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Math Help - How do I find the surface normal

  1. #1
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    Exclamation How do I find the surface normal

    This was on my lecture page, but I don't understand how they went from step 2 to step 3.

    How does 2 & 4 produce -6? and 5 & -3 produce -20?

    My homework problem is
    A= [3,-5,7]
    B= [-1,0,6]
    and I'm having trouble trying to figure what to do. I've googled, but I think my terms might be confused.
    All I know is that I need to obtain the cross product, and I don't even know what that is
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by Keysle View Post
    This was on my lecture page, but I don't understand how they went from step 2 to step 3.

    How does 2 & 4 produce -6? and 5 & -3 produce -20?

    My homework problem is
    A= [3,-5,7]
    B= [-1,0,6]
    and I'm having trouble trying to figure what to do. I've googled, but I think my terms might be confused.
    All I know is that I need to obtain the cross product, and I don't even know what that is
    Its evident you don't know how to evaluate a determinant. The deteminant for a 2 x 2 matrix is given by \begin{vmatrix}a&b\\c&d\end{vmatrix} = ad-bc.

    So with this, you should be able to verify the values they get going from step 2 to step 3.

    I hope this helps.
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