# a post with math

October 20, 2015

[** 2015](https://alextisyoung.com/blog/2015) · [** formatting](https://alextisyoung.com/blog/tag/formatting) [** math](https://alextisyoung.com/blog/tag/math) · [** sample-posts](https://alextisyoung.com/blog/category/sample-posts)

This theme supports rendering beautiful math in inline and display modes using [MathJax 3](https://www.mathjax.org/) engine. You just need to surround your math expression with `$$`, like `$$ E = mc^2 $$`. If you leave it inside a paragraph, it will produce an inline expression, just like \(E = mc^2\).

To use display mode, again surround your expression with `$$` and place it as a separate paragraph. Here is an example:

 \[\sum_{k=1}^\infty |\langle x, e_k \rangle|^2 \leq \|x\|^2\]

You can also use `\begin{equation}...\end{equation}` instead of `$$` for display mode math. MathJax will automatically number equations:

\begin{equation} \label{eq:cauchy-schwarz} \left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right) \end{equation}

and by adding `\label{...}` inside the equation environment, we can now refer to the equation using `\eqref`.

Note that MathJax 3 is [a major re-write of MathJax](https://docs.mathjax.org/en/latest/upgrading/whats-new-3.0.html) that brought a significant improvement to the loading and rendering speed, which is now [on par with KaTeX](http://www.intmath.com/cg5/katex-mathjax-comparison.php).

Source: [a post with math | Alexander Strudwick Young](https://alextisyoung.com/blog/2015/math/)