When x ∈ (0, π), the minimum value of F (x) = 1 + cos2x + 3sin2xsinx is () A. 22B. 3C. 23D. 4

When x ∈ (0, π), the minimum value of F (x) = 1 + cos2x + 3sin2xsinx is () A. 22B. 3C. 23D. 4

From cos2x = 1-2sin2x, f (x) = SiNx + 2sinx (0 < x < π). Let t = SiNx, 0 < t ≤ 1, then the function y = t + 2T has a minimum value of 3 when t = 1