Mathematics

Writing mathematics

You have two modes for writing mathematics: inline and block (also called “display”). Inline math is the small formulas you include in a sentence, inside the flow of text. Blocks are optentially bigger formulas that break the flow of text.

In order to write inline math, enclose it between $. For instance: The irrational $\sqrt 2$ is the positive number that equals $2$ when squared.

In order to write display math, either enclose it between $$, or put it inside a math code block

The formula $$\sum \vec F = m\vec a$$ is from Newton. When applied to free fall, we get:

``` math
m\vec g = m\vec a
```

The syntax for mathematics is the same as the one for LaTeX math mode.

The math renderer: MathJax

Slipshow uses a third-party renderer to render mathematics. The rendering happens currently when you load your presentation (as opposed to when you compile it). The renderer is MathJax, version 3.2.2. It is included in the html file, as soon as you are using mathematics, so the html file is still completely standalone, and you don’t need anything installed locally to have it work.

Configure your renderer

You can add configure the renderer simply by setting a value anywhere in your document. This allows, for instance, to define macros, or decide which extensions are loaded.

<style>
window.MathJax = {
  tex: {
    macros: { RR: '{\\mathbb R}' }
  }
};
</script>

The list of options can be found on MathJax’s docs.

Use MathJax extensions

Note that Slipshow uses a bundle of MathJax that contains all extensions available in version 3.2 of MathJax.

Reveal content bit by bit

MathJax, when loaded with the html extension (which is the case by default in Slipshow) allows to assign classes and identifiers to the HTML elements. One can use \cssId{id-name}{math} and \class{class-name}{math} to respectively assign an identifier, and a class.

This allows to easily make them target of actions. For instance, one can use the pause action with a target to reveal content bit by bit. The reveal action and unrevealed class are also useful.

Remember to use the external-ids field of the frontmatter to tell the compiler not to warn you that it cannot find the given ids.

Editor

Presentation

Both

⛶

--- external-ids: pause1 pause2 --- # Some title to make it more realistic ```math \begin{array}{rcrcrcrcr} S &=& 1 &+& 2 &+& \dots &+& 100 \\ \cssId{pause1}{+} \quad S &=& 100 &+& 99 &+& \dots &+& 1 \cssId{pause2}{} \\ \hline 2S &=& 101 &+& 101 &+& \dots &+& 101 \end{array} ``` {pause=pause1 unreveal=pause1} {reveal=pause1} {pause=pause2}

Alternative renderer: KaTeX

You can chose to use an alternate renderer: KaTeX, version 0.16.28. Unless you have a specific requirement, you have no reason to do this.

The reason I include two renderers is that the latest version of MathJax is 4.x, while the one used by Slipshow is 3.x, and I have technical issues when trying to upgrade from version 3 to version 4 (see this post). The latest version of KaTeX can be included, but its integration in Slipshow is less mature.

In order to chose between the two renderers, use the math-mode frontmatter field with either the mathjax or katex value. Or alternatively, the --math-mode cli flag with the same values.

In order to configure KaTeX, you also just define an object:

<style>
window.Katex = {
  macros: {"\\RR": "\\mathbb{R}"}
};
</style>

whose default value is:

window.Katex = {
  delimiters: [
    {left: '\\(', right: '\\)', display: false},
    {left: '\\[', right: '\\]', display: true}
  ],
  throwOnError : false,
  strict: false,
  trust:true
};

In order to give a class or an id, use htmlClass{class}{math} and htmlId{id}{math}. However, from personal but shallow testing, KaTeX does not always preserve the order of elements from source to math, so the pause action might work less well. Other actions, such that reveal, should work well.