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Solve the following.
Evaluate: ∫ x tan⁻¹ x dx
Evaluate: $\int x \tan^{-1} x\,dx$
Answer
Answer
Integrate by parts with $u=\tan^{-1}x$, $v=x$:
$\int x\tan^{-1}x\,dx=\frac{x^2}{2}\tan^{-1}x-\frac12\int\frac{x^2}{1+x^2}dx$
$=\frac{x^2}{2}\tan^{-1}x-\frac12\int\left(1-\frac{1}{1+x^2}\right)dx$
$=\frac{x^2}{2}\tan^{-1}x-\frac12\left(x-\tan^{-1}x\right)+C$
Hence the integral is $\frac{x^2+1}{2}\tan^{-1}x-\frac{x}{2}+C$.
Final answer: $\frac{x^2+1}{2}\tan^{-1}x-\frac{x}{2}+C$