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can you help me? by Phoebe Wankinwater - Wed, 17 Dec 2014 15:56:58 EST ID:K92q/1nw No.14537 Ignore Report Reply Quick Reply
File: 1418849818247.gif -(24799B / 24.22KB, 303x362) Thumbnail displayed, click image for full size. 24799
Hey guys, can anyone help with the following question? I am really stuck with it (and not through lack of trying, believe me)

A microphone has a polar pattern described as e = 1 + 1.5 * cos(angle).
Its on-axis sensitivity is given as -40dBV/Pa.
A sound source is such that it produces 75dB SPL at the microphone diaphragm.
What is the microphone output in miliVolts if the source angle is 90 degrees to the right of the microphone.

V(angle) / V(on axis) = (1+1.5 * cos(angle)) / (1+1.5 * cos(0))


haalp by Angus Worthingshaw - Fri, 05 Dec 2014 16:44:51 EST ID:wdBv6x7g No.14503 Ignore Report Reply Quick Reply
File: 1417815891494.jpg -(55091B / 53.80KB, 500x471) Thumbnail displayed, click image for full size. 55091
i need to find the area of the polar curve 2(a)sin(theta)

i keep getting 2(pi)(a)^2 but the book says its just (pi)(a)^2

i used the bounds 0 to 2pi which could be wrong but i dont see why.
>>
Angus Worthingshaw - Fri, 05 Dec 2014 16:48:52 EST ID:wdBv6x7g No.14504 Ignore Report Quick Reply
>>14503
ugh fuck im an idiot guys ill the bounds are 0 to pi for this curve
>>
Nigel Depperham - Sat, 06 Dec 2014 00:41:32 EST ID:XpKKr8Wn No.14505 Ignore Report Quick Reply
the fuck is (a) supposed to be? what are you integrating with respect to?
>>
Betsy Drocklekudging - Sat, 06 Dec 2014 23:47:00 EST ID:qz3c7Bt+ No.14506 Ignore Report Quick Reply
1417927620903.gif -(3740B / 3.65KB, 338x155) Thumbnail displayed, click image for full size.
DICKS EVERYWHERE
>>
Phineas Mellyshit - Wed, 17 Dec 2014 04:30:13 EST ID:xatex5Q1 No.14536 Ignore Report Quick Reply
The shape you are finding the area of is under the polar curve. You only integrate over the interval of theta that it takes the polar curve to draw the shape. After that its just tracing itself.


Is there an easy way to learn math? by Simon Budgewick - Wed, 10 Dec 2014 18:07:16 EST ID:OMni8G61 No.14510 Ignore Report Reply Quick Reply
File: 1418252836985.jpg -(2385910B / 2.28MB, 1920x1080) Thumbnail displayed, click image for full size. 2385910
23 year old male going back to college, here.

I will be attending college very soon, but the thing is, I struggle with mathematics, horribly. Even pre-algebra is an issue for me, sadly, and I really, really want to change this. My entire future depends upon it.

I don't know how to describe my issue with mathematics.. I try very hard to comprehend the concepts that escape me, but it's like no matter how hard I try and focus, I simply cannot grasp certain concepts.

Does /math/ have any easy learning tips, or any online resources to recommend me? Thank you very much in advance.
>>
James Sasslenot - Thu, 11 Dec 2014 06:53:18 EST ID:MTIV7/tU No.14514 Ignore Report Quick Reply
>>14510
I never used it, but I often see it recommended here: https://www.khanacademy.org
Best of luck with your studies, have fun.
>>
Isabella Turveywell - Mon, 15 Dec 2014 15:49:46 EST ID:I7kVXtAY No.14527 Ignore Report Quick Reply
Hi. I would suggest it, too.
Hopefully you will start next fall, or else it will be very futile.
That's why I want to drop out and try a trade and pay back my debts, learn enough and then get back.
How can something soo difficult be soooo desirable?
>>
Phineas Tootlock - Tue, 16 Dec 2014 13:19:18 EST ID:+c74Tbl7 No.14532 Ignore Report Quick Reply
>>14510
Hey OP, I too struggled with math when I first started college, high school was a joke to me, I didn't take pre-calc, instead we had "accounting" which is a nice way of saying "basic math" lol. It was basic addition, subtraction, division, and multiplication and that was it. Needless to say math got fuckin hard when I got to college and physics was a bitch (uses a lot of math.) My best advice is to start at the beginning and work your way up. I didn't really understand the basics at first and that fucked me up in a few classes where the professor expected us to already understand the basics from high school classes. Khanacademy is an awesome site to learn on and youtube has a ton of videos that are useful (they'll show you how to work the problems step by step).


