在三角形ABC中,若
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=
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+
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+
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,则角A等于( )
A.30
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A.60
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C.150
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D.120
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∵
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=
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+
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+
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及正弦定理得
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,∴
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,由余弦定理得
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,故角A等于120

,故选D
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