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Thread: Planes and Lines IV

  1. #1
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    Post Planes and Lines IV

    Question 4: u, v and w are three vectors in three-dimensional space. |u| = 5, |v| = 2 and |w| = 1. The angle between u and w is π/3. What should the angle between u and v be so that |u + 2v + w| = |u + v + 2w|?
    Last edited by topsquark; May 22nd 2019 at 01:50 PM.
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  2. #2
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    Re: Planes and Lines IV

    $\displaystyle (u+2v+w) \cdot (u+2v+w)=(u+v+2w) \cdot (u+v+2w)$

    that's the dot product. expand, simplify, replace
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