Subject: "Upgrade" to Maxima 5.23.2 kills integration
From: Stavros Macrakis
Date: Thu, 17 Mar 2011 11:37:18 -0400
This appears to be related to the recent adoption of stricter simplification
rules for sqrt -- 1/sqrt(x) and sqrt(1/x) are no longer considered
equivalent, since the principal value of 1/sqrt(-1) = -%i and sqrt(1/-1) =
%i.
integrate(sqrt(1/(x^2+x)),x) => 'integrate(sqrt(1/(x^2+x)),x)
integrate(1/sqrt(x^2+x),x) => log(2*sqrt(x^2+x)+2*x+1)
The workaround is to set radexpand:all :
integrate(sqrt(1/(x^2+x)),x),radexpand:all => log(2*sqrt(x^2+x)+2*x+1)
Fateman has pointed out many times that trying to manipulate symbolic
expressions in such a way that principal value is preserved is a fool's
errand unless we get *much* more sophisticated in their handling (with a
significant burden in usability). But even naive users are confused when
sqrt(x^2) simplifies to x and not abs(x).... So it's not clear what the
solution is.
-s
On Thu, Mar 17, 2011 at 10:51, Henry Baker <hbaker1 at pipeline.com> wrote:
> sqrt(1/(BdotB*t^2+2*AdotB*t+AdotA));
>