Mathematical formulas
You can easily include mathematical formulas on your site with the math plugin:
$$ J_\alpha(x) = \sum_{m=0}^\infty \frac{(-1)^m}{m! \, \Gamma(m + \alpha + 1)}{\left({\frac{x}{2}}\right)}^{2 m + \alpha} $$ or $$ a^2 + b^2 = c^2 $$
The plugin uses Javascript from mathjax.org (https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js) or images created by codecogs (if javascript is disabled) and is thus dependent on these services being up and running.
Installation
Download the plugin from http://get-simple.info/extend/plugin/math/211/ and unzip it to the plugins directory of your GetSimple installation.
Make sure, jQuery is included in your template.
Alternatively you can set the variable $math_mode at the top of the plugin file to 1 (image from codecogs) or 3 (MathJax and image as noscript fallback). In both cases you need to adhere to the usage policy of codecogs.
Usage
Include your LaTeX formulas within $$ and $$, e.g. $$ a^2 + b^2 = c^2 $$.