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force variable to be real

• To: mathgroup at smc.vnet.net
• Subject: [mg91736] force variable to be real
• From: phillman5 <PHILLMAN5 at gmail.com>
• Date: Sun, 7 Sep 2008 05:33:03 -0400 (EDT)

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

• Follow-Ups:
  • Re: force variable to be real
    • From: Benjamin Reedlunn <breedlun@umich.edu>
  • Re: force variable to be real
    • From: "peter lindsay" <pl.0@me.com>