## Search found 855 matches

- Wed Mar 11, 2009 11:17 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Favorite math jokes

Root can mean to have sex with. I don't think we've fully explored the possibilities here. To wit: A mathematician and his wife are at a couples therapy session. The counselor, to break the ice, asks them to briefly describe their sexual histories, at which point the mathematician admits that he's ...

- Wed Mar 11, 2009 5:16 pm UTC
- Forum: Mathematics
- Topic: Definitions & explanations in English/Actual uses for math
- Replies:
**19** - Views:
**1680**

### Re: Definitions & explanations in English/Actual uses for math

It is possible to be a very good mathematician, and it is possible to be a very good math teacher. The two are (mostly) independent. From my experience with the OSU math department of doom, I'd guess that they're negatively correlated. I don't know about that. Certainly the skills needed to be a go...

- Wed Mar 11, 2009 5:10 pm UTC
- Forum: Mathematics
- Topic: Matrices
- Replies:
**26** - Views:
**2499**

### Re: Matrixes

The top-right entry is correct, but the others are not. Could you maybe show your calculations so I can see where you're going wrong?

- Wed Mar 11, 2009 1:39 pm UTC
- Forum: Mathematics
- Topic: Definitions & explanations in English/Actual uses for math
- Replies:
**19** - Views:
**1680**

### Re: Definitions & explanations in English/Actual uses for math

Wildcard, I sort of agree with you at this point, but I still think you're focusing on the wrong thing. The "why" of mathematics (science!) has been drilled into students' heads for decades, but it rarely causes people to change their minds. I think the "how" is more important. T...

- Mon Mar 09, 2009 11:18 pm UTC
- Forum: Mathematics
- Topic: combinations that confuse
- Replies:
**13** - Views:
**1445**

### Re: combinations that confuse

That's a cute little tool. I like that it lists the possibilities for you.

- Mon Mar 09, 2009 11:15 pm UTC
- Forum: Mathematics
- Topic: Love note
- Replies:
**3** - Views:
**774**

### Re: Love note

<3 is a bit overplayed. (About four years ago, I wooed someone with a note containing a triangle of side lengths I, U and 2U.) You should pioneer the "ε>" love note instead.

- Mon Mar 09, 2009 12:44 pm UTC
- Forum: Mathematics
- Topic: how do I solve these number sequences?
- Replies:
**19** - Views:
**3879**

### Re: how do I solve these number sequences?

I think auteur52 is correct here. We shouldn't assume that serious employers are conducting evaluations of job applicants via Scantron. Rather, these sorts of tests are often oral, and the emphasis is usually on explaining the thought process.

- Sat Mar 07, 2009 7:48 pm UTC
- Forum: Mathematics
- Topic: Real life arguments solved with math
- Replies:
**12** - Views:
**1363**

### Re: Real life arguments solved with math

I'm not sure what you mean when you say that the points of Sierpinski's triangle are chosen at random. Can you explain this?

- Sat Mar 07, 2009 4:53 pm UTC
- Forum: Mathematics
- Topic: dexa- rotation of mathematical proportion/equations
- Replies:
**7** - Views:
**1140**

### Re: dexa- rotation of mathematical proportion/equations

Yes, I believe I've seen this before. You might look into the research of Lilly, Otsuka, and Janssen and Cilag.

- Wed Mar 04, 2009 12:23 am UTC
- Forum: Mathematics
- Topic: Favourite Erroneous "Proofs"
- Replies:
**194** - Views:
**41592**

### Re: Favourite Erroneous "Proofs"

DavCrav wrote:How about the diagonal fallacy?

Googling this yields startlingly few results. Would something like

qualify?one of my students wrote:{a^{n}: n in N} is regular, and {b^{n}: n in N} is regular, and the regular languages are closed under concatenation, therefore {a^{n}b^{n}: n in N} is regular.

- Tue Mar 03, 2009 10:36 pm UTC
- Forum: Mathematics
- Topic: combinations that confuse
- Replies:
**13** - Views:
**1445**

### Re: combinations that confuse

You can see a similar problem (albeit with a very different wording) tackled here.

- Mon Mar 02, 2009 11:39 pm UTC
- Forum: Mathematics
- Topic: Sum of Corners
- Replies:
**11** - Views:
**1316**

### Re: Sum of Corners

Indeed, AHDag, there is no polyhedron, regular or otherwise, made only out of hexagons, nor is there one made solely out of any n-gon for n > 5.

- Mon Mar 02, 2009 8:28 pm UTC
- Forum: Mathematics
- Topic: Sum of Corners
- Replies:
**11** - Views:
**1316**

### Re: Sum of Corners

I think what the OP is trying to calculate is the sum of the sum of the interior angles of all the polygons that make up the polyhedron. Oh, that's what he was trying to compute! Gotcha. Fortunately, this is easy. For a polyhedron with n vertices, the sum is 360n-720. To see why, read about angle d...

