#2570 Make acos(cos(x)) simplify to x when on correct interval

None
closed
nobody
5
2013-05-24
2013-04-21
kcrisman
No

Stavros comments at this Maxima thread that

The simplification acos(cos(x)) => x is only valid when 0 <= x <= %pi, so
Maxima by default does not perform that simplification. (And unfortunately,
it is not clever enough to perform it when x is declared to be in that
range.)

This still seems to be the case - see this ask.sagemath.org question. So... I nominate this as a bug, or at least a candidate for improvement, since asin(sin(x)) does seem to be smart enough.

Discussion

  • Robert Dodier

    Robert Dodier - 2013-05-24
    • labels: --> Lisp Core - Simplification
    • status: open --> closed
     
  • Robert Dodier

    Robert Dodier - 2013-05-24

    Fixed by commit 5fefd4750. It was a simple cut-n-paste error: some code was copied from corresponding stuff for asin but someone forgot to change sin to cos. No big deal.

    There might be some other simplifications which are known for asin but not for acos. Maybe I'll open another bug report.

     

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