Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Continuity and Differentiability

Question:

Let $f(x)=\sin x, g(x)=x^2$ and $h(x)=\log _e x$. If F(x) = (hog of)(x), then F''(x) is equal to

Options:

$2 ~cosec^3 x$

$2 \cot x^2-4 x^2 ~cosec^2 x^2$

$2 x \cot x^2$

$-2 ~cosec^2 x$

Correct Answer:

$-2 ~cosec^2 x$

Explanation:

We have,

F(x) = (hogof)(x)

$\Rightarrow F(x) = h \{g(f(x)\}=h\{g(\sin x)\}=h\left(\sin ^2 x\right)$

$\Rightarrow F(x)=\log _e \sin ^2 x=2 \log _e \sin x$

$F'(x)=2 \cot x$  and  $f''(x)=-2 ~cosec^2 x$