Question

COSπ /3-2X)的单调递减区间?

Answer 1

由于y=cosx是偶函数,所以 cos(π/3-2X)=cos(2x-π/3)

令 2kπ≤2x-π/3≤π+2kπ

解得 π/6+kπ≤x≤2π/3+kπ

即y=cos(π/3-2X)的单调减区间为[π/6+kπ,2π/3+kπ],k∈Z