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把Rt△ABC各边的长度都扩大3倍得Rt△A′B′C′,那么锐角A、A′的余弦值...
把Rt△ABC各边的长度都扩大3倍得Rt△A′B′C′,那么锐角A、A′的余弦值的关系为( )
A.cosA=cosA′
B.cosA=3cosA′
C.3cosA=cosA′
D.不能确定
考点分析:
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