LaTeX
Unfortunately Google Sites does not have a "natural" way to enter in equations. In fact it doesn't even offer a simple way to insert greek letters or other symbols! Here are a few ways to insert pretty equations into your page.
Follow the instructions here: https://sites.google.com/site/gencoreoperative/index/articles-and-hacks/google-s-latex
Basically start in <HTML> editing. At the point you want to insert an equation, type
<img src="http://www.google.com/chart?cht=tx&chf=bg,s,FFFFFF00&chco=000000&chl=
after the chl= you type your LaTeX formatted equation, such as e^z=\sum^{\infty}_{n=0}\frac{z^n}{n!}
end with " />
In this example we have put this in the <HTML> editor and got out the corresponding LaTeX formatted equation
<img src="http://www.google.com/chart?cht=tx&chf=bg,s,FFFFFF00&chco=000000&chl=e^z=\sum^{\infty}_{n=0}\frac{z^n}{n!}" />
Find your favorite online LaTeX editor, such as https://www.codecogs.com/latex/eqneditor.php
Type your out your equation using LaTeX
Save your equation as picture
Upload picture to your google site
Create your equation using Microsoft Word or Google Doc equation editor, take screenshot of that equation, upload it to google site