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Homework Help: Dot product, i don't see what they want from me

  1. Sep 22, 2005 #1
    hello everyone, i understand the dot product and its properties but i don't get what they want! They say....
    The dot product of two vectors are perpendicular if a.b = 0.
    Then any vector in R^3 perpendicular to


    note: that is a matrix above.

    can be written in the form:
    and it looks like parameteric forum they want, because they want a column of s and a column of t. but i don't see where i'm suppose to find more numbers.
  2. jcsd
  3. Sep 22, 2005 #2


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    Call the vector you are given A, you need to find, and descripe the family of vectors (b) which satisfy the condition:

    [tex] A \cdot b = 0 [/tex]
  4. Sep 22, 2005 #3
    thanks for the responce!
    how do you find a family of vectors?
  5. Sep 23, 2005 #4


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    First, take anoter "general" vectors, let's say (x,y,z). Take the dot product with (-5,-6,-3) and let it equal 0.
    Now you have 1 equation with 3 variables which has infinite many solutions. Solve it by choosing two variables (e.g. let x = s and y = t, then solve for z)
  6. Sep 23, 2005 #5
    Awesome! thanks again TD, you should be getting paid for this hah. :tongue:
  7. Sep 23, 2005 #6


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    You're welcome :smile:
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