### A Poor Workman Blames His Tools

The “Formula does not parse” message in Friday’s post isn’t (entirely) my fault. The “editor” (computer interface where I enter my copy) changes the code around at whim. It can get pretty infuriating. In this case, I’m inclined to be rather more forgiving than usual: the “less than” sign $<$ happens to be a Special Character in HTML (the “markup language” that Web pages are coded in), so its appearance in a formula (i.e., in the TeX code—our host, WordPress.com, uses the same math markup language as the hardcopy journals—kind of [at the level of the formula rather than the page or the chapter, alas])—the appearance of a special HTML character in the TeX, I say, probably oughta be expected to cause problems. I’ll soon work around it almost unconsciously. The need for random “null” characters here and there to make things work is another story.

Enough about production. Sometimes it seems like that’s all anybody wants to talk about. It’s interesting enough I suppose and hugely important to a publishing junky like me, but if you want documentation of computer tools, I expect you know where to get it. There’s a blue million technophiles out there flogging every conceivable application. What was I saying?

No, wait. Nobody took me up on my challenge to produce TeX code in a comment. DOLLARSIGNlatex [write your formula here] DOLLARSIGN gets it; mouse over an existing formula to see some code. If you’re embarrassed at having your every effort published with no chance to clean it up, start your own blog (free and easy … I know, everybody always says that …).

Now. $\null [x_1 < x_2] \Rightarrow [f(x_1) < f(x_2)] (\forall x_1, x_2 \in S)$ sez “f is increasing on S” (recall that $f:{\Bbb R} \rightarrow {\Bbb R}$ and $S \subset {\Bbb R}$f is a real-valued function of a real variable and S is a set of real numbers). In words, “bigger x‘s get bigger y‘s” (but this is slangy—notice that y doesn’t occur at all and that the x‘s that do appear are so-called “dummy variables” [that could be replaced with, say, a and b without changing the meaning of the code]).

I actually put some code like this into yesterday’s “sample quiz” (in the 2-hour afternoon class; the daily classes get it in an hour or two). I probably won’t have the nerve to put it on the quiz itself but it’s already been a pretty good conversation starter. One more or less constant refrain with material like this: “we’ll begin by using the pictures and the verbal descriptions to understand the code … but if all goes well, we’ll eventually be able to use the code to understand the diagrams better …”.

1. I’ll give it a try to include TeX in a comment: $latex\null\Gamma(x+1) = x \Gamma(x)$

I see your TeX code correctly rendered when I look at your web site directly, but Google Reader still says “formula does not parse.”

2. good heavens.
there go some more potential readers, i guess.
anyhow, wow. that was fast.
i was still editing this post
when this comment appeared.

$\null\Gamma(x+1) = x \Gamma(x)$
looks like good TeX to me …

3. We’ll keep reading while you experiment with TeX. :-)

Good for you for trying something new.

I’m more cautious. I either manually create gif files of TeX output or use HTML for math symbols. But it sure would be convenient to type TeX directly into blogging software.

1. 1 Carnival of Mathematics 47, where no, well… « JD2718

[…] Michi on the Chromatic Number of Lichtenstein. John Kemeny has photos of mathematicians … and more of the same … but is looking for their names. They come from Time/Life’s archives. Ξ at 360 found some polygons in the Smithsonian. Any with 7 sides? Look at the photos closely. Vlorbik is having some issues with WordPress’ implementation of TeX. […]

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Vlorbik On Math Ed ('07—'09)
(a good place to start!)