Extended real arithmetic (was Re: inf - inf = 0 ??)



I too am skeptical 

 

Example : 

 

(sqrt(x+1)-sqrt(x))*cos(x)   ========?   0 X UND = 0 

 

 

(sqrt(x+1)-sqrt(x))*tan(x)   ========?   0 X UND = UND   

 

jean 

 

 

De : maxima-bounces at math.utexas.edu [mailto:maxima-bounces at math.utexas.edu]
De la part de Richard Hennessy
Envoy? : vendredi 10 septembre 2010 20:48
? : Stavros Macrakis; Barton Willis
Cc : maxima List
Objet : Re: [Maxima] Extended real arithmetic (was Re: inf - inf = 0 ??)

 

I am a little skeptical about it.  My biggest concern is that the axioms of
extended real or complex arithmetic may not be self consistent.  If that is
the case then you could prove that an answer is correct and incorrect at the
same time by using different methods perhaps.  If they are in fact self
consistent and complete than I am all for it.

 

Rich

 

 

From: Stavros <mailto:macrakis at alum.mit.edu>  Macrakis 

Sent: Friday, September 10, 2010 10:03 AM

To: Barton Willis <mailto:willisb at unk.edu>  

Cc: maxima List <mailto:maxima at math.utexas.edu>  

Subject: Re: [Maxima] Extended real arithmetic (was Re: inf - inf = 0 ??)

 

Especially disappointing because extended real arithmetic can in fact solve
this correctly: 

 

   p1: sqrt(x+1)-sqrt(x)$

   p2: cos(x)$

 

limit(p1,x,inf) => 0

limit(p2,x,inf) => IND

 

from which Maxima should be able using extended real arithmetic that
limit(p1*p2) => 0

On Fri, Sep 10, 2010 at 08:52, Barton Willis <willisb at unk.edu> wrote:

(((sqrt(x+1)-sqrt(x)))*cos(x),x,inf);

 

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