Let f (x) = ax + cosx, X ∈ [0, π]. (I) discuss the monotonicity of F (x); (II) Let f (x) ≤ 1 + SiNx, find the value range of A

Let f (x) = ax + cosx, X ∈ [0, π]. (I) discuss the monotonicity of F (x); (II) Let f (x) ≤ 1 + SiNx, find the value range of A

(I) for the derivative function, f '(x) = a-SiNx, X ∈ [0, π], SiNx ∈ [0, 1]; when a ≤ 0, f' (x) ≤ 0 is constant, f (x) decreases monotonically; when a ≥ 1, f '(x) ≥ 0 is constant, f (x) increases monotonically; when 0 < a < 1, from F' (x) = 0, X1 = arcsina, X2 = π - arcsi