Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Relations and Functions

Question:

The value of $c \in [0, \pi ]$ for which the function $f(x)=e^x\, sin x $ satisfies Rolle's theorem is :

Options:

$\frac{\pi}{2}$

$\frac{\pi}{4}$

$\frac{\pi}{6}$

$\frac{3\pi}{4}$

Correct Answer:

$\frac{3\pi}{4}$

Explanation:

The correct answer is Option (4) → $\frac{3\pi}{4}$

$f(0)=0$  $f(π)=0$

so for some c $f'(c)=0$

$f'(x)=e^x(\sin x+\cos x)=0$  (at $x=c$)

so $\sin c+\cos c=0$

$⇒c=\frac{3\pi}{4}$