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Re: Square root of a square

• To: mathgroup at smc.vnet.net
• Subject: [mg107845] Re: Square root of a square
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Sun, 28 Feb 2010 04:54:28 -0500 (EST)
• References: <201002270813.DAA11868@smc.vnet.net>

On 27 Feb 2010, at 09:13, Mariano Su=E1rez-Alvarez wrote:

> Hi all,
>
> Mathematica evaluates FullSimplify[Sqrt[x^2]] to Sqrt[x^2], while it
> tells me that FullSimplify[Sqrt[x^2] == x] is True.
> Are these the expected answers?
>
> -- m
>

The second certainly not the answer I would expect, in fact this looks 
to me like a serious (perhaps even "shocking")  bug. It certainly 
contradicts this answer:

 FindInstance[Sqrt[x^2] != x, x]

 {{x -> -(109/5) + (11*I)/5}}


Andrzej Kozlowski

• References:
  • Square root of a square
    • From: Mariano Suárez-Alvarez <mariano.suarezalvarez@gmail.com>