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Re: Another question on Assuming

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85909] Re: Another question on Assuming
  • From: sikokaj at iit.edu
  • Date: Wed, 27 Feb 2008 04:30:19 -0500 (EST)
  • References: <fq0to0$k3s$1@smc.vnet.net>

Don't have that much experience with Assuming[], but from the
documentation:

Assuming[assum,expr]
evaluates expr with assum appended to $Assumptions, so that assum is \
included in the default assumptions used by functions such as Refine,
\
Simplify and Integrate.

So it seems to me like perhaps only certain functions can take
assumptions, and Sqrt can't you need to use refine around it.

Kajetan Sikorski

On Feb 26, 5:38=A0am, "Kevin J. McCann" <Kevin.McC... at umbc.edu> 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
> --
>
> Kevin J. McCann
> Research Associate Professor
> JCET/Physics
> Physics Building
> University of Maryland, Baltimore County
> 1000 Hilltop Circle
> Baltimore, MD 21250



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