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Re: Incompletely simplified Square root.

  • To: mathgroup at
  • Subject: [mg121064] Re: Incompletely simplified Square root.
  • From: Bill Rowe <readnews at>
  • Date: Fri, 26 Aug 2011 05:22:05 -0400 (EDT)
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On 8/25/11 at 7:04 AM, paulvonhippel at (paulvonhippel at
yahoo) wrote:

>Can someone tell me why the following input doesn't produce an
>output of 0.68....? Why is the output under the radical? Thanks!

>In[574]:= Sqrt[\!\(\* TagBox[ FractionBox["926", "2025"],
>PolynomialForm]\)] // N

>Out[574]= Sqrt[\!\(\* TagBox["0.45728395061728394`",

You are getting this result because of PolynomialForm. The Sqrt
function doesn't know how to evaluate something with a head of
PolynomialForm. That is when I copy paste your input into
Mathematica and use FullForm on the output I get

In[8]:= FullForm[%]

Out[8]//FullForm= Power[PolynomialForm[0.45728395061728394`],Rational[1,2]]

If I simply type the problem in

In[9]:= Sqrt[926/2025] // N

Out[9]= 0.676228

I get the expected result.

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