I understand that computer-algebra systems are useful for physists, engineers, or other users of mathematics. But are they useful in mathematics itself?
Specifically,
- Are they usually taught in undergraduate or graduate education in (pure) mathematics?
- Do the majority of professional mathematicians use them?
- Can they be replaced with free and open source ones like Maxima, PARI/GP and Sage?
- Would there be a serious problem if a student or a resercher in mathematics did not use them?
My main concern is that if mathematics students or reserchers have to use blackbox software like Mathematica, it seems to me against the spirit of mathematics: never treat results as truth until their proof is provided.
0.Yes.
They are not blackboxes, and not against the spirit of mathematics. (In everyday life you use a lot of blackboxes.) In math if a researcher want to prove a statement he/she uses other statements but not verifies each of them. They hope it was checked others and results are correct. In many cases checking is almost impossible because the university isn't subscribed for many journals or the researcher does not understand that language.
As I know (i'm not a specialist of this topic, sorry if I say wrong things) computer scientists develop a method or a software that in principle could verify other source code. So I encourage you to use CAS, but "be prepare".