[KevinH]

To be fair, the version of mathml you used includes a full copy of the latex equation in the annotations, and lots of attributes settings that are in fact default and not needed.

You can write that equation in mathml with 485 characters.
The nice thing is that with MathJax, you can automatically create the svg (or css and html) from the mathml on the fly so that only one form is needed (mathml) in the epub saving space.

Of course Mathjax will work with Latex input as well and happily convert that on the fly to svg or css and html too.

Unfortunately, the epub3 spec went with html5/mathml not the latex format, and of course only Firefox and Safari even include some native mathml support.

Chrome's Blink and therefore QtWebEngine decided to toss all of mathml instead relying on MathJax for support.

Because of Chrome's decision, mathml has faced huge adoption issues.

It has all become quite the mess.