Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Continuity and Differentiability

Question:

If $f(x)=\frac{1-\sin x}{(\pi-2 x)^2}$, when $x \neq \pi / 2$ and $f(\pi / 2)=\lambda$, then f(x) will be continuous function at $x=\pi / 2$, when $\lambda=$

Options:

1 / 8

1 / 4

1 / 2

none of these

Correct Answer:

1 / 8

Explanation:

f(x) will be continuous at $x=\pi / 2$, if

$\lim\limits_{x \rightarrow \pi / 2} f(x)=f\left(\frac{\pi}{2}\right)$

$\Rightarrow \lim\limits_{x \rightarrow \pi / 2} f(x) \frac{1-\sin x}{(\pi-2 x)^2}=\lambda$

$\Rightarrow \frac{1}{4} \lim\limits_{x \rightarrow \pi / 2} \frac{1-\cos (\pi / 2-x)}{(\pi / 2-x)^2}=\lambda$

$\Rightarrow \frac{1}{4} \times \frac{1}{2}=\lambda$           $\left[∵ \lim\limits_{x \rightarrow 0} \frac{1-\cos x}{x^2}=\frac{1}{2}\right]$

$\Rightarrow \lambda=\frac{1}{8}$