[Maxima-bugs] [ maxima-Bugs-2477834 ] sin(x + (e + 1/2)*%pi) for even e

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Bugs item #2477834, was opened at 2008-12-30 17:36
Message generated for change (Comment added) made by dgildea
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Category: Lisp Core - Trigonometry
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Alexey Beshenov (beshenov)
Assigned to: Nobody/Anonymous (nobody)
Summary: sin(x + (e + 1/2)*%pi) for even e

Initial Comment:
According to the user manual, Maxima was able to do

(%i1) declare(j, integer, e, even, o, odd)$
(%i2) sin(x + (e + 1/2)*%pi);
(%o2) cos(x)
(%i3) sin(x + (o + 1/2)*%pi);
(%o3) -cos(x)

But in the current CVS version:

(%i1) declare(j, integer, e, even, o, odd)$
(%i2) sin(x + (e + 1/2)*%pi);
(%o2) sin(x+%pi*(e+1/2))
(%i3) sin(x + (o + 1/2)*%pi);
(%o3) sin(x+%pi*(o+1/2))

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>Comment By: Dan Gildea (dgildea)
Date: 2008-12-30 20:12

Message:
The behavior was changed in order to avoid calling expand in the core
simplifier
(trigi.lisp rev 1.31)
See http://www.math.utexas.edu/pipermail/maxima/2008/010919.html.



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Comment By: Alexey Beshenov (beshenov)
Date: 2008-12-30 20:11

Message:
Another stange thing. Was:

(%i1) c: %pi/3 - a - b$
(%i2) bc: sin(a)*sin(3*c)/sin(a+b);
(%o2) sin(a)*sin(3*b+3*a)/sin(b+a)

Now:

(%i1) c: %pi/3 - a - b$
(%i2) bc: sin(a)*sin(3*c)/sin(a+b);
(%o2) sin(a)*sin(3*(-b-a+%pi/3))/sin(b+a)

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You can respond by visiting: 
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