help? by Cyril Doffingfield - Mon, 15 Dec 2014 14:21:23 EST ID:K92q/1nw No.14525 Ignore Report Reply Quick Reply
File: 1418671283825.jpg -(89879B / 87.77KB, 1196x260) Thumbnail displayed, click image for full size. 89879
hello friends,

not entirely sure if this is the right section but if anyone could offer an insight into these it was be greatly appreciated.

Thankyou.


Logic cw help by Martha Trotwater - Thu, 11 Dec 2014 16:07:45 EST ID:FYItrjmk No.14517 Ignore Report Reply Quick Reply
File: 1418332065440.jpg -(33613B / 32.83KB, 420x319) Thumbnail displayed, click image for full size. 33613
Hey if anybody could take a look at this and give me the answers and or help me understand whats expected.
Suppose you are given an algorithm R that can test for any propositional
formula in Conjunctive Normal Form whether it has a resolution refutation or not.
(a) Describe (informally) how to construct from the algorithm R an algorithm T that can
test for any propositional formula in Disjunctive Normal Form whether it a tautology
or not.
(b) Demonstrate how your algorithm T works using the DNF
A ∨ (¬A ∧ B ∧ ¬C) ∨ (¬A ∧ ¬B ∧ ¬C) ∨ (¬A ∧ C)
(c) Explain how the computational complexities of the algorithms R and T related?


How to formalize this? by Emma Secklebury - Sat, 25 Oct 2014 08:42:51 EST ID:8Yw0Br5B No.14438 Ignore Report Reply Quick Reply
File: 1414240971360.png -(27330B / 26.69KB, 280x345) Thumbnail displayed, click image for full size. 27330
How to mathematically formalize that the belief in God is absurd because there are infinitely many "supernatural" beings that can exist, and God is just one of them, and that THERE ARE INFINITELY MANY BEINGS WHICH EXCLUDE GOD'S EXISTENCE out of possibility. Ex: Out of invisible flying goblins, invisible pink unicorns, invisible demon alien reptiles, etc.
15 posts and 2 images omitted. Click Reply to view.
>>
Lydia Gimmlehall - Tue, 09 Dec 2014 11:09:31 EST ID:Dk8yywxc No.14508 Ignore Report Quick Reply
>>14507

Well, many of the theories have their basis and motivation rooted in empirical observation
>>
Cornelius Bummlenud - Thu, 11 Dec 2014 13:05:48 EST ID:L5NP4VLn No.14515 Ignore Report Quick Reply
>>14438
What's God?
>>
Fanny Snoddale - Thu, 11 Dec 2014 13:23:45 EST ID:dL8jDLUE No.14516 Ignore Report Quick Reply
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>>14515
God is mathematics. Resurrecting itself through our application of it in technology.
NJ... Where art thou?
>>
Edwin Hattingworth - Wed, 03 Jun 2015 15:39:16 EST ID:4aRbvkOu No.14774 Ignore Report Quick Reply
>>14507
Mathematics is built on Aristotelian first-order logic, using Zermelo-Fraenkel Set Theory (along with the Axiom of Choice). The axioms of mathematics are *chosen* so that the natural numbers (i.e. the counting numbers) can be constructed logically, step-by-step, and end up with all the usual properties we expect natural numbers to have. Yes, it is "all theory," but that theory is rooted heavily in elementary observations we make about quantity and measurement.

