I guess the question is, what can you do with this mod expression
next? It's not nice to look at, and maybe not good to compute with...
If you leave R= atan(tan(x)) alone, then later if you do this:
tan(R), you can simplify that to tan(x).
It is also true of the mod expression, assuming the expression is right,
but how clever would the simplifier have to be to know that
tan (mod (....)) was tan(x)?
Another possibility is to ask the user if -pi/2<x<pi/2 before doing
the simplification, but people don't seem to like ASKSIGN.
Anyway, these are uncomfortable options, all of them.
RJF
----- Original Message -----
From: "Robert Dodier" <robert.dodier at gmail.com>
To: "Richard Fateman" <fateman at cs.berkeley.edu>
Cc: "Maxima" <maxima at math.utexas.edu>
Sent: Monday, March 13, 2006 9:01 AM
Subject: Re: [Maxima] simplification of atan(tan(x)), etc
>> I suggest that atan(tan(x)) not simplify unless we know -%pi/2 <x <%pi/2
>
> how about atan(tan(x)) => mod (x + %pi/2, %pi) - %pi/2 ?
> current version of mod does what we want here
> (although maybe there's a simpler equivalent).
>
> robert
>
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