:51 2017 No.9277444 What drove some of the greatest scientists to dedicate their lives towards creating breakthroughs in their respective fields?What drives you in creating a better understanding of science?I ask these questions in the hopes that someone could give me some insights that would better help me along.I have fallen flat in the face of my limitations as an individual, and some of my weakest areas, in regards to IQ, is in memory retention and mathematics. With my memory being below average, and my mathematics knowledge being average. Although I feel these bouts which make me desire to rail against these things by attempting to further my knowledge of math, I seem to always end up back at square one.
 >> /psy/mon|0-X's|/sci/mon Sun Nov 5 12:52:25 2017 No.9277447
 >> Anonymous Sun Nov 5 12:54:10 2017 No.9277449 >>9277447>Rwhat did you mean by this?
 >> Anonymous Sun Nov 5 13:04:12 2017 No.9277458 File: 151 KB, 819x725, 1.png [View same] [iqdb] [saucenao] [google] [report] Stupid Question: Is it possible to get the probability of an event re-ocurring?I know about the gambler's fallacy, if I toss coin and I have 50% probability of the result being heads and 50% probability of the result being tails, can I calculate the probability of heads appearing lets say 5 times in a row? How?Intuitively it's obvious that is less likely that heads appears 100 times in a row compared to heads appearing 5 times in a row. How can you calculate this? I know it also has to do with the number of times you toss the coin. I want to make a simple probability calculator. Any help or resource would be greatly appreciated!
 >> Anonymous Sun Nov 5 13:05:42 2017 No.9277461 >>9277458Search Bernoulli process/Bernoulli trial
 >> Anonymous Sun Nov 5 13:06:06 2017 No.9277462 >>9271541Orange is the typical sodium emission color. Either is not borax (I doubt for you) or the sodium emission just cover the weaker green color. Try boric acid instead. Also, as long as you don't put milligrams of substance in liters of methanol, concentration should not matter.
 >> Anonymous Sun Nov 5 13:09:35 2017 No.9277464 >>9271833z^2 - 5*z + 7+i = 0=> (z-5/2)^2 + 3/4+i = 0=> (z-5/2) = sqrt(-3/4-i)=> 2z-5 = sqrt(-3-4i)complex square root:(u+vi)^2 = a+bi=> u^2+2uvi-v^2 = a+bi=> u^2-v^2 = a, 2uv = ba=-3,b=-4=> u^2-v^2=-3, 2uv = -4=> v^2-u^2=3, uv=-2=> u=1,v=-2 or u=-1,v=2=> 2z-5 = 1-2i or -1+2i=> 2z = 6-2i or 4+2i=> z = 3-i or 2+i
 >> Anonymous Sun Nov 5 13:15:12 2017 No.9277468 File: 258 KB, 2183x1229, 2017-11-05.png [View same] [iqdb] [saucenao] [google] [report] can someone explain the algebra used to get the final answer? this subject is very tricky and confusing to me.
 >> Anonymous Sun Nov 5 13:19:56 2017 No.9277475 >>9277458>can I calculate the probability of heads appearing lets say 5 times in a row? How?No you can't. You need to specify how many times you are going to toss it.>How can you calculate this?https://math.stackexchange.com/questions/59738/probability-for-the-length-of-the-longest-run-in-n-bernoulli-trials/59749#59749
 >> Anonymous Sun Nov 5 13:23:11 2017 No.9277480 >>9277468point where you got confused
 >> Anonymous Sun Nov 5 13:25:25 2017 No.9277484 >meet a friend at university>he's an astrophysicist>ask him 'if my balls magically turned into neutronium, would they have enough mass to alter the state of earths gravity'>apparently it's just under the markcan any astrofags confirm this?
 >> Anonymous Sun Nov 5 13:29:04 2017 No.9277490 >>9277484How big are your balls?1 teaspoon of neutronium (assuming neutronium is what neutron stars are made of) is100 billion tons (metric??) I was told
 >> Anonymous Sun Nov 5 13:33:41 2017 No.9277498 >>9277490I'd say I'm probably around the average, so about 2 or 3 cubic centimeters i think
 >> Anonymous Sun Nov 5 13:43:55 2017 No.9277523 So people often say that one argument for General Relativity is that gravity and accelerating are indistinguishable. I don't believe this is the case. Gravity is a body force, acceleration is felt as a surface force. So in the classic example of being in a room with no windows, you could tell if your weight was from gravity or acceleration by precisely measuring the air pressure in the room at different heights. An accelerating room will have slightly higher air pressure at the bottom of the room, while a room experiencing gravity will have equal air pressure throughout. Right?
