(a)
Given, $x = \frac{1}{2}\left( \sqrt{3} + \frac{1}{\sqrt{3}} \right)$
$\therefore x^{2} = \frac{1}{4}\left( 3 + \frac{1}{3} + 2 \right) = \frac{4}{3}$
Now, $\frac{\sqrt{x^{2} - 1}}{x - \sqrt{x^{2} - 1}} \times \frac{x + \sqrt{x^{2} - 1}}{x + \sqrt{x^{2} - 1}}$
$= \frac{x\sqrt{x^{2} - 1} + (x^{2} - 1)}{1}$
$= \frac{1}{2}\left( \sqrt{3} + \frac{1}{\sqrt{3}} \right)\sqrt{\frac{4}{3} - 1} + \left( \frac{4}{3} - 1 \right)$
$= \frac{1}{2}\left( \frac{4}{\sqrt{3}} \right)\frac{1}{\sqrt{3}} + \frac{1}{3} = \frac{2}{3} + \frac{1}{3} = 1$