double integrals seem to give different answers

I can't fix this with pw.mac.  Maybe trigsimp() should sometimes call 
asksign and then with ni.mac loaded (a modified noninteractive.mac that I 
have been playing with) it could give all the possible answers.

Rich


--------------------------------------------------
From: "Richard Hennessy" <rich.hennessy at verizon.net>
Sent: Saturday, November 21, 2009 7:36 PM
To: "Richard Fateman" <fateman at cs.berkeley.edu>; "Maxima List" 
<maxima at math.utexas.edu>
Cc: "G. Jay Kerns" <gkerns at ysu.edu>
Subject: Re: [Maxima] double integrals seem to give different answers

> I think (w^2)^(3/2) should simplify to abs(w^3) or abs(w)^3 when the 
> domain
> system variable is set to "real".  Maybe I should add this to pw.mac, 
> since
> it's true if you stick to the assumption that all variables are real 
> (which
> is what domain I think should mean).  Since domain does not work maybe I 
> can
> add a new feature to pw, which always assumes only real numbers.  I 
> haven't
> checked to see if pw can can do this case.
>
> Rich
>
>
> --------------------------------------------------
> From: "Richard Fateman" <fateman at cs.berkeley.edu>
> Sent: Saturday, November 21, 2009 7:14 PM
> To: "Maxima List" <maxima at math.utexas.edu>
> Cc: "G. Jay Kerns" <gkerns at ysu.edu>
> Subject: Re: [Maxima] double integrals seem to give different answers
>
>> Richard Hennessy wrote:
>>> This is a bug,
>> ...
>> If you think that  (w^2)^(3/2)   should simplify to  abs(w^3), then you
>> inevitably run into problems.
>> That is what trigsimp, or some component of it, believes.
>> If you believe, as I do, that there are 2 values, +w^3 and -w^3, and the
>> computation should proceed
>> using Both values until
>> (a) it is determined that It Doesn't Matter Which You Use.
>> or
>> (b) the user (or some other computation) decides that Only One Value
>> Works and uses it.
>> or
>> (c) you have to produce an answer Including Both Values.
>>
>> From this perspective it isn't a bug in integration or trigsimp. And I
>> suspect the same trick will catch you in
>> Mathematica or Maple, if they do the same "simplification". There are a
>> large number of system-independent
>> mathematical "gotchas".
>>
>> RJF
>>
>>
>>
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