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    reaallly stuck - i know its using the cosine rule at some point but i dont know how to start
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    To start: calculate the area of the whole circle, and use that to work out the angle between OA and OB. Then try and continue from there
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    The sector has area 5 pi. You know area = theta/360 pi r ^2 --> theta/360 r^2 = 5 --> theta/360 x 36 = 5 --> theta/10 = 5 --> theta = ?

    So you got the angle and 2 sides and you have to find AB. Cosine rule. Then find arc length and sum.
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    (Original post by xnotapplicablex)
    Name:  cosine prob.png
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    reaallly stuck - i know its using the cosine rule at some point but i dont know how to start
    (x/360) * (6^2) x pi = 5 pi

    Use this to find x, the angle AOB.
    Use that angle in the cosine rule to find length AB.
    Arc length APB = (x/360) * diameter. (It is x/360 of the circumference of the whole circle).
    Add AB to APB.
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    (Original post by JSG29)
    To start: calculate the area of the whole circle, and use that to work out the angle between OA and OB. Then try and continue from there
    (Original post by thekidwhogames)
    The sector has area 5 pi. You know area = theta/360 pi r ^2 --> theta/360 r^2 = 5 --> theta/360 x 36 = 5 --> theta/10 = 5 --> theta = ?

    So you got the angle and 2 sides and you have to find AB. Cosine rule. Then find arc length and sum.
    (Original post by Loci Pi)
    (x/360) * (6^2) x pi = 5 pi

    Use this to find x, the angle AOB.
    Use that angle in the cosine rule to find length AB.
    Arc length APB = (x/360) * diameter. (It is x/360 of the circumference of the whole circle).
    Add AB to APB.
    yiikez i got 1.51, the answer is 1.77 apparently

    it wont let me upload my working but
    i got theta as 9.5, ab as 0.987, and apb as 0.9936.
    ab and apb as 1.51
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    (Original post by xnotapplicablex)
    yiikez i got 1.51, the answer is 1.77 apparently

    it wont let me upload my working but
    i got theta as 9.5, ab as 0.987, and apb as 0.9936.
    ab and apb as 1.51
    I can show working but I will spoiler block:
    Spoiler:
    Show

    Angle = 360 * (5 pi / 36 pi) = 50 degrees
    AB = ROOT [ 6^2 + 6^2 - 2(6)(6)(cos50)] = 5.071419141 cm
    APB = (50/360) * 12 * pi = 5.235987756
    AB + ABP = 5.235987756 + 5.071419141 = 10.3074069
    = 10.3 cm (3sf)
 
 
 
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