若sin(α+π⼀6)=1⼀3,则cos(2π⼀3-2α)的值为

2025-03-22 18:41:19
推荐回答(1个)
回答1:

cos(2π/3-2α)
=-cos[π-(2π/3-2α)]
=-cos(π/3+2α)
=-cos[2(π/6+α)]
=-{1-2[sin(π/6+α)]^2}
=-(1-2/9)
=-7/9