## Search found 130 matches

- Tue Apr 20, 2010 12:44 pm UTC
- Forum: Mathematics
- Topic: Interesting infinite series for phi
- Replies:
**2** - Views:
**1195**

### Interesting infinite series for phi

on the middle of its Wolfram page , this thing pops up: \phi = \frac{13}{8}+\sum_{n=0}^{\infty} \frac{(-1)^{n+1}(2n+1)!}{(n+2)!n!4^{2n+3}} Everything else on the page is understandable, but this seems to come out of left field, and I don't know where to begin Basically, I was...

- Tue Mar 16, 2010 2:20 pm UTC
- Forum: Mathematics
- Topic: easy permutation group problem
- Replies:
**1** - Views:
**348**

### easy permutation group problem

I picked up a copy of "Fearless Symmetry" on a couple recommendations/good reviews and so far I love it. There was one example problem they gave at the end of the section on permutation groups though: Verify the following equality, \sum_{\{a,b,c,d,e\}}:(ab)(cde)\circ (a...

- Tue Mar 16, 2010 12:31 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0714: "Porn For Women"
- Replies:
**298** - Views:
**67111**

### Re: "Porn For Women" Discussion

Does Randall not know what the phrase "Porn for ____" means?

Or if he does, is the only point of this comic pointing out that its meaning isn't sexual, as most internet porn is?

Either way, this comic seems pretty lame.

Or if he does, is the only point of this comic pointing out that its meaning isn't sexual, as most internet porn is?

Either way, this comic seems pretty lame.

- Sun Mar 14, 2010 4:20 pm UTC
- Forum: Mathematics
- Topic: Famous Math Quotes!
- Replies:
**32** - Views:
**8012**

### Famous Math Quotes!

It doesn't appear we have a thread for this yet, but I saw a few good ones in "Math Jokes" A few of my favorite are attributed to John von Neumann: "In mathematics you don't understand things. You just get used to them." and, "If people do not believe that mathematics is sim...

- Sun Mar 07, 2010 11:14 pm UTC
- Forum: Mathematics
- Topic: Limit of a sum - I'm stuck.
- Replies:
**7** - Views:
**1751**

### Re: Limit of a sum - I'm stuck.

Have you gone over formal definition of an integral using a Riemann sum?

- Mon Feb 22, 2010 2:09 pm UTC
- Forum: Logic Puzzles
- Topic: Puzzles from the xkcd book (big puzzle SOLVED!)
- Replies:
**147** - Views:
**161514**

### Re: Puzzles from the xkcd book

Are we sure part 3 (from page 1111, the crypto conference) is correct, and it is just the numbers on the screen? That and assumed part 4 bother me, since neither are directly labelled like the other parts. regarding part 3: Yes, the comic was also altered regarding the hair of the audience, which s...

- Wed Feb 17, 2010 1:07 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0703: "Honor Societies"
- Replies:
**234** - Views:
**59324**

### Re: Honor Societies

I just submitted my National Honors Society application 10 minutes ago (literally). Randall, stop-following-high-school-curricula-so-you-can-make-relevant-comics-to-your-high-school-target-audience my head!

- Tue Feb 16, 2010 1:14 pm UTC
- Forum: Mathematics
- Topic: Favorite math jokes
- Replies:
**1452** - Views:
**489371**

### Re: Favorite math jokes

Henri PoincarĂ©, once grew suspicious and started to weigh the bread loaves he was getting at the bakery. Indeed, he discovered that the average weight was 900 grammes (rather than 1 kg, as required). Accordingly, he reported the matter to the prefecture. A year later Poincare again visited the poli...

- Wed Feb 10, 2010 9:23 pm UTC
- Forum: Mathematics
- Topic: today's blag problem
- Replies:
**23** - Views:
**3550**

### today's blag problem

This cool puzzle (and solution) comes from my friend Mike. Alice secretly picks two different real numbers by an unknown process and puts them in two (abstract) envelopes. Bob chooses one of the two envelopes randomly (with a fair coin toss), and shows you the number in that envelope. You must now ...

