ISRO Electronics & Communication (ECE) 2010 - Question 48

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Topic: Electronics Engineering

What does the following integral evaluate to?
$\int_{0}^{\pi/2}sin^{6}\theta\cdot d\theta$

  • A. $5\pi/16$
  • B. $5~\pi/8$
  • C. 0
  • D. $5~\pi/32$

Answer: D. $5~\pi/32$

Explanation: Using Wallis' integral formula for even powers of sine: $\int_{0}^{\pi/2}sin^{6}x~dx = \frac{5}{6}\cdot\frac{3}{4}\cdot\frac{1}{2}\cdot\frac{\pi}{2} = \frac{5\pi}{32}$.

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