 >> Anonymous Sun Nov 5 13:47:24 2017 No.9277530 >>9277461>>9277475Thanks! Specially that stackexchange link helped a lot pointing me towards the right place.
 >> Anonymous Sun Nov 5 13:47:36 2017 No.9277531 >>9277480where it is simplified to 2 * 2^(k+1) -1 and then the final answer.the actual algebraic simplification is confusing me
 >> Anonymous Sun Nov 5 13:53:07 2017 No.9277537 >>9277523>a room experiencing gravity will have equal air pressure throughouthttps://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html
 >> Anonymous Sun Nov 5 13:57:01 2017 No.9277548 >>9277537I got the idea from this:https://www.youtube.com/watch?v=y8mzDvpKzfYYes, the air pressure won't be perfectly equal in a room experiencing gravity, but will the difference be as great as what we see in this video?
 >> Anonymous Sun Nov 5 14:53:00 2017 No.9277607 more of an english question, but how do i interpret:"... there exists a $\delta>0$ such that $|f(x)|>\delta$ for all $x\in X$"?as $\exists\delta>0\forall x\in X\ |f(x)|>\delta$or $\forall x\in X\exists\delta>0\ |f(x)|>\delta$?
 >> Anonymous Sun Nov 5 14:56:46 2017 No.9277617 File: 75 KB, 594x592, bird2.jpg [View same] [iqdb] [saucenao] [google] [report] I need help giving a combinatorial argument that[eqn]\sum_{k = 0}^{N} (-1)^k S(N,k) = (-1)^N[/eqn]where $S(N,k)$ are the stirling numbers of the 2nd kind. I am fairly certain that it uses inclusion-exclusion, but I am not quite sure how.
 >> Anonymous Sun Nov 5 14:58:31 2017 No.9277619 >>9277617Oops, it should be[eqn]\sum_{k=0}^{N} (-1)^k k! S(N,k) = (-1)^N[/eqn]
 >> Anonymous Sun Nov 5 15:05:41 2017 No.9277629 >>9277607the first oneorder matters
 >> Anonymous Sun Nov 5 15:06:27 2017 No.9277630 >>92775312^(k+1)+2^(k+1) = 2*2^(k+1)
 >> Anonymous Sun Nov 5 15:15:38 2017 No.9277642 File: 2.00 MB, 325x271, 1498246165495.gif [View same] [iqdb] [saucenao] [google] [report] "Calculate the sum of the series (Infinity, Sigma, n=1)An whose partial sums are given by Sn = 2 - 3(.08)^n"I'm a little confused about some of the notation for series and sequences. I thought if something was denoted with an "A(sub n)" it's implied to be an infinite sequence, and that "S(sub n)" is implied to be an infinite series. So logically "An" with a Sigma in front of it would just be another way of denoting a series.Sn = 2 - 3(.08)^n , solved as a series equals infinity but the answer to the problem is 2. Can someone explain to a brainlet what partial sums means to me in this particular problem, and what the relation between "An" and "Sn" is?
 >> Anonymous Sun Nov 5 15:21:41 2017 No.9277647 >>9277642All that is being told is that $\sum_{k=1}^n A_k = S_n$ so $\sum_{k=1}^{\infty} A_k = S_{\infty} = \lim_{n \to \infty} S_n = 2$
 >> Anonymous Sun Nov 5 15:24:15 2017 No.9277653 >>9277647So "Sn" doesn't imply a series?
 >> Anonymous Sun Nov 5 15:28:06 2017 No.9277661 >>9277642>relation between "An" and "Sn" is?$\displaystyle \sum_{n=1}^\infty A_n$Means that you are looking at an infinite series you can think of $A_n$ as a function , where $A_1$ is the first term of the series $A_n$.In this case $A_n$ also does not need to be finite:$\displaystyle \sum_{n=1}^3 A_n$ means $A_1 + A_2 + A_3$.$S_n$ in this case is just a regular infinite sequence, where the terms are given by the sum, as >>9277647 points out.You are confused because $S_n$ is just a regular sequence and $A_n$ is also a regular sequence.But $S_n$ is generated by adding up the first n terms of $A_n$ .Formally $A_n$ and $S_n$ are the same type of object.
