f(x)=(sinx)^2+2sinxcosx+3(cosx)^2=1+2(cosx)^2+sin2x=1+cos2x+1+sin2x=√2sin[2x+(π/4)]+2 最小正周期:T=2π/2=π 单调递减区间:2x+(π/4)∈[2kπ+π/2,2kπ+3π/2](k∈Z) x∈[kπ+π/8,kπ+5π/8](k∈Z)...