MCQ
If $2{\cos ^{ - 1}}\sqrt {\frac{{1 + x}}{2}} = \frac{\pi }{2},$ then $x = $
  • A
    $1$
  • $0$
  • C
    $-1/2$
  • D
    $1/2$

Answer

Correct option: B.
$0$
b
(b) Given equation is $2{\cos ^{ - 1}}\sqrt {\left( {\frac{{1 + x}}{2}} \right)} = \frac{\pi }{2}$

==> ${\cos ^{ - 1}}\sqrt {\left( {\frac{{1 + x}}{2}} \right)} = \frac{\pi }{4} $

$\Rightarrow \cos \frac{\pi }{4} = \frac{{\sqrt {1 + x} }}{{\sqrt 2 }}$

==> $\frac{1}{{\sqrt 2 }} = \frac{{\sqrt {1 + x} }}{{\sqrt 2 }} $

$\Rightarrow 1 = \sqrt {1 + x} \Rightarrow x = 0$.

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