While there are a few mathematicians who look at other axioms for the basis of their mathematical system (dropping the axiom of choice, for instance), even these don't stray far from the general intuition we expect from counting. Don't even get me started on how COMPLETELY unrelated mathematics and metaphysics are: math is *not* number-wizardry.
>>
William Drenkingold - Thu, 01 Dec 2016 03:46:14 EST ID:I4oaqfW8 No.15282 Ignore Report Quick Reply
Psssssssssst. Here's something I understood when I was 17.

> Infinite exclusive gods can be thought of
> => probability of one of them existing is an infinitesimal

> Infinite non-exclusive gods can be though of
> => probability of any such god existing is 50%

It's really not that hard, folks.
/thread


Theta by Samuel Clissleridge - Thu, 11 Dec 2014 00:07:47 EST ID:zBSUDYOt No.14511 Ignore Report Reply Quick Reply
File: 1418274467054.png -(5718B / 5.58KB, 302x450) Thumbnail displayed, click image for full size. 5718
I'm currently trying to relearn some math skills that became a little blurry over the years so I can make the transition back into college a little bit easier, I'm using Khanacademy as my guide and I'm having trouble with trigonometry or with them?

So on the site I can't ever tell what angle I'm supposed to be solving for since there is no theta symbol. For example it gives me the following parameters: cos(<ABC) AC=12, BC=16, AB=20. I'll also make a diagram on MS paint showing exactly as the site does.

With the information listed above I'd assume theta would be at angle A because its Triangle ABC and not BAC, is my assumption correct? Can someone help me understand which angle I should use as my prospective so I can get the correct adjacent and opposites angles.
>>
Samuel Clissleridge - Thu, 11 Dec 2014 00:56:07 EST ID:zBSUDYOt No.14512 Ignore Report Quick Reply
Yeah If a mod can just kill this post that'd be great I figured it out, plus it was asking for an angle and not triangle(misinterpreted the symbol) so that was part of the confusion, thanks.


What kind of graph is this? by Polly Wammlelock - Mon, 01 Dec 2014 06:14:44 EST ID:pok0PfIZ No.14500 Ignore Report Reply Quick Reply
File: 1417432484691.jpg -(205525B / 200.71KB, 850x850) Thumbnail displayed, click image for full size. 205525
Weird question I know, but I'm really high and this thing is reading like a fucking fractal

%Wasn't quite sure where to post this, apologies if I'm on the wrong board%
>>
Lydia Parringhall - Mon, 01 Dec 2014 12:22:59 EST ID:L5NP4VLn No.14501 Ignore Report Quick Reply
>>14500
It's a Venn diagram
Doesn't look very fractal really..
>>
Lydia Blondlemudge - Thu, 04 Dec 2014 07:43:36 EST ID:ZfGYcL4C No.14502 Ignore Report Quick Reply
>>14501

It did to me at the time I like it though


Clearly I need to review something... by user - Wed, 26 Nov 2014 17:42:16 EST ID:RzQObfiO No.14496 Ignore Report Reply Quick Reply
File: 1417041736839.png -(102378B / 99.98KB, 852x620) Thumbnail displayed, click image for full size. 102378
Can someone explain this to me? It seems like I do not understand factoring at all.

I have no idea how x = 0, 3, and -2.

Thanks in advance.
>>
Angus Nenkinson - Wed, 26 Nov 2014 21:50:46 EST ID:LS/jID0L No.14497 Ignore Report Quick Reply
http://www.wtamu.edu/academic/anns/mps/math/mathlab/col_algebra/col_alg_tut18_polyeq.htm
>>
Cornelius Summernedge - Thu, 27 Nov 2014 04:04:42 EST ID:RzQObfiO No.14498 Ignore Report Quick Reply
>>14497
Thanks, I'll use this from now on.


