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Question
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Solution
\[\int \sin^{- 1} \left( \frac{2x}{1 + x^2} \right) \text{ dx }\]
\[\text{ Let x }= \tan \theta\]
\[dx = \text{ sec}^2 \text{ θ }\text{ dθ }\]
\[ \therefore \int \sin^{- 1} \left( \frac{2x}{1 + x^2} \right)dx = \int \sin^{- 1} \left( \frac{2 \tan \theta}{1 + \tan^2 \theta} \right) . \sec^2 \text{ θ dθ }\]
\[ = \int \sin^{- 1} \left( \sin 2\theta \right) . \sec^2 \text{ θ dθ }\]
\[ = \int \left( 2\theta \right) \sec^2 \text{ θ dθ }\]
\[ = 2\int \theta_I \sec^2_{II} \text{ θ dθ }\]
\[ = 2\left[ \theta\int \sec^2 \text{ θ dθ }- \int\left\{ \frac{d}{d\theta}\left( \theta \right)\int s {ec}^2 \text{ θ dθ } \right\}d\theta \right]\]
\[ = 2\left[ \theta . \tan \theta - \int1 . \tan \text{ θ dθ }\right]\]
\[ = 2\left[ \theta \tan \theta - \text{ log }\left| \sec \theta \right| \right] + C\]
\[ = 2\left[ \theta \tan \theta - \text{ log }\left| 1 + \tan^2 \theta \right|^\frac{1}{2} \right] + C\]
\[ = 2\left[ \left( \tan^{- 1} x \right) \times x - \text{ log }\left( 1 + x^2 \right)^\frac{1}{2} \right] + C\]
\[ = 2 x \tan^{- 1} x - 2 \times \frac{1}{2}\text{ log}\left| 1 + x^2 \right| + C\]
\[ = 2 x \tan^{- 1} x - \text{ log }\left| 1 + x^2 \right| + C\]