 >> Anonymous Sun Nov 5 15:28:24 2017 No.9277663 >>9277653Sn is a series. But they are giving you the nth term of that series. Similar to how you can write either $\sum_{k=1}^n k$ or $\frac{n(n+1)}{2}$
 >> Anonymous Sun Nov 5 15:36:36 2017 No.9277687 >>9277630thanks, i see that but.. 2 * 2^(k+1)-1 = 2^(k+2)-1?What rule are they following to reach that answer? I'm not seeing how that is algebraically correct.
 >> Anonymous Sun Nov 5 15:45:42 2017 No.9277711 >>9277653A series is a sequence of partial sums of another sequence."Evaluating" the series is finding the limit of that sequence of partial sums.
 >> Anonymous Sun Nov 5 15:46:29 2017 No.9277713 >>9277663>>9277661Still confused, but does "∑An whose partial sums are given by Sn"mean that ∑A(sub 3) = A(1) + A(2) +A(3) = S(sub 3) = 2 - 3(.08)^3So "An" is an unknown function and "Sn" is not said function but somehow gives the sums for "nth" terms in the series "An"
 >> Anonymous Sun Nov 5 15:51:49 2017 No.9277723 >>9277713>So "An" is an unknown function and "Sn" is not said function but somehow gives the sums for "nth" terms in the series "An"Yeah, exactly.
 >> Anonymous Sun Nov 5 15:57:19 2017 No.9277736 >>9277723It's a little weird but I think I get it, thank you.
 >> Anonymous Sun Nov 5 16:15:01 2017 No.9277769 What's that cringy physics/mathematics song again, that was the official(?) song of an American university like MIT or Harvard? I'm not sure from which it was anymore.
 >> Anonymous Sun Nov 5 16:21:23 2017 No.9277784 >>9277769This one? https://www.youtube.com/watch?v=UTby_e4-RhgBtw this is the best song ever made, if you think it is cringey, fuck you :)
 >> Anonymous Sun Nov 5 16:25:47 2017 No.9277791 >>9277784Nah it's not that one I'm sure, this is indeed pretty sweet.
 >> Anonymous Sun Nov 5 17:17:43 2017 No.9277876 >>9277687a*a^x = a^(x+1)
 >> Anonymous Sun Nov 5 17:28:54 2017 No.9277895 File: 17 KB, 321x239, ejercicio 6 pregunta.jpg [View same] [iqdb] [saucenao] [google] [report] The magnetic field is 5.6mT and the current is 2 A.How can I find the resulting magnetic force without a value for any side of this "triangle"?
 >> Anonymous Sun Nov 5 17:54:21 2017 No.9277932 File: 9 KB, 608x52, c61543767edbf5901194295582549ff7.png [View same] [iqdb] [saucenao] [google] [report]
 >> Anonymous Sun Nov 5 17:55:40 2017 No.9277935 >>9277932forgot text, can anyone help me set up the bounds for this? I have my bounds as 0
 >> Anonymous Sun Nov 5 18:09:41 2017 No.9277963 File: 14 KB, 458x233, pfdue6V.png [View same] [iqdb] [saucenao] [google] [report] What's going on in this pic? Does (-1)^x actually equal a phase shift + horizontal compression of sin(x)? That seems like it should definitely not be true...
 >> Anonymous Sun Nov 5 18:12:32 2017 No.9277967 >>9277935Of course it is 0. You don't even need to do the integral. The disc has center (something,0). The integral on the north semicircle is the same as the integral on the south semicircle but negative. Therefore on the entire circle it is 0.
 >> Anonymous Sun Nov 5 18:14:08 2017 No.9277972 >>9277967It's only the semi circle above the x - axis.
 >> Anonymous Sun Nov 5 18:18:41 2017 No.9277986 >>9277967Wrong. He is only integrating half the circe.>>9277935The bounds are wrong. Theta should only go from 0 to pi/2
 >> Anonymous Sun Nov 5 18:20:57 2017 No.9277989 >>9277986Ok thanks, can you explain why it is pi/2? I thought that only traced out a quarter circle?
 >> Anonymous Sun Nov 5 18:23:10 2017 No.9277992 >>9277989>I thought that only traced out a quarter circle?You have to graph your region. Your entire circle is contained within the top-right part of the plane.
