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Question: If [cos<sup>-1</sup>x] + [cot<sup>-1</sup>x] = 0, where [.] denotes the greatest integer function, t...

If [cos-1x] + [cot-1x] = 0, where [.] denotes the greatest integer function, then complete set of values of x is

A

(cos 1,1]

B

(cos 1, cot 1)

C

(cot 1, 1]

D

[0, cot 1)

Answer

(cot 1, 1]

Explanation

Solution

We have [cos−1 x] ≥ 0 ∀ x ∈ [-1, 1]

and [cos-1x] ≥ 0 ∀ x ∈ R

⇒ [cos−1x] + [cot-1x] = 0

⇒ [cos-1x] = [cot-1x] = 0 If [cos-1x] = 0

⇒ x ∈ (cos 1, 1]

If [cot-1x] = 0

⇒ x ∈ (cot-1x, ∞)

⇒ x ∈ (cot 1, 1]