Problem with integration



Hi James-

   I disagree that Maxima is trustworthy. There are little bugs here
and there. More than I have time to report or annotate.
   I gave up on using it for graphics altogether.
   I hope for better days.

   Let me give you another bug, involving differentiation:

(C1) f1(x):= (cos^3*(sin*(2*x)));
(C2) diff(f1(x),x);
   This evaluates to the bizarre answer:

   2 x cos^3 DEL(sin) + 6 x cos^2 sin DEL(COS) + 2 cos^3 sin DEL(x)

   The correct answer, by hand and confirme with Maple, is:

   6 cos^2(sin(2x))*sin(sin(2x))*cos(2x);

   Regs,

   Henry
   synthespian@uol.com.br





James Amundson writes:
 > Great. Not too long ago, I wrote that none of the bugs found recently in
 > Maxima resulted in mathematically incorrect answers. Now you have to go
 > an ruin the streak.
 > 
 > This bug deserves *careful* consideration.
 > 
 > Thanks for the report.
 > 
 > --Jim
 > 
 > 
 > On Fri, 2002-04-05 at 14:36, C Y wrote:
 > > I've run into a problem with the Maxima integration ability.  I tried
 > > to integrate 3^log(x), and according to both hand and mathematica
 > > calculations the answer should be (x*3^log(x))/(1+log(3)).  Maxima,
 > > however, gives 3^(2*log(x))/(2*log(3)).  Here is a simple test to show
 > > the problem:
 > > 
 > > (C1) c:3^log(x);
 > > 
 > >                                      LOG(x)
 > > (D1)                                3
 > > (C2) diff(integrate(c,x),x);
 > > 
 > >                                     2 LOG(x)
 > >                                    3
 > > (D2)                               ---------
 > >                                        x
 > > 
 > > 
 > > CY
 > > 
 > > 
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