Exam

JEE Advanced

Year

2011

Paper

Paper 2

Subject

Mathematics

Chapter

Functions

JEE Advanced 2011 · Paper 2 · Mathematics · Functions

Match the statements given in Column I with the intervals/union of...

Match the statements given in Column I with the intervals/union of intervals given in Column II.

Step-by-step solution

(A) Given, $|z|=1 \Rightarrow z \cdot \bar{z}=1 \therefore \quad \frac{2 i z}{1-z^2}=\frac{2 i z}{z \cdot \bar{z}-z^2}=\frac{2 i}{\bar{z}-z} \text{, }$ Let $\quad z=x+i y \therefore z-\bar{z}=2 i y=\frac{2 i}{-2 i y}=-\frac{1}{y}$ where, $y=\sqrt{1-x^2}\therefore \quad-1 \leq y \leq 1 \Rightarrow-1 \leq y$ and $y \leq 1 \Rightarrow-1 \geq \frac{1}{y}$ and $\frac{1}{y} \geq 1\Rightarrow \operatorname{Re}\left(\frac{2 i z}{1-z^2}\right) \in(-\infty,-1] \cup[1, \infty)$ (B) $f(x)=\sin ^{-1} \left(\frac{8 \left(3^{x-2}\right)}{1-3^{2(x-1)}}\right),$$\begin{aligned} \text{ For domain, }-1 \leq \frac{8\left(3^{x-2}\right)}{1-3^{2(x-1)}} \leq1 \\ & \Rightarrow \quad-1 \leq \frac{9 \cdot\left(3^{x-2}\right)-\left(3^{x-2}\right)}{1-3^{2(x-1)}} \leq1 \\ & \therefore \quad-1 \leq \frac{3^x-3^{x-2}}{1-3^x \cdot 3^{(x-2)}} \leq1 \\ \frac{3^x-3^{x-2}}{1-3^x \cdot 3^{x-2}} \geq-1 \\ & \Rightarrow \frac{\left(3^x-1\right)\left(3^{x-2}-1\right)}{\left(3^{x-1}+1\right)\left(3^{x-1}-1\right)} \geq0 \\ & \Rightarrow \quad x \ in(-\infty,0] \cup(1, \infty)\\ \text{ and } \frac{3^x-3^{x-2}}{1-3^x \cdot 3^{x-2}} \leq1 \\ & \Rightarrow \frac{\left(3^{x-2}-1\right)\left(3^x+1\right)}{\left(3^{x-1}+1\right)\left(3^{x-1}-1\right)} \geq0 \\ & \end{aligned}$ \\ and $x \$in(-\infty,$1) \cup[2, $\infty)\therefore \quadx \in(-\infty,$0] \cup[2, $\infty) (C) f(\theta)=$\left| $$\begin{array}{ccc}1 & \tan \theta& 1 \\ -\tan \theta& 1 & \tan \theta\\ -1 & -\tan \theta& 1\end{array}$$ \right|$\begin{aligned} R_1 & → R_1+R_3, \\ f(\theta) =\left|\begin{array}{ccc}0 & 0 & 2 \\ -\tan \theta& 1 & \tan \theta\\ -1 & -\tan \theta& 1 \end{array} \right| \\ =2\left(\tan ^2 \theta+1\right)=2 \sec ^2 \theta \geq2 \\ f(\theta)& \in[2, \infty) \end{aligned}$$\text{ (D) }$$\begin{aligned} f(x) & =x^{3 / 2}(3 x-10) ; x \geq 0 \\ f^{\prime}(x) & =x^{3 / 2} \ cdot₃⁺\frac{3}{2} \cdotx^{1 / 2}(3 x-10) \\ & =3 x^{1 / 2}\left\{x+\frac{1}{2}(3 x-10)\right\} \end{aligned}$$\begin{aligned} =\frac{3}{2} x^{1 / 2}\{2 x+3 x-10\} \\ =\frac{15}{2} x^{1 / 2}(x-2) \\ & \\ \therefore \quad & x \geq 2 \end{aligned}$