If f (x) = cosx, (− π 2 ≤ x < 0) SiNx, (0 ≤ x < π), then f (− 15 π 4) is equal to () A. 22B. 1C. 0D. −22

If f (x) = cosx, (− π 2 ≤ x < 0) SiNx, (0 ≤ x < π), then f (− 15 π 4) is equal to () A. 22B. 1C. 0D. −22

∵ f (x) = cosx, − π 2 ≤ X & lt; 0sinx, 0 ≤ X & lt; π, the minimum positive period is 3 π 2F (− 15 π 4) = f (3 π 4 − 3 × 3 π 2) = f (3 π 4) = sin 3 π 4 = 22, so a