coefficients of a polynomial in two or more variables
Subject: coefficients of a polynomial in two or more variables
From: Richard Fateman
Date: Sat, 05 Dec 2009 07:33:42 -0800
Christian Stengg wrote:
> Hello,
>
> I have experimented on your suggestions and came across the following problem:
>
> (%i1) p1:a*x^2+b*x*y+c*y^2+d*x+e*y+f;
> ratcoef(p1,x*y);
> hipow(p1,x*y);
> bothcoef(p1,x*y);
> hipow(p1,b*x*y);
> bothcoef(p1,b*x*y);
>
I think that you will get the behavior you wish if you do this:
p1 : rat(p1);
bothcoef(p1,x*y).
with such input in rat form, bothcoef uses ratcoef, which seems to
work correctly.
otherwise, bothcoef uses coef, which seems to do the wrong thing here.
RJF