Re: Simplification question

*To*: mathgroup at smc.vnet.net*Subject*: [mg59092] Re: Simplification question*From*: "David W. Cantrell" <DWCantrell at sigmaxi.org>*Date*: Thu, 28 Jul 2005 02:27:58 -0400 (EDT)*References*: <dc76pp$jvg$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

"snoofly" <snoofly at snoofly.com> wrote: > Can someone explain this to me please. > > Clear[m] > > Simplify[Sin[3 m Pi], Assumptions -> m \[Element] Integers] > 0 > > Simplify[Cos[3 m Pi], Assumptions -> m \[Element] Integers] > > Cos[3 m \[Pi]] > > I'm not sure why Mathematica cannot deduce that the second simplification > should be (1)^m. I presume you meant to say (-1)^m. Anyway, Peter Pein recently posted a nice way to handle this, in sci.math.symbolic: In[1]:= Refine[TrigFactor[Cos[3 m Pi]], Element[m, Integers]] Out[1]= (-1)^m David