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420chan is Getting Overhauled - Changelog/Bug Report/Request Thread (Updated July 26)

Big O

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- Sun, 28 Feb 2016 18:08:48 EST uLlpzKkX No.15059
File: 1456700928519.png -(675671B / 659.83KB, 1106x1012) Thumbnail displayed, click image for full size. Big O
This may be better suited for /prog/ but I'll try here.

15n + 62 = O(n)
15n + 62 <= c * f(n)

I need to find a C less than 40 and solve for k.
The answer is C = 16, K = 62, where 15n + 62 <= 16n, simplified to give you 62 <= n. This is what my textbook has as the answer.

Can anyone explain this to me? I don't understand, why is K = 62? I understand this is marking the point where one side of the equation passes the other side, but I don't know how 62 plays into that at all.
Esther Nazzlebig - Sun, 28 Feb 2016 18:14:55 EST uLlpzKkX No.15060 Reply
Hey nevermind, it's 62 because 15(62) + 62 <= 16(62). That was easy.

Diff Equations: Exact Equations

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- Tue, 23 Feb 2016 00:53:02 EST qCDKBx4v No.15052
File: 1456206782611.jpg -(123714B / 120.81KB, 945x945) Thumbnail displayed, click image for full size. Diff Equations: Exact Equations
Please help.
Determine the constant c so that the differential equation is exact.
(x+cy+ 2)dx + (y-x)dy = 0
1 posts omitted. Click View Thread to read.
Hedda Dirrydog - Tue, 23 Feb 2016 13:50:22 EST A2j/BW/W No.15055 Reply
That's correct, but your work >>15053 is all screwed up. You're supposed to be integrating, not taking partial derivatives.
Hedda Dirrydog - Tue, 23 Feb 2016 13:58:11 EST A2j/BW/W No.15056 Reply
You're supposed to find the potential function, which turns out to be F(x, y) = 1/2x^2 + 1/2y^2 + 2x - xy + z where z is the constant of integration.

for a er secret project

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- Wed, 30 Dec 2015 04:20:23 EST 8sbm1RBU No.15010
File: 1451467223718.png -(15640B / 15.27KB, 819x460) Thumbnail displayed, click image for full size. for a er secret project
got an answer??

it goes line by line not a whole sentence x
Nicholas Pockdock - Thu, 31 Dec 2015 07:58:38 EST WhsPRodl No.15011 Reply
Penny = million
Hundred penny = 100 million = pound
Hundred million pound = Hundred million pound
Angus Sorryforth - Thu, 31 Dec 2015 08:05:36 EST 8sbm1RBU No.15012 Reply

isnt it to do with money so
hundred penny = £100million
£100million x £100million = hundred penny x hundred penny?
= £10000
Shit Snodbury - Sun, 21 Feb 2016 14:11:34 EST WhsPRodl No.15051 Reply
No because you see that a
penny = million
100 penny v 100 million = 1 pound
1 million = 0.01 pound
0.01 pound * 100 million/penny = 1 pound

f(x)= 0.01x

It has nothing to do with money, but with the prefixes and the specific numeral system (base 10 decimal)
I could might as well have been apples and pies

Where to start?

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- Mon, 14 Dec 2015 02:29:48 EST hlhZo5V6 No.15000
File: 1450078188284.jpg -(226445B / 221.14KB, 1000x744) Thumbnail displayed, click image for full size. Where to start?
Hey /math/,
I need some help. I have always been shit at math. I never studied throughout high school and got mostly C's or D's in math while maintaining straight A's in the rest of my classes. It was mostly due to me not completing homework, but I also failed to grasp a lot of concepts.

So now that I'm in college I'm fucking up hard in math. I have to take a class I already took in high school because I did so bad on the placement exams. And I just failed it. My goal is to get serious and focus on math more, however I have no idea where to start.

I'm in "Intro to College Algebra" which basically covers pre- algebra through algebra 2 with a little geometry sprinkled in. With that in mind, where the hell do I start? What material is out there that I should cover? Could you guys be so kind as to show me in the right direction as to where to study, whether it be Khan Academy or a particular set of text books. I feel as if I need to start towards the bottom of math knowledge because I honestly don't even remember the rules for working with fractions all the way back in elementary school.

