On 2017-08-12, rjf <fate...@gmail.com> wrote:

> seems to me that asking for the "sign" of b^(1/3) in the complex domain
> is nonsense.

After thinking about this some more, I think maybe you're right --
SIGNDIFF-SPECIAL, which is doing the c^3 - b*c --> c - (b*c)^(1/3) that
leads into trouble, should maybe inhibit that approach when domain =
complex, since it can't work in general. But in this case, b and c are
assumed to be positive (and they're declared real for good measure)
so taking roots doesn't lead to any strangeness. So maybe the answer
is that the usual simplification (b*c)^(1/3) --> b^(1/3)*c^(1/3) should
be allowed even though domain = complex.

I'm just thinking out loud here, sorry it doesn't make sense yet. All
present are invited to join in.

best

Robert Dodier

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