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, da...@axiom-developer.org 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

http://en.wikipedia.org/wiki/Square_root

and do not spot a date on this.

--Nasser