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From: Scott Hemphill on 24 Jan 2010 05:42
Simon <simonjtyler(a)gmail.com> writes:

> On Jan 22, 6:40 pm, pippo <marco....(a)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(a)alumni.caltech.edu
"This isn't flying. This is falling, with style." -- Buzz Lightyear

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