(a)
$\int_{}^{}{\begin{matrix}
x \\
II
\end{matrix}\begin{matrix}
\log x \\
I
\end{matrix}}\ dx = \log x.\frac{x^{2}}{2} - \int_{}^{}\frac{1}{x}.\frac{x^{2}}{2}\ dx$
$= \frac{x^{2}}{2}\log x - \frac{1}{2}\ \frac{x^{2}}{2} + c$
$= \frac{x^{2}}{4}\left( 2\log x - 1 \right) + c$