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420chan is Getting Overhauled - Changelog/Bug Report/Request Thread (Updated July 10)
TAKE THIS SURVEY SINCE YOU HAVE NOTHING BETTER TO DO
Clara Ducklock - Sat, 29 Oct 2016 17:03:32 EST ID:uIooC5VR
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https://surveyplanet.com/57fe252dc45a3306bc0eea87

Linear Programming (Decision Mathematics Query)
Wesley Billingshit - Fri, 28 Oct 2016 13:53:23 EST ID:tyLg+ghU
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I am having difficulty formulating the following in terms of linear programming

A pig farmer uses at least 800kg of feed daily. The feed is a mix of corn and maize.
The special feed mixture must contain at least 25% protein and a maximum of 6% fibre

Conditions:
The composition of corn per kg is as follows:
Protein: 32g per kg ; Fibre; 27g per kg ; Price £ 0.3 per kg

The composition of maize per kg is as follows:
Protein: 360g per kg ; Fibre: 65g per kg ; Price £0.9 per kg

What is the minimum daily cost for the farmer, for food with at least 25% protein and max 6% fibre.
----------------------------------

I initially poised the following

Let var1 = Corn_inKG // the amount of corn in kg
Let var2 = Maize_inKG // the amount of maize in kg

Minimise the following cost:
y = (£0.3)*(Corn_inKG) + (£0.9)*(Maize_inKG)

Total Protein:
0.032kg*(Corn_inKG) + 0.360kg*(Maize_inKG)

Total Fibre
0.027kg*(Corn_in_KG) + 0.065kg*(Maize_inKG)
 >> Beatrice Sushspear - Fri, 28 Oct 2016 16:54:06 EST ID:ZjFavw7f Ignore Report Reply Without more information I would assume that you can take the amount of feed the farner needs to be exactly 800kg. Since there is no deal or discount for buying more corn or maize, any additional mass of feed will cost more money. As you are asked to minimize the cost to the farmer, you should always use the least mass possible.Now it may be that you cannot minimize the cost and attain 800kg at the same time without buying some fraction of a kilogram of feed. This is probably why the question says "at least" 800kg. You will then need to take your answer and round up to the nearest integer if the feed is sold strictly by the kg and not just weighed en masse.
 >> George Foffingworth - Mon, 31 Oct 2016 09:30:26 EST ID:tyLg+ghU Ignore Report Reply >>15253Thank you, this was the only information provided so I shall do as formulated in OP. Thank you Beatrice Sushspear

muh math
Betsy Pushridge - Mon, 16 May 2016 20:04:48 EST ID:RHLOntyV
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Is mathematics a discovered (natural) or man-made phenomena?
Personally I think it's natural because it can precisely describe natural events and laws which those events must conform to.
Thoughts on this?
 >> Celty !Iv58NJh.IE - Tue, 11 Oct 2016 20:20:20 EST ID:v3boz4eW Ignore Report Reply >>15119That's reasonable.*shit eating grin*
 >> Mr. Schwitters - Sun, 16 Oct 2016 00:37:47 EST ID:xB0tAwHQ Ignore Report Reply 1476592667678.jpg -(172000B / 167.97KB, 472x570) Thumbnail displayed, click image for full size. It's both natural and man-made. Look at that documentary where Zizek is standing in a pile of garbage, and saying, "This is the most natural thing in the world!". Nature is man. Culture is nature. Man is not separate from nature. You can't take biology out of the environment from which the gene evolves.Well, you hear "Time/space/maths doesn't exist, man" so often. But for whom does it not exist?I perceive its existence. How do I perceive it? Through my nervous system. My nervous system is receiving billions of signals every second.Luckily there is a brain there which categorizes those signals for me into distinct tracks based on what has been evolutionary fit. That way, when I see a bear in the forest, I don't take out my ruler and try to measure every hair on his body in order to determine if the bear is a threat. Automatically my brain detects a threat and different glands fire off hormones, etc. and I find some way to keep my pic-a-nick basket.To get a real answer to this, you have to look at the nervous systems evolved through time, and how nervous systems react to the phenomenal world. We still have amoeba, reptile, mammal, etc. sense, and that affects our perception. The 'tracks' where we store imprints about previous threats/comforts determines our perception.Euclidean geometry is only an explanation of the world as it relates to the perception of domesticated primates. We wouldn't see space in 3D if our nervous systems were different. We wouldn't plot points in 3D space if our nervous systems were different. Phenomenal existence only appears as it does because we evolved through all of the other species in the environment and atmosphere that we did.tl;dr perception is everything, practice magick and cast spells dude
 >> Shitting Trotdale - Sat, 22 Oct 2016 10:53:25 EST ID:ussIY8P4 Ignore Report Reply >>15244>We wouldn't plot points in 3D space if our nervous systems were different.No, we would still plot points in space regardless of how we evolved. Euclidean geometry may be somehow favored'' by our biology because it is a good local approximation of the acutal curved space in which we live, but even if a creature evolved in a truly alien geomtery it would still make up the geometry we live in if it was intelligent, just like how we have made up infinite families of alien geometries that don't obviously correspond to our physical reality.

