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Math Help - Circles

  1. #1
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    Circles

    Okay, I have a question on an exam paper that I just can't seem to do.

    Well okay. It's a circle. It's been cut. So we have a triangle and a sector.

    The radius is 4cm. The sector area is Acm^2 and the perimeter is Xcm and X = 3A.

    Now. I have to show with that information that the angle is 0.4radians.

    I can't figure it out.

    I need to figure out the perimeter. Then I can just sub it into 1/2*R^2*the angle in radians and then BAM I should have showed it.
    Last edited by mr fantastic; February 25th 2010 at 02:09 AM. Reason: Changed post title
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  2. #2
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    Quote Originally Posted by StephenPoco View Post
    Okay, I have a question on an exam paper that I just can't seem to do.

    Well okay. It's a circle. It's been cut. So we have a triangle and a sector.

    The radius is 4cm. The sector area is Acm^2 and the perimeter is Xcm and X = 3A.

    Now. I have to show with that information that the angle is 0.4radians.

    I can't figure it out.

    I need to figure out the perimeter. Then I can just sub it into 1/2*R^2*the angle in radians and then BAM I should have showed it.


    clarify your question.When you cut the circle you have a sector which consists of a . triangle and a segment What is A?
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  3. #3
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    Silly me. Suddenly all makes sense.

    Well you see. I read the question a bit queerly. You see, I thought X was the perimeter of the triangle, but upon reading again I found out X was actually the perimeter of the sector.

    So X = rθ +2r = 4θ + 8
    A = 0.5rēθ = 8θ
    So X = 24θ = 4θ + 8

    From then I got that θ = 0.4

    I always make these damned silly mistakes.
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