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: firstname.lastname@example.org
- References: <201108251104.HAA24880@smc.vnet.net> <C57A4BC6-3DE6-426C-8C2D-03A19E2D51F2@mimuw.edu.pl> <201108260923.FAA04524@smc.vnet.net>
- Reply-to: murray at math.umass.edu
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:= Sqrt[\!\(\* >> TagBox[ >> FractionBox["926", "2025"], >> PolynomialForm]\)] // N >> >> Out= 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 > > InputForm + 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