Step-by-Step Solution
Key Concept: General
Put $x = 2 \sin \theta \Rightarrow dx = 2 \cos \theta d\theta$<br>$\therefore \int \frac{dx}{\sqrt{4 - x^2}} = \int \frac{2 \cos \theta d\theta}{2 \cos \theta} = \theta + C = \sin^{-1} \frac{x}{2} + C$
Correct Answer: $\sin^{-1} \frac{x}{2} + C$