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Re: Forcing Re[]'s to be Real
*To*: mathgroup at smc.vnet.net
*Subject*: [mg18256] Re: Forcing Re[]'s to be Real
*From*: "Neal E. Tornberg" <neal.e.tornberg at boeing.com>
*Date*: Thu, 24 Jun 1999 14:24:39 -0400
*Organization*: Boeing
*References*: <7kpbj1$4b8@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
try
Re[Sqrt[1.+I]]
i.e. use a real constant to force Mathematica to do the numerics
Try defining k[w_Real]:=....
Anthony Foglia wrote:
>
> I seem to have found an interesting problem involving computing the
> real part of complex numbers. (Interesting, in that it wasn't there a few
> weeks ago when I ran the (as-far-as-i-can-remember) exact same code.)
>
> I have a complex function:
>
> k[w] := Sqrt[w^2 (1 + (2 / (1 + I w)))]
>
> I want to graph the real and imaginary parts, but Mathematica doesn't want
> to express the Re[k[w]] as a real number. What do I mean? Well, if I
> type:
>
> Re[Sqrt[1+I]]
>
> I get out
>
> Re[Sqrt[1+I]]
>
> Same if I do Re[ComplexExpand[Sqrt[1+I]]], or Re[(1+I)^(1/2)]. But if I
> enter:
>
> Re[ComplexExpand[(1+I)^(1/2)]
>
> Mathematica is kind enough to respond with:
>
> 2^(1/4) Cos[Pi/8]
>
> I'm certain that this is the root of my problem, but I'll be damned if I
> know why Mathematica doesn't like it now, but did a few weeks ago. Any
> help?
>
> --Anthony
--
Neal E. Tornberg
neal.e.tornberg at boeing.com
Nobody here thinks I speak for Boeing.
You shouldn't either.
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