Thanks guys.
6 posts omitted. Click View Thread to read.
Shitting Fushbury - Wed, 03 Feb 2016 10:45:39 EST OD6ADxvT No.15037 Reply
Im somewhat impressed that you really do wish to turn your issues in mathematics around. Usually once someone has put Math off for so long they just dont have the will to get back to it.

Khan Academy is the best free resource and you should be on it every day for at least 20 minutes for extra practice. Do all the homework to the best of your ability and turn it in conpleted. On exams answer everything to the best of your ability and try and leave nothing blank. Partial points are better than nothing but this is more crucial in higher level classes.

Start at geometry and equation solving. If your unsure about algebra rules find examples before you practice something illegal for a week straight. Ive seen plenty of kids try and simplify the sum of two squares inside a square root :/

This was my study progressio before college after I spent 2 years washing dishes after high school.
Algebra1/geometry >> algebra2 >> pre calc 1/2 >> calculus
Differential >> integral >> vector >> series >> multivariable

Linear Algebra and Diff.Eq can be taken anytime after integral calculus.
Henry Fommlefield - Mon, 15 Feb 2016 19:36:38 EST RHLOntyV No.15047 Reply
not to be that guy, but I think you're thinking of Velleman's how to prove it, Polya wrote "How to Solve It," which is a great book in its own right.
Doris Nundlechodging - Wed, 17 Feb 2016 03:50:13 EST aLV1scJv No.15048 Reply
symbolab is free though

wolfram is just mathematica stripped down so you could just pirate that

Prolem Sets for Group Theory Class

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- Sat, 07 Nov 2015 07:06:32 EST q3ZVtHN5 No.14966
File: 1446897992036.png -(8060B / 7.87KB, 220x229) Thumbnail displayed, click image for full size. Prolem Sets for Group Theory Class
So I'm taking a Group Theory class and we are using the book Undergraduate Algebra by Serge Lang.

It's a good book except that there's not solution manual so it is pretty useless to practice problems.

Can any of you please share any problem sets with solution, you had if you also took this class?

Or maybe a book on group theory that has both practice problems and solutions?

Pic unrelated.
3 posts omitted. Click View Thread to read.
Archie Murdbury - Wed, 06 Jan 2016 02:44:58 EST iXKR5G5E No.15014 Reply
But the pic is related.
Edwin Cocklemane - Tue, 02 Feb 2016 20:35:30 EST voE+OnYz No.15036 Reply
>Pic unrelated.
Oh, you'll be surprised annon.
Albert Dublingkork - Sat, 06 Feb 2016 02:57:12 EST peflw+mo No.15042 Reply
1454745432405.jpg -(10424B / 10.18KB, 200x200) Thumbnail displayed, click image for full size.
>Pic unrelated.

Linear ODEs

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- Wed, 03 Feb 2016 22:38:05 EST 0k+KCTnX No.15038
File: 1454557085767.jpg -(57503B / 56.16KB, 592x127) Thumbnail displayed, click image for full size. Linear ODEs
I don't understand how this equation is linear. Can someone explain?
Lillian Sugglestock - Thu, 04 Feb 2016 02:04:38 EST Zrg8t7vN No.15039 Reply
Because sine is a function of t; if it were a function of y, then the equation would be non-linear.

Compass Math Practice

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- Tue, 19 Jan 2016 11:58:07 EST OMB8xTL7 No.15025
File: 1453222687845.jpg -(74281B / 72.54KB, 700x483) Thumbnail displayed, click image for full size. Compass Math Practice
I'm going back to college after a 4 year hiatus, and I have to take the Compass test. I'm in desperate need of help on the math section since it's been about 8 years since i had to do high school math. I was wondering if any one here knows of any good sites, or maybe where to find workbooks relating to Algebra, Geometry, Precalc, and Trigonometry. I have ordered a test prep book, but I'm looking for somewhere/something to practice as much as I can.

