y=cos(π/4-2x)=cos(2x-π/4)2kπ-π<=2x-π/4<=2kπ，则kπ-3π/8<=x<=kπ+π/8所以，函数的单调递增区间是[kπ-3π/8,kπ+π/8]
y=cos(-x)=cosx，所以单调递增区间为[2kπ-π，2kπ],k∈Z
