Math and Equations

There are several ways to make writing math in your documents as familiar as possible. Math can either be (1) inline or (2) displayed as an equation block. In addition to the usual MyST syntax, you can also use “dollar math”, which is derived from $\LaTeX$ and surrounds inline math with single dollar signs ($), and equation blocks with two dollar signs ($$). The details of using inline math and equations are below.

For example, here is an example of a cross-product, which we reference in the docs below!

\mathbf{u} \times \mathbf{v}=\left|\begin{array}{ll}u_{2} & u_{3} \\ v_{2} & v_{3}\end{array}\right| \mathbf{i}+\left|\begin{array}{ll}u_{3} & u_{1} \\ v_{3} & v_{1}\end{array}\right| \mathbf{j}+\left|\begin{array}{ll}u_{1} & u_{2} \\ v_{1} & v_{2}\end{array}\right| \mathbf{k}

(1)

Inline Math¶

There are two ways to write inline math; (1) with a math role or (2) by wrapping it in single dollar signs.

The output of these is the same (which you can see by looking at the AST and $\LaTeX$ outputs in the demo above). Using a math role is much less likely to collide with your writing if it includes dollars (e.g. $2.99).

Occasionally, dollar signs that you do not intend to wrap math need to be escaped. These can be preceded by a backslash, that is \$2.99, and the \ will not be displayed in your output. If using $\LaTeX$ as an output, these dollar-signs will also be properly escaped again!

Equations¶

There are three ways to create an equation block: (1) a math directive (rather than a role for inline math); (2) wrap the equation in two dollar-signs, $$; or (3) use a \begin{equation} statement directly (i.e. using AMS math).

Math directives¶

The math directive takes no arguments and the body of the directive is the $\LaTeX$ style math. You can have an optional label parameter, which will label this equation for later cross-referencing, see Referencing Equations below for more on that!

Dollar math equations¶

You can also create equations by wrapping content with two dollar signs ($$). In this syntax, you can use the \label{label-name} command to add a label. This can be quite convenient if your equations are small, the entire syntax can fit on a single line.

Referencing Equations¶

As you have seen above, any equation can be labelled and cross-referenced in other parts of your document. For example, the start of this document had Equation 1, which can be referenced here with a link and inline-preview. There are a few different ways to reference equations, with more details in Cross-references.

Labelling equations¶

The examples above all show how to label an equation in the interactive demos. With a directive, you can use the label option; with dollar-math and AMS math, you can use the \label{} syntax that is native to $\LaTeX$ .

For example, a directive can be labelled as follows:

```{math}
:label: my_label
my_math
```

To reference equations you can use a markdown link with the target, for example:
[](#cross) will create: (1)

Customizing Numbering¶

To change the reference format for math, you can use the frontmatter under the numbering field see numbering. To override numbering for a specific equation you can use the {math.enumerated} option on the math directive.

:::{math}
:enumerated: false
Ax = b
:::

Math Macros¶

Macros allow you to create reusable math components that can simplify the writing of a document. These macros can be defined for a single document through the frontmatter, or shared in project frontmatter. These macros are used throughout HTML and $\LaTeX$ exports and are written declaratively so that they can be easily parsed. Macros are the same as \newcommand or \renewcommand in $\LaTeX$ , and use the math object in the frontmatter.

The math macros are parsed as yaml in the frontmatter and can easily be shared or inherited through project to page frontmatter. These are also inserted into any $\LaTeX$ outputs for creating professional PDF documents.

The key is the command that you are defining, in the demo above \dobs, \dpred, and \mref; the command should include the leading \. The value of the entry should be the macro definition. If the definition contains #1 then there will be one required argument for the macro that should be supplied in braces when you use it (e.g. \dpred{m}). The macros can be nested as in the example where \dpred{\mref} uses two macros.

In the macro in the example above, \mathbf{d}_\text{pred}\left( #1 \right), the #1 is the first and only required argument, and is placed in between left and right brackets. The numbering for arguments starts at one, and other arguments can be added with #2, #3, etc. and then input in a command using \command{arg1}{arg2}.

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