- Mon Mar 02, 2009 4:55 pm UTC
- Forum: Mathematics
- Topic: Sum of Corners
- Replies:
**11** - Views:
**1316**

### Re: Sum of Corners

In any case, I don't think there's any way of making a polyhedron out of 27 hexagons, not even an irregular one. Indeed. Such a polyhedron would have 81 (= 27*6/2) edges and therefore 56 vertices. But 81*2/56 = 2.89, so the average degree of a vertex is less than 3, which is impossible. (And in gen...

- Mon Mar 02, 2009 2:17 pm UTC
- Forum: Mathematics
- Topic: Sum of Corners
- Replies:
**11** - Views:
**1316**

### Re: Sum of Corners

Well, if you think of a polygon as a cycle of points \lbrace p_0,p_1,\dots,p_{n-1}\rbrace in the plane, then the angle at a "corner" i is just the angle between the vectors \overline{p_ip_{i-1}} and \overline{p_ip_{i+1}} , where the indices are taken modulo n. It's easy to see that for n=2...

- Fri Feb 27, 2009 7:27 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Favorite math jokes

(I believe the joke was that 59 is LIX.)

- Thu Feb 26, 2009 2:40 pm UTC
- Forum: Mathematics
- Topic: Limit comparison test
- Replies:
**20** - Views:
**1723**

### Re: Limit comparison test

Isn't it true that if the known function is in the denominator and convergent, and you get zero, then the unknown function is convergent too?

- Thu Feb 26, 2009 1:59 pm UTC
- Forum: Mathematics
- Topic: Number of primes...
- Replies:
**8** - Views:
**1289**

### Re: Number of primes...

Of the first p

_{k}integers, k of them are prime, namely p_{1}through p_{k}.- Thu Feb 26, 2009 4:50 am UTC
- Forum: Mathematics
- Topic: solve this triangle for x
- Replies:
**10** - Views:
**1703**

### Re: solve this triangle for x

Are the red segments supposed to have the same length? Alternately, are the two vertical-looking lines supposed to be parallel? If not, I don't believe there's enough information.

- Thu Feb 26, 2009 12:52 am UTC
- Forum: Mathematics
- Topic: So that's why math is awesome.
- Replies:
**19** - Views:
**1934**

### Re: So that's why math is awesome.

Yeah, that was unreasonably harsh, Tac-Tics. (Also, since when are words like "omniscient" considered obscure?)

- Wed Feb 25, 2009 11:07 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Favorite mathematics jokes

That filter is gonna be a problem. Did it just get implemented?

(Also, it's 69, haha, get it? Like the sex act!)

EDIT: You're kidding. There's a filter on the word f-i-l-t-e-r?

(Also, it's 69, haha, get it? Like the sex act!)

EDIT: You're kidding. There's a filter on the word f-i-l-t-e-r?

- Wed Feb 25, 2009 10:52 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Favorite mathematics jokes

That's an interesting avatar for someone who hasn't done calculus.

- Wed Feb 25, 2009 8:58 pm UTC
- Forum: Mathematics
- Topic: Number of primes...
- Replies:
**8** - Views:
**1289**

### Re: Number of primes...

I believe the constant is called "zero", and its decimal expansion begins 0.00000....

It is odd that the ratio would appear to remain "high" for such large values, but primes do not have positive density on the naturals, so it cannot converge to a positive number.

It is odd that the ratio would appear to remain "high" for such large values, but primes do not have positive density on the naturals, so it cannot converge to a positive number.

- Wed Feb 25, 2009 4:53 pm UTC
- Forum: Mathematics
- Topic: Easy Fractals
- Replies:
**5** - Views:
**2761**

### Re: Easy Fractals

Kids these days! When I was your age, we didn't have fractals to draw in class; we just had that S thing.

- Sun Feb 22, 2009 6:34 pm UTC
- Forum: Mathematics
- Topic: Traveling across a square
- Replies:
**24** - Views:
**6503**

### Re: Traveling across a square

This is covered pretty well here.

- Fri Feb 20, 2009 5:58 pm UTC
- Forum: Mathematics
- Topic: Redefining Division, a non-multiplicative inversion
- Replies:
**6** - Views:
**892**

### Re: Redefining Division, a non-multiplicative inversion

While this looks similar to normal algebraic division with the divisor -1, there are some interesting side effects. I dunno about that. All you've done is defined a new operation (let's call it \) such that x\y = x/(y+1). So "dividing" by zero is what we would normally call division by 1....

- Fri Feb 20, 2009 4:26 am UTC
- Forum: Mathematics
- Topic: Straightedge and graph paper geometry
- Replies:
**25** - Views:
**2331**

### Re: Straightedge and graph paper geometry

One nice fact is that any polygon you create must have rational area. (Hint: Pick's Theorem.) I'm not quite sure how, but I suspect it's possible to turn that into another proof that you can't make an n-gon (for n > 4).

