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Thread: resultant between two vectors

  1. #1
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    resultant between two vectors

    given vectors $\displaystyle \vec{a}$ and $\displaystyle \vec{b}$ such that the angle between the vectors is $\displaystyle 60^o$, $\displaystyle |\vec{a}|=3$ and $\displaystyle |\vec{b}|=2$ determine $\displaystyle |\vec{a}+\vec{b}|$
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  2. #2
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    Quote Originally Posted by william View Post
    given vectors $\displaystyle \vec{a}$ and $\displaystyle \vec{b}$ such that the angle between the vectors is $\displaystyle 60^o$, $\displaystyle |\vec{a}|=3$ and $\displaystyle |\vec{b}|=2$ determine $\displaystyle |\vec{a}+\vec{b}|$


    Writing simply $\displaystyle a$ instead of $\displaystyle \vec{a}$ , and assuming these are real vectors, we get

    $\displaystyle |a+b|^2=(a+b)\cdot(a+b)=a\cdot a+2a\cdot b+b\cdot b=9+4+2|a||b|\cos 60=13+6=19$

    Tonio
    Last edited by tonio; Feb 4th 2010 at 06:46 PM. Reason: Misread the question
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