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Re: Re: FindInstance what inspite ?

• To: mathgroup at smc.vnet.net
• Subject: [mg84030] Re: [mg83907] Re: [mg83861] FindInstance what inspite ?
• From: DrMajorBob <drmajorbob at bigfoot.com>
• Date: Fri, 7 Dec 2007 03:04:51 -0500 (EST)
• References: <fire9m$roc$1@smc.vnet.net> <200712020914.EAA07009@smc.vnet.net> <200712031039.FAA18775@smc.vnet.net> <13196714.1196783150798.JavaMail.root@m35> <op.t2wlabliqu6oor@monster.gateway.2wire.net> <18337187.1196965410208.JavaMail.root@m35>
• Reply-to: drmajorbob at bigfoot.com

The summary of Root calling patterns (first thing in Help for Root) should  
include Root[f,k,0] and Root[f,k,1].

Bobby

On Thu, 06 Dec 2007 09:46:02 -0600, Daniel Lichtblau <danl at wolfram.com>
wrote:

> DrMajorBob wrote:
>> Help for Root (version 6.0.1) says:
>>  Root[poly,x,k]
>> gives the k\[Null]^th root of the polynomial poly in x.
>>  and later it says:
>>  The setting of ExactRootIsolation is reflected in third argument of a  
>> Root  object:
>>  a = Root[#^40 - 15 #^17 - 21 #^3 + 11 &, 20, ExactRootIsolation -> 
>> False];
>> b = Root[#^40 - 15 #^17 - 21 #^3 + 11 &, 20, ExactRootIsolation -> 
>> True];
>>  {a, b} // InputForm
>>  {Root[11 - 21*#1^3 - 15*#1^17 + #1^40 & , 20, 0],
>>  Root[11 - 21*#1^3 - 15*#1^17 + #1^40 & , 20, 1]}
>>  The two descriptions seem, at first glance, incompatible, but the  
>> problem  is only that the second usage isn't included in the  
>> top-section summary of  calling patterns.
>>  Here are EIGHT ways of specifying the same number (unless exact root 
>> isolation is actually necessary, as I gather it should never be):
>>  Root[1 + 2 #1 + #1^5 &, 1] ==
>>  Root[1 + 2 #1 + #1^5 &, 1, ExactRootIsolation -> False] ==
>>  Root[1 + 2 #1 + #1^5 &, 1, ExactRootIsolation -> True] ==
>>  Root[1 + 2 #1 + #1^5 &, 1, 0] == Root[1 + 2 #1 + #1^5 &, 1, 1] ==
=
>>  Root[1 + 2 x + x^5, x, 1] ==
>>  Root[1 + 2 x + x^5, x, 1, ExactRootIsolation -> False] ==
>>  Root[1 + 2 x + x^5, x, 1, ExactRootIsolation -> True]
>>  True
>>  Bobby
>
> I note this is in response to my response. But I'm not seeing a  
> question. If there is one, and if it is something I should address,  
> you'll need to spell it out. In particular if you think the  
> documentation needs work, let me know and I can raise the issue in house.
>
> Daniel
>
>
>



-- 

DrMajorBob at bigfoot.com

• References:
  • Re: Interpolation in 2 D, bug?
    • From: Hugh <h.g.d.goyder@cranfield.ac.uk>
  • FindInstance what inspite ?
    • From: Artur <grafix@csl.pl>