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Re: about real part

  • To: mathgroup at smc.vnet.net
  • Subject: [mg41210] Re: about real part
  • From: "Dr. Wolfgang Hintze" <weh at snafu.de>
  • Date: Wed, 7 May 2003 03:57:33 -0400 (EDT)
  • References: <b982nm$67m$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

You can even simplify the problem thus

In[1] = Re[Sqrt[a + I ]]

leading "at most" (using //ComplexExpand) to

Out[1] = Sqrt[Abs[I + a] * Cos[1/2 Arg[I + a]]

If you assign a value to a, say a=1 then the result is ok, viz.

2^(1/4) * Cos[Pi/8]

But in general one would expect something like

(1+a*a)^(1/4) * Sqrt[(1 + a/Sqrt(1+a*a)) / 2]

I couldn't find that expression using Mathematica's Simplifying means.

Regards,
Wolfgang

Duanxiang Xu wrote:

> Hi, all
> 
> I have problem when I was trying to get the real part
> of a complex expression,
> like 
> Re[(Iwt+(L+1)LtD)^1/2]
> here w,L,D are real paramaters and t is real variable
> Mathematica seems could do nothing about this
> 
> Anyone could help me?
> 
> Thanks,
> Duanxiang
> 
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