已知cos(30°+α)=根号3/3,则cos(150°-α)等于
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![已知cos(30°+α)=根号3/3,则cos(150°-α)等于](/uploads/image/z/3176546-50-6.jpg?t=%E5%B7%B2%E7%9F%A5cos%2830%C2%B0%2B%CE%B1%29%3D%E6%A0%B9%E5%8F%B73%2F3%2C%E5%88%99cos%28150%C2%B0-%CE%B1%29%E7%AD%89%E4%BA%8E)
已知cos(30°+α)=根号3/3,则cos(150°-α)等于
已知cos(30°+α)=根号3/3,则cos(150°-α)等于
已知cos(30°+α)=根号3/3,则cos(150°-α)等于
cos(30°+α)=√3/3
cos(150°-α)
=cos(180°-(30°+α) )
=-cos(30°+α)
=-√3/3
因为cos(180-a)=-cosa
所以cos(150-a)=-cos[180-(150-a)]
=-cos(30+a)
=-√3/3
cos(150°-α)=cos[180°-(30°+α)]=-cos(30°+α)=负根号3/3
cos(150-a)=cos[180-(30+a)]=-cos(30+a)=负根号3/3
cos(150°-α)=cos(180°-30°-α)=cos[180°-(30°+α)]=-cos(30°+α)=-根号3/3