Answer
$7$
Work Step by Step
Using the fact that $\int\frac{dx}{x^2+1}=\tan^{-1}x$, we have
$$\int^{\tan 8}_{\tan 1}\frac{dx}{x^2+1}=\tan^{-1}x|^{\tan 8}_{\tan 1}\\
=\tan^{-1}\tan 8-\tan^{-1}\tan 1=8-1=7.$$
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