Practicing Success
If $ [cot^{-1}x] +[cos^{-1}x]=0$ where x is a non-negative real number and [.] denotes the greatest integer function, then complete set of values of x, is |
(cos 1, 1] (cos 1, cot 1) (cot 1, 1] none of these |
(cot 1, 1] |
We have, $cot^{-1} x ∈[0, \pi ]$ and $ cos^{-1} x ∈[0, \pi]$ $∴ [cot^{-1}x] > 0 $ and $[cos^{-1}x] ≥ 0$ Now, $[cot^{-1}x] +[cos^{-1}x]=0$ $⇒ [cot^{-1}x]= 0 = [cos^{-1}x]$ $⇒ 0 < cot^{-1}x < 1$ and $ 0 ≤ cos^{-1}x < 1 $ $⇒ cot 1 < x < ∞ $ and $ cos 1 < x ≤1$ $⇒ x ∈ (cot 1, ∞)$ and $ x ∈ (cos 1, 1]⇒ x ∈(cot 1, 1].$ |