- Wed Feb 03, 2010 1:06 pm UTC
- Forum: Mathematics
- Topic: Another implicit differentiation problem...
- Replies:
**4** - Views:
**773**

### Re: Another implicit differentiation problem...

What you had after "some simplification" is close, but I got this: y' = \frac{25x-4x^3-4xy^2}{4yx^2+4y^3+25y} Which doesn't simplify much further (you can put -x/y in the front and make it look more symmetric if you wish) You just dropped an x somewhere, these things happen edit: Sorry...

- Tue Jan 19, 2010 8:15 pm UTC
- Forum: Mathematics
- Topic: Question on formulae for series
- Replies:
**4** - Views:
**608**

### Re: Question on formulae for series

Well what you wrote should have a summation i believe, and also \frac{}{} and \sum_{}^{} can be very useful

[imath]\sum_{r=1}^{n}r^2 = \frac{n(n+1)(2n+1)}{6}[/imath]

[imath]\sum_{r=1}^{n}r^3 = \frac{n^2(n+1)^2}{4}[/imath]

[imath]\sum_{r=1}^{n}r^2 = \frac{n(n+1)(2n+1)}{6}[/imath]

[imath]\sum_{r=1}^{n}r^3 = \frac{n^2(n+1)^2}{4}[/imath]

- Thu Jan 14, 2010 7:16 pm UTC
- Forum: Mathematics
- Topic: RSA explanation
- Replies:
**23** - Views:
**2654**

- Sun Jan 10, 2010 5:28 am UTC
- Forum: Mathematics
- Topic: The "KGB" isn't all that ...
- Replies:
**27** - Views:
**3518**

### Re: The "KGB" isn't all that ...

whats a gogolplex?

- Fri Jan 01, 2010 12:13 am UTC
- Forum: School
- Topic: Awesome Teacher Quotes
- Replies:
**1764** - Views:
**399893**

### Re: Awesome Teacher Quotes

My chem/bio teacher had this poster by her safety glasses cabinet:

- Mon Dec 28, 2009 6:12 am UTC
- Forum: Logic Puzzles
- Topic: Puzzles from the xkcd book (big puzzle SOLVED!)
- Replies:
**147** - Views:
**161514**

### Re: Puzzles from the xkcd book

regarding 101110 (the red and white block) We've already established that 207 factors into 9x23 which is the pixel dimensions of the block on 101110. However, you have to wonder if 1407 is actually relevant to this puzzle. After all, it is just the joke of the comic (2:07pm becoming 14:07 wh...

- Thu Dec 17, 2009 12:24 pm UTC
- Forum: Mathematics
- Topic: Integration of e^( x^2)
- Replies:
**24** - Views:
**4215**

### Re: Integration of e^( x^2)

Hi everybody. I wanted to know if it was possible to integrate e^ (x^2) to get an exact function i. e not using the Taylor series... It is not possible to express the antiderivative of e^{x^{2}} in terms of elementary functions, but it is possible to find the exact value of some definite integrals ...

- Mon Dec 14, 2009 2:48 am UTC
- Forum: Forum Games
- Topic: Maximize the post:views ratio! (if you look, you must post)
- Replies:
**36936** - Views:
**2427037**

### Re: Maximize the post:views ratio! (if you look, you must post)

oh damnit i accidently this thread again im not good with computer

- Mon Dec 14, 2009 12:47 am UTC
- Forum: Mathematics
- Topic: Question on Monty Hall problem
- Replies:
**5** - Views:
**1139**

### Re: Question on Monty Hall problem

It seems to not change anything to me, except that now he can screw you over by picking the door with the car, then asking if you want to switch from a goat to another goat.

