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Re: problem of evaluating SQRT

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28002] Re: problem of evaluating SQRT
  • From: Yossi Lonke <jrl16 at po.cwru.edu>
  • Date: Wed, 28 Mar 2001 02:40:30 -0500 (EST)
  • Organization: Case Western Reserve University, Cleveland, OH, USA
  • References: <99pd51$leb@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com


> From: "Pek" <phsoh at alum.mit.edu>
To: mathgroup at smc.vnet.net
> Organization: Steven M. Christensen and Associates, Inc and MathTensor, Inc.
> Newsgroups: comp.soft-sys.math.mathematica
> Date: 27 Mar 2001 01:49:05 -0500
> Subject: [mg28002] problem of evaluating SQRT
> 
> Hi,
> 
> We have a question of how sqrt can be evaluated.
> 
> In[1]:=
> Sqrt[x^2]
> 
> Out[1]=
> (This part is just sqrt[X^2])
> 
> Below we expect the result to be zero but it isn't. How can we get the
> correct answer in this case?
> 
> In[2]:=
> Sqrt[x^2] - x
> 
> Out[2]=
> (This part is -x + sqrt[x^2] )
> 
> Will really appreciate your help. Thanks.
> 
> Pek
> 
> 
There is actually no reason to expect the result to be zero. For example, it
is 2 if x = -1. Since Sqrt[x^2] = |x| ( the absolute value of x ) the result
will be zero only if x is positive.

Yossi Lonke



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