Re: Simplification question
- To: mathgroup at smc.vnet.net
- Subject: [mg59082] Re: [mg59032] Simplification question
- From: Pratik Desai <pdesai1 at umbc.edu>
- Date: Thu, 28 Jul 2005 02:27:17 -0400 (EDT)
- References: <200507270525.BAA19953@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
snoofly 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 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] >>-1 Simplify[Cos[(3*Pi*n)], Assumptions -> Mod[n, 2] == 0] >>1 Best regards -- Pratik Desai Graduate Student UMBC Department of Mechanical Engineering Phone: 410 455 8134
- References:
- Simplification question
- From: "snoofly" <snoofly@snoofly.com>
- Simplification question