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Math Help - Dot Product Problem

  1. #1
    Del
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    Dot Product Problem

    Assume that , , and . What is the value of ?

    Please help!
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  2. #2
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    Quote Originally Posted by Del View Post
    Assume that , , and . What is the value of ?

    Please help!
    From |\vec u| = 3 you know that \vec u \cdot \vec u = 9

    Now expand the given term:

    7 \vec u \left(4 \vec u - 3 \vec v \right) = 28 \vec u \cdot \vec u - 21 \vec u \cdot \vec v = 28 \cdot 9 - 21 \cdot 3 = 189
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