       Re: How to define the coefficients of a polynomial to be real?

• To: mathgroup at smc.vnet.net
• Subject: [mg100932] Re: How to define the coefficients of a polynomial to be real?
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Thu, 18 Jun 2009 06:18:16 -0400 (EDT)
• Organization: Uni Leipzig
• References: <h1cvbi\$ji2\$1@smc.vnet.net>
• Reply-to: kuska at informatik.uni-leipzig.de

```Hi,

\$Assumptions = {Element[a0, Reals]}

and

Simplify[Re[a0]]

will work.

Regards
Jens

BHUPALA wrote:
> I have a 10th order polynomial (a0+a1 z+a2 z^2 + ... + an z^10). I
> want to define all the coefficients to be real. I want to substitute z
> = 1+i and extract only real part of it.
>
> I have done this by defining
>
> Element[a0,Reals];
> Element[a1,Reals];
> .
> .
> .
> Element[a10,Reals];
>
> Ply = a0+a1z+a2 z^2 + ... + an z^10;
> Ply/. z-> 1+I
>
> I am getting
>
> -2 Im[a2]+Re[a0+(1+i) a1-(2-2i)a3- 4a4]
>
> which I should not have got as I have defined already defined the
> coeffs to be real.
>
> Any help please!
>
> bhupala
>

```

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