uhhh
Reuben Honeyhood - Sun, 25 Sep 2016 22:57:20 EST ID:Z131bdYa
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Can someone please explain to me what's happening here?
The idea of a fraction being made up of other fractions is already weird to me, but why is the answer just flipping them?
 >> George Dezzlesudging - Fri, 07 Oct 2016 21:30:10 EST ID:GmQCz3Ds Ignore Report Reply 1/2 over 1/4. you flip 1 wrong fraction and multiply the 2 fractions together.instead of .5 / .25 you're doing .5 times 4.
 >> Lillian Daddlekeg - Sat, 08 Oct 2016 22:03:58 EST ID:A2j/BW/W Ignore Report Reply (1/x)/(1/y) = 1*(1/x)/(1/y) = (xy/xy)*(1/x)/(1/y) = (xy/x)/(xy/y) = y/xIf you multiply the numerator and denominator of a fraction by the same value, the value of the fraction stays the same. Here you're just multiplying the top and bottom of the fraction by 2^5*7^2. The 2^5s cancel in the top and the 7^2 cancel in the bottom.
 >> Ernest Cashfeck - Mon, 10 Oct 2016 10:20:43 EST ID:WotAVLKX Ignore Report Reply >>15219 lol man, dislexia? thats harecore

Help evaluate this integral?
Clara Bardwater - Sun, 25 Sep 2016 02:55:07 EST ID:os0KtXjb
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So I'm working on a Calc II assignment, and I'm stuck on a problem that asks for the volume of the infinitely long solid attached.

f(x) = xe^(-x^3), so I can prove that the integral converges. I'm a lazy cunt so I used Wolfram Alpha to evaluate the integral and the answer involves the gamma function, which puts solving it beyond the level of this class.

So is there a more obvious way to go about this problem, or did my prof. assign a problem that we can't actually do at this level?
 >> Hannah Wummerham - Wed, 05 Oct 2016 14:21:15 EST ID:QUTqUdS2 Ignore Report Reply >>15214Yes you integrate by parts, no need for a Gamma function.
 >> Charlotte Cunkinfoot - Fri, 07 Oct 2016 20:57:03 EST ID:q1podWFh Ignore Report Reply >>15221I tried this. It only takes a u-substitution this way.Also, the gamma function can be covered in a class at this level, although it isn't needed here.
 >> Lillian Daddlekeg - Sat, 08 Oct 2016 21:13:04 EST ID:A2j/BW/W Ignore Report Reply >>15221>>15237This. The integrand is pi*x^2*e^(-2x^3). Set u = -2x^3, the answer comes out to be pi/6.

