MCQ
The value of $\int\limits^\pi_{-\pi}\sin^3\text{x}\cos^2\text{x}\text{ dx}$ is :
  • A
    $\frac{\pi^4}{2}$
  • B
    $\frac{\pi^4}{4}$
  • $0$
  • D
    none of these

Answer

Correct option: C.
$0$
$\int\limits^\pi_{-\pi}\sin^3\text{x}\cos^2\text{x}\text{ dx}$
$=\int\limits^\pi_{-\pi}\sin\text{x}(1-\cos^2\text{x})\cos^2\text{x}\text{ dx}$
Let $\cos\text{x}=\text{t},$ then $-\sin\text{x}\text{ dx}=\text{dt}$
When, $\text{x}=-\pi,\text{t}-1,\text{x}=\pi,\text{t}=-1$
Therefore the integral becomes
$\int\limits^{-1}_{-1}(1-\text{t}^2)\text{t}^2\text{ dt}$
$=0$

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