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

*To*: mathgroup at smc.vnet.net*Subject*: [mg100947] Re: How to define the coefficients of a polynomial to be real?*From*: Peter Breitfeld <phbrf at t-online.de>*Date*: Thu, 18 Jun 2009 20:45:06 -0400 (EDT)*Organization*: SFZ Bad Saulgau*References*: <h1cvbi$ji2$1@smc.vnet.net>

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 > pol = a0 + a1 z + a2 z^2 + ... dom = Element[#,Reals]& /@ CoefficientList[pol,z] Simplify[Re[pol/.z->1+I],dom] should do it -- _________________________________________________________________ Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de