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Re: How to get sqrt(Year^2)===Year?

• To: mathgroup at smc.vnet.net
• Subject: [mg75761] Re: [mg75724] How to get sqrt(Year^2)===Year?
• From: Sseziwa Mukasa <mukasa at jeol.com>
• Date: Thu, 10 May 2007 05:08:44 -0400 (EDT)
• References: <200705090833.EAA14797@smc.vnet.net>

On May 9, 2007, at 4:33 AM, Hatto von Aquitanien wrote:

> If I have some expression which takes the square root of a square, it
> evaluates leaving the whole square root expression unchanged.
>
> Year == (Year^2)^(1/2)
>
> just returns what I entered when evaluated.
>
> Year == Year
>
> evaluates to True.
>
> How do I persuade Mathematica to evaluate the first expression  
> completely?

It is evaluating it completely, Year == (Year^2)^(1/2) is True only  
when Year is non-negative, so you have to tell Mathematica that  
that's the case:

Simplify[Year==(Year^2)^(1/2),Year>=0]

Regards,

Ssezi

• References:
  • How to get sqrt(Year^2)===Year?
    • From: Hatto von Aquitanien <abbot@AugiaDives.hre>