- A$\frac{\pi }{4} + \frac{1}{2}\log 2$
- ✓$\frac{\pi }{4} - \frac{1}{2}\log 2$
- C$\frac{\pi }{2} + \log 2$
- D$\frac{\pi }{2} - \log 2$
Put ${\sin ^{ - 1}}x = t$
$\Rightarrow \frac{1}{{\sqrt {1 - {x^2}} }}dx = dt$ and $x = \sin t$
Also $t = 0$ to $\frac{\pi }{4}$
as $x = 0$ to $\frac{1}{{\sqrt 2 }}$
$ \Rightarrow I = \int_0^{\pi /4} {t.{{\sec }^2}t\,dt = \frac{\pi }{4} - \frac{1}{2}\log 2} $.
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$-x+2 y+5 z=b_1$
$2 x-4 y+3 z=b_2$
$x-2 y+2 z=b_3$
has at least one solution. Then, which of the following system(s) (in real variables) has (have) at least one solution for each$\left[\begin{array}{l}b_1 \\ b_2 \\ b_3\end{array}\right]$ $\in$ $S$ ?
$(A)$ $x+2 y+3 z=b_1, 4 y+5 z=b_2$ and $x+2 y+6 z=b_3$
$(B)$ $x+y+3 z=b_1, 5 x+2 y+6 z=b_2$ and $-2 x-y-3 z=b_3$
$(C)$ $-x+2 y-5 z=b_1, 2 x-4 y+10 z=b_2$ and $x-2 y+5 z=b_3$
$(D)$ $x+2 y+5 z=b_1, 2 x+3 z=b_2$ and $x+4 y-5 z=b_3$