> I see. But I did not not write this latex. It seems to work OK in mathjax.
> This is how the latex came from a Mathematica newsletter which is emailed each
> week.
Yes I know. As I wrote: it sometimes work if you are lucky.
And people are lazy and so often try their luck and leave of the
braces. And then they complain when it doesn't work after some change
or when using another engine or workflow.
But the rule is: use braces unless you are very, very sure, that you
know it works, and that is will continue to work, even if commands are
changed internally. Which basically means you should only leave them out
for stuff like x^2.
See also
https://tex.stackexchange.com/a/342272/2388
https://github.com/josephwright/beamer/issues/599
--
Mit freundlichen Grüßen
Ulrike Fischer