10101011010101
Betsy Fuckingway - Wed, 28 Sep 2016 20:51:12 EST ID:dJCwm4mq
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When u come onto the math board
 >> Beatrice Subberbanks - Fri, 30 Sep 2016 16:50:22 EST ID:9fX9//hV Ignore Report Reply What in the blue fuck are you talking about?
 >> Charlotte Brezzlecheg - Fri, 30 Sep 2016 17:11:16 EST ID:ZD4TCLS2 Ignore Report Reply >>15231I think that by posting a picture of the green vertical "code" from the movie The Matrix along with a binary string for a subject the OP is trying to indicate that they felt awed by the discussions taking place here.
 >> Angus Blackbury - Fri, 30 Sep 2016 21:04:04 EST ID:sWygU/VW Ignore Report Reply >>15231OP high as fuck

Basic trig question
Geraldo juarez - Tue, 13 Sep 2016 14:35:19 EST ID:wFiRC6TB
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Ok so long story short - my math teacher this semester is the wort teacher ive ever had in my entire life. Asked him what formula they used to cme up with the xy coordinates on a unit circle. Example: terminal leg of 45* aka pi/4 on the unit circle intercepts at p=(root2/2, root2/2). He said there is no formula you just have to memorize. Are you kidding me i studied the chapter over and over and realized its the pythagorean theorum no matter what the radius equals. What a shit teacher.

Anyway my question is how does sin=y, but the fundamental idenitity of sin is 1/csc? Does this mean that y=1/csc?
Part 2: can that one be interchanged with any value of r? For example does it apply for circles that are not unit circles?

I know this is super basic, and my book explains it in a complex way, but its not like i have a good enough teacher to ask any questions to fill in the holes. Ive had straight a's and b's in my previous classes up til this guy.
 >> Vesuvius - Sat, 17 Sep 2016 11:24:58 EST ID:9fX9//hV Ignore Report Reply >>15202it's like asking why do we call dogs, dogs? Because that's just what we call them.
 >> John Bundlefoot - Sun, 18 Sep 2016 04:18:43 EST ID:9fX9//hV Ignore Report Reply >>15204I should say the same to you.
 >> John Bundlefoot - Sun, 18 Sep 2016 04:20:21 EST ID:9fX9//hV Ignore Report Reply >>15204I never said I didn't understand the post. I said you were overcomplicating it. If you don't understand the difference you probably shouldn't be giving people advice about anything.

Sett theory
Graham Fingerhat - Thu, 01 Sep 2016 05:16:48 EST ID:NsqdJ6Lc
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Is there a way to find the equivalence relation corresponding to any partition?
Like p = {{1,4,7},{2,5,8},{3,6},{9}} with is an example i have in front of my nose. Can I find the relation from wich i get that partition of {1,2,3,4,5,6,7,8,9} ?
 >> Charlotte Gobberhood - Tue, 06 Sep 2016 18:06:06 EST ID:4JPlB6jB Ignore Report Reply >>15186>This is the same as having that b in P_i and a in P_i, so (b,a) in R, so the relation R is reflexive.This should say symmetric at the end instead of reflexive.>>15187>manually define an equivalenceDo you mean the realtion induced by a partition or something else? I'm not sure what constitutes "manually" defining a relation. Also, it's not rigorous to say that>numbers are in the equivalence class here if they are 3 more than some other number in the equilance classsince the partition {{1,4,7},{2,5,8},{3,6,8}} also has that property and induces a different equivalence relation.
 >> Charlotte Gobberhood - Tue, 06 Sep 2016 18:07:01 EST ID:4JPlB6jB Ignore Report Reply >>15190>{{1,4,7},{2,5,8},{3,6,8}}This should be {{1,4,7},{2,5,8},{3,6,9}} obviously.
 >> Nathaniel Fembledatch - Wed, 07 Sep 2016 18:46:55 EST ID:DsqbErs4 Ignore Report Reply >>15190Oh I misread the OP, you're right. What I mean by manually defining an equivalence is to identify all the elements of one of partition sets. You could rephrase what I said by identifying the orbits of the action of adding 3 to elements of the set, with the caveat that 9 is in its own equivalence class separate from everyone else.

A Geometry(?) Question
Henry Bugglewill - Thu, 31 Mar 2016 20:43:14 EST ID:Z131bdYa
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What is the mathematical/geometric name for the shape of a peanut butter cup like this?

