Re: declaring variables

*To*: mathgroup at smc.vnet.net*Subject*: [mg4761] Re: declaring variables*From*: vvs124 at rsphy1.anu.edu.au (Victoria Steblina)*Date*: Fri, 13 Sep 1996 13:54:47 -0400*Organization*: Australian National University*Sender*: owner-wri-mathgroup at wolfram.com

dh61 at rs3.hrz.th-darmstadt.de (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? There is a package <<Algebra`ReIm` that lets you specify that given variables are purely real. Try the following: In[5]:= Needs["Algebra`ReIm`"] Im[x]^=0; Im[y]^=0; Re[x + I y] Im[x + I y] Out[8]= x Out[9]= y The up definitions make the assignment associated with x and y rather than with Im... Hope this helps Vicki ________________________________________________________________________ Victoria Steblina Email: vvs124 at rsphy1.anu.edu.au Optical Sciences Centre Tel: 61 6 249 5129 Australian National University Fax: 61 6 249 5184 ==== [MESSAGE SEPARATOR] ====