(本題滿分14分)在
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中,角
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所對的邊是
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,且滿足

。
(1)求角

的大��;
(2)設
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,求
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的最小值。
(1)

; (2)
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本試題主要是考查了解三角形中余弦定理和向量的數(shù)量積公式的綜合運用。
(1)由于角
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所對的邊是
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,且滿足
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,結(jié)合余弦定理可知角B的值。
(2)根據(jù)
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,那么可以知道
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,利用三角函數(shù)的性質(zhì)得到最值。
解:(1)∵
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,∴

,…….. 4分
又∵
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,∴
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. ………………………..6分
(Ⅱ)
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……..12分
∵

,∴
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.
∴當
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時,取得最小值為
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�!�..14分
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,
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,
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
、

、

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
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
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
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,
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
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
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
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
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
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
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
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
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
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
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
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
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,

。
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
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