[Maxima-bugs] [ maxima-Bugs-1607567 ] trigexpand([atan(sin(a)/cos(a))]) => [ atan(tan(a)) ]

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Bugs item #1607567, was opened at 2006-12-02 16:49
Message generated for change (Comment added) made by rtoy
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Category: Lisp Core - Trigonometry
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: trigexpand([atan(sin(a)/cos(a))]) => [ atan(tan(a)) ]

Initial Comment:
trigexpand( [ atan(sin(a)/cos(a)) ] ) => atan(tan(a))
        (UNSIMPLIFIED!)

whereas

  trigexpand( atan(sin(a)/cos(a)) ) => a

and

  atan(tan(a)) => a

Though the simplification atan(tan(a))=> is questionable (it needs to do reduction), it is weird that putting the argument to trigexpand in a list changes the behavior.




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>Comment By: Raymond Toy (rtoy)
Date: 2006-12-04 11:49

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What version?  

With 5.10.0 and cmucl, trigexpand([atan(sin(a)/cos(a))]) =>
[atan(sin(a)/cos(a))]

Corresponding result if the arg is not a list.

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Comment By: Stavros Macrakis (macrakis)
Date: 2006-12-02 16:53

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Oops, it's actually

trigexpand( [ atan(sin(a)/cos(a)) ] ) => [ atan(tan(a)) ]
(UNSIMPLIFIED!)

It doesn't simplify atan of tan, but it does preserve the list...


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