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Cross product for parallel vectors 
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#1
Mar1310, 08:11 PM

P: 72

1. The problem statement, all variables and given/known data
Is the line through (4,1,1) and (2,5,3) parallel to the line through (3,2,0) and (5,1,4)? 2. Relevant equations 3. The attempt at a solution Line one 'direction' = (2,4,4) = A Line two 'direction' = (8,1,4) = B I remember that the cross product of two vectors is zero if they are parallel, but AxB is not the zero vector; the answer in the book says they are indeed parallel... Is this not the right method? Cheers, Adrian ^^ 


#2
Mar1310, 08:52 PM

HW Helper
P: 6,202

If they were parallel, you could write one direction as a scalar multiple of the other. Since you cannot do that as well as the crossproduct is not zero, the vectors are not parallel.



#3
Mar1610, 02:49 AM

P: 72

Cheers, thanks for that. I got it all figured out now..
Thanks, Adrian 


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