- ✓$\pi + 2$
- B$\pi + \frac{3}{2}$
- C$\pi + 1$
- DNone of these
$\Rightarrow dx = - 2\sin \theta \,d\theta ,$ then
$\int_0^2 {\sqrt {\frac{{2 + x}}{{2 - x}}} } dx = - 2\int_{\pi /2}^0 {\sqrt {\frac{{1 + \cos \theta }}{{1 - \cos \theta }}} } \sin \theta \,d\theta $
$ = 4\int_0^{\pi /2} {\frac{{\cos (\theta /2)}}{{\sin (\theta /2)}}\sin \frac{\theta }{2}\cos \frac{\theta }{2}d\theta } $
$ = 2\int_0^{\pi /2} {(1 + \cos \theta )\,d\theta } $
$ = 2[\theta + \sin \theta ]_0^{\pi /2} $
$= 2\left[ {\frac{\pi }{2} + 1} \right] = \pi + 2$.
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$\vec{a}=3 \hat{i}+\hat{j}-\hat{k},$
$\vec{b}=\hat{i}+b_2 \hat{j}+b_3 \hat{k}, b_2, b_3 \in R ,$
$\vec{c}=c_1 \hat{i}+c_2 \hat{j}+c_3 \hat{k}, c_1, c_2, c_3 \in R$
be three vectors such that $b_2 b_3>0, \vec{a} \cdot \vec{b}=0$ and
$\left(\begin{array}{ccc}0 & -c_3 & c_2 \\ c_3 & 0 & -c_1 \\ -c_2 & c_1 & 0\end{array}\right)\left(\begin{array}{l}1 \\ b_2 \\ b_3\end{array}\right)=\left(\begin{array}{c}3-c_1 \\ 1-c_2 \\ -1-c_3\end{array}\right)$.
Then, which of the following is/are TRUE?
$(A)$ $\overrightarrow{ a } \cdot \overrightarrow{ c }=0$
$(B)$ $\vec{b} \cdot \vec{c}=0$
$(C)$ $|\vec{b}|>\sqrt{10}$
$(D)$ $|\vec{c}| \leq \sqrt{11}$