 >> Anonymous Sun Nov 5 18:27:01 2017 No.9277998   >>9277963Taking some values and computing sin(3x + pi/2) - (-1)^x I get....6597 1.511628186574595 1.952770666614653 0.3814026616726107 1.719054328964195 1.975860274893321 0.4678814148517192 -0.1032139315577001 0.8825858928456925 0.06139020980372423 1.798858978969828 -1.9883265344902 -1.979104007692598 -1.957850200224181 0.8098346739668607 0.0310826663961375 1.952385411567978 -0.778227975123941 0.7246048243061002 -1.875575981683214 -1.899511535541891 1.754219037625040 -1.88446892567752 -0.05607556044786063 1.681149870497167 1.998193266866382 -0.5772956499943364 -0.641743602535322 -0.08942961325648993 1.542228671788712 -1.461851499824175 0.137147365482700 -0.8459272540816509 1.417653823984873 0.609280145752445 0.185451647508357 0.03980444887738850 -1.920872207783345 1.729596599469502 -0.3117619077078556 -0.62650284599142 -0.005389208680936517 0.3543458419338102 -1.876448277928578 -1.348735797716176 -0.5584500114489278 -0.1277004888476432 -0.05655426869898529 0.7057861689274451 1.333085527068766 -1.963207775582507 1.999630447969784 -1.995020374022048 -0.422579353817567 0.8284311431045202 -0.8619490088533524 -1.85733793618844 -1.31528399071933 0.012622498564835 0.592110588289554 -1.315112344087924 -1.908293529578447 1.6108551139977 0.005607008586022224 -0.2634197863358221 1.073061848934026 -1.146513958418171 0.3381226975038362 -1.927674297556225 1.196247241619305 1.369505244847485 1.449770591045712 -1.181853441525298 -1.775830827229552 -1.037381008164662 -0.0678513271515202 -1.946887399233438 -1.988573219825072 -1.299356030525011 0.112614071542758 -0.1287638040469536 -0.2083530419369434 -1.8206685997247 1.91476671505938 -0.3528968018333232 -0.4981595035246197 1.585480292351919 0.9685428936687123 1.993596361635743 1.8747446472265 1.97562269792So my assumption they are not actually related seems right, maybe this is just a graphing coincidence that they look similar.
 >> Anonymous Sun Nov 5 18:27:54 2017 No.9278002 File: 14 KB, 965x535, visualaid.png [View same] [iqdb] [saucenao] [google] [report] >>9277989Okay. I made some visual aid because desu it is impossible to explain this because I've always had an intuitive understanding of this.When you do polar coordinates the "r" is simply a stick that is swiping through the plane. With the theta argument you tell the stick from where to where it has to swipe.In here you see that your circle is completely in the right region. So if you can see that if you want r to "swipe" just that region, you need to tell it to go from theta=0 to theta= pi/2. If it goes all the way to pi then r will also swipe the left part of the plane, which is not in region.
 >> Anonymous Sun Nov 5 18:28:56 2017 No.9278004 >>9277963Taking some values and computing sin(3x + pi/2) - (-1)^x I get....9142: -0.00538920868093, 6517: 0.354345841933, 8102: -1.87644827792, 8578: -1.34873579771, 6176: -0.558450011448, 9278: -0.127700488847, 6432: -0.0565542686989, 8529: 0.705786168927, 4451: 1.33308552706, 8766: -1.96320777558, 2507: 1.99963044796, 9784: -1.99502037402So my assumption they are not actually related seems right, maybe this is just a graphing coincidence that they look similar.
 >> Anonymous Sun Nov 5 18:31:49 2017 No.9278010 File: 13 KB, 965x535, visualaid.png [View same] [iqdb] [saucenao] [google] [report] >>9278002>>9277989Ah, mistake. I fixed it.
 >> Anonymous Sun Nov 5 18:34:01 2017 No.9278013 >>9278010this makes much more sense, thank you
 >> Anonymous Sun Nov 5 18:34:42 2017 No.9278015   >>9277932You region is (1,0)+r(cosθ,sinθ)=(1+rcosθ,rsinθ) where θ varies from 0 to π, and r varies from 0 to 1.Therefore you integrate sinθ rdrdθ , r from 0 to 1, θ from 0 to π. The result is 1.
 >> Anonymous Sun Nov 5 18:54:52 2017 No.9278058 >>9278004Nvm some more googling reveals this is a consequence of some complex number stuff that I don't really understand, but involves pi.
 >> Anonymous Sun Nov 5 20:49:09 2017 No.9278258 File: 71 KB, 187x317, 1509080413880.png [View same] [iqdb] [saucenao] [google] [report] What are your thoughts on the nature of consciousness and qualia? Is it fair to just reduce it down to neuron-chemical reactions or is there more to it? Just starting out on understanding the topic so some pointers and thoughts would be very appreciated.Pic mildly related
 >> Anonymous Sun Nov 5 20:49:50 2017 No.9278262 Is this proof okay?>Prove that between every rational number and every irrational number there is an irrational number.let A be rational and B be irrational such that A < B. Let X = the absolute value of the square root of B. Then, X is irrational and X < B. Furthermore, A + X is irrational and A < A + X < B.