Intro Adv Math Book

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- Wed, 20 Jan 2016 20:37:00 EST 0k+KCTnX No.15027
File: 1453340220299.jpg -(44469B / 43.43KB, 307x457) Thumbnail displayed, click image for full size. Intro Adv Math Book
For those who've had experience with this class about proofs, do you think this book is necessary?

1 posts omitted. Click View Thread to read.
Augustus Blollerville - Wed, 20 Jan 2016 22:25:34 EST Dk8yywxc No.15029 Reply
There was an extra "understanding" in my post but you should be able to figure it out if you're taking that sort of class
Doris Grimman - Thu, 21 Jan 2016 16:47:58 EST J4OUpAxW No.15030 Reply
Can you prove it B)

But yeah I will take your advice. Proofs are probably my most hated part of math though. Didn't realize that I was taking a whole course on them.
Albert Pickridge - Thu, 21 Jan 2016 19:43:00 EST Dk8yywxc No.15031 Reply

Proofs are the best part of math! You take that back!

Games throwing math at you...

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- Tue, 03 Nov 2015 23:19:50 EST tE5uLpV5 No.14963
File: 1446610790884.jpg -(86737B / 84.70KB, 750x600) Thumbnail displayed, click image for full size. Games throwing math at you...

I've just reinstalled Vampire: The Masquerade - Bloodlines to play the Antitribu mod. In the mod, they've added a locked door to the Tremere Chantry downtown that cannot be picked open, but instead requires a 4 digit code to open. A piece of paper is added on the table in the room you find Strauss and it has these equations on it, and I'm pretty sure that the values of the letters are going to be my 4 code digit. The problem is I have no idea how to figure them out.

Can /math/ give a gamer a helping hand?
If you can tell me the answer straight up, great, but if anybody feels like telling me how to solve the problem and others like it in the future, it'd be much appreciated.
3 posts and 1 images omitted. Click View Thread to read.
Sidney Clommerhall - Thu, 07 Jan 2016 13:33:32 EST gEBlLN+c No.15016 Reply

not OP but I did graduate highschool. Never learned matrix shit or anything


so this matrix thing, Im reading about how it works and so far I understand it, at least I think I do.

given the equations OP listed my matrix should look something like this right?
2a -b 0 8d -41
0 4b 6c -d -11
4a 7b 2c d -10
9a 12b -3c 2d -25

and then I just do row reduction?
should I be including the numbers without variables in the rows? also row 2 is the row I made for 4b+6c-d-11, am I right to put a zero in the first column because there is no value of a in this equation?
Oliver Bodgewell - Fri, 08 Jan 2016 15:28:42 EST gEBlLN+c No.15018 Reply
nb but holy shit I remember formatting the fuck out of that matrix yesterday so it was legible but its totally not
Nigel Drenderman - Sun, 10 Jan 2016 13:47:20 EST 3lJiHBSn No.15020 Reply
it's so easy man put it in wolfram

install octave


A = [4 7 2 1; 9 12 -3 2; 0 4 6 1; 2 -1 9 8]
B = [10 25 11 41]

C = A\B

The result C will give you your answer in the form

C =



C = [a b c d]


high thought

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- Sun, 10 Jan 2016 00:41:57 EST 3lJiHBSn No.15019
File: 1452404517332.gif -(641B / 641bytes, 156x80) Thumbnail displayed, click image for full size. high thought
my understanding is that people don't like gravity because it's weak and it doesn't make sense why it's so weak

my thought is that maybe it isn't as weak as we say it is? a heavy object dilates time around it right? so hold that thought

if I told you i built a time machine, what are a few things you'd expect from my machine? for one, it probably consumes a lot of energy right?

maybe gravity's true power comes from being able to dilate time

maybe gravity dilates time through an unknown force?

maybe I have no understanding of general relativity at all.

if we can control gravity, we can control time and space

am i totally wrong here?
Fucking Simmletore - Wed, 13 Jan 2016 08:03:43 EST Zrg8t7vN No.15021 Reply
Well, you at least seem to know what gravitational time dilation is. For those not in the know, gravitational time dilation is the effect of time ticking slower closer to sources of gravitation (relative to clocks at higher gravitational potential). This is predicted in Einstein's general theory of relativity and has been confirmed in experiment. While gravity can be thought of as a force, it is distinguished from the other forces as the curvature of spacetime itself. This means that the force you feel standing on the Earth is fundamentally the same as the force you would feel standing in a rocket ship accelerating at ~9.8 m/s^2 in microgravity.

