cosπ/6-a=根号3/3,则cos(5π/6+a),sin(π/3+a)分别是多少

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答案和解析

cos(5π/6+a)
=cos[π-(π/6-a)]
=-cos(π/6-a)
=-根号3/3
sin(π/3+a)
=sin[π/2-(π/6-a)]
=cos(π/6-a)
=根号3/3

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