The best I can come up with is "crennelated truncated cone" but I feel like there's some ten-word name I could use that would very accurately describe it....
 >> Molly Suvingham - Tue, 19 Apr 2016 21:39:48 EST ID:dFkJK1jc Ignore Report Reply should call it the Reese Cup. if anyone's qualified to name it it's us
 >> Nell Penderfedging - Sun, 15 May 2016 20:38:08 EST ID:1eeqYqTy Ignore Report Reply >>15075Upside down star fort.
 >> John Funkinshaw - Thu, 25 Aug 2016 10:53:32 EST ID:n7MnP1ar Ignore Report Reply >>15075crennelated frustum

Probability question (probably beneath most you)
Esther Dirringlore - Mon, 16 Nov 2015 07:50:43 EST ID:TdrCDJzk
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I'd appreciate it if someone could answer a probability question for me. I can't remember exactly how to work it out.

Question: How many combinations of 3As and 5Bs are there? For example, one combination would be: 'AAABBBBB' ; another would be 'ABABABBB'.
 >> Lillian Povingstone - Tue, 17 Nov 2015 01:03:27 EST ID:TdrCDJzk Ignore Report Reply >>14973Okay. Ignore this thread. I found an online combinations calculator.
 >> Whitey Gobbleson - Tue, 17 Nov 2015 14:30:55 EST ID:J4OUpAxW Ignore Report Reply >>14977Magnets how do they work?
 >> John Divingmetch - Tue, 23 Aug 2016 13:31:10 EST ID:TANb9lmN Ignore Report Reply 8!/(3!*5!)

Help me help someone get a math-boner
Hannah Sollernodge - Fri, 22 Apr 2016 13:02:27 EST ID:WD6PkLOh
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Ok, so how would you introduce someone to the fun bits of mathematics? My girlfriend has maths at standard grade (8/9th grade for Americans I think), and she's interested in seeing why I do it just for fun. She isn't too patient with it, I tried to explain that x^1/3 is the cube root of x and she just got angry after a while and quit, so it needs to have the most 'wow' for the least amount of difficulty (basically math porn). I was going to show her some very basic calculus and some quadratic equation shit, but I'm doubting myself now.
What should I be showing her, or is it a lost cause?
 >> Martin Goodfoot - Sun, 17 Jul 2016 21:20:51 EST ID:9K7KtQWq Ignore Report Reply >>15100explain what she enjoys in terms of math. Whenever I tell people you can explain biology/taxes/cooking in terms of math they get intrigued.
 >> George Gennerstock - Mon, 01 Aug 2016 12:05:29 EST ID:yxQzbAra Ignore Report Reply 1470067529481.gif -(1562229B / 1.49MB, 340x242) Thumbnail displayed, click image for full size. I have the same problem. I can't seem to be all that interested in mathematics. The only thing that serves as a motivation is when I solve a problem, which I see as moderate to hard, by myself. Too bad I am bad at maths, so that dopamine release doesn't happen a lot. I see the proposal of mixing maths with something you find genuinely interesting being mentioned. The only thing is, I find everything from astronomy and botany to politics and art interesting. I do not have many hobbies, because I usually lose interest in them after a period. I have brewed, planted, and written graffiti, but they never stick for more than a few projects.How do I get myself interested in the amazing world of mathematics? I really want to be able to do complex equations one day. Is it really nothing else than forcing myself to do a few problems every day? I have the attention span of a pornstar's pubic hair, so I don't think that will work for me.
 >> Shit Benningbury - Sat, 06 Aug 2016 03:29:45 EST ID:ijd+nKqH Ignore Report Reply Measurement by Lockharthttp://www.hup.harvard.edu/catalog.php?isbn=9780674057555Here's Looking at Euclid by Belloshttp://www.alexbellos.com/numberlandPatterns of the Universe: A Coloring Adventure in Math and Beauty by BellosFind it on amazon, interesting math colouring book where you reveal patterns.Loop, the gamehttp://www.loop-the-game.com/ Bellos also reinvented pool using an ellipse

