Hi All --
Is there a bug in the integration routine that involve square roots?
1) Why does Maxima not accept -sqrt(something) and proceeds to do
sqrt(-something)?
(%i8) integrate(r,z,-sqrt(20-r^2),sqrt(20-r^2));
2
Is r - 20 positive, negative, or zero?
positive;
Defint: Lower limit of integration must be real.
-- an error. Quitting. To debug this try debugmode(true);
(%i9)
Maxima encountered a Lisp error:
Ctrl-C: User break
Automatically continuing.
To reenable the Lisp debugger set *debugger-hook* to nil.
(%i9) integrate(r,z,-sqrt(20-r^2),sqrt(20-r^2));
Defint: Lower limit of integration must be real.
-- an error. Quitting. To debug this try debugmode(true);
(%i10)
Maxima encountered a Lisp error:
(%i10)
...restarting...
2) This time, I'll answer that what's inside the sqrt is negative:
Maxima 5.9.3 http://maxima.sourceforge.net
Using Lisp CLISP 2.38 (2006-01-24)
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
This is a development version of Maxima. The function bug_report()
provides bug reporting information.
(%i1) integrate(r,z,-sqrt(20-r^2),sqrt(20-r^2));
2
Is r - 20 positive, negative, or zero?
negative;
When I answer negative, it works
(%o1) 2 r sqrt(20 - r^2 )
(%i2)
Any comments.
Henry