Question

如果|cosx|=cos(x+π),则x的取值集合是(    )

A.-+2kπ≤x≤+2kπ                        B.-+2kπ≤x≤+2kπ

C. +2kπ≤x≤+2kπ                       D.(2k+1)π≤x≤2(k+1)π(以上k∈Z)

Answer 1

解析:由|cosx|=-cosx,可知cosx≤0,所以+2kπ≤x≤+2kπ,k∈Z.

答案:C