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Math Help - perimeter of a quarter circle and two equilateral triangles

  1. #1
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    perimeter of a quarter circle and two equilateral triangles

    hi,

    i have a shape made from a quarter circle with a radius of 3 and two equilateral triangles.

    perimeter of a quarter circle and two equilateral triangles-shape.jpg
    i need to know how i would go about working out the perimeter of this?

    thanks!
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  2. #2
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    The perimeter (circumference) of a quarter-circle is one-fourth of the circumference of a circle. Furthermore, the length of each side of the equilateral triangles is equal to the radius of the circle. Can you find the perimeter now?
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  3. #3
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    is it equal to the whole radius or 1/4 of the radius?
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  4. #4
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    Is what equal to the radius or one-fourth of the radius?
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  5. #5
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    the length of each side os the triangles
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  6. #6
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    It is equal to the radius. To see why, extend the quarter-circle to produce a circle. Two of the sides of each equilateral triangle are radii, so each of the two sides have the same length as the length of the radius of the circle. Because all sides of an equilateral triangle are equal, the third side of each equilateral triangle also has the same length as the length of the radius of the circle.
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  7. #7
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    so would i do:

    2 x pi x 0.75=4.71
    3x3= 9
    3x3=9

    4.71+9+9= 22.71
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  8. #8
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    Both of those should be 3 + 3, not 3 \times 3.
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  9. #9
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    +? i thougt to get the perimeter of an equilateral triangle to do 3 times the length of the sides so for this 3x3=9?
    Last edited by andyboy179; April 7th 2011 at 10:45 AM.
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  10. #10
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    oh sorry, i have spotted why it is +, thanks!
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  11. #11
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    Last edited by Archie Meade; April 8th 2011 at 02:50 PM.
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  12. #12
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    The perimeter of any shape is the distance around.Lines inside are not counted.


    bjh
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