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Sectors, Arcs and Radians

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    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.
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    Hint: You have been given three sides of the triangle OCD.
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    (Original post by Spoon123)
    Click image for larger version. 

Name:	imag0091xs.jpg 
Views:	23 
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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Updated: May 10, 2012
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