MCQ
$\int_{}^{} {\cos x\sqrt {4 - {{\sin }^2}x} } \;dx = $
  • A
    $\frac{1}{2}\sin x\sqrt {4 - {{\sin }^2}x} - 2{\sin ^{ - 1}}\left( {\frac{1}{2}\sin x} \right) + c$
  • $\frac{1}{2}\sin x\sqrt {4 - {{\sin }^2}x} + 2{\sin ^{ - 1}}\left( {\frac{1}{2}\sin x} \right) + c$
  • C
    $\frac{1}{2}\sin x\sqrt {4 - {{\sin }^2}x} + {\sin ^{ - 1}}\left( {\frac{1}{2}\sin x} \right) + c$
  • D
    None of these

Answer

Correct option: B.
$\frac{1}{2}\sin x\sqrt {4 - {{\sin }^2}x} + 2{\sin ^{ - 1}}\left( {\frac{1}{2}\sin x} \right) + c$
b
(b) Putting $\sin x = t \Rightarrow \cos x\,dx = dt,$ we get
$\int_{}^{} {\cos x\sqrt {4 - {{\sin }^2}x\,} dx} = \int_{}^{} {\sqrt {4 - {t^2}} dt = \int_{}^{} {\sqrt {{{(2)}^2} - {t^2}} dt} } $
$ = \frac{t}{2}\sqrt {4 - {t^2}} + \frac{4}{2}{\sin ^{ - 1}}\frac{t}{2} + c$
$ = \frac{1}{2}\sin x\sqrt {4 - {{\sin }^2}x} + 2{\sin ^{ - 1}}\left( {\frac{1}{2}\sin x} \right) + c.$

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