 >> Anonymous Sun Nov 5 21:12:46 2017 No.9278309 >>9277963a^b = e^(b*log(a))So (-1)^x = e^(x*log(-1)) = e^(x*pi*i)Note that e^(i*x) = cos(x)+i*sin(x)So e^(x*pi*i) = cos(pi*x)+i*sin(pi*x)The real part is cos(pi*x).If you're limited to real numbers, then (-1)^x is only defined for rational x where the denominator is odd. If the denominator is even then (-1)^x is imaginary; if x is irrational then (-1)^x is complex.
 >> Anonymous Sun Nov 5 21:15:31 2017 No.9278313 >>9278262> Is this proof okay?No.> A + X < BThis isn't necessarily true.
 >> Anonymous Sun Nov 5 21:23:01 2017 No.9278331 What tools are being used in CRISPR it's just explained like it's magic gene editing bullshit. What are the lab techs and scientists actually doing in the lab?
 >> Anonymous Sun Nov 5 21:23:53 2017 No.9278336 >>9278262you dont need to make it that complicated. the sum of a rational and irrational is irrational, thus(A+B)/2 is irrational and inbetween A and B
 >> Anonymous Sun Nov 5 21:28:18 2017 No.9278344 >>9278313>>9278336Thanks, guys
 >> Anonymous Sun Nov 5 21:37:02 2017 No.9278361 In physics, is the concept of "temperature" literally the kinetic energy of particles? When I'm eating hot soup, is it hot because the molecules in the soup are jiggling around very quickly? And when it cools down, the soup molecules are not moving around so fast anymore?When it's a hot day outside, is it because the air molecules are actually jiggling around faster? And when it's a cool day the air molecules are not bouncing around as quickly?How can I get a better intuitive understanding of what temperature actually is in the real world?
 >> Anonymous Sun Nov 5 22:21:07 2017 No.9278413 File: 5 KB, 526x257, ideal transformer.png [View same] [iqdb] [saucenao] [google] [report] /sci/, please help me, I feel like a fucking retard for not getting this. I have to solve an Ideal Transformer problem and solve for the voltage at the loops and the current flowing through each side. I thought I understood this, but we have to submit our answer online and it doesn't accept what i'm coming up with.We're given the voltage source Vs= 40sin(wt), R1= 128 Ohms, R2= 15 Ohms and the loop ratio is 4:1 from left to right. Everything in each side is linear and said to follow the same frequency while ignoring loss and all that, so finding sin(wt) is unnecessary. It seems like a really simple problem.So shouldn't then the voltage V1 also be 40sin(wt) and the current V1/R1? and the ratio of V1/V2 equal to the loop ratio? So V2=10sinwt and so on? Those answers aren't accepted so I think I must be missing something. Either that or my professor just fucked something up, but it seems more likely that I'm the one making a mistake.Sorry for the shitty mspaint drawing.
 >> Anonymous Mon Nov 6 01:08:44 2017 No.9278672 File: 720 KB, 699x637, 1509391787550.png [View same] [iqdb] [saucenao] [google] [report] I doubt any geology people are browsing but how do I answer this? I can find barely anything in my notes or textbook about it aside from 'horizontal stress generated to change in overburden' and 'changing crustal depth'.
 >> Anonymous Mon Nov 6 01:14:38 2017 No.9278676 >>9278361that's correct yes
 >> Anonymous Mon Nov 6 01:19:34 2017 No.9278683 How do I find dy and delta y for a function if I don't know what dx and delta x are? either missed that lecture or professor is an ape, but we are using the openstax calc 1 textbook so there's thatBTW, the question in hand>Find formulas for dy and Δy.> y = x2 - 2x + 1
 >> Anonymous Mon Nov 6 01:24:04 2017 No.9278692 >>9278672Draw a Morh's stress circle maybe. A stress ellipse as well? Discuss what those imply.
