Definite Integration Question 262

Question: $ \int_0^{\pi /2}{{{\sin }^{4}}x{{\cos }^{6}}xdx} $ equals

[RPET 1999]

Options:

A) $ \frac{5\pi }{512} $

B) $ \frac{3\pi }{512} $

C) $ \frac{\pi }{512} $

D) None of these

Show Answer

Answer:

Correct Answer: B

Solution:

$ I=\int_0^{\pi /2}{{{\sin }^{4}}x{{\cos }^{6}}x.dx} $

$ \Rightarrow I=\frac{\Gamma (5/2)\Gamma (7/2)}{2\Gamma (6)} $ , (Applying gamma function)

therefore $ I=\frac{3/2.1/2.\sqrt{\pi }.5/2.3/2.1/2.\sqrt{\pi }}{2.5.4.3.2.1} $

$ =\frac{3\pi }{512} $ .