Search found 17 matches

by lgonick
Fri Oct 10, 2008 2:40 pm UTC
Forum: Mathematics
Topic: Tricky Counting Problem, any ideas?
Replies: 11
Views: 2397

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?
by lgonick
Sun Sep 28, 2008 2:12 pm UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6281

Re: Naughty Functions

OK, then, a non-negative continuous function that doesn't -> 0 but has finite integral as x -> infinity.
by lgonick
Sat Sep 27, 2008 1:55 am UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6281

Re: Naughty Functions

Right you are, and wrong I was!
by lgonick
Fri Sep 26, 2008 3:40 pm UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6281

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) ...
by lgonick
Fri Sep 26, 2008 2:04 pm UTC
Forum: Mathematics
Topic: Naughty Functions
Replies: 59
Views: 6281

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...
by lgonick
Sat Sep 13, 2008 2:24 am UTC
Forum: Mathematics
Topic: Balls in balls in R^n
Replies: 25
Views: 4225

Re: Balls in balls in R^n

This problem is what professional mathematicians call, um, a ball-buster.
by lgonick
Sat Aug 30, 2008 1:12 am UTC
Forum: Mathematics
Topic: Favorite mental math tricks/shortcuts
Replies: 61
Views: 10062

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...
by lgonick
Tue Jul 22, 2008 1:36 am UTC
Forum: Mathematics
Topic: Differential Equations question
Replies: 8
Views: 1480

Re: Differential Equations question

And in the original equation was the square root also divided by x? I'm guessing not.
by lgonick
Tue Jul 22, 2008 12:13 am UTC
Forum: Mathematics
Topic: Mathematicians on wikipedia display liberal bias
Replies: 35
Views: 6227

Re: Mathematicians on wikipedia display liberal bias

As Stephen Colbert once said, "Reality has a notorious liberal bias."
by lgonick
Tue Jul 22, 2008 12:09 am UTC
Forum: Mathematics
Topic: Differential Equations question
Replies: 8
Views: 1480

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]

?
by lgonick
Fri Jul 11, 2008 3:00 am UTC
Forum: Your art and links
Topic: Raw Materials
Replies: 4
Views: 1876

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?
by lgonick
Fri Jul 11, 2008 2:45 am UTC
Forum: Mathematics
Topic: Question About the Pythagorean Theorem
Replies: 40
Views: 7769

Re: Question About the Pythagorean Theorem

The trig functions can be defined analytically, without reference to right triangles.
by lgonick
Mon Jul 07, 2008 4:21 pm UTC
Forum: Your art and links
Topic: Raw Materials
Replies: 4
Views: 1876

Re: Raw Materials

keozen wrote:Love it, very cute


Cute... is that good? Yours is cute too--and good.
by lgonick
Sat Jul 05, 2008 10:23 pm UTC
Forum: Your art and links
Topic: Raw Materials
Replies: 4
Views: 1876

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...
by lgonick
Sat Jul 05, 2008 10:12 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0443: "Know Your Vines"
Replies: 167
Views: 31876

Re: "Know Your Vines" Discussion

Um... what happened to your hands?
by lgonick
Sun Jun 22, 2008 3:11 pm UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 494134

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.
by lgonick
Sun Jun 22, 2008 2:57 pm UTC
Forum: Mathematics
Topic: Majoring in Math
Replies: 48
Views: 7935

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,...

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