If $\cos^{-1} x > \sin^{-1} x$, then
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → $-1 \le x < \frac{1}{\sqrt{2}}$ ##
We know the identity:
cos⁻¹x + sin⁻¹x = π/2
Given:
cos⁻¹x > sin⁻¹x
Substitute:
π/2 − sin⁻¹x > sin⁻¹x
⇒ π/2 > 2 sin⁻¹x
⇒ sin⁻¹x < π/4
Now applying sine on both sides:
x < sin(π/4) = 1/√2
Also, domain of x ∈ [−1, 1]
So,
−1 ≤ x < 1/√2
Alternatively
We know that,
Range of $\cos^{-1} x = [0, \pi]$
and range of $\sin^{-1} x = \left[ \frac{-\pi}{2}, \frac{\pi}{2} \right]$
From the graph,
$\cos^{-1} x > \sin^{-1} x$
When $x \in \left[ -1, \frac{1}{\sqrt{2}} \right]$
$⇒-1 \le x < \frac{1}{\sqrt{2}}$