       Re: Re: Simplify

```On 14 Jul 2005, at 15:48, Andrzej Kozlowski wrote:

>
> On 13 Jul 2005, at 16:29, paulvonhippel at yahoo wrote:
>
>
>> I'm having some trouble getting an expression to simplify in an
>> obvious
>> way. (There seems to be a long tradition of users posting to this
>> group
>> with similar troubles.)
>>
>> The expression is
>>
>>  poly = p (p - 1) b^2 + s^2
>>  prod = Sqrt [poly] Sqrt[1/poly]
>>  Simplify[prod, {0 < p < 1, s > 0, bÏµReals}]
>>
>> which should return one, I think, but doesn't.
>>
>> I'd be grateful for suggestions.
>>
>> Thanks!
>> Paul
>>
>>
>>
>
>
> prod /. {p -> 1/2, s -> 0, b -> 1}
>
>
> -1
>
>
> prod /. {p -> 1/2, s -> 1, b -> 0}
>
>
> 1
>
>
> FullSimplify[Abs[prod], {0 < p < 1, s > 0, bÏµReals}]
>
>
> 1
>
>
> Andrzej Kozlowski
>
>

I just noticed that my first example
prod /. {p -> 1/2, s -> 0, b -> 1}
violates the assumption that s>0.

A correct example is

prod /. {p -> 1/2, s -> 1/10, b -> 1}

-1

I find it curious that some people seem to be recommending a "work
around" (using PowerExpand) that will give the "desired" answer 1
since this "desired answer" is  simply wrong (of course on the
assumption that one follows the usual mathematical conventions that
are needed to make Sqrt (a single valued) function).

Andrzej Kozlowski

```

• References:
• Simplify
• From: "paulvonhippel at yahoo" <paulvonhippel@yahoo.com>
• Re: Simplify
• From: Andrzej Kozlowski <akozlowski@gmail.com>
• Prev by Date: Re: Superscript Problem
• Next by Date: How can get the Path of current Notebook ?
• Previous by thread: Re: Simplify
• Next by thread: Re: Simplify