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**Fratricide** $\displaystyle f(x) = xtan^{-1}x$

Find $\displaystyle f'(x)$ and hence find $\displaystyle \int_{0}^{1} tan^{-1}(x) dx$.

I can find $\displaystyle f'(x)$, but I don't know how to *hence *find the integral. We've covered (in the context of this forum) basic integration techniques in class, but not inverse tan. I looked up how to do it in general, but my confusion arises from the wording -- *hence* -- which suggests that I should be able to figure it out from the derivative. Any help is greatly appreciated.