Sectors, Arcs and Radians

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  1. Spoon123's Avatar
    1 10-05-2012  18:50
    • New Member
    • Posts: 4
    Sectors, Arcs and Radians
    Click image for larger version.  Name: imag0091xs.jpg  Views: 20  Size: 99.8 KB  ID: 146889
    Hi,

    I'm looking for help with the first question in this page. I'm only given the radius (which presumably isn't enough) and I have to work out the angle.

    I know I'm missing an observational thing I can use in the question, any help would be great.

    Thanks.
  2. Jiggle's Avatar
    2 10-05-2012  20:02
    • New Member
    • Posts: 8
    Re: Sectors, Arcs and Radians
    Hint: You have been given three sides of the triangle OCD.
  3. raheem94's Avatar
    3 10-05-2012  22:58
    • TSR Demigod
    • Posts: 5,512
    Re: Sectors, Arcs and Radians
    (Original post by Spoon123)
    Click image for larger version.  Name: imag0091xs.jpg  Views: 20  Size: 99.8 KB  ID: 146889
    Hi,

    I'm looking for help with the first question in this page. I'm only given the radius (which presumably isn't enough) and I have to work out the angle.

    I know I'm missing an observational thing I can use in the question, any help would be great.

    Thanks.
    See the diagram below:




    Use the triangle highlighted in green to find the angle.

    Hint: You need to use the cosine rule.

    See the spoiler if you still can't do it.

    Spoiler:
    Show

    7^2 = 5^2 + 5^2 - 2(5)(5)cos\theta
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