On the other hand, if I define/assign
$F = Formula( "cos(theta)" ) ;
then the resulting TeX string is "\cos(theta)" rather than "\cos(\theta)".
Am I overlooking something fairly simple to fix this?
TeX=>'\theta 'with a space. I don't remember whether the system will insert the space for you if the theta is followed by another letter, for example. It probably should, but my recollection is that it might not. You could test it by entering an answer of 'theta x' for example (but you'd also have to add the variable 'x'), and seeing if the typeset answer is properly processed or not.