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Math Help - the cross product

  1. #1
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    Exclamation the cross product

    i wasn't @ school the day we learned the cross product.
    heres my first question, just help me get this one so i can complete the worksheet please!!!

    <-8,13,-2> X <-2,19,1>
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  2. #2
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    Quote Originally Posted by needmathhelptoujours View Post
    i wasn't @ school the day we learned the cross product.
    heres my first question, just help me get this one so i can complete the worksheet please!!!

    <-8,13,-2> X <-2,19,1>
    Do you know how to find determinants? There isn't really anything fancy to understand, the cross product is just a defintion.

    If "a" and "b" are the vectors:

    a=<a_1,a_2,a_3>
    b=<b_1,b_2,b_3>

    The cross-product is the vector defined by:

    a X b=<a_2b_3-a_3b_2,a_3b_1-a_1b_3,a_1b_2-a_2b_1>

    This is difficult to remember, it's best if you know how to find determinants.

    http://en.wikipedia.org/wiki/Cross_product

    If you scroll down to "matrix" notation, you'll see how the determinant definition makes 3-by-3 cross products a little easier to remember.
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