Question

Range of function f(x) = cos(x/3) is

(A) (0, ∞)

(B) (-1/3, 1/3)

(C) [-1, 1]

(D) [0, 1]

Answer 1

Answer is (C)

Let y = cos(x/3)​​​

-1 ≤ cos(x/3)​​​ ≤ 1

-1 ≤ y ≤ 1

x is defined if -1 ≤ y ≤ 1

Hence, required range = [-1, 1]