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Re: Another question on Assuming

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  • Subject: [mg85891] Re: Another question on Assuming
  • From: dh <dh at>
  • Date: Wed, 27 Feb 2008 04:21:00 -0500 (EST)
  • References: <fq0to0$k3s$>

Hi Kevin,

the manual tells you that Assuming does nothing else than append the 

assumptions to $Assumptions and then evaluates expr. Your expression is 

Sqrt[a^2] that does not care about $Assumptions. Therefore, you need 

Refine that will care.

hope this helps, Daniel

Kevin J. McCann wrote:

> The first example in the Mathematica Help on Assuming is (in part)


> Assuming[a > 0, Refine[Sqrt[a^2]]]


> which results in the answer a, as it should; however if I type instead


> Assuming[a > 0, Sqrt[a^2]]


> I get back Sqrt[a^2]], but I should get a, since there is no other 

> correct answer, because the assumption that a > 0 implies that it a is a 

> positive real.


> Bug?


> Kevin

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