[Maxima-bugs] [ maxima-Bugs-812968 ] is(equal(...)) says unknown, ratsimp says 0

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Bugs item #812968, was opened at 2003-09-26 05:29
Message generated for change (Comment added) made by macrakis
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=104933&aid=812968&group_id=4933

Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Joel Ray Holveck (piquan)
Assigned to: Nobody/Anonymous (nobody)
Summary: is(equal(...)) says unknown, ratsimp says 0

Initial Comment:
The way I understood EQUAL, it seems that it's supposed

to answer true if ratsimp returns true.  But in the

following equation, it is clear that this is not

happening.  Sorry about the mess; this was the simplest

reproduction scenario I could find.



(C112) is(equal(x/(2*x*sqrt(2)) - 1/(2*x*sqrt(2)),

(x-1)/(2*x*sqrt(2))));

(D112) 				    UNKNOWN

(C113) is(equal(x/(2*x*sqrt(2)) - 1/(2*x*sqrt(2)),

(x)/(2*x*sqrt(2))-1/(2*x*sqrt(2))));

(D113) 				     TRUE

(C114) ratsimp(x/(2*x*sqrt(2)) - 1/(2*x*sqrt(2)) -

(x-1)/(2*x*sqrt(2)));

(D114) 				       0

(C115) facts();

(D115) 			       [NOT EQUAL(x, 0)]



I did consider that the problem may be related to the

fact that ratsimp simplifies the two sides of the

equation differently, so I tried putting them on the

same side.  In the following, the left side of the

equal ratsimp's to 0 (as seen in D114), and yet equal

doesn't assert that it's equal to 0.



(C130) is(equal(x/(2*x*sqrt(2)) - 1/(2*x*sqrt(2)) -

(x-1)/(2*x*sqrt(2)), 0));

(D130) 				    UNKNOWN



I may be missing something obvious here-- I'm just

learning Maxima-- but this seems off to me.

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>Comment By: Stavros Macrakis (macrakis)
Date: 2003-09-27 13:58

Message:
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user_id=588346

You are absolutely right: this is a bug.



Worse, is(equal(1/sqrt(2),sqrt(2)/2)) and even is(equal(1/sqrt

(2)-sqrt(2)/2,0)) return False!



As you say, it should be using ratsimp(1/sqrt(2)-sqrt(2)/2) -- 

which does correctly return 0.



It is also a known problem (bug?) that 1/sqrt(2) and sqrt(2)/2 

do not simplify to the same thing, but as you say, even when 

you put them on the same side, it doesn't work....



5.9.0 gcl 2.5.0 W2k



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