MCQ
Let $\alpha \in R$ be such that the function

$f(x)=\left\{\begin{array}{ll} \frac{\cos ^{-1}\left(1-\{x\}^{2}\right) \sin ^{-1}(1-\{x\})}{\{x\}-\{x\}^{3}}, & x \neq 0 \\ \alpha, & x=0 \end{array}\right.$

is continuous at $x=0,$ where $\{x\}=x-[x],[x]$ is the greatest integer less than or equal to $X$.

Then :

  • A
    $\alpha=\frac{\pi}{\sqrt{2}}$
  • B
    $\alpha=0$
  • no such $\alpha$ exists
  • D
    $\alpha=\frac{\pi}{4}$

Answer

Correct option: C.
no such $\alpha$ exists
c
$\operatorname{Lim}_{x \rightarrow 0^{+}} f(x)=f(0)=\operatorname{Lim}_{x \rightarrow 0^{-}}(x)$

$\operatorname{Lim}_{x \rightarrow 0^{+}} \frac{\cos ^{-1}\left(1-x^{2}\right) \cdot \sin ^{-1}(1-x)}{x(1-x)(1+x)}$

$\operatorname{Lim}_{x \rightarrow 0^{+}} \frac{\cos ^{-1}\left(1-x^{2}\right)}{x \cdot 1 \cdot 1} \cdot \frac{\pi}{2}$

Let $1-x^{2}=\cos \theta$

$\frac{\pi}{2} \operatorname{Lim}_{ x \rightarrow 0^{+}} \frac{\theta}{\sqrt{1-\cos \theta}}$

$\frac{\pi}{2} \operatorname{Lim}_{\theta \rightarrow 0^{+}} \frac{\theta}{\sqrt{2} \sin \frac{\theta}{2}}=\frac{\pi}{\sqrt{2}}$

Now, $\operatorname{Lim}_{x \rightarrow 0^{-}} \frac{\cos ^{-1}\left(1-(1+x)^{2}\right) \sin ^{-1}(-x)}{(1+x)-(1+x)^{3}}$

$\operatorname{Lim}_{x \rightarrow 0^{-}} \frac{\frac{\pi}{2}\left(-\sin ^{-1} x\right)}{(1+x)(2+x)(-x)}$

$\operatorname{Lim}_{x \rightarrow 0^{-}} \frac{\frac{\pi}{2}}{1 \cdot 2} \cdot \frac{\sin ^{-1} x}{x}=\frac{\pi}{4}$

$\Rightarrow RHL \neq LHL$

Function can't be continuous

$\Rightarrow$ No value of $\alpha$ exist

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Similar questions

Three numbers are in $G.P.$ such that their sum is $38$ and their product is $1728$. The greatest number among them is
Consider the differential equation ${y^2}dx + \left( {x - \frac{1}{y}} \right)dy = 0$ . If value of $y$ is $1$ when $x = 1$, then the value of $x$ for which $y = 2$, is
A lady gives a dinner party for six guests. The number of ways in which they may be selected from among ten friends, if two of the friends will not attend the party together is
If $\cot \theta + \cot \left( {\frac{\pi }{4} + \theta } \right) = 2$, then the general value of $\theta $ is
The sum of all the solution $(s)$ of the equation $sin^{-1}\ 2x = cos^{-1}\ x$ is
If by dropping a stone in a quiet lake a wave moves in circle at a speed of  $3.5 \,cm/sec,$ then the rate of increase of the enclosed circular region when the radius of the circular wave is  $10$  $cm,$ is ......... $c{m^2}/sec$. $\left( {\pi = {{22} \over 7}} \right)$
For the curve $C :$ $\left(x^{2}+y^{2}-3\right)+\left(x^{2}-y^{2}-1\right)^{5}=0$, the value of $3 y^{\prime}-y^{3} y^{\prime \prime}$, at the point $(\alpha, \alpha), \alpha>0$, on $C$, is equal to.
Let $A =\left(\begin{array}{ll}2 & -2 \\ 1 & -1\end{array}\right)$ and $B =\left(\begin{array}{ll}-1 & 2 \\ -1 & 2\end{array}\right)$. Then the number of elements in the set $\left\{( n , m ): n , m \in\{1,2, \ldots . .10\}\right.$ and $\left.nA ^{ n }+ mB ^{ m }= I \right\}$ is
The value of $\int_{}^{} {\frac{{{e^x}}}{{{e^x} + 1}}} \,dx$ is
If $\alpha $ is the interior angle of a regular octagon, then $\mathop {\lim }\limits_{\theta  \to {\alpha ^ + }} \frac{{\tan \theta  - 1}}{{\left[ {\sin \theta  + \cos \theta } \right]}}$ is equal to (Note : $[k]$ denotes greatest integer less than or equal to $k$ )