I would think a total of 175000 words (though I'd be curious how they get the count, are these roots, entries in the dictionary, something else?) will be quite sufficient. There's however, apart from the actual specific mathematical concepts you were talking about, a good chance that mathematical papers use some specific sentence structures and colloquial expressions that may look strange even to native speakers, as is the case with most things written for a closed set of people (I'll take as an example patent papers which, while using standard words, seem to me to combine them in the most obscure way ;-)).
It's not general language. I need to translate a short (~6 pages) modern mathematical paper from French to English. It is inevitable that the more advanced mathematical vocabulary won't be on any dictionary I can afford. But that shouldn't be a problem. I should be able to infer it based on context, equations, and similarity accross Western European languages.
I would assume that you were exposed to such papers in french through the course of your studies, so that might not be an issue, but if such is not the case I would advise in preparation for your exam to try and find such papers and check if a dictionary is enough for you to be able to translate them. I can give a hand if necessary.
Cyrille