- Sat Dec 12, 2009 9:54 pm UTC
- Forum: Mathematics
- Topic: Integration of e^( x^2)
- Replies:
**24** - Views:
**4215**

### Re: Integration of e^( x^2)

mikhail's definition isnt very useful because

[math]erf(x) = \frac{2}{\sqrt{\pi}}\int_0^x e^{-t^2} dt.[/math]

[math]erf(x) = \frac{2}{\sqrt{\pi}}\int_0^x e^{-t^2} dt.[/math]

- Fri Dec 11, 2009 12:54 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0674: "Natural Parenting"
- Replies:
**100** - Views:
**23748**

### Re: "Natural Parenting" Discussion

Is it just me or does this comic also contain a terribad pun (besides the "mother of sampling bias" one)?

"Do what comes naturally"

"Do what comes naturally"

- Fri Nov 27, 2009 2:46 am UTC
- Forum: General
- Topic: Is your ZIP code prime?
- Replies:
**90** - Views:
**7584**

### Re: Is your ZIP code prime?

when i ran mine in my head i thought is was prime (44857) but then i checked with google, and apparently its 31*1447

- Mon Oct 05, 2009 1:25 am UTC
- Forum: General
- Topic: what would you choose as your super power?
- Replies:
**636** - Views:
**73728**

### Re: Super-ish Powers

Very good coordination/reflexes/balance so I would never trip and would become an amazing dancer.

- Sat Sep 19, 2009 4:35 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0638: "The Search"
- Replies:
**139** - Views:
**35123**

### Re: "The Search" Discussion

am I the only one saying Scale fail here? It may be equivalent if the ants searched the entire earth, then concluded they were the only sentient life. Even that's less than how far weve reached out (on every conceivable electomagnetic spectrum too).

- Wed Sep 09, 2009 2:15 pm UTC
- Forum: Gaming
- Topic: Guild Wars 2
- Replies:
**266** - Views:
**79621**

### Re: Guild Wars 2

Idk about that zergrush comment. Sway has become the dominant build among bad/inexperienced players. Anet is going to be nerfing the R/A dagger spammers soon though. Also, Anet announced they were going to eliminate Team arenas and Hero battes and add a new "sealed deck" arena; where you h...

- Wed Sep 02, 2009 7:13 pm UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0631: "Anatomy Text"
- Replies:
**270** - Views:
**79438**

### Re: "Anatomy Text" Discussion

Just a quit warning to people hoping to check this. The top two results for "human genitals" on wikipedia are "Genital modification and mutilation" and "Genital Cutting".

- Fri Aug 21, 2009 6:33 am UTC
- Forum: Individual XKCD Comic Threads
- Topic: 0626: "Newton and Leibniz"
- Replies:
**213** - Views:
**58739**

### Re: "Newton and Leibniz" Discussion

Well yes, but some could say Leibniz's contributions to calculus were..... INTEGRAL!

**Spoiler:**

- Wed Jul 15, 2009 7:18 pm UTC
- Forum: Mathematics
- Topic: Random Secretary problem
- Replies:
**5** - Views:
**1220**

### Re: Random Secretary problem

Thanks a lot, and yeah its possible I did I just wrote that out from memory.

- Wed Jul 15, 2009 6:38 pm UTC
- Forum: Mathematics
- Topic: Random Secretary problem
- Replies:
**5** - Views:
**1220**

### Re: Random Secretary problem

well, yeah I suppose so, I guess it could be better worded as the probability is ~.623 for sufficiently large n.

- Wed Jul 15, 2009 6:04 pm UTC
- Forum: Mathematics
- Topic: Random Secretary problem
- Replies:
**5** - Views:
**1220**

### Random Secretary problem

While reading through my entry-level Intro to Statistics textbook, this problem was outlined in a sidebar: Suppose a secretary has 50 letters and 50 addressed envelopes, but the letters get jumbled so that they are placed into the envelopes randomly. What is the probability that at least one envelop...

- Wed Jul 15, 2009 5:46 pm UTC
- Forum: Mathematics
- Topic: Mathematics: Discovered or Invented?
- Replies:
**39** - Views:
**4782**

### Re: Mathematics: Discovered or Invented?

I voted invented. Obviously things like our decimal numbering system are crafted by us. Until you get heavily involved with quantum mechanical quations (i.e. "qubit" factoring computers) everything is derived from simple axioms (usually those of Peano Arithmetic). for example from addition...

