Services & Resources / Wolfram Forums / MathGroup Archive

MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Another question on Assuming

  • To: mathgroup at
  • Subject: [mg85903] Re: Another question on Assuming
  • From: "David W.Cantrell" <DWCantrell at>
  • Date: Wed, 27 Feb 2008 04:27:14 -0500 (EST)
  • References: <fq0to0$k3s$>

"Kevin J. McCann" <Kevin.McCann at> 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 you didn't ask that anything be _done_ to Sqrt[a^2].

Note that we can use Simplify instead of Refine:

In[5]:= Assuming[a > 0, Simplify[Sqrt[a^2]]]

Out[5]= a

> but I should get a, since there is no other correct answer,

No. Sqrt[a^2] is correct also; it's just not as simple as you want.


> because the assumption that a > 0 implies that it a is a
> positive real.
> Bug?
> Kevin

  • Prev by Date: Efficiency and ReplacePart?
  • Next by Date: Re: How to import a Matlab mat-file
  • Previous by thread: Re: Another question on Assuming
  • Next by thread: Re: Another question on Assuming