Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Applications of Derivatives

Question:

The function $f(x) = \tan x-x$

Options:

is a decreasing function on $[0,\frac{\pi}{2})$

is an increasing function on $[0,\frac{\pi}{2})$

is a constant function

is neither increasing nor decreasing function on $[0,\frac{\pi}{2})$

Correct Answer:

is an increasing function on $[0,\frac{\pi}{2})$

Explanation:

The correct answer is Option (2) → is an increasing function on $[0,\frac{\pi}{2})$

$f(x)=\tan x - x$

$f'(x)=\sec^{2}x - 1$

$\sec^{2}x - 1=\tan^{2}x$

$\tan^{2}x \ge 0$ for all $x$ in $\left[0,\frac{\pi}{2}\right)$.

Thus $f'(x) > 0$ for all $x>0$, so the function is increasing on the entire interval.

Final answer: the function is increasing on $\left[0,\frac{\pi}{2}\right)$