Compared to the other forces (electromagnetism, strong force, weak force), gravity is very weak. And you're right, the reason for this is not understood. It's one of physics' unsolved mysteries called the hierarchy problem.

The only sure methods of time travel, such as orbiting close to a black hole, do indeed require immense amounts of energy e.g. the thrust required to lower and raise the spacecraft into and out of orbit around a black hole. By such means, you can only travel into the future. Time travel into the past is probably impossible.

Lrn2 math for a smart guy

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- Sun, 06 Sep 2015 01:34:58 EST N0VIeVLI No.14878
File: 1441517698394.gif -(249137B / 243.30KB, 281x240) Thumbnail displayed, click image for full size. Lrn2 math for a smart guy
Hey folks, I got a big ol' question and I'm hoping there may be some people here like me who could give me some good advice. I'll try to spare details but I have an.. issue. My issue is I'm too smart damnit. I didn't go to college for a really dumb and unfortunate reason, and while my issue would have surely popped up there it wasn't why I didn't go. But at the moment, all I have under my belt is high- school geometry and algebra II. I would have gone higher, but along with it being drilled in my head that "poor people don't go to private schools" and so I'm already over qualified for the schools I have to choose among, I just hated how slow everything went. Maybe none of it matters because I went to a dreadfully average school, but I was kind of the freak. After commenting about the insane amount of homework assigned for simple concepts my teacher simply refused to believe I was capable of doing it all in my head, even after I proved it on the spot. I was the freak in academic challenge, I'm in my schools hall of fame (lol), I got a 35 on the ACT and it was so damn easy Idk how I didn't get a 36.

I guess I'm venting a little but my point is I'm pretty smart, or at least I think I am. I want to just teach myself but I'm not sure where to start and I'm impatient. I tried Khan academy and I'm sorry but I feel like that site is remedial as fuck. I can't handle how slow it goes.

So my question is to other autodidacts. What sites or books or series of books would you recommend for someone who doesn't really know much but also isn't for dumb guys? I guess my starting point would be trigonometry and calculus.

And another question I have is, where do I go from there? I'd like to get a well rounded knowledge of all the different subjects. So at the moment, I'm not looking to dig into one specific subject too much. I want a working knowledge that would allow me to dig in where I want after I'm actually capable of understanding the subjects in the first place.

Computer science, programming, calculus, physics, quantum...stuff... statistics, pure math, the different planes, that's about the extent of what I even know exists. I'd like to just hop on Wikipedia and familiarize myself with everything but I need a good starting point. I can't even read the stuff that those pages are filled with so I certainly can't understand what I'm looking at.

So do you have any recommendations for books or sites with a sufficiently accelerated pace? And in which order would you place the "big subjects" on the path to learning them? Primarily I want to understand the fundamentals of computer science, physics, and I guess pure math, not that I'm even totally sure what that is.

Thanks I advance and here's a gif
6 posts omitted. Click View Thread to read.
Defalt503 - Sat, 07 Nov 2015 10:36:46 EST GNz4wLxQ No.14967 Reply
AOPS (Art of Problem Solving)
It's expensive, but very rigorous in its coverage.
Phoebe Gottingnadge - Sun, 20 Dec 2015 05:54:08 EST 4PxD5/q2 No.15006 Reply
>hurr durr i'm so smart i wanna learn mafs but i cant even use teh googles and muh brain power 2 narrow down a gud source
lel i hope you don't talk to people irl with that attitude

Calc promblem help,

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- Sun, 11 Oct 2015 09:08:49 EST q3ZVtHN5 No.14929
File: 1444568929865.png -(9425B / 9.20KB, 662x157) Thumbnail displayed, click image for full size. Calc promblem help,
How do I solve this for m or for n? I.e. get something like m =....