 >> Anonymous Mon Nov 6 04:28:25 2017 No.9278840 File: 246 KB, 480x360, halp.png [View same] [iqdb] [saucenao] [google] [report] >>9271297If anyone into electrodynamics or complex analysis or both could help me out, I'd be really grateful https://physics.stackexchange.com/questions/367233/complex-potential-of-an-array-of-wires
 >> Anonymous Mon Nov 6 05:51:56 2017 No.9278896 File: 17 KB, 271x318, 1442309617584.jpg [View same] [iqdb] [saucenao] [google] [report] Got an awesome science project for my master, and a very experienced and invested PI.However, this PI is a bit strange. Strict, and very intimidating. I don't know how to not feel intimiated and treat my PI with confidence, because that's what I think is correct and would make our relationship better. If I need to ask a question, i always seems so difficult to ask without looking like an idiot and leaving an impression of disappointment. It happens every time. MyPI ends up worried I may fuck up the experiment, or seems aggressive, even though I doubt that is the intention. Previous students have told me to look further and ignore the seemingly aggressive interactions, and not be too sensitive, but I have a hard time becoming that student that can answer confidently.
 >> Anonymous Mon Nov 6 06:47:53 2017 No.9278950 >>9278413> So shouldn't then the voltage V1 also be 40sin(wt)No; you're forgetting the voltage drop across R1: V1=Vs-I1*R1> and the current V1/R1?The primary current will be dictated by the secondary current; I1=I2/4.> and the ratio of V1/V2 equal to the loop ratio? So V2=10sinwtAt least that part's right.V2 = V1/4I2 = V2/R2I1 = I2/4 = V2/(4*R2) = (V1/4)/(4*R2) = V1/(16*R2)V1 = Vs-I1*R1 = Vs - V1*R1/(16*R2)=> V1*(1+R1/(16*R2)) = Vs=> V1*(16*R2+R1)/(16*R2) = Vs=> V1 = Vs*(16*R2)/(16*R2+R1)I1 = V1/(16*R2)= Vs/(16*R2+R1)Basically, putting a resistance behind a transformer increases its magnitude by the square of the voltage ratio. So you can replace the transformer primary with 16*R2, then you have a voltage divider.
 >> Anonymous Mon Nov 6 06:50:11 2017 No.9278952 >>9278683The formulae would have dx and Δx as independent variables.
 >> Anonymous Mon Nov 6 06:57:22 2017 No.9278961 >>9278950Thank you so much dude, I had a feeling I was just missing something simple.
 >> Anonymous Mon Nov 6 07:36:53 2017 No.9279014 >>9278672fellow geology undergrad herewhat the fuck class is this for? that shit seems whack and I would have no idea how to answer.
 >> Anonymous Mon Nov 6 07:42:53 2017 No.9279020 File: 39 KB, 500x250, elliot.jpg [View same] [iqdb] [saucenao] [google] [report] The last time I studied math (pre-calculus) was in high school, seven years ago. I've realized recently that I need to know a lot more fucking math. I have a Calculus I textbook that I can start studying with immediately.Question is, how much of an obstacle will I face considering the gap between my pre-calc days and today? Should I study pre-calc again?
 >> Anonymous Mon Nov 6 07:51:09 2017 No.9279029 >>9278361More or less.Same concept with evaporation/condensation. Hot water has a lot of kinetic energy, and because those molecules are moving around really fast, some of them "escape" into the atmosphere. In terms of condensation, when the temperature of the atmosphere sufficiently cools (partly because molecules also "escape" back onto solids, taking heat with them), the molecules remaining slow down and condense, effectively "raining" on any surface.
 >> Anonymous Mon Nov 6 08:34:31 2017 No.9279078 What's a good site/program to solve a system of linear equations?
 >> Anonymous Mon Nov 6 08:44:36 2017 No.9279091 >>9279078Matlab?or GNU Octave if you want a free (as in freedom and beer) software?What size are we talking about? More then ~10^4 rows/columns? Then you probably should look into finding some decent algorithms for your problems first.
 >> Anonymous Mon Nov 6 08:45:38 2017 No.9279092 >>9279020>Question is, how much of an obstacle will I face considering the gap between my pre-calc days and today?Nobody here knows, the only option you have is to try it and if you do not understand something read up on it again.
 >> Anonymous Mon Nov 6 08:47:47 2017 No.9279095 >>9279091Nah, it's only 25x25. I'll look into this GNU Octave, thanks.
 >> Anonymous Mon Nov 6 09:09:12 2017 No.9279110 >>9279092>11/06/17(Mon)13:45:38 No.9279092Yeah, seems like that's the only way I'm going to find out.Thanks. I never thought I'd ever say this but I'm pretty excited to do some calculus. I can't wait for Calculus II.
