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Question about real numbers by Doris Blimmerladge - Mon, 15 Dec 2014 11:40:37 EST ID:akf5zfsA No.14524 Ignore Report Reply Quick Reply
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Is there a function that can project the entire set of real numbers onto an arbitrarily sized interval within the real numbers?
2 posts omitted. Click Reply to view.
Cedric Crebbercocke - Tue, 16 Dec 2014 10:09:36 EST ID:xrV+VzTJ No.14530 Ignore Report Quick Reply
Ah thanks, that's exactly what I meant
Isabella Blidgeville - Tue, 16 Dec 2014 13:07:43 EST ID:sPd/0oB/ No.14531 Ignore Report Quick Reply
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Beatrice Wommergold - Tue, 16 Dec 2014 15:53:58 EST ID:uPru0qmD No.14533 Ignore Report Quick Reply
Hyperbolic tangent :
tanh(x)=(e^x-e^-x)/(e^x+e^-x) maps R->(-1,1)
atanh(x)=1/2 ln((1+x)/(1-x)) maps (-1,1)->R
a*tanh(x)+b maps R->(-a+b,a+b)
atanh((x-b)/a) maps (-a+b,a+b)->R

The nicest functions you're going to find
Esther Fabberhall - Tue, 23 Dec 2014 20:47:35 EST ID:K8qJv5EF No.14542 Ignore Report Quick Reply
^This guy's post is correct if you're looking for continuous bijections. If you're looking for just a continuous map from the reals to [a,b], you can just choose f(x) = [(b-a)/2]sin(x) + (b+a)/2
Thomas Bangerham - Fri, 26 Dec 2014 18:20:04 EST ID:SlKfpVpP No.14546 Ignore Report Quick Reply
another interesting question is whether you can project an arbitrarily sized interval within the real numbers onto the set of real numbers

answer is yes

also you can map a line of length 1 onto a cube of volume 1 etc.

Majoring in Math by Cornelius Sollerwone - Tue, 02 Sep 2014 22:17:23 EST ID:kQQi+WA1 No.14343 Ignore Report Reply Quick Reply
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I want to know are good options for me career wise if I major in math. I just finished my first term and I don't really know what I'm doing. All I know is I enjoy math. The only thing I've had recommended to me is to become an engineer. I'm not great with electronics, computers, or mechanics. I think I could handle physics since that seems like just more applied math. I need college advice. I have a career advising appointment in a couple weeks but I would appreciate your advice!
Cornelius Brebbleford - Thu, 04 Sep 2014 00:46:14 EST ID:kQQi+WA1 No.14347 Ignore Report Quick Reply
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bumping for math majors
Nell Drennerdock - Sat, 06 Sep 2014 21:16:28 EST ID:Dk8yywxc No.14350 Ignore Report Quick Reply

I'm a math major but I don't expect to get a job from pure math. I do it because I enjoy it and find beauty in the subject. As far as getting a job, I'm double majoring in computer science so I can program and shit.

But there aren't many careers in pure math other than being a researcher, actuary, or teacher. Otherwise you will have to get some kind of certification. And yes, physics is just a specific subbranch of mathematics. All the time in my upper level classes I meet physics majors trying to understand exactly what it is they're learning about.

If you like proofs, be a math major. If you want a fulfilling pasttime that will develop you as a person, be a math major. A math major will make you stand out if you pair it with anything else, people assume mathematics = intelligence so it will get you to the top of many lists if you have other skills.

tl;dr math won't give you a career by itself but paired with something else it supercharges it and makes you even more awesome in the eyes of employers
Archie Worthingfield - Sun, 07 Sep 2014 18:17:12 EST ID:xvgqavvT No.14352 Ignore Report Quick Reply
Functional programming. since you need to think like a mathematician to do it. Designing algorithms is another high demand job, especially in the finance/trading industry. Artificial Intelligence is all based of real analysis (proofs) so another field you can go into. Any stats job for the government like an environment agency, lot's of options.
Cedric Hollertudge - Fri, 19 Dec 2014 05:04:22 EST ID:lx6v5XWF No.14540 Ignore Report Quick Reply
Analytics and machine learning is in very high demand right now, and is where a large part of the field of CS in industry is heading, due to the big data problem.

These are very math heavy. I'd recommend getting into computational math.
Learn C. Learn Python. See if you can find some open source projects and make some contributions.

Programs can be very proof-like, in my own experience.
Sophie Turveyhood - Fri, 19 Dec 2014 15:50:10 EST ID:4kDzPiCs No.14541 Ignore Report Quick Reply
If you want a career in math you really have to get a PhD. That said, mathematician is regularly listed as one of the best, if not the best, job to have by many metrics. Grad school for math is always paid for. Schools will actually pay you a stipend to go there, even if you're not a top student.

Don't listen to people saying you can't get a job doing math. It has very high growth and almost no one wants to do it.

Maths tutoring by Hugh Pupperford - Sun, 14 Dec 2014 17:18:22 EST ID:8T5tyzEs No.14523 Ignore Report Reply Quick Reply
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I wanna make some money on the side but by doing little work. I'm a maths undergrad so I was thinking of doing tutoring online. Anyone done this kind of thing before? How did you go about it? How much should I charge?
Cedric Hollertudge - Fri, 19 Dec 2014 04:56:04 EST ID:lx6v5XWF No.14539 Ignore Report Quick Reply
Your skill has probably taken years of work, so you should charge something above double minimum. I've charged $20 before, and $30 is not unreasonable.

I did my tutoring at a community college, and while I was a student, there were numerous tutors who weren't. You can see if any local CCs have openings.

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
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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
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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
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
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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
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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
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
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
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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.


Logic cw help by Martha Trotwater - Thu, 11 Dec 2014 16:07:45 EST ID:FYItrjmk No.14517 Ignore Report Reply Quick Reply
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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
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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

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
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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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
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.

Theta by Samuel Clissleridge - Thu, 11 Dec 2014 00:07:47 EST ID:zBSUDYOt No.14511 Ignore Report Reply Quick Reply
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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
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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
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

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
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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
Cornelius Summernedge - Thu, 27 Nov 2014 04:04:42 EST ID:RzQObfiO No.14498 Ignore Report Quick Reply
Thanks, I'll use this from now on.

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