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Re: *newbie* output of ScalarTripleProduct

  • To: mathgroup at smc.vnet.net
  • Subject: [mg106834] Re: *newbie* output of ScalarTripleProduct
  • From: Scott Hemphill <hemphill at hemphills.net>
  • Date: Sun, 24 Jan 2010 05:44:08 -0500 (EST)
  • References: <hjbvbk$2st$1@smc.vnet.net> <hjeq8h$fpj$1@smc.vnet.net>
  • Reply-to: hemphill at alumni.caltech.edu

Simon <simonjtyler at gmail.com> writes:

> On Jan 22, 6:40 pm, pippo <marco.... at email.it> wrote:
>> I'm (almost) new to mathematica ...
>> I coped this from some tutorial ...
>>
>> Needs["VectorAnalysis`"]
>> r1 = {1, -3, 2}
>> r2 = {3, 7,-5}
>> r3 = {4, 1, 6}
>> r={x,y,z}
>> ScalarTripleProduct[r-r1,r2-r2,r3-r1]==0
>>
>> the output i get is:
>> Out[6]= True
>>
>> :-(
>>
>> What am I missing ?
>>
>> Thank you
>
> I like easy questions...  and so does everyone else - I bet you'll get
> about 15 replies.
> Here's my answer:
>
> r2-r2={0,0,0}
>
> So of course the result will be zero.

And another thing:  r-r1 may not do what you want.

Scott
-- 
Scott Hemphill	hemphill at alumni.caltech.edu
"This isn't flying.  This is falling, with style."  -- Buzz Lightyear


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