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MathGroup Archive 2007

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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76001] Re: How to get sqrt(Year^2)===Year?
  • From: Szabolcs <szhorvat at gmail.com>
  • Date: Mon, 14 May 2007 05:49:02 -0400 (EDT)
  • Organization: University of Bergen
  • References: <f1s1v4$fip$1@smc.vnet.net> <f1upol$8hr$1@smc.vnet.net> <f26na5$421$1@smc.vnet.net>

Hatto von Aquitanien wrote:
>> Simplify[x==Sqrt[x^2],x>0]
>>
>> hope this helps, Daniel
> 
> Well, it helps in this circumstance.  I believe Convert will do the same,
> but I'm not sure if it works in all circumstances.

In what circumstances?

> I do wish there were
> some way for Mathematica to know that something such as a physical constant
> is real and positive.

You didn't mention that you want to treat Year as a unit.

> Perhaps doing that under all circumstances would
> turn into a major performance hit, but it would be nice in circumstances in
> which it is inappropriate to consider cases of x < 0, or x not real in
> Sqrt[x].

$Assumptions = {Year > 0}


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