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Daniel Berdine
01/26/09 4:19pm

I believe this might be a problem with assumptions, but I'm not sure.

In the attached file, I attempt to simplify the expression:

(Abs[ Sin[y] Cos[x] ])^2

where x,y are assumed to be real and some constraints are placed on their possible values. As far as I can tell, there is no reason why the Abs[] function cannot be done away with, and Mathematica in fact agrees that simply removing it doesn't change anything (using == to test returns true in the attached notebook).

I thought perhaps Simplify and FullSimplify just don't recognize the added instance of Abs[] to be less simple than removing it, but performing the same exercise with a single trig function happily removes the superfluous Abs[] function, implying that my perception of simpler does agree with Mathematica's in this case.

I experience the same issue with a variety of trig products, either alone or embedded in more complicated expressions. This and similar problems that seem to indicate mathematica isn't using the assumptions I give it have been giving me headaches for a quite some time, so any insight would be much appreciated.

Attachment: SinCos simplification problem.nb, URL: ,

Subject (listing for 'Mathematica fails to make obvious simplificatio...')
Author Date Posted
Mathematica fails to make obvious simplificatio... Daniel Berdine 01/26/09 4:19pm
Re: Mathematica fails to make obvious simplific... Roman 01/27/09 2:12pm
Re: Mathematica fails to make obvious simpl... Daniel Berdine 01/27/09 4:52pm
Re: Re: Mathematica fails to make obvious simpl... Daniel Berdine 01/28/09 4:35pm
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