Services & ResourcesWolfram ForumsMathGroup Archive

[Date Index] [Thread Index] [Author Index]

Re: Re: Are points co-planar in (numDimensions-1)?

• To: mathgroup at smc.vnet.net
• Subject: [mg43368] Re: [mg43340] Re: Are points co-planar in (numDimensions-1)?
• From: Peter Pein <peter1963 at totalise.co.uk>
• Date: Tue, 26 Aug 2003 07:13:48 -0400 (EDT)
• References: <bi195e$akp$1@smc.vnet.net> <bi7nu3$pc8$1@smc.vnet.net> <bia0al$cr7$1@smc.vnet.net> <200308250810.EAA01898@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

AngleWyrm wrote:
> "AngleWyrm" <no_spam_anglewyrm at hotmail.com> wrote in message news:bia0al$cr7$1 at smc.vnet.net...
> 
>>Thus, to summarize, if a,b, and c are coplanar (and not 0), then there exists some relation of the
>>form:
>>k1 a + k2 b + k3 c = 0
> 
> 
> Which brings up a good point about logic:
> IF [points are coplanar] THEN [formula holds]
> does not necessarily mean:
> IF [formula holds] THEN [points are coplanar]
> 
> Does anyone know how to test this situation?
> 
> 
You're right, but in this case:
   [points are coplanar]
IF AND ONLY IF
   [formula holds (with at least one k_i =!= 0)]

You might have read "iff" sometimes. That means "if and only if", which is
equivalence (often written as "<=>").

Peter

• References:
  • Re: Are points co-planar in (numDimensions-1)?
    • From: "AngleWyrm" <no_spam_anglewyrm@hotmail.com>