Let f (x) = cos (2 π − x) + 3cos (π 2 − x), then the minimum positive period of the function is () A. π2B. πC. 2πD. 4π

Let f (x) = cos (2 π − x) + 3cos (π 2 − x), then the minimum positive period of the function is () A. π2B. πC. 2πD. 4π

The function f (x) = cosx + 3sinx = 2 (32sinx + 12cosx) = 2Sin (x + π 6), so its minimum positive period is 2 π 1 = 2 π, so C