marked up Formulas in class documentation should actual render in doxygen

It seems like the only place a fair amount of the math used in our implementations is documented is in the actual source. But most of it does not render in our doxygen output since most of it is either bad/incomplete latex or not marked up properly.

see https://doxygen.nl/manual/formulas.html

This is important because there are often significant differences between implementation and them manual or some paper from 5-50 years ago.

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Folks should fix these as they find they're doing work in relevant files. Do it in a small PR before or after your significant work. It will help your metrics.

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