Re: force variable to be real

*To*: mathgroup at smc.vnet.net*Subject*: [mg91791] Re: [mg91736] force variable to be real*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Sun, 7 Sep 2008 22:55:35 -0400 (EDT)*Reply-to*: hanlonr at cox.net

w = x + I 2 x z; y = Simplify[Re[w], Element[{x, z}, Reals]] x or more simply y = ComplexExpand[Re[w]] x D[y, x] 1 Bob Hanlon ---- phillman5 <PHILLMAN5 at gmail.com> wrote: ============= How do you force variables to be real? I have w:=x + I 2 x z, and y:=Re[w] and want the derivative of y wrt x, x and z are Real D[y, x] gives Re'[x] - 2 z Im'[x z] where I'd expect just 1. Or I need to evaluate Re[w] forcing x and z to be real, then take the derivative. Thank you for any help Paul -- Bob Hanlon