已知sin(a-π/3)=1/3,则cos(a+π/6)等于
人气：364 ℃ 时间：2020-03-28 23:33:19
解答
cos(a+π/6)
=sin[π/2-(a+π/6)]
=sin(π/3-a)
=-sin(a-π/3)
=-1/3
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