(本小題滿分10分)請選做一題,都做時按先做的題判分,都做不加分.
(1)已知向量
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①求函數(shù)
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的最小正周期和值域;
②在△ABC中,角A、B、C所對的邊分別是a、b、c,若
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且
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,試判斷△ABC的形狀.
(2)已知銳角
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.
①求證:
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;
②設(shè)
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,求AB邊上的高CD的長.
(1)①
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,值域為[—2,2]
②△ABC為等邊三角形
(2)①證明見解析。
②
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(1)①
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,值域為[—2,2].… ………5分
②△ABC為等邊三角形. ……………
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…10分
(2)①由
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展開可整理得:
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………5分
②
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,
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… ……10分
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