设α为锐角,若cos(α+π/3)=4/5,则sin(2α+π/6)=?
人气:100 ℃ 时间:2020-03-19 03:41:08
解答
sin(2α+π/6)
=sin(α+π/3+α-π/6)
=sin(α+π/3)cos(α-π/6)+cos(α+π/3)sin(α-π/6)
=sin(α+π/3)cos(α+π/3-π/2)+cos(α+π/3)sin(α+π/3-π/2)
=3/5×3/5+4/5×(﹣4/5)
=﹣7/25
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