# Sometimes MathJax does not render some valid symbols: an example.

In this answer, a line of $$\LaTeX$$ doesn't render. (See the picture.)

It appears that this is happening with other people too.

It happens on the mobile site:

Refreshing the page doesn't make a difference.

The group $$G\cong H\times K$$ with $$H\cong \langle S_H\mid R_H\rangle$$ and $$K\cong \langle S_K\mid R_K\rangle$$ has as a presentation $$G\cong \langle S_H\cup S_K\mid R_H\cup R_K\cup X\rangle,$$ where $$X=\{hk=kh\mid h\in S_H\text{ and } k\in S_K\}$$, from which it is easy to see that $$H\cong L$$ such that $$L\unlhd G$$. (Why?)
• I will just add that I see the same when I use HTML-CSS as Math Renderer. When I use SVG, I can see it. (I am on Chrome. I have observed similar behavior in this recent bug report - HTML-CSS was problematic, other renderers worked fine. Perhaps it's worth mentioning that formula in the linked post contains \text{...} - similarly as in the problematic formulas in the other bug report.) – Martin Sleziak Oct 25 '19 at 16:04
• @Shaun With that linked answer, the HTML-CSS renderer works fine for me with FireFox $70.0$ on Windows $7$. – John Omielan Oct 26 '19 at 0:15
• @MartinSleziak Using $\land$ instead seems to work. – Shaun Oct 26 '19 at 0:20