Q. The value of $\int_{0}^{\frac{\pi}{2}}\frac{\cos\theta}{\sqrt{4 - \sin^{2}\theta}}\ d\theta$ is

A) $\frac{\pi}{2}$
B) $\frac{\pi}{6}$
C) $\frac{\pi}{3}$
D) $\frac{\pi}{5}$
Explanation

(b)
Let $I = \int_{0}^{\pi/2}{\frac{\cos\theta}{\sqrt{4 - \sin^{2}\theta}}d\theta}$
Put $\sin{\theta = t\ \Rightarrow \ \cos{\theta d\theta = dt}}$
$\therefore\ I = \int_{0}^{1}\frac{dt}{\sqrt{4 - t^{2}}}$
$= \left\lbrack \sin^{- 1}\frac{t}{2} \right\rbrack_{0}^{1}$
$= \sin^{- 1}{\frac{1}{2} = \frac{\pi}{6}}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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