- Thu Feb 19, 2009 11:09 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Favorite math jokes

That's not true. Drinking can make one disoriented.

- Wed Feb 18, 2009 2:57 am UTC
- Forum: Mathematics
- Topic: I challenge you!
- Replies:
**15** - Views:
**1616**

### Re: I challenge you!

Funny you should post this today. You didn't happen to go to this, did you?

- Tue Feb 17, 2009 6:02 pm UTC
- Forum: Mathematics
- Topic: Stacking a deck of cards
- Replies:
**16** - Views:
**1417**

### Re: Stacking a deck of cards

Would it be too hard to simply memorize an ordering? I decided a while ago that it would be useful to know a nontrivial permutation of the alphabet, so I memorized the one California generated as a ballot ordering for the recall election (RWQOJMVAHBSGZXNTCIEKUPDYFL), which isn't too hard if you sing...

- Tue Feb 17, 2009 2:35 pm UTC
- Forum: Mathematics
- Topic: Stacking a deck of cards
- Replies:
**16** - Views:
**1417**

### Re: Stacking a deck of cards

Oh, I see. You want to be able to find a given card from the start, not just know what the next card in the deck is. Well, there is the simpler solution of taking multiples of k mod 53, rather than powers. The individual elements are easy to compute, since the nth term is just n*k. But it does have ...

- Tue Feb 17, 2009 3:59 am UTC
- Forum: Mathematics
- Topic: Stacking a deck of cards
- Replies:
**16** - Views:
**1417**

### Re: Stacking a deck of cards

Take a primitive root mod 53 (2, say). Its powers mod 53 will form a permutation on [52] with no "patterns," assuming I'm understanding what you mean by "pattern." That is: (2 4 8 16 32 11 22 44 35 17 34 15 30 7 14 28 3 6 12 24 48 43 33 13 26 52 51 49 45 37 21 42 31 9 18 36 19 3...

- Mon Feb 16, 2009 11:48 pm UTC
- Forum: Mathematics
- Topic: Number of paths in a maze
- Replies:
**9** - Views:
**864**

### Re: Number of paths in a maze

Oh, nice. I love the matrix tree theorem.

But, uh, doesn't that overcount? I thought we want the number of spanning trees in which each vertex has degree 1 or 2. (In other words, the number of "spanning paths.") I could be misreading your reference, though.

But, uh, doesn't that overcount? I thought we want the number of spanning trees in which each vertex has degree 1 or 2. (In other words, the number of "spanning paths.") I could be misreading your reference, though.

- Mon Feb 16, 2009 11:29 pm UTC
- Forum: Mathematics
- Topic: Number of paths in a maze
- Replies:
**9** - Views:
**864**

### Re: Number of paths in a maze

Correct. Though if you remove the clause about rotations and mirror images, it seems to be at least partially answered with A120443. (This is different from NathanielJ's link, in that here we don't assume you start at the top left.)

- Mon Feb 16, 2009 11:06 pm UTC
- Forum: Mathematics
- Topic: 1 + 1 = ?
- Replies:
**44** - Views:
**5431**

### Re: 1 + 1 = ?

You'd rather throw out the rule log xy = log x + log y than accept that e x is not injective? Inverses of noninjective functions are multivalued. There's nothing physics-y about that. I'm all for narrowing the range in a given situation, of course. But I would hardly say that log x = 2pi*i "has...

- Mon Feb 16, 2009 9:57 pm UTC
- Forum: Mathematics
- Topic: 1 + 1 = ?
- Replies:
**44** - Views:
**5431**

### Re: 1 + 1 = ?

Tac-Tics wrote:The trick is it is NOT true that log xy = log x + log y for all real x and y.

Sure it is. It's well known that log 1 = 2pi*i, among other things. There's nothing wrong with the rule that log xy = log x + log y, so long as you don't assume that the result is the only value log xy equals.

- Mon Feb 16, 2009 4:55 am UTC
- Forum: Mathematics
- Topic: Convergent Series question
- Replies:
**10** - Views:
**2469**

### Re: Convergent Series question

Are you suggesting that [imath]\sum_{k=1}^\infty 1[/imath] converges absolutely?

- Wed Feb 11, 2009 3:33 am UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Math joke

zee-bar is more common, I believe. Except in Britain, where they say zed-pub. (Also, I'm just one person.)

- Wed Feb 11, 2009 2:20 am UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Math joke

Nlelith wrote:This might work on a T-shirt if you have an imaginary function become real (too lazy to think of an example but you know what I'm getting at) and underneath have it read "shit just got real."

Thus?

- Tue Feb 10, 2009 2:11 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**465037**

### Re: Math joke

Shit just got complex?