Target Exam

CUET

Subject

Maths. Section B1

Chapter

Continuity and Differentiability

Question:

Find $\frac{d^2y}{dx^2}$, if $y = x^3 + \tan x$.

Options:

$3x^2 + \sec^2 x$

$6x + 2\sec^2 x \tan x$

$6x + \sec^2 x \tan x$

$6x + 2\sec x \tan x$

Correct Answer:

$6x + 2\sec^2 x \tan x$

Explanation:

The correct answer is Option (2) → $6x + 2\sec^2 x \tan x$ ##

Given that $y = x^3 + \tan x$. Then

$\frac{dy}{dx} = 3x^2 + \sec^2 x$

Therefore $ \frac{d^2y}{dx^2} = \frac{d}{dx} (3x^2 + \sec^2 x)$

$= 6x + 2 \sec x \cdot \sec x \tan x = 6x + 2 \sec^2 x \tan x$