Re: Annoying Little Problem
- To: mathgroup at smc.vnet.net
- Subject: [mg24870] Re: Annoying Little Problem
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sat, 19 Aug 2000 04:45:46 -0400 (EDT)
- References: <8mdm1e$5li@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Clear[v2]
v2 = {4, 0, -6}
N[Sqrt[v2.v2], 3]
7.2111
N is concerned with output and its precision not with how the output is
displayed.
For the latter we can use NumberForm
NumberForm[N[Sqrt[v2.v2]], 3] (*1*)
"7.21"
The output is the underlying decimal.
%
7.2111
And even this is the display of a stored number with 16 decimal places
We can see the situation if we look at the cell expression of the output
from (*1*); which is (using Format>ShowExpression)
Cell[BoxData[
TagBox[
InterpretationBox["\<\"7.21\"\>",
7.2111025509279782,
AutoDelete->True],
(NumberForm[ #, 3]&)]], "Output",
CellLabel->"Out[132]//NumberForm="]
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
"Nalanji Dreaming" <ayrton at rac1.wam.umd.edu> wrote in message
news:8mdm1e$5li at smc.vnet.net...
> I'm having an annoying little problem with version 4.0.1.0. I wrote the
> following info in a notebook and ran it:
>
> Clear[v2]
> v2 = {4, 0, -6}
> N[Sqrt[v2.v2]]
> N[Sqrt[v2.v2], 3]
>
> Now the third line gives me 7.2111 but the fourth line gives me the
> same instead of 7.21. Does anyone have any idea what may be the problem?
> Am I doing something wrong?
>
> thanks,
> Nalanji Dreaming
>