Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Inverse Trigonometric Functions

Question:

If $cos^{-1} x > sin^{-1} x$, then x belong to the internal

Options:

(-∞ , 0)

(-1, 0)

$[0, \frac{1}{\sqrt{2}})$

$[-1, \frac{1}{\sqrt{2}})$

Correct Answer:

$[-1, \frac{1}{\sqrt{2}})$

Explanation:

We know that $ cos^{-1}x$ and  $sin^{-1}x$ exist for  x ∈ [-1, 1].

Now, 

$cos^{-1}x > sin^{-1}x $

$⇒ cos^{-1}x> \frac{\pi}{2}- cos^{-1}x$

$⇒ 2cos^{-1} x > \frac{\pi}{2}⇒cos^{-1} x > \frac{\pi}{4} ⇒ x ∈ [-1, \frac{1}{\sqrt{2}})$