Maxima 5.9.3 bug in limit, not really



Your sense of humor is always on, great! ;)


Sunday, August 27, 2006, 8:09:13 PM, you write:

RF> You could contribute to getting a better answer than "ind", perhaps
RF> the right answer or perhaps returning the limit as unevaluated, 
RF> by writing another program. e.g. vblimit(...) := ....

RF> For a start,  vblimit(a,b,c):= limit(trigsimp(a),b,c);

RF> Another possibility is 
RF>   vblimit(a,b,c):=block([ans:limit(a,b,c)], if (ans=ind) then 'limit(a,b,c)
RF> else ans);


 

>> -----Original Message-----
>> From: maxima-bounces at math.utexas.edu 
>> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Vladimir 
>> Bondarenko
>> Sent: Sunday, August 27, 2006 9:00 AM
>> To: maxima at math.utexas.edu
>> Cc: Richard Fateman
>> Subject: Re: [Maxima] Maxima 5.9.3 bug in limit, not really
>> 
>> Hello,
>> 
>> 1. I fully agree with you that
>> 
>> RJF>  It is a difficult engineering question to figure  out how much 
>> RJF> work to do on simplifying input  without special requests, like 
>> RJF> trigsimp.  If you  do too much, commands can take too much time.
>> 
>> I would even say, "It is a very difficult engineering question"
>> 
>> 2. I could agree with you - if Maxima would return the
>>    input unevaluated. Well... the system just cannot do
>>    it.
>> 
>>    However, in the given case, Maxima returns an answer
>>    which is mathematically incorrect, namely,  ind.
>> 
>> 3. Some other system handles this successfully, say, any
>>    version of Derive since 1980 to 2006, and Mathematica,
>>    at least MMA 5.2. Here we are
>> 
>>    LIM(SIN(SIN(z)^2+COS(z)^2),z,inf)
>>    Limit[Sin[Sin[z]^2 + Cos[z]^2], z -> Infinity]
>>    
>>    SIN(1)
>>    Sin[1]
>> 
>>    LIM(SIN(SIN(SIN(SIN(SIN(SIN(z)^2+COS(z)^2))))),z,inf)
>>    Limit[Sin[Sin[Sin[Sin[Sin[Sin[z]^2 + Cos[z]^2]]]]], z -> Infinity]
>>    
>>    SIN(SIN(SIN(SIN(SIN(1)))))
>>    Sin[Sin[Sin[Sin[Sin[1]]]]]
>>    
>>    So why Maxima cannot achieve what other have done OK?
>> 
>> 
>> Sincerely,
>> 
>> VB
>> 
>> http://www.cybertester.com/  Cyber Tester, LLC
>> http://maple.bug-list.org/   Maple Bugs Encyclopaedia
>> http://www.CAS-testing.org/  CAS Testing
>> 
>> 
>> Sunday, August 27, 2006, 5:42:27 PM, you write:
>> 
>> RF> Yet again you conflate a problem with limit with a 
>> simplification problem.
>> RF> trigsimp( sin(sin(z)^2+cos(z)^2) );   gives sin(1).
>> RF> It is a difficult engineering question to figure out how 
>> much work 
>> RF> to do on simplifying input without special requests, like 
>> trigsimp.  
>> RF> If you do too much, commands can take too much time.
>> RF> RJF
>> 
>> 
>> >> -----Original Message-----
>> >> From: maxima-bounces at math.utexas.edu 
>> >> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Vladimir 
>> >> Bondarenko
>> >> Sent: Sunday, August 27, 2006 2:02 AM
>> >> To: maxima at math.utexas.edu
>> >> Subject: Maxima 5.9.3 bug in limit
>> >> 
>> >> Hello,
>> >> 
>> >> (%i1) limit(sin(sin(z)^2+cos(z)^2),z,inf);
>> >> 
>> >> (%o1)                                ind
>> >> 
>> >> 
>> >> Of course, the correct answer is sin(1).
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