- Mon Jul 06, 2009 5:59 pm UTC
- Forum: Science
- Topic: What happens if you accelerate a neutron star?
- Replies:
**5** - Views:
**1815**

### Re: What happens if you accelerate a neutron star?

I believe "sparse" is the word you're looking for.

- Sun Jun 28, 2009 2:21 am UTC
- Forum: Mathematics
- Topic: x^x = n, solving for x?
- Replies:
**18** - Views:
**2804**

### Re: x^x = n, solving for x?

if X^X equals N, then then N is exp(W(ln(N))) where W() denotes the Lambert W Function.

Edit: The Lambert W function is non-elementary, but the wiki page has some python code for computing a numeric value.

Edit: The Lambert W function is non-elementary, but the wiki page has some python code for computing a numeric value.

- Thu Jun 25, 2009 12:11 am UTC
- Forum: Science
- Topic: How would you create a star?
- Replies:
**49** - Views:
**4494**

### Re: How would you create a star?

Is there some Godwin's law corollary that states as a science discussions length approaches infinity, the probability of a discussion on black holes occurring approaches 1?

- Tue Jun 23, 2009 12:46 am UTC
- Forum: General
- Topic: Reset - In real life
- Replies:
**30** - Views:
**2779**

### Re: Reset - In real life

Actually, I think in the comic it was one of those paper-flipdown thingies. (where each day you flip to the next number on the right, then after 9, you flip to zero and move the left up one.)

- Sun Jun 07, 2009 2:07 am UTC
- Forum: Gaming
- Topic: Plants Vs. Zombies
- Replies:
**51** - Views:
**9683**

- Sat Jun 06, 2009 3:33 pm UTC
- Forum: Mathematics
- Topic: Why does the letter "b" represent the y-intercept?
- Replies:
**23** - Views:
**5811**

### Re: Why does the letter "b" represent the y-intercept?

I always though "m" stood for modulus? As in "The modulus of x; otherwise known as slope in 1st degree polynomials"

- Tue Jun 02, 2009 8:23 pm UTC
- Forum: Gaming
- Topic: Guild Wars!
- Replies:
**58** - Views:
**3447**

### Re: Guild Wars!

I'm going to be honest that I don't play PvE hardly at all. If you ever get into PvP though, I could help you ascend from the ranks of nublet ASAP.

Don't let that discourage you from PMing me to ask for advice or w/e IGN: Klawron Crowcall

Don't let that discourage you from PMing me to ask for advice or w/e IGN: Klawron Crowcall

- Tue Jun 02, 2009 11:33 am UTC
- Forum: Mathematics
- Topic: Why does the Limit of Sin(x)/x as x approaches 0 equal 1?
- Replies:
**37** - Views:
**11934**

### Re: Why does the Limit of Sin(x)/x as x approaches 0 equal 1?

This is similar to the statement:

lim x->0 (exp(x)-1)/x = exp(0) = 1

In that it is not intuitively algebraically or geometrically proovable. Its one of the fundamental pillars of calculus and limits in particular.

lim x->0 (exp(x)-1)/x = exp(0) = 1

In that it is not intuitively algebraically or geometrically proovable. Its one of the fundamental pillars of calculus and limits in particular.

- Tue Jun 02, 2009 11:30 am UTC
- Forum: Mathematics
- Topic: Strange bases
- Replies:
**14** - Views:
**2350**

### Re: Strange bases

There's a wiki article on complex bases . The most famous is the quater-imaginary base, which is basicaly quatanery with a radix of 2i (and much more common radix point notations, cause 1/i = -i). Also, base 1+i (or 1-i), which I dub "Biinary" is interesting because of its approximation of...

- Mon Jun 01, 2009 7:45 pm UTC
- Forum: Mathematics
- Topic: Dreaming up mathematical principles.
- Replies:
**16** - Views:
**2496**

### Re: Dreaming up mathematical principles.

So basically, pi~3?

Shocking.

Shocking.