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# Sectors, Arcs and Radians Watch

1. 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. Hint: You have been given three sides of the triangle OCD.
3. (Original post by Spoon123)

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

Updated: May 10, 2012
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