TeX in HTML

It is really easy to add TeX in HTML. I use MathJax.

Define the string that indicate the TeX block. Add this in the <head>. This is not needed in Jekyll, since the kramdown Markdown parser handles it.

 <script type="text/x-mathjax-config">
   MathJax.Hub.Config({
   tex2jax: {inlineMath: [ ['$','$'], ['\\(','\\)'] ]}
   });
 </script>

Add in <head> the .js that converts these blocks. I add this in _includes/themes/bootstrap-3/default.html in my Jekyll Bootstrap installation (with Bootstrap 3 theme used).
```
<script type="text/javascript" async
   src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML">
</script>
```
Add your TeX block in your .html or .md.
```
$$a_1$$ \$a_2\$
```
Will show as $a_1$ $a_2$.