Also if an equation is in the edit history, you can press "view source" and get a plaintext document of the markdown from the question / answer. BTW, if you want to put MathJax into something like a github pages site, you can just include this in the `<head>` section:
```
<script type="text/javascript"
src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>
```