1:y=2sin(π/4-x)=-2sin(x-π/4)
单调增:2kπ+π/2≤x-π/4≤2kπ+3π/2,2kπ+3π/4≤ x≤ 2kπ+7π/4
单调减:2kπ-π/2≤x-π/4≤2kπ+π/2,2kπ-π/4≤ x≤ 2kπ+3π/4
2:
3:
4:
1:y=2sin(π/4-x)=-2sin(x-π/4)
单调增:2kπ+π/2≤x-π/4≤2kπ+3π/2,2kπ+3π/4≤ x≤ 2kπ+7π/4
单调减:2kπ-π/2≤x-π/4≤2kπ+π/2,2kπ-π/4≤ x≤ 2kπ+3π/4
2:
3:
4: