Subject: couple of questions about complex expressions
From: Robert Dodier
Date: Tue, 25 Sep 2012 06:38:07 +0000 (UTC)
Hi, I've run into a couple of things that I'm wondering about.
(1) principal branch for (-x)^(1/n) when n is an odd integer. I know
we've gone back and forth on this one, and at present it looks like the
real branch is chosen. Is there a way to choose the principal branch?
For the record, m1pbranch doesn't seem to have any effect here.
(2) division of complex literals: how can I get (a + b*%i)/(c + d*%i) =>
e + %i*f when a, b, c, and d are numbers.
I can't seem to cause it to happen. realpart(foo) + %i*imagpart(foo) has
the expected result but it just seems clumsy.
(%i2) foo : (5 + %i)/(3 - 2*%i);
(%o2) (%i+5)/(3-2*%i)
(%i3) expand (foo);
(%o3) %i/(3-2*%i)+5/(3-2*%i)
(%i4) ratsimp (foo);
(%o4) -(%i+5)/(2*%i-3)
(%i5) radcan (foo);
(%o5) -(%i+5)/(2*%i-3)
(%i6) foo, numer;
(%o6) (%i+5)/(3-2*%i)
(%i7) float (foo);
(%o7) (%i+5.0)/(3.0-2.0*%i)
(%i8) expand (float (foo));
(%o8) %i/(3.0-2.0*%i)+5.0/(3.0-2.0*%i)
Thanks for your help,
Robert Dodier