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Math Help - Cross product

  1. #1
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    Cross product

    Hi!

    Could you please explain what is wrong with the expression:  u \times v \times w ?

    I know that  u \times (v \times w) and  (u \times v) \times w are correct. But why the above one isn't?

    Thanks!
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by saeros View Post
    Hi!

    Could you please explain what is wrong with the expression:  u \times v \times w ?

    I know that  u \times (v \times w) and  (u \times v) \times w are correct. But why the above one isn't?

    Thanks!
    the cross product is a very specific kind of operation. it is a binary operation, which means it operates on two elements at a time. the kind of elements it operates on is 3-dimensional vectors. so you have to apply the cross product on two 3-d vectors at a time. so your first expression is essentially mathematically meaningless, while the other two would be acceptable.
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