Date: Jul 24, 2013 2:17 AM
Author: Nasser Abbasi
Subject: Re: An independent integration test suite

On 7/24/2013 12:21 AM, Albert Rich wrote:
> On Tuesday, July 23, 2013 2:32:20 PM UTC-10, wrote:

>> We differ on some results because Rubi (or whatever program you are using
>> to create the optimal results) assumes that square roots have only a single
>> positive value. Axiom does not want to make this simplification so given
>> sqrt(3)*sqrt(7)*sqrt(21) - 21
>> Axiom will not simplify this to zero but the Rubi test suite does.


> Surly there must be a way to tell Axiom to choose the principal
> branch so sqrt(4)-2 will simplify to zero?
> Albert

I remember reading that some math people, 100 or 200 years ago,
decided that sqrt (of non-negative, non-complex values) was single valued
function and its value is the non-negative root (ie. principal
square root).

Does any one have a reference if this is true and when this
change was decided on? Or may be it always was like this?

I looked at wiki now
and do not spot a date on this.