A:when it was that
B:that it was whe
C:where was it that
D:it was where that
新中国成立以来的土地改革、人民公社化运动和十一届三中全会后的农村改革是三次非常重要的探索。请回答:
(Ⅰ)求函数f(x)的最小正周期和单调递增区间;
(Ⅱ)当x∈(0, π2 )时,求函数f(x)的值域.