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    I suspect I went wrong somewhere/am stuck on part (b)

    Sigh, I need some sleep.
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    (Original post by edothero)
    I suspect I went wrong somewhere/am stuck on part (b)

    Sigh, I need some sleep.
    my approach would be different

    Midpoint of AB is (2, -1/2, 1/2)

    M must also be the midpoint of OC

    Since O(0,0,0), C(4,-1,1)

    any good?


    EDIT: Rubbish on my part. I read OACB instead of OABC

    I can also do one with "vector vectors"
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    (Original post by edothero)
    I suspect I went wrong somewhere/am stuck on part (b)

    Sigh, I need some sleep.
    sorry I misread part (b)

    Do you know dot product, cross product or both?
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    (Original post by TeeEm)
    sorry I misread part (b)

    Do you know dot product, cross product or both?
    just the dot product

    a.b=\left | a \right |\left | b \right |cos\theta
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    (Original post by edothero)
    just the dot product

    a.b=\left | a \right |\left | b \right |cos\theta
    numbers are bad

    are you on a calculator course or non calculator?
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    (Original post by TeeEm)
    numbers are bad

    are you on a calculator course or non calculator?
    It's Edexcel C4; calculator.
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    (Original post by edothero)
    It's Edexcel C4; calculator.
    then I doubt if they want exact answer

    Use the OA and AB to find angle OAB (dot product)

    then trigonometric area of the triangle x2
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    I got around 20.7
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    (Original post by TeeEm)
    then I doubt if they want exact answer

    Use the OA and AB to find angle OAB (dot product)

    then trigonometric area of the triangle x2
    Thanks again!
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    (Original post by edothero)
    Thanks again!
    no problem
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    (Original post by edothero)
    I suspect I went wrong somewhere/am stuck on part (b)

    Sigh, I need some sleep.
    I managed to get through A2 maths without being able to do the most basic vectors questions so i'm no use, good luck!
 
 
 
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