#### Question

Which of the following functions are strictly decreasing on (0, pi/2)?

(A) cos *x *

(B) cos 2*x *

(C) cos 3*x *

(D) tan *x*

#### Solution

(A) Let `f_1 (x) = cos x`

(B) Let `f_2(x) = cos 2x`

(C) Let `f_1(x) = cos 3x`

Hence, *f*_{3} is neither increasing nor decreasing in interval `(0, pi/2)`

Hence, the correct answers are A and B

(D) Let `f_4(x) = tan x`

Hence, the correct answers are A and B.

Is there an error in this question or solution?

Solution Which of the Following Functions Are Strictly Decreasing on (0, Pi/2)? Concept: Increasing and Decreasing Functions.