In Google Docs' document editor, there's a rudimentary support for adding mathematical equations.
I didn't find anything like that in Google Docs presentation editor.
Anyone know a workaround?
See this thread in the Google Docs forums.
I found this online LaTeX editor. It allows you to type LaTeX and download an image of the resulting equation. It even shows in real time what the equation looks like.
I'm going to use the online LaTeX equation editor to place an equation in Google Presentations, just like you wanted to.
Here's an example:
It's a kind of REST interface that generates the image, similar to Google Chart API: