Step 1: Let:
\[
t=\log\sec x
\]
Step 2: Differentiate:
\[
dt=\tan x\,dx
\]
Step 3: Therefore:
\[
\int(\log\sec x)\tan x\,dx
=
\int t\,dt
\]
Step 4:
\[
\int t\,dt=\frac{t^2}{2}+c
\]
Step 5: Substitute \(t=\log\sec x\):
\[
\frac{1}{2}(\log\sec x)^2+c
\]
\[
\boxed{\frac{1}{2}(\log\sec x)^2+c}
\]