Archie Nemmerhock - Tue, 05 Apr 2016 18:49:37 EST ID:cTPi6AuQ
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There's two guys:
If guy #1 borrows 2 dollars from guy #2, they have the same amount.
If guy #2 borrows 2 dollars from guy #1. he has twice the amount of guy #1.
How much money do they have from the start?
 >> Phyllis Nivingshit - Mon, 11 Apr 2016 07:47:21 EST ID:A2j/BW/W Ignore Report Reply 1460375241260.gif -(2532232B / 2.41MB, 452x256) Thumbnail displayed, click image for full size. >>15086Wow! Such math! So amaze! Wow!
 >> Phineas Condlenore - Sat, 07 May 2016 17:02:14 EST ID:3U6ZTH6i Ignore Report Reply >>15086Sooo.....Lekta thought Phoebe was serious...Lekta should be a cop.
 >> Priscilla Pinkinstone - Sat, 16 Jul 2016 01:31:09 EST ID:Tg2WbKCI Ignore Report Reply >>15086poor guy skipped reading comprehension class, wait that isn't real, you should still feel bad

Gamedev is great
Ian Dundleludging - Wed, 04 May 2016 00:31:32 EST ID:7yI2oiC+
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it's a great way to see the impact of changes in your model. Of course this applies mostly to folks interested in applied mathematics. But what is "pure" mathematics, but math that hasn't been yet applied? Give me a physical interpretation of the fractional calculus. Better yet, show me it in a Game.

There's also the fact that a lot of gamedevs struggle with some basic maths, mostly stuff regarding linalg, quaternions come up a lot. You could probably help!

Did you know: There's a 420chan amateur gamedev community, >>>/vg/664016

And from a pedagogical pov, who'd bet against gamedev working its way into the classroom? It's the perfect confluence of any applied area you can think of, Fourier series to taxicab metric
 >> Clara Fadgebit - Fri, 20 May 2016 17:24:26 EST ID:WHIrmu8h Ignore Report Reply 1463779466259.jpg -(153794B / 150.19KB, 610x261) Thumbnail displayed, click image for full size. > gamedev in the classroomIt would take the fun out of it eventually if it's forced. My first program was a game and later gamedev had me apply trig. It is still a lot of boring work, too, a lot of pure programming, so to speak, as pure maths is applied to maths.Planning is required when fleshing out an game from scratch. There could be too much freedom in a project to grade it. Gamification works better if fit to the audience, eg. in a logic puzzle game.
 >> Ian Goodworth - Sat, 11 Jun 2016 17:23:59 EST ID:+Gs8DK3Y Ignore Report Reply >>15127True, making games is lots of programming and boring work until you get the interesting math part.I think programming shaders is a better way of teaching maths https://www.youtube.com/watch?v=0ifChJ0nJfMAnd to be honest most maths you will do in gamedev has to do with graphics.
 >> Shitting Crimmerfield - Mon, 20 Jun 2016 01:47:59 EST ID:ZiObD4pn Ignore Report Reply >>15159Maybe gamedev isn't that good for applying maths, but I'm pretty sure it's good for making physics simulations.

How do I recover the signs of integrals and derivatives?
Nell Penderfedging - Sun, 15 May 2016 20:44:52 EST ID:1eeqYqTy
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I can define derivatives and integrals in terms of the Lebesgue
measure but how do I recover signs?

$$\left. \left\lvert \frac{\mathrm{d} y}{\mathrm{d} x} \right\rvert \right\rvert_{x = a}= \lim_{C \rightarrow \left\{a\right\}}\frac{\lambda^*\left( \left\{ y_x \, \vert \, x \in C \right\} \right)}{\lambda^*\left( C \right)}$$

$$\left\lvert \, \underset{\, \, x \in C}{\int} y \, \mathrm{d} x \right\rvert = \lambda^* \left( \left\{ \left( x , y_x \right) \, \vert \, x \in C \right\} \right)$$
 >> Martha Pudgestedging - Tue, 14 Jun 2016 12:22:55 EST ID:c7Q4EFJt Ignore Report Reply So there's two ways to do this. The first is to define the integral in terms of the lebesgue measure and use the doublet distribution to define the derivative in terms of an integral transform and the second is to define a delta as the lebesgue measure of the increasing sections of a function minus the measure of the decreasing sections of a function and then define the derivative using the delta as normal.

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