f(x)=2(1/2sinx+√3/2cosx)
=2sin(x+π/3)
∴f(x)最小正周期T=2π
由2kπ+π/2≤x+π/3≤2kπ+3π/2
得2kπ+π/6≤x≤2kπ+7π/6,k∈Z
∴单调递减区间为[2kπ+π/6,2kπ+7π/6]k∈Z