Re: declaring variables
- To: mathgroup at smc.vnet.net
- Subject: [mg4767] Re: declaring variables
- From: Dr Stephen P Luttrell <luttrell at signal.dra.hmg.gb>
- Date: Fri, 13 Sep 1996 13:54:51 -0400
- Organization: Defence Research Agency
- Sender: owner-wri-mathgroup at wolfram.com
Burkhardt Goedde wrote: > > Dear math users, > just a simple problem, but I got no answer from thew book. > > Re[x + I y] gives > > Re[x + I y] > > whereas > > Re[2 + 3 I] > > gives 2 > > How could I tell Mathematica that x and y are real numbers? > Try this: ClearAll[x,y]; r = Re[x + I y] ComplexExpand[r] which produces the output: Re[x + I y] x -- Dr Stephen P Luttrell luttrell at signal.dra.hmg.gb Adaptive Systems Theory 01684-894046 (phone) Room EX21, Defence Research Agency 01684-894384 (fax) Malvern, Worcs, WR14 3PS, U.K. http://www.dra.hmg.gb/cis5pip/Welcome.html ==== [MESSAGE SEPARATOR] ====