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How to find if a vector is parallel to another 
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#1
Sep1906, 05:31 PM

P: 9

Okay, so I have two vectors a = <6, 9, 3> and b = <2, 3, 1>. How can I test to see if these two vectors are parallel or not?
Thanks 


#2
Sep1906, 05:41 PM

HW Helper
P: 3,224

Vectors a and b are parallel if there exists a real number c such that a=cb. In your case it is pretty obvious.



#3
Sep1906, 05:49 PM

P: 9

What if it is not so obvious like the one I presented. Is there another approach to it (cross product of dot product ??)
Thanks 


#4
Sep1906, 06:07 PM

HW Helper
P: 3,224

How to find if a vector is parallel to another
Think about the definition of the cross product, and see what happens. Btw, just use axb=[tex]det \left(\begin{array}{ccc}\vec{i} & \vec{j} & \vec{k}\\a_{1} & a_{2} & a_{3}\\b_{1} & b_{2} & b_{3}\end{array}\right)[/tex] for a=cb.



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