Re: Incompletely simplified Square root.

• To: mathgroup at smc.vnet.net
• Subject: [mg121110] Re: Incompletely simplified Square root.
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Sun, 28 Aug 2011 04:06:55 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201108251104.HAA24880@smc.vnet.net> <C57A4BC6-3DE6-426C-8C2D-03A19E2D51F2@mimuw.edu.pl> <201108260923.FAA04524@smc.vnet.net>

```As a general rule (or more-or-less general?), once you apply a thisForm
kind of function to an object, you have a nice output form, but no
longer something you can do evaluations with before you gave it the form.

The grandaddy of all examples of this is MatrixForm.

On 8/26/11 5:23 AM, Paul von Hippel wrote:
> PolynomialForm served a useful purpose in an previous step, when the expression was a polynomial. I didn't realize it would remain attached to the expression and cause trouble in this way.
>
>
>
> ________________________________
> From: Andrzej Kozlowski<akoz at mimuw.edu.pl>
> To: paulvonhippel at yahoo<paulvonhippel at yahoo.com>
> Cc: mathgroup at smc.vnet.net
> Sent: Thursday, August 25, 2011 1:47 PM
> Subject: Incompletely simplified Square root.
>
>
>
> On 25 Aug 2011, at 13:04, 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[\!\(\*
>> TagBox["0.45728395061728394`",
>> PolynomialForm]\)]
>>
>
> Because PolynomialForm[926/2025] is not a number so you can't extract a square root of it or even perform any arithmetical operations on it. For example, try
> 1 + PolynomialForm[926/2025].
>
> The same will be true with any other "Forms", e.g.
>
> 1 + InputForm[1]
>
> InputForm[1] + 1
>
> You have obviously misunderstood what these wrappers are. Also, why are you using PolynomialForm in this way, anyway, it's obviously not doing anything useful?
>
> Andrzej Kozlowski
>

--
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

```

• Prev by Date: Re: Function of N variable
• Next by Date: Re: undocumented limits on subprocesses?
• Previous by thread: Re: Incompletely simplified Square root.
• Next by thread: Re: Incompletely simplified Square root.