latex-type-tutor: allow only valid LaTeX math

[jfine2358]

This is prompted by a post made by Fernando Gouvea to texhax (URL below). He wrote:

My students often write things like F’(x) = $\int sin(x)$. Catching the incorrect placement of $ would help them learn. Catching sin vs \sin would be even nicer.

Your program is presumably adding ( and ) before passing to MathJax? (Those are valid LaTeX, by the way.) could it also strip $ before and after?

See: https://tug.org/pipermail/texhax/2020-January/024147.html

Out of the box, MathJax allows things that LaTeX doesn't. For example, the use of '$' as a dollar sign. As this is a LaTeX typing tutor, perhaps some effort should be made to report or prevent such constructions.

As for 'sin' vs '\sin', perhaps #3 might help.

This issue is related to #5