Negligible terms in polynomials



On Thursday 08 January 2009 02:05:24 Stefano Ferri wrote:
> How could I indicate to Maxima that in a polynomial some terms are
> negiglible with respect to others?
> In example, if
>
> expr: a+b;
>
> how could I make a>>b, so expr will be simplified to a? I should do
> this in a sum like the one shown, so I think I cannot use
> ratweights because there are not multiplications or
> exponentiations. Thanks.

Try tellrat:

(%i1) expr : rat(a+b)$
(%i2) tellrat (b)$
(%i3) expr;
(%o3)/R/                    b + a
(%i4) expr, algebraic;
(%o4)/R/                      a


Or you can do it manually:

(%i1) set_to_zero (expr,[terms]) :=
        at (expr, map (lambda([x],x=0), terms))$
(%i2) set_to_zero (a+b+c+d+e, b,d);
(%02)                     e + c + a 

-- 
Pungenday, Chaos 8 YOLD 3175
Alexey Beshenov  http://beshenov.ru/