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