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Homework Help: Coplanar math problem

  1. Apr 12, 2008 #1
    1. The problem statement, all variables and given/known data
    Find all values of t so that the three vectors a=(1,2,3) b=(4,5,6) and c=(7,8,t) are coplanar.


    2. Relevant equations
    (axb) [tex]\bullet[/tex] c=0


    3. The attempt at a solution

    (1, 2, 3) x (4, 5, 6)
    (-3,6,-3)
    (-3,6,-3)[tex]\bullet[/tex](7,8,t)
    27=3t
    t=9

    it says find ALL values of t. i keep getting 9 through different combinations. is there only one value of t? thnks
     
    Last edited: Apr 12, 2008
  2. jcsd
  3. Apr 12, 2008 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Yes, there is only one value of t. If you'd gotten 27=0*t for your last equation then any t would work. But you didn't.
     
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