I found radexpand option variable in the reference manual:
> radexpand
> Option variable
> Default value: true
> radexpand controls some simpli?cations of radicals.
> When radexpand is all, causes nth roots of factors of a product which
> are powers
> of n to be pulled outside of the radical. E.g. if radexpand is all,
> sqrt (16*x^2)
> simpli?es to 4*x.
> More particularly, consider sqrt (x^2).
> ? If radexpand is all or assume (x > 0) has been executed, sqrt(x^2)
> simpli?es
> to x.
> ? If radexpand is true and domain is real (its default), sqrt(x^2)
> simpli?es to
> abs(x).
> ? If radexpand is false, or radexpand is true and domain is complex,
> sqrt(x^2)
> is not simpli?ed.
> Note that domain only matters when radexpand is true.
But it does not work for me(version of maxima is 5.25.1):
(%i1) radexpand:true;
(%o1) true
(%i2) b: ((1-x)/sqrt(1-2*x+x^2));
1 - x
(%o2) ------------------
2
sqrt(x - 2 x + 1)
(%i3) radcan(b);
(%o3) - 1
(%i4) radexpand: false;
(%o4) false
(%i5) radcan(b);
(%o5) - 1
any ideas?
> We have a question at
> http://ask.sagemath.org/question/767/simplification-errors-in-simple-expressions
> which seems to find a bug in radcan. Here is the relevant Maxima
> session.
>
>
> (%i3) b:((1-x)/sqrt(1-2*x+x^2));
> 1 - x
> (%o3) ------------------
> 2
> sqrt(x - 2 x + 1)
> (%i4) radcan(b);
> (%o4) - 1
>
> which seems a little aggressive. But
>
> (%i7) d:((1-x)/sqrt((1-x)^2));
> 1 - x
> (%o7) ----------
> abs(x - 1)
>
>
> Radcan's documentation is a little confusing.
>
> radicals, by converting it into a form which is canonical over a
> large class of expressions and a given ordering of variables; that
> is, all functionally equivalent forms are mapped into a unique
> form. For a somewhat larger class of expressions, `radcan'
>
> doesn't give very many details. But I'm certainly not an expert in
> making expressions canonical :)
>
> Thanks for any help!
> _______________________________________________
> Maxima mailing list
> Maxima at math.utexas.edu
> http://www.math.utexas.edu/mailman/listinfo/maxima
>
>
>