Mathematics

A formula is written in LaTeX notation — the notation of every mathematics paper — in one of two ways.

In the line, as a mark: the formula in square brackets, {math} after it.

Persian has 32 letters, [28 + 4 = 32]{math}: the 28 of the Arabic alphabetand four of its own. The area of a circle is [\pi r^2]{math}.

On its own, between a line :::math and a line ::: — the fence an exercise has, one word shorter:

Ten new words a day for a month::::math\sum_{d=1}^{30} 10 = 10 \times 30 = 300 \text{ words}:::

1. The rules#

Neither $ nor \[ is a marker.

$ is a character somebody writing about money types by accident — it cost $4 billion stays a sentence — and \(…\), \[…\] and $$…$$ are shown as typed. The square brackets and {math} are what every other mark of the dialect looks like.

The formula may hold brackets.

[x \in [0,1]]{math} and [\sqrt[3]{x}]{math} are ordinary mathematics: the formula runs to the ]{math} that ends it, and no formula holds that. Spaces inside the braces are fine, { math }.

A formula on its own may take several lines

; they are one formula. Break it the way LaTeX breaks one — \\, an aligned environment — not with blank lines. :::MATH is read like :::math.

A formula is left to right

, whatever the line around it: in a Persian or Arabic paragraph it stands as its own left-to-right island.

It goes wherever a line of prose goes

: a paragraph, a list item, a table cell, a footnote, a box, an exercise. It may not go inside the blank of a fill-in exercise.

- the interval [x \in [0,1]]{math}- a cube root, [\sqrt[3]{27} = 3]{math}| Word | Letters ||---|---|| کتاب | [4]{math} |

:::math\begin{aligned}(a+b)^2 &= a^2 + 2ab + b^2 \\(a-b)^2 &= a^2 - 2ab + b^2\end{aligned}:::

2. On the screen and on paper#

On the screen a formula is drawn by MathJax, which comes with the toolbox and is fetched only by a page that has a formula on it. Bad notation is not hidden: MathJax draws what it can and marks the fault, and the page keeps the notation as you wrote it. A page whose script does not run — a page printed from the browser, a document opened from the disk — still shows the notation itself.

On paper there is nothing to draw: the PDF is made with LaTeX, so the notation goes through exactly as written and TeX sets it.

3. In the editor#

math

wraps the selected text in […]{math}, brackets inside it kept, or puts an empty one at the cursor.

∑ Maths

opens a sheet: a box for the notation, the formula drawn under it as you type — with what is wrong said in MathJax’s own words, Missing close brace — and the choice in the line or on its own. In the preview, pointing at a formula offers ✎ to open it in the same sheet again.

4. Two rough edges#

A formula after a bracket that is only prose.

A formula starts at its own square bracket, and a coloured word, a transliterated word, a link or a blank before it in the same paragraph stays what it is: [تند]{teal} and [x^2]{math} is a coloured word and a formula. A formula may hold brackets of its own (\sqrt[3]{x}, an interval such as [0,1) or ]0,1[), so a bracket that is only prose — [sic], [1] — earlier in the same paragraph cannot be told from one, and is taken into the formula. Put the formula first, or in a paragraph, an item or a cell of its own, or on its own lines with :::math.

A :::math must be closed.

Without its closing ::: it takes the rest of the document into the formula.

What MathJax cannot draw

— a reaction with mhchem, a molecule with chemfig, a TikZ drawing, a plot — LaTeX itself draws, in a latex block, ::::latex with four colons. It needs TeX on the computer; a formula never does.

[sic] and its square [x^2]{math}                 <- one broken formulaIts square [x^2]{math}, and [sic]                <- both as meant[تند]{teal} fast, and its square [x^2]{math}     <- both as meant