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    hi,
    can anyone do part iii) of the attached question? thanks
    part i) is (x-8)² + (y-1)² = 16
    ive done part 2: (-5/12) < m < (3/4)
    im stuck on part 3.
    thanks
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    (Original post by Undry1)
    hi,
    can anyone do part iii) of the attached question? thanks
    part i) is (x-8)² + (y-1)² = 16
    ive done part 2: (-5/12) < m < (3/4)
    im stuck on part 3.
    thanks
    Let c be circle centre.

    CA=4
    CO = √65

    So AO = 7 (Pythag)

    tan AOC = 4/7

    AOB = 2AOC

    Double Angle tan formula

    Tan 2t = 2tant/(1-tan²t)

    Tan 2t = (8/7)/(33/49)
    = 56/33

    Aitch
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    Here's another method.

    From your working:
    gradient of OA = 3/4
    => tan(AOx) = 3/4
    gradient of OB = -5/12
    => tan(BOx) = 5/12

    So:
    tan(AOB) = tan(AOx+BOx)
    = [tan(AOx) + tan(BOx)]/[1 - tan(AOx)tan(BOx)]
    = (3/4 + 5/12)/(1 - 15/48)
    = 56/33
    • Thread Starter
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    ah of course..
    i got to the tan theta = 4/7 part
    got confused after that
    thanks
 
 
 
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