Answer
1. Substitution: $u=\tan x$
then
2. Log Rule
Work Step by Step
The derivative of $\tan x$ is $\sec^{2}x, $which is in the numerator...
1. we substitute
$\left[\begin{array}{ll}
u=\tan x, & \\
du=\sec^{2}xdx &
\end{array}\right]$
after which the integral takes the form
$\displaystyle \int\frac{1}{u}du$
2. The form $\displaystyle \int\frac{1}{u}du$ is solved by applying the
Log Rule
