Often in your writing you will want to reference a variable, or perhaps a small equation. Well org-mode has fantastic support for LaTeX, which can be very helpful. Often you might want to reference some variable "x", which perhaps you might write in italics, like x, but it's much clearer to use inline latex like $x$ which renders an \(x\) which more clearly stands out as a symbol. Also, if you need a symbol from the Greek alphabet, just do $\alpha$ for \(\alpha\) or $\tau$ for \(\tau\) as an example.

With the inline syntax you can do full equations, not only symbols. For example:

$x=\sqrt{b}$

Will render inline as \(x=\sqrt{b}\).

But often you might want to emphasize an equation, or have something larger to express. For example, let's add the following two LaTeX blocks:

Small example: \begin{equation} \forall a . a \to a \end{equation} Large example: \begin{align*} \text{Eq} \,=\, &\{\, \text{Bool, Char, Int, Integer, Float, Double} \,\}\, \cup \\ &\{\, [\tau ] \mid \tau \in \text{Eq} \,\}\, \cup \\ &\{\, (\tau_1, \tau_2) \mid \tau_1,\tau_2 \in \text{Eq} \,\}\, \cup \\ &\{\, (\tau_1, \tau_2, \tau_3) \mid \tau_1,\tau_2,\tau_3 \in \text{Eq} \,\}\, \cup \\ &\{\, (\tau_1, \tau_2, \tau_3, \tau_4) \mid \tau_1,\tau_2,\tau_3,\tau_4 \in \text{Eq} \,\}\, \cup \\ &\dots \end{align*}

Figure 6: First LaTeX equation blocks!

Maybe you'd like the equation to be larger? Most likely MathJax is rendering the LaTeX so a snippet like the following should scale up the equations:

#+HTML_MATHJAX: scale:100 dscale:190 align:center messages:none

The pertinent parameter is dscale but included above are a few other parameters to get started on controlling the MathJax library.