Well, this is documented, see section 8.3 of FriCAS book. In
short: FriCAS represents roots by symbols and to get full info
you need to use functions like 'definingPolynomial'. Some time
ago Ralf gave nice example.
BTW: I plan to change this and emit rootSum objects. ATM this change
waits for time when other parts of FriCAS can handle root sums.
Generating root sums is easy, in fact easier than current code for
roots. And root sums are much more managable than roots, but we
need to write code handling them.
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Waldek Hebisch