Math essay by Doris Chabblesadge - Fri, 17 Oct 2014 15:57:47 EST ID:GWtHalR/ No.14416 Ignore Report Reply Quick Reply
File: 1413575867752.jpg -(496136B / 484.51KB, 768x4096) Thumbnail displayed, click image for full size. 496136
I'm taking a forced module that requires you to write an essay and do a presentation on a topic in math that isn't normally covered in the standard syllabus. For the essay you basically need to rewrite a chapter of a text book including theorems, proofs, examples, diagrams etc.

Could anyone recommend some interesting topics? Some topics that people have done in the past are:

-rubik's cubes and group theory
-cryptography
-p-adic numbers
-set theory and axiom of choice
-hilbert spaces
-algebraic curves
-queuing systems

I'm in my second year so it can't be a topic that's too difficult to understand.
3 posts omitted. Click Reply to view.
>>
Shit Gabblemug - Sat, 25 Oct 2014 15:55:16 EST ID:GWtHalR/ No.14440 Ignore Report Quick Reply
>>14437
Thank you for this
>>
Jarvis Blimmerhall - Tue, 28 Oct 2014 18:44:58 EST ID:1xiHvl+b No.14454 Ignore Report Quick Reply
>>14437
"In one sense, there are twice as many numbers between 0 and 2 as there are between 0 and 1 (because 0 to 2 is twice as "long" as 0 to 1); but in another sense there are exactly the same number of numbers between 0 and 2 as there are between 0 and 1.

>[Undefined, grammatical filler] there are twice as many numbers between 0 and 2 as there are between 0 and 1
>[Undefined, grammatical filler] there are exactly the same number of numbers between 0 and 2 as there are between 0 and 1.

"This is beginning to approach the level of comfort you need with the quirks of infinite collections of numbers to understand the Banach-Tarski theorem. If you're not quite comfortable with this so far, please go back and reread before continuing on. "


>>14440
you shouldn't have
>>
Cornelius Blackwater - Tue, 28 Oct 2014 21:04:48 EST ID:EsiytcUg No.14455 Ignore Report Quick Reply
1414544688473.gif -(9127B / 8.91KB, 410x276) Thumbnail displayed, click image for full size.
Check out Ramsey theory, it's about inveitable structures, pretty juicy stuff philosophically. "Total disorder is impossible". It's one of those lovely areas that have problems that are (relatively, given a certain audience) simple to formulate but difficult to solve.

"Suppose aliens invade the earth and threaten to obliterate it in a year's time unless human beings can find the Ramsey number for red five and blue five. We could marshal the world's best minds and fastest computers, and within a year we could probably calculate the value. If the aliens demanded the Ramsey number for red six and blue six, however, we would have no choice but to launch a preemptive attack." - Erdos
>>
Edward Wodgebanks - Tue, 18 Nov 2014 03:09:28 EST ID:pAQz9OgX No.14492 Ignore Report Quick Reply
ooo ooo ooo non-standard analysis
>>
Lillian Demmlepodge - Fri, 21 Nov 2014 06:56:16 EST ID:GWtHalR/ No.14493 Ignore Report Quick Reply
>>14455
Good idea but unfortunately we've already covered it in a combinatorics module. My lecturer used that quote too :)

>>14492
I'll look into it. Good topic too as I could present the criticisms against it too.


sound synthesis by Jarvis Huddlefuck - Mon, 17 Nov 2014 08:55:10 EST ID:RJugJy5x No.14488 Ignore Report Reply Quick Reply
File: 1416232510655.jpg -(44823B / 43.77KB, 500x500) Thumbnail displayed, click image for full size. 44823
So, I put this in music and production seing as its sound synthesis but the mods locked the thread so will try here..

can ANYONE help with these questions? any input appreciated.
>>
Jarvis Fuckletire - Mon, 17 Nov 2014 18:56:03 EST ID:d/+G3sr/ No.14489 Ignore Report Quick Reply
frequency modulation

