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Help! Sin[n Pi] (n Integer)

• To: mathgroup at smc.vnet.net
• Subject: [mg8942] Help! Sin[n Pi] (n Integer)
• From: dwarf at wam.umd.edu (Dwarf)
• Date: Sat, 4 Oct 1997 22:08:18 -0400
• Organization: University of Maryland, College Park, MD
• Sender: owner-wri-mathgroup at wolfram.com

Does anyone know if there's a way to specify that a variable is an
integer? 

I'm taking a conduction class (with *lots* of separation of variables
problems) and the quantities Sin[n Pi] or Cos[(2n+1)/2 Pi] come
up constantly.  I can dispose of them with replacement rules, but I was
wondering if there's a way to "tag" n as an integer so that Mma will
automatically kill the Sin and Cos terms later in the derivations.

It seems like the "specify that a is real so that Sqrt[a^2] automatically
reduces to a without using PowerExpand" problem from way back and I don't
remember the solution (if there was one)

Thanks!

Greg Anderson
dwarf at wam.umd.edu