Services & Resources / Wolfram Forums
MathGroup Archive
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Simplification question

  • To: mathgroup at
  • Subject: [mg59082] Re: [mg59032] Simplification question
  • From: Pratik Desai <pdesai1 at>
  • Date: Thu, 28 Jul 2005 02:27:17 -0400 (EDT)
  • References: <>
  • Sender: owner-wri-mathgroup at

snoofly wrote:

>Can someone explain this to me please.
>Simplify[Sin[3 m Pi], Assumptions -> m \[Element] Integers]
>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 think the reason is simple as Cos[even*Pi]=+1 and Cos[odd*Pi]=-1
Hence your expression does not specify whether m is odd or even, hence 
Mathematica returns the expression unevaluated
Using a recent reply on a post we can try this

Simplify[Cos[(3*Pi*n)], Assumptions -> Mod[n, 2] == 1]
Simplify[Cos[(3*Pi*n)], Assumptions -> Mod[n, 2] == 0]

Best regards

Pratik Desai
Graduate Student
Department of Mechanical Engineering
Phone: 410 455 8134

  • Prev by Date: Re: silly questions?
  • Next by Date: Re: Why won't Horner[] work?
  • Previous by thread: Simplification question
  • Next by thread: Re: Simplification question