Re : Re: Re : how to handle roots of unity symbolically ?
Subject: Re : Re: Re : how to handle roots of unity symbolically ?
From: Roberto Fernandez
Date: Sun, 25 Nov 2012 11:14:05 +0100 (CET)
----- Stavros Macrakis <macrakis at alum.mit.edu> a ?crit?:
> Because that gets you the *primitive* root of unity, which is what I think
> the Original Poster was looking for.
>
> Actually, I am not sure what the original poster was looking for. Maybe he
> wanted map(tellrat,args(factor(x^12-1))), for example.
the Original Poster doesn't actually know himself what he wants :)
but he would like something like that:
(%i1) val[i,j] := w^mod((i-1)*(j-1),5)$
(%i2) F:genmatrix(val,5,5);
(%o2) matrix([1,1,1,1,1],[1,w,w^2,w^3,w^4],[1,w^2,w^4,w,w^3],[1,w^3,w,w^4,w^2],[1,w^4,w^3,w^2,w])
(%i3) simplifie(invert(F),5);
(%o3) matrix([1,1,1,1,1],[1,w^4,w^3,w^2,w],[1,w^3,w,w^4,w^2],[1,w^2,w^4,w,w^3],[1,w,w^2,w^3,w^4])/5