Subject: couple of questions about complex expressions
From: Raymond Toy
Date: Tue, 25 Sep 2012 14:45:52 -0700
On Tue, Sep 25, 2012 at 3:38 AM, Barton Willis <willisb at unk.edu> wrote:
> It's a mess. I think domain : complex and m1pbranch : true is supposed
> to give the principle branch,
> and domain : real and m1pbranch : false the real branch, I think. But
> sometimes numer matters (and maybe
> radexpand too)
>
> OK -- real branch:
>
> (%i8) block([domain : real, m1pbranch : false], (-8)^(1/3));
> (%o8) -2
>
> Not OK -- principle branch (more-or-less)
>
> (%i9) block([domain : real, m1pbranch : false, numer : true],
> (-8)^(1/3));
> (%o9) 2.0*(-1)^0.33333333333333
>
> (%i10) rectform(%);
> (%o10) 2.0*%i*sin(0.33333333333333*%pi)+2.0*cos(0.33333333333333*%pi)
>
Isn't %o10 correct, given that domain, m1pbranch, and numer have their
default values for rectform? Even then, what would be the real branch
(-1)^(0.333333...) since 0.3333..3 is not 1/3?
I agree that %o9 is confused.
Ray