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Math Help - finding radius of circle

  1. #1
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    finding radius of circle

    hello,

    calculate the radius of a circle in which the perimeter of a sector of angle 0.5 radians is 20 cm.

    can someone please explain how a question of this sort is solved.

    i know the length of the arc = r \theta but that is just a part of the perimeter. how do i form an expression for the other side which encloses the arc.
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  2. #2
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    The perimeter of a sector would be (length of arc) + 2*(length of radius)

    therefore,  20=2r+r\theta
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  3. #3
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    Quote Originally Posted by nahduma View Post
    The perimeter of a sector would be (length of arc) + 2*(length of radius)

    therefore,  20=2r+r\theta

    ohh man, i never realized that the question was so simple. this was one of the last questions so i though it was hard and even though i read that it was the perimeter of the sector, for some strange reason i mixed it up and had it to be the perimeter of the cord, bad judgement on my part. thanks alot for clearing it up though... i would slap myself for that.
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