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# math

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a sector of a circle is used to make a hat shaped like a right cone. the cone has a height of 4 in. and a base diameter of 8 inches. the outside of the hat is to be covered in red crepe paper. determine the area that will be covered in crepe paper to the nearest square inch.

Guest Sep 25, 2017
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We can use the Pythagorean Theorem  to find the "slant height"  of the cone....note that the raduis of the cone  = 4 inches

Slant Height  = sqrt  [ height^2  + radius^2]  =   sqrt [  4^2  + 4^2 ]   =  sqrt [ 16 + 16 ] =  sqrt [ 32]  = 4sqrt (2) inches

The amount of crepe paper needed  =  the surface area of the cone  =    pi * radius * slant height  =

pi * (4 inches) ( 4 sqrt (2) inches) =

pi  *  16 sqrt (2)    inches ^2    ≈      71.086  in^2

CPhill  Sep 25, 2017

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