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

*To*: mathgroup at smc.vnet.net*Subject*: [mg100955] Re: [mg100925] How to define the coefficients of a polynomial to be real?*From*: "David Park" <djmpark at comcast.net>*Date*: Thu, 18 Jun 2009 20:46:33 -0400 (EDT)*References*: <18883255.1245315881604.JavaMail.root@n11>

The command you want is ComplexExpand, which is often overlooked by new users. ComplexExpand assumes all symbols are real, except those you specify to be complex. poly[z_] = a0 + a1 z + a2 z^2 + a3 z^3; poly[1 + I] ComplexExpand[Re[%]] a0 + (1 + I) a1 + 2 I a2 - (2 - 2 I) a3 a0 + a1 - 2 a3 David Park djmpark at comcast.net http://home.comcast.net/~djmpark/ From: BHUPALA [mailto:bhupala at gmail.com] 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];