设k∈Z,函数y=sin(π/4+x/2) sin(π/4-x/2)的单调递增区间为

Question

设k∈Z,函数y=sin(π/4+x/2) sin(π/4-x/2)的单调递增区间为

Answer 1

y=sin(π/4+x/2)sin(π/4-x/2)
=-1/2(cosπ/2-cosx)
=1/2(cosx)
递增区间是x∈[2kπ+π,2(k+1)π] k∈Z