Re: number types

*To*: mathgroup at smc.vnet.net*Subject*: [mg21650] Re: number types*From*: Harald Giese <giese at dkrz.de>*Date*: Fri, 21 Jan 2000 03:59:59 -0500 (EST)*Organization*: Institut fuer Meereskunde, Universitaet Hamburg*References*: <861529$jjr@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Naum Phleger wrote: > > I feel sort of silly asking something that should be so clear but after > LOTS of trying I can't seem to get it right. > > How can I make Mathematica know that a variable is real or positive so that > > Conjugate[a] gives a > > Sqrt[ a^2 ] gives a > > when I evaluate integrals with a in them it doesn't give me an If statement > like > Hi, You have to tell Mathematica the property within the expression: In[1]:= Simplify[Conjugate[a], a \[Element] Reals] Out[1]= a In[2]:= Simplify[Sqrt[a^2], a \[Element] Reals] Out[2]= Abs[a] > If[ Im[a]=0, answer I want , unevaluated integral ] Please note: "Equal[]" is abbreviated as "==", not "=". Regards, Harald --- This message was entirely written using recycled electrons --- Harald Giese Email: giese at dkrz.de Phone: +49 (0)40 42838 5796; Fax: +49 (0)40 5605724 Institut fuer Meereskunde der Universitaet Hamburg (Institute of Oceanography of the University of Hamburg) Troplowitzstrasse 7, D-22529 Hamburg