Is there some general way that does not depend on the function of P(x)?

Otherwise P(x) = sin^2(x)
3 posts omitted. Click View Thread to read.
Hedda Tillingman - Mon, 12 Oct 2015 08:21:13 EST q3ZVtHN5 No.14934 Reply

I worked it out the long way, eventually and got the same solution. Thanks guys.
Barnaby Dommerbick - Sun, 06 Dec 2015 09:23:04 EST kb5uOcCo No.14992 Reply
It doesn't have to be periodic.
Imagine a function that is zero everywhere outside of some interval, and one inside the interval. If this interval is larger than b-a then, for a fixed n, there will be a continuous range of m for which the statement is true, unless n is chosen such that the RHS is neither zero nor b-a (that is, the integral is taken over a region neither entirely in the zero part of the function, nor entirely in the non-zeropart), in which case there are only two values of m that satisfy it.
The condition in OP's pic defines a subspace of R^2, which for the function above is not connected (try plotting it). It is interesting to consider the different possible subsets of R^2 you can get with various classes of functions.
William Murdham - Wed, 16 Dec 2015 20:12:35 EST C1tA08VQ No.15004 Reply
This depends on the OP equation holding for pecific a, b, as opposed to all a,b. In the latter cans, you do require P to be periodic.

In general, this seems to be a bit of a dumb exercise though, but I guess that's subjectiive.

Advanced Calculus

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- Mon, 10 Aug 2015 18:35:46 EST AuFFnCvz No.14855
File: 1439246146147.jpg -(35151B / 34.33KB, 640x480) Thumbnail displayed, click image for full size. Advanced Calculus
Hey math,

I'm taking the first Advanced Calculus (intro to proof writing) course this fall. I've done some of the work in advance and am not too worried. What were your experiences in your homeland's analogous class?
6 posts omitted. Click View Thread to read.
Caroline Fubberforth - Mon, 26 Oct 2015 13:56:36 EST nDKmqEtd No.14954 Reply
I'd like to see a game theory course graded this way.
Martin Hippershaw - Fri, 30 Oct 2015 22:31:17 EST AuFFnCvz No.14961 Reply
I go to a very science-y state university, so the math major is pretty competitive -- a positive thing, but then we have instructors who do this kind of stuff to weed people out. Pretty stressful, man.
Walter Nenderbury - Mon, 14 Dec 2015 02:09:04 EST VQWIWcoe No.14999 Reply
Do you have a copy of Galois' Dream? It's a nice text, you might like it.

I wanna be a master

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- Wed, 02 Dec 2015 06:52:11 EST tkxf2V39 No.14988
File: 1449057131350.png -(8745B / 8.54KB, 790x595) Thumbnail displayed, click image for full size. I wanna  be a master
Can somebody here give me a beginning, to end list of how I should study complete field of math?
5 posts omitted. Click View Thread to read.
Caroline Brookcocke - Sat, 12 Dec 2015 16:11:59 EST k9kkb1hx No.14996 Reply

This site tries to enumerate all proofs and how they are connected. You can't really do anything with it though and trying to learn Mathematics using it would be like trying to learn driving by watching assembly line robots build cars.
Hannah Fandale - Sun, 13 Dec 2015 12:10:00 EST Dk8yywxc No.14997 Reply

Yep that's the one.
Walter Nenderbury - Mon, 14 Dec 2015 02:01:28 EST VQWIWcoe No.14998 Reply
The correct answer is "it's impossible". There's already more math than a person could digest in a lifetime, and more is made/found every day.

But doing the standard progression arithmetic->algebra/geometry/precalc -> calc, then some proof fundamentals, then hit intro level of diff eq, linear algebra, combinatorics and probability, group theory, and you'll be in a good place to head off in whatever direction you like.

ie read off a programme listing for most undergrad math programs.

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