# Testing MathML

September 14, 2023 at 10:53 AM by Dr. Drang

As I mentioned on Mastodon yesterday, I expect to be be including more equations in future posts, and I’d like the equations to appear readable in my RSS feed. This is a test to see if MathML will work.

I’ve been using MathJax (and its predecessor, jsMath) for many years, and it works quite well here on the blog itself, but because it formats the equations via JavaScript, the equations aren’t formatted in the RSS feed. The RSS feed just shows the LaTeX code for each equation—not bad for short equations, but increasingly hard to read as the equations get longer. If you’re an RSS subscriber, you’ve noticed that the following disclaimer appears at the bottom of each article in the feed:

If there are equations in this post, you will see them rendered properly in the original article.

where “the original article” is a link to the blog, where MathJax can do its magic.

So I’m thinking about ways to get the equations to look right in RSS readers. One obvious way is to render them as images, upload them, and insert `<img>`

tags at the appropriate spots,^{1} but this seems crude and very Web 1.0. Although I suppose I could render the equations as SVGs, which would allow users to zoom in without seeing jaggies.

MathML is the “right” way to do equations and is supported by all the browsers I can think of, so the math should look right for everyone who visits the blog directly.^{2} The question is whether it’ll be rendered properly in RSS readers. My guess is that it will be, since I believe that RSS readers use the same rendering engines used by browsers. But the only way to know for sure is to write a post with MathML and see how it looks. So here goes:

The general formula for the mass moment of inertia about the x-axis, $\begin{array}{r}{I}_{xx}\end{array}$, is

$\begin{array}{r}{I}_{xx}={\int}_{V}\rho \phantom{\rule{0.167em}{0ex}}({y}^{2}+{z}^{2})dV\end{array}$

This can be specialized for certain geometries. For example, the moment of inertia of a thin rod about an axis through the rod’s center and perpendicular to it is

$\begin{array}{r}{I}_{xx}=\frac{1}{12}m{L}^{2}\end{array}$

Finally, for Dan Moren, the parallel axis theorem is

$\begin{array}{r}{I}_{xx}^{P}={I}_{xx}^{C}+m{d}^{2}\end{array}$

where $\begin{array}{r}{I}_{xx}^{C}\end{array}$ is the moment of inertia about an axis through the centroid of the body and $\begin{array}{r}{I}_{xx}^{P}\end{array}$ is the moment of inertia about a parallel axis a distance $\begin{array}{r}d\end{array}$ from the centroid.

After I publish this post, I’ll check my RSS feed in NetNewsWire and update the post with a note on how the equations looked.

**Update 14 Sep 2023 10:54 AM**

As I hoped, NetNewWire shows the equations rendered properly (apart from some baseline misalignment for the inline math) in my RSS feed. I’m interested in hearing how other feedreaders perform.