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


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];



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