Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

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



  • Prev by Date: Re: Use of delayed assignment, :=, with a list
  • Next by Date: Re: ListDensityPlot with Axes, Ticks, TicksStyle
  • Previous by thread: Re: force variable to be real
  • Next by thread: Re: force variable to be real