Wc = carrier frequency; i = modulation index; Wm = modulation frequency
>>
Faggy Pinkinhick - Mon, 17 Nov 2014 22:32:49 EST ID:sVDeU0lu No.14490 Ignore Report Quick Reply
>>14488
I don't know what's up with that mod, seemed like it belonged in /m/. It's called music & production board after all.
>>
Charles Geblingworth - Mon, 17 Nov 2014 23:01:06 EST ID:bccTK08l No.14491 Ignore Report Quick Reply
>>14489

thankyou friend, it is appreciated


Is this a problem? by Clara Chisslesore - Sun, 19 Oct 2014 21:54:03 EST ID:IJ85y6zt No.14423 Ignore Report Reply Quick Reply
File: 1413770043603.jpg -(13898B / 13.57KB, 225x225) Thumbnail displayed, click image for full size. 13898
Is it a problem that set theory is based on mathematical logic, whereas mathematical logic is based on set theory? If so, why?
4 posts and 1 images omitted. Click Reply to view.
>>
Polly Dambleville - Mon, 27 Oct 2014 20:56:01 EST ID:jEbtLayo No.14452 Ignore Report Quick Reply
>>14429
I think he's referring to the fact that in order to define truth in first order logic you have to use structures, which are sets equipped with functions and relations. You need to know how these things work in order to set up FOL but in order to formalize sets you need FOL.
>>
Edward Cuzzlehall - Sat, 01 Nov 2014 13:25:09 EST ID:Dk8yywxc No.14461 Ignore Report Quick Reply
>>14452

A first order theory doesn't have a truth function. A first order theory has axioms, rules of deduction, and a language to express it in. There are no sets, only names that are being manipulated using rules, and the resulting theorems. Of course you can talk about a model (structure) for a first order logic where you can have sets and a truth function but the theory itself is more fundamental and acts as a building block.

It's confusing because when you come up with a theory, you intuitively have in mind what the theory means, i/e you already have a structure in mind. So if I'm talking about the theory of natural numbers then 1=1 is valid (true in every structure), but when you separate the theory from the structure 1=1 is only a theorem, there is no notion of true or false. In a theory you only have the starting place and the theorems that result from it. 1=1 here isn't a statement about numbers, it is just symbols that are neither true or false, we just got it from manipulating some symbols that we started with.

I should mention that there is already the idea of a functions and predicates within the language, but there is formally not a truth function until you have a model. You do, however, need some set theoretic notions to begin talking about structures and models as you mentioned. But it is really basic stuff that doesn't seem to be problematic in this case, questions like "what is a set". My main point though is that a first order theory doesn't need set theory. Set theory needs the first order theory, while structures and models need (basic) set theory.
>>
Phoebe Turveyspear - Tue, 04 Nov 2014 02:03:56 EST ID:jEbtLayo No.14465 Ignore Report Quick Reply
>>14461
If you take deductive systems as your primitive constructions then you can construct set theory without ever referring to sets. The only problem here is that you can't have any notion of soundness or completeness until you define some notion of truth. I see what you're saying though, usually it's taught by defining truth first and then talking about deductive systems which never quite sat well with me since you had to use sets/functions/relations and all of that stuff without ever formally defining them.
>>
Hamilton Buddlemack - Wed, 05 Nov 2014 12:24:47 EST ID:Dk8yywxc No.14466 Ignore Report Quick Reply
>>14465

Completeness can be interpreted as meaning for every formula A, you either have A or -A as a theorem, i/e every formula A is decidable. You don't quite need truth to do that. You're right about soundness though, it refers to the validity of a formula, which is a statement about models essentially. Can't have models without sets.
>>
Molly Goodgold - Sat, 08 Nov 2014 21:47:13 EST ID:jEbtLayo No.14471 Ignore Report Quick Reply
>>14466
I meant completeness in the sense that every true statement in first order logic is deducible. http://en.wikipedia.org/wiki/G%C3%B6del%27s_completeness_theorem
They really need to have another name for this.


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