如圖,菱形
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的邊長為
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,
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,
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為
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的中點,若
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為菱形內(nèi)任意一點(含邊界),則
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的最大值為( )
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A. | B. | C.9 | D.6 |
試題分析:由數(shù)量積的幾何意義知,當
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在
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上的投影最大時,
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最大.
從圖可以看出,當N點在點C處,
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在
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上的投影最大,所以
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的最大值為:
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.
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設向量
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,
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,
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滿足
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,且
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,則
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,則
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=_____________.
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在
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中,D是BC的中點,AD=3,點P在AD上且滿足
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則
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( )
A.6 | B. | C.-12 | D. |
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已知
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、
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是圓
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上的兩個點,
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是
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線段上的動點,當
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的面積最大時,則
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的最大值是( )
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已知
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中,
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,
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,點
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是線段
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(含端點)上的一點,且
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,則
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的取值范圍是
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在平面四邊形
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中,已知
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,
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,點
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分別在邊
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上,且
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,
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,若向量
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與
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的夾角為
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,則
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