MCQ
$\int_0^a {{x^4}\sqrt {{a^2} - {x^2}} } \,dx = $
  • A
    $\frac{\pi }{{32}}$
  • $\frac{\pi }{{32}}{a^6}$
  • C
    $\frac{\pi }{{16}}{a^6}$
  • D
    $\frac{\pi }{8}{a^6}$

Answer

Correct option: B.
$\frac{\pi }{{32}}{a^6}$
b
(b) Put $x = a\sin \theta $

$\Rightarrow dx = a\cos \theta \,\,d\theta $

Now $\int_0^a {{x^4}\sqrt {{a^2} - {x^2}} } dx = {a^6}\int_0^{\pi /2} {{{\sin }^4}\theta \cos \theta \cos \theta \,d\theta } $

$ = {a^6}\int_0^{\pi /2} {{{\sin }^4}\theta\, {{\cos }^2}\theta \,d\theta } $

$ = {a^6}\frac{{\Gamma \left( {\frac{5}{2}} \right).\Gamma \left( {\frac{3}{2}} \right)}}{{2\Gamma 4}} = \frac{\pi }{{32}}{a^6}$,

(Using gamma function).

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