搜搜做题作业网求转换公式
来源：学生作业帮 编辑：搜搜做题作业网作业帮 分类：数学作业 时间：2024/05/03 18:01:16
求转换公式
sin(π/6 -α)
=cos[π/2 - (π/6 - α)]
=cos(π/3 + α)
=1/3
那么,
cos(2π/3 + 2α)
=cos[2(π/3 + α)]
=2*[cos(π/3 + α)]^2 - 1
=2*(1/3)^2 - 1
=2/9 - 1
= - 7/9
因此,答案应该是 A
=cos[π/2 - (π/6 - α)]
=cos(π/3 + α)
=1/3
那么,
cos(2π/3 + 2α)
=cos[2(π/3 + α)]
=2*[cos(π/3 + α)]^2 - 1
=2*(1/3)^2 - 1
=2/9 - 1
= - 7/9
因此,答案应该是 A