The least value of (cos2θ-6sinθ cosθ+3sin2θ+2) is [2026]
(1)
f(θ)=1+cos2θ2-3sin2θ+3(1-cos2θ2)+2
f(θ)=4-3sin2θ-cos2θ
f(θ)∈[4-10, 4+10]