factor(b)
On Sep 23, 2011 2:56 AM, "Dmitry Shkirmanov" <piminusmeson at bk.ru> wrote:
> 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!
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>>
>>
>>
>
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