## Search found 17 matches

Fri Oct 10, 2008 2:40 pm UTC
Forum: Mathematics
Topic: Tricky Counting Problem, any ideas?
Replies: 11
Views: 2354

### Re: Tricky Counting Problem, any ideas?

How about finding the number of combinations in which some pair is next to each other, and subtracting from the total?
Sun Sep 28, 2008 2:12 pm UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6196

### Re: Naughty Functions

OK, then, a non-negative continuous function that doesn't -> 0 but has finite integral as x -> infinity.
Sat Sep 27, 2008 1:55 am UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6196

### Re: Naughty Functions

Right you are, and wrong I was!
Fri Sep 26, 2008 3:40 pm UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6196

### Re: Naughty Functions

Based on my previous post, how about this (easy?) exercise: I described a function identically = 0 on an interval that then rises continuously at the interval's end. Now let's try smoothing it out at the corners. So... imagine any old function f and a real number a such that f(x) = 0 for x ≤ a f(x) ...
Fri Sep 26, 2008 2:04 pm UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6196

### Re: Naughty Functions

How about a continuous function f with finite integral as x --> infinity but f(x) doesn't --> 0 as x -> infinity? An example would be f(x) = 0 everywhere except for intervals of length (1/2)^n centered on n. On those intervals, f rises to 1 and returns to 0 in series of ever-narrower triangular spik...
Sat Sep 13, 2008 2:24 am UTC
Forum: Mathematics
Topic: Balls in balls in R^n
Replies: 25
Views: 4168

### Re: Balls in balls in R^n

This problem is what professional mathematicians call, um, a ball-buster.
Sat Aug 30, 2008 1:12 am UTC
Forum: Mathematics
Topic: Favorite mental math tricks/shortcuts
Replies: 61
Views: 9859

### Re: Favorite mental math tricks/shortcuts

1. In doing everyday calculations, I try to treat everything as a common fraction. 15 is 3/2, 25 is 1/4, etc. Forget the decimal point and put it back at the end. Makes a lot of multiplication and division easier. 2. When computing discounted prices, use the distributive law. If something is 15% off...
Tue Jul 22, 2008 1:36 am UTC
Forum: Mathematics
Topic: Differential Equations question
Replies: 8
Views: 1446

### Re: Differential Equations question

And in the original equation was the square root also divided by x? I'm guessing not.
Tue Jul 22, 2008 12:13 am UTC
Forum: Mathematics
Topic: Mathematicians on wikipedia display liberal bias
Replies: 35
Views: 6148

### Re: Mathematicians on wikipedia display liberal bias

As Stephen Colbert once said, "Reality has a notorious liberal bias."
Tue Jul 22, 2008 12:09 am UTC
Forum: Mathematics
Topic: Differential Equations question
Replies: 8
Views: 1446

### Re: Differential Equations question

I don't follow your very first step. Maybe it's because you haven't included enough parentheses? If the original eqn is

[imath]xy' = (y/x) + [sqrt(x^2 + y^2)]/x[/imath]

then isn't

[imath]y' = y/x^2 + sqrt[(1/x^2) + (y/x^2)^2][/imath]

?
Fri Jul 11, 2008 3:00 am UTC
Topic: Raw Materials
Replies: 4
Views: 1857

### Re: Raw Materials

Curious, to me, this trend toward comic strips where the art is getting more and more minimal and iconic. Even more curious to me is that I like 'em! 'Cause I was raised at a time when drawing was at least as important as writing in comics. What do it all mean?
Fri Jul 11, 2008 2:45 am UTC
Forum: Mathematics
Topic: Question About the Pythagorean Theorem
Replies: 40
Views: 7669

### Re: Question About the Pythagorean Theorem

The trig functions can be defined analytically, without reference to right triangles.
Mon Jul 07, 2008 4:21 pm UTC
Topic: Raw Materials
Replies: 4
Views: 1857

### Re: Raw Materials

keozen wrote:Love it, very cute

Cute... is that good? Yours is cute too--and good.
Sat Jul 05, 2008 10:23 pm UTC
Topic: Raw Materials
Replies: 4
Views: 1857

### Raw Materials

I'm a full-time cartoonist now, but I used to be a mathematician. Well, math grad student, really. Then a lot of my hair fell out. I just started a new web comic http://blogs.discovery.com/raw_materials/ that's tech-based. It may seem a bit, er, expressive compared to what we see here, but do let me...
Sat Jul 05, 2008 10:12 pm UTC
Replies: 167
Views: 31382

### Re: "Know Your Vines" Discussion

Um... what happened to your hands?
Sun Jun 22, 2008 3:11 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 489194

### Re: Favorite math jokes

This may be lame, but I invented it myself:

Q. Why did the mathematical biologist get her nose pierced?
A. She wanted to change her genus.
Sun Jun 22, 2008 2:57 pm UTC
Forum: Mathematics
Topic: Majoring in Math
Replies: 48
Views: 7803

### Re: Majoring in Math

I say hang in there too, if you like math. The world needs mathematicians! I can tell you from my own experience that it's possible to convince yourself you're "not good enough" at just about any level of the game. Back in the Jurassic Period, I graduated Harvard w/ highest honors in math,...