 >> Anonymous Mon Nov 6 10:30:31 2017 No.9279180 Question, why did plants, fungi or algae never develop mineral structures to protect themselves from herbivores, like animals did? Why aren't there things like glass algae, or rocky plants?Why do they only use sugars as support and protection? And why animals don't?
 >> Anonymous Mon Nov 6 11:34:02 2017 No.9279266 why is the autonomic nervous system separated from the somatic nervous system
 >> Anonymous Mon Nov 6 13:05:58 2017 No.9279408 >>9279014'Earth Structure'. Heavy amount of stereonet usage during our labs as well as stuff like stress/strain, brittle/ductile behavior>>9278692Thanks, I can sort of see where you're coming from with that
 >> Anonymous Mon Nov 6 14:01:30 2017 No.9279548 what's a simple (i.e. nothing more complicated than what is described here: https://autohotkey.com/docs/commands/Math.htm) function that will do something like this?f(200) = 400f(400) = 200(numbers don't have to be exatly those, that's just the general idea)
 >> Anonymous Mon Nov 6 14:25:25 2017 No.9279614 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4839960/This article implies a lack of dystrophin expression causes improper polarization of satellite cells during asymmetric division, leading to senescent cells.http://www.sciencedirect.com/science/article/pii/S1873506114001172This study indicates however that transplanting myosatellites from mdx mice to a dystrophin expressing environment leads to fully functional cells capable of muscle regeneration.This confuses me. If the DMD gene is expressed by the satellite cell, why would transplanting it to a different environment enable it to produce dystrophin again and allow it to differentiate?
 >> Anonymous Mon Nov 6 14:33:39 2017 No.9279638 >>9272234agrobacterium tumefaciens or viral vectors
 >> Anonymous Mon Nov 6 14:34:42 2017 No.9279641 >>9273875no no
 >> Anonymous Mon Nov 6 14:37:48 2017 No.9279647 >>9277257>tele see>port gowtf? tele means far, and port means carry
 >> Anonymous Mon Nov 6 14:40:29 2017 No.9279652 >>9278258>Is it fair to just reduce it down to neuron-chemical reactions or is there more to it?physical, chemical, subcellular, neuronal, network, sociological levels, they all intertwine and interact, but nothing supernatural going on.
 >> Anonymous Mon Nov 6 14:41:29 2017 No.9279654 |x| + |y| ≤ |x + y| + |x − y| Any hints on how to show that this is true for all real x,y? I tried replacing the |x − y| with reverse triangle inequality, but got nowhere. I also tried squaring it, which just turned it into a massive clusterfuck. No clue what to do next.
 >> Anonymous Mon Nov 6 14:43:30 2017 No.9279659 File: 21 KB, 700x204, crispr-cas9-mrna-transfection-workflow-protocol.png [View same] [iqdb] [saucenao] [google] [report]
 >> Anonymous Mon Nov 6 14:45:25 2017 No.9279664 >>9279180they have cell walls, which are very stable, have you ever bitten into a coconut?also they do use minerals a lot>ajcn.nutrition.org/content/31/10/S94.full.pdf
 >> Anonymous Mon Nov 6 14:52:17 2017 No.9279673 >>9279654I can tell you the answer but you will literally kill yourself afterwards
 >> Anonymous Mon Nov 6 14:53:09 2017 No.9279675 >>9279673That's fine; I already want to.
 >> Anonymous Mon Nov 6 14:56:06 2017 No.9279682 >>9279675nevermind, I read it wrong. anyway, since x and y are real numbers, you can always work this case by case.
 >> Anonymous Mon Nov 6 14:58:42 2017 No.9279689 >>9279682True. There's probably a more elegant way, but hey, whatever works.
 >> Anonymous Mon Nov 6 15:03:00 2017 No.9279703 >>9271297Why is bread not always gluten free
 >> Anonymous Mon Nov 6 15:03:38 2017 No.9279707 >>9279654|x|+|y| = |x|+|-y| = |x+y-y| + |x-y-x| <= |x+y| + |y| + |x-y| + |x| <= |x+y| + |x-y|
 >> Anonymous Mon Nov 6 15:03:39 2017 No.9279708 >>9279654|2x| = |x + y +(x-y) | ≤ |x+y| + |x-y||2y| = |x + y - (x-y) | ≤ |x+y| + |x-y|therefore|x|+|y| = (|2x|+|2y|)/2 ≤ |x+y| + |x-y|
 >> Anonymous Mon Nov 6 15:06:54 2017 No.9279719 >>9279707>|x+y| + |y| + |x-y| + |x| <= |x+y| + |x-y|This last inequality is false
 >> Anonymous Mon Nov 6 15:07:57 2017 No.9279721 >>9279708Genius
 >> Anonymous Mon Nov 6 15:15:09 2017 No.9279734
 >> Anonymous Mon Nov 6 15:18:51 2017 No.9279740 Does anyone have the /sci/ copypasta that says "I don't see how this post is informative blah blah blah in any way..."?
