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Math Help - length of arc of circle

  1. #1
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    Post length of arc of circle

    circle.doc

    length of arc of circle-circle.bmp


    In the figure above, if the radius of the circle is 8, and triangle TRS is inscribed in the circle, then the length of arc TRS is
    A.
    16π/3

    B.
    (32 π)/3

    C.
    16 π

    D.
    (128 π)/3

    E.
    64 π

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  2. #2
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    Quote Originally Posted by mths View Post
    circle.doc

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    In the figure above, if the radius of the circle is 8, and triangle TRS is inscribed in the circle, then the length of arc TRS is
    A.
    16π/3

    B.
    (32 π)/3

    C.
    16 π

    D.
    (128 π)/3

    E.
    64 π

    Since the triangle is equilateral (all interior angles are equal) the arc in question is \frac23 of the complete circumference of the circle:

    a = \frac23 \cdot 2\pi \cdot 8

    So it is answer B.
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