题目内容
扇形OAB的半径OA=1,圆心角∠AOB=90°,点C是弧AB上的动点,连结AC和BC,记弦AC,CB与弧AC、CB围成的阴影部分的面积为S,则S的最小值为( )
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A.
B.
C.
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A.
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B.
试题分析:如图,连接AB, 要使阴影部分的面积最小,就需要满足四边形AOBC的面积最大,只需满足△ABC的面积最大即可,从而可得当点C位于弧AB的中点时,△ABC的面积最大.
取
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则OC'⊥AB,AB=
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∴
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∴S的最小值为=
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故选B.
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