## How do I do a matrix in WordPress LaTeX?

I wanted to walk through the calculation that Atlas the Mental Giant did in that installment of Barnaby which I shared on Monday. I’ve been stymied, though. To have anything comprehensible, I need a matrix. (To be precise, I need the determinant of a matrix.) It needs to be typeset in a particular way.

In normal mathematics communications this is easy. We can use the LaTeX typesetting standard, and I would write something like this:

\left(U - TS\right)\left|\begin{tabular}{cc} -dT^2 & S \\ e^{\imath \pi} & \zeta(0) L \end{tabular} \right|

I haven’t checked that I have the syntax precisely right, but it’s something like that.

WordPress includes a bit of support for LaTeX expressions. Here I mean the standard free account that I have; I can write in some line like

\int_0^M \sum_{j=1}^{N} a_j x^j dx

and it will get displayed neat and clean as

$\int_0^M \sum_{j=1}^{N} a_j x^j dx$

Thing is, the standard installation only has a subset of LaTeX’s commands. This is fair enough. It’s ridiculous to bring the entire workshop out when all you need is one hammer. What I can’t find, though, is a description of what LaTeX tools are available to the standard default WordPress free-account user. My experiments in my own comments suggest that the tabular, and the table, structures aren’t supported. But I can’t find a reference that says what’s allowed and what isn’t. I might, after all, be making a silly error in syntax, over and over. When you make an error in WordPress LaTeX you get a sulky note that the formula does not parse. There’s no hint given to what went wrong, or where. You have to remove symbols until the error disappears, and then reverse-engineer what should have been there.

(And the new WordPress editor does not help either. There is not a single point in the new editor where I am fully sure what clicking the mouse will do, or why. Whether it’ll pop up a toolbar I don’t need, or open a new section I don’t want, or pop up a menu where items have moved around from the last time, or whether it’ll jump back to the start of my post and challenge me to remember what I was doing. I realize it is always popular to complain about a web site change, but usually the changes make at least one thing better than it used to be. I can’t find the thing this has made at all better.)

So I’m hoping to attract information. Does anyone have a list of what LaTeX commands WordPress can use? And how the set of what’s available differs between the original post and the comments on the post? And what, for a basic subscription, you can use to represent a matrix?

Incidentally, here’s how to make WordPress print a line of LaTeX larger. Put a &s=N just before the closing \$ of your symbol. That N can be 1, 2, 3, or 4. The bigger the N, the bigger the print. You can also put in 0 or negative numbers, if you want the expression to be smaller. I can’t imagine wanting that, but it’s out there.

## How To Build Infinite Numbers

I had missed it, as mentioned in the above tweet. The link is to a page on the Form And Formalism blog, reprinting a translation of one of Georg Cantor’s papers in which he founded the modern understanding of sets, of infinite sets, and of infinitely large numbers. Although it gets into pretty heady topics, it doesn’t actually require a mathematical background, at least as I look at it; it just requires a willingness to follow long chains of reasoning, which I admit is much harder than algebra.

Cantor — whom I’d talked a bit about in a recent Reading The Comics post — was deeply concerned and intrigued by infinity. His paper enters into that curious space where mathematics, philosophy, and even theology blend together, since it’s difficult to talk about the infinite without people thinking of God. I admit the philosophical side of the discussion is difficult for me to follow, and the theological side harder yet, but a philosopher or theologian would probably have symmetric complaints.

The translation is provided as scans of a typewritten document, so you can see what it was like trying to include mathematical symbols in non-typeset text in the days before LaTeX (which is great at it, but requires annoying amounts of setup) or HTML (which is mediocre at it, but requires less setup) or Word (I don’t use Word) were available. Somehow, folks managed to live through times like that, but it wasn’t pretty.