Practicing Success
$\int \frac{x \cos x}{(x \sin x+\cos x)^2} d x$ is equal to |
$\frac{1}{(x \sin x+\cos x)^2}+k$ $-\frac{1}{(x \sin x+\cos x)}+k$ $\frac{1}{(x \sin x+\cos x)^3}+k$ $\frac{1}{(x \sin x+\cos x)^4}+k$ |
$-\frac{1}{(x \sin x+\cos x)}+k$ |
Let $I=\int \frac{x \cos x}{(x \sin x+\cos x)^2} d x$ Let $\frac{1}{x \sin x+\cos x}= t \Rightarrow \frac{(x \sin x+\cos x) . 0-1(x \cos x+\sin x-\sin x)}{(x \sin x+\cos x)^2}=\frac{d t}{d x}$ $\Rightarrow \frac{-x \cos x}{(x \sin x+\cos x)^2}=\frac{d t}{d x}$ ∴ $I=-\int d t=-\frac{1}{x \sin x+\cos x}+c$ Hence (2) is the correct answer. |