已知sin(30°+α)=3/5,60°<α<150°,求cosα的值?
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已知sin(30°+α)=3/5,60°<α<150°,求cosα的值?
已知sin(30°+α)=3/5,60°<α<150°,求cosα的值?
已知sin(30°+α)=3/5,60°<α<150°,求cosα的值?
因为60°<α<150°
所以90°<30°+α<180°
在这个区间的余弦值为负值.
即cos(30°+α)
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