 >> Anonymous Mon Nov 6 15:24:17 2017 No.9279748 >>9279614who said mdx mice had no dystrophin?
 >> Anonymous Mon Nov 6 15:29:22 2017 No.9279758 >>9279719you're right. sorry
 >> Anonymous Mon Nov 6 18:00:43 2017 No.9280047 Is it me or all explanations for quantum physical phenomenon to the masses is shit? Or rather, their explanation why it's spooky physics. I am a brainlet myself, but the whole point is to explain the weirdness to brainlets."observations affect the results" Ok yeah turns out any shit you'd fling at an electron to get a result back has a fairly large energy compared to the electron, so you're forced to change both it's position and velocity. Like trowing ping pong balls at a bowling ball in space and measuring the speed at which they bounce back/time of arrival. Except every part has some uncertainty to it, the amount of energy of the ping pong when launched, and the exact speed when it comes back etc. Where's the quantum woo weirdness?Or rather is there a way to explain it to brainlets, or not and the popsci entertainers just want to pretend they're conveying anything useful?
 >> Anonymous Mon Nov 6 19:11:45 2017 No.9280135 Is it possible to make a lattice 12-gon that is convex? I know it is possible to make concave ones, but haven't had luck messing around in geogebra.
 >> Anonymous Mon Nov 6 19:41:18 2017 No.9280179 “Some ants are trying to climb a wall and they can stack on one another (r) times, with (a) stacks existing and (t) ants, how many combinations are there?” How would I solve this, recurrence form if possible. Say as an example a=6, t=4, r=3
 >> Anonymous Mon Nov 6 21:53:14 2017 No.9280368 can someone solve this for me? no one math stack exchange helpedhttps://math.stackexchange.com/questions/2506874/triple-integral-bounded-by-a-cylinder-and-a-plane
 >> Anonymous Mon Nov 6 22:30:23 2017 No.9280406 File: 3.05 MB, 280x280, 1508286824114.gif [View same] [iqdb] [saucenao] [google] [report] Where can I find math papers otherwise hidden behind a paywall? I'm not paying $45 to look at a 17-page pdf  >> Anonymous Tue Nov 7 01:24:50 2017 No.9280596 File: 53 KB, 978x307, Screenshot_20171107-142246.jpg [View same] [iqdb] [saucenao] [google] [report] Can anyone give a step by step rundown on how to get the hyperbolic solution?  >> Anonymous Tue Nov 7 01:53:42 2017 No.9280653 When people say that the region inside of a conductor is an equipotential, do they mean that the potential is the same at every point or simply that the average potential over the region is constant?  >> Anonymous Tue Nov 7 05:22:12 2017 No.9280849 Do you have any online resource to study DE and ODE on? I need to be able to solve cauchy problems. I studied linear algebra by myself and I know that is used for the subject. Thanks.  >> Anonymous Tue Nov 7 05:25:13 2017 No.9280854 Ordinary Differential Equations by Tenenbaum & Pollard. You can download it or pay all of$20 dollars for it on Amazon.
 >> Anonymous Tue Nov 7 05:30:37 2017 No.9280859 >>9280854Thanks
 >> Anonymous Tue Nov 7 06:00:10 2017 No.9280868 >>9280406>just 17 pagesYou could write it yourself.
 >> Anonymous Tue Nov 7 06:01:25 2017 No.9280870 >>9280368Clearly the integral is zero, as the region is symmetric about z=0.But do do it the long way, it's easier using Cartesian coordinates. The bounds are:0
 >> Anonymous Tue Nov 7 06:04:04 2017 No.9280872 >>9280870Forgot an underscore:... so \int_{-a}^{a}z\ dz is zero
 >> Anonymous Tue Nov 7 06:29:12 2017 No.9280892 Consider an insulating sphere with +q surface charge. Can a Gaussian surface within the sphere prove the field inside is zero for: (a) a uniform surface charge distribution; (b) a variable surface charge distribution?
 >> Anonymous Tue Nov 7 07:19:41 2017 No.9280924 >>9279548>>9279548>>9279548pls respond
 >> Anonymous Tue Nov 7 07:23:14 2017 No.9280928
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