On Thu, 21 Nov 2013, Richard Fateman wrote:
> On 11/21/2013 8:34 AM, Hugo Coolens wrote:
>> I found the following in the documentation:
>> sqrt (x^2);
>> gives abs(x)
> Mathematically speaking this is false and the result given
> by Maxima can lead to errors. There are two square roots.
> abs(x) is not one of them, as you can see by plotting x, -x, and abs(x).
Some people use the sqrt-symbol to give you only the positive root,
therefore I thought Maxima imitated this somehow by answering with abs(x).
As a matter of fact I'm only interested in positive solutions, therefore
I'd really like to see a method in Maxima which transforms
sqrt(x^4-2*x^2+1) into abs(x^2-1)
hope you understand me
regards
hugo
>
>>
>> However:
>>
>> sqrt(x^4-2*x^2+1);
>>
>> does not result in
>> abs(x^2-1)
> This too is false.
>> but leaves the expression untouched.
>>
>>
>> It puzzles me why, can I make Maxima do it?
> You can try radcan(%), which returns one of the roots, x^2-1,and ignores the
> other.
> This is a feature of radcan. It shouldn't be a feature of the general
> simplifier.
>
> You can try map(factor,%) which returns the dubious abs(x-1)*abs(x+1).
>
> RJF
>