MathML and Mozilla

What does Itex do?

Itex is a way of describing math, including subscripts, superscripts, Greek letters, and all the other symbols of math, using only the standard characters available on a keyboard. It is based on Latex, which is the de facto standard for formula intensive documents. However, it differs in some respects from standard Latex. In particular, itex's method of handling of arrays and matrices is more allied to that of HTML than latex's.

How does Itex do it?

A brief review of itex follows. Itex, by a process of co-evolution, is a superset of WebEq's webtex. Thus the WebEq tutorial and example pages are very relevant. Itex differs from WebTex primarily in that it adds some features making it easier to use by novices. For example by giving natural synonyms for WebTex's (and Latex's) less obvious (but more concise) control sequences: `\infinity' as well as `\infty', `\Union' as a synonym for `\bigcup' etc.

Enclose math in $ ... $ to include math in a line of text (inline math) or \[ ... \] if you wish the math to be displayed on its own (display math).
Letters (for variables) and numbers should be entered as one would expect. So write $x$ for the variable x and $3.14159$ for the first few digits of pi. Most other characters available on the keyboard either as a single key press or `shift' and a single keypress, should also be entered in the obvious way. So $x < 1$ will indeed give `x < 1'. All other characters will be obtained by special `control' sequences. The characters: { } \ _ ^ and & are special to itex, and if needed as math characters will also be entered as control characters.
To get `x subscript 1' (x₁) enter $x_1$. To get `y superscript 2' (ie `y squared': y²) write $y^2$. To get a subscript and superscript together, say `x subscript 1 squared', write $x_1^2$.
To avoid ambiguity group together expressions using { ... }. For example, to get `x to the power of n +1' (xⁿ⁺¹) enter $x^{n+1}$. -If you type $x^n+1$ instead, you will get `x to the power of n, added to 1' (xⁿ+1).
How, then, do we get `{', `}', `_' or `^' in a math expression? Answer: prefix the character with `\'. Thus, $\{ x : x^2 < 2\}$ is `the set of all x strictly less than 2' ({ x : x² < 2 }). And similarly, to get `\', enter $\\$.
There are many other `control' sequences starting with `\'. In general, if there is no easily accessible key on the keyboard for a symbol, type `\' and the name of the symbol (no space between `\' and `symbol name').
Examples: $\alpha \beta \gamma$ are the first few Greek letters; $\sum_{n=0}^\infinity$ is `the sum from 0 to infinity (note to Latex users, \infty also works - as in Latex - for infinity); $\integral f(x) dx$ is `the integral of f(x)'.
Further examples: $x \in T$ `x in the set T', $S \subset T$ `S is a (strict) subset of T'. To get `S is a subset of (or equal to) T' use $S \subseteq T$.
Names for standard functions are entered in the same way: $\sin (x)$ for `sin x'.
The natural numbers, integers, reals, rationals, irrationals can be given by the natural control sequences: $\naturals \integers \reals \rationals \irrationals$. They will appear as `blackboard bold'. To get other letters is blackboard bold enter $\mathbb{D}$, for example. Similarly use $\mathcal{...letter...}$ to obtain calligraphic letter.
To include small fragments of text in a math expression there is the control sequence `\text{...some text ...}'. So $x<1 \text{ if } y \ne 0$ for `x is strictly less than 1 if x is not equal to 0'.
Dots are often useful in math expressions. $\cdot$ is a single centered dot, $\cdots$ is three centered dots, $\vdots$ is three descending dots.
To get fractions use the `\frac' control sequence followed by `{numerator}{denominator}'. Thus $\frac{1}{n} for `1/n'; and $\int_{1}^\infinity \frac{1}{x^2} dx$ for `the integral from 1 to infinity of 1/x²'.
The last construct we consider here are arrays and matrices. To get the 2 by 2 identity matrix enter $\array{ 1 & 0 \\ 0 & 1}$. Here we write `\array{ ...array contents...}' to state we want an array (or matrix). Then list the elements of the first row separated by &. To show that a row is finished enter `\\' (a `\\' is not needed at the end of the last row).
Note however, that arrays and matrices dont fit well into lines of text. You may well wish to use a display equation for your matrix: \[ \array{1 & 0 \\ 0 & 1} \cdot \array{1 & 0 \\ 0 & 1} = \array{ 1 & 0 \\ 0 & 1}\].
The `\array' control sequence only constructs a two dimensional table of rows - it doesnt put brackets around the matrix. To make sure itex is aware exactly what is being bracketed it is advisable to either type \[ { ( \array{1 & 0 \\ 0 & 1} ) } \] (use `{' and `}' to make clear the grouping; or type \[ \left( \array{1 & 0 \\ 0 & 1} \right)\] (as in Latex). Not that a `\left' must be accompanied by a `\right'.
For a final example, to define a function f constantly 1 on the rationals and constantly 0 on the irrationals:
```
\[ f(x) = { \{ \array{ 1 & \text{ if } x \in \rationals \\
                   0 & \text{ if } x \in \irrationals} }
\]
```
Arrays have many options available to get precisely the right look. These are markedly different from Latex's system. Itex and WebTex do exactly the same thing regarding array options. See this page for details.