(b)
$\tan{\alpha\tan{2\alpha\ldots\tan{(2n - 1)\alpha\tan{(2n - 1)\alpha}}}}$
$= \left\{ \tan{\alpha\tan{(2n - 1)\alpha}} \right\}\left\{ \tan{2\alpha\tan{(2n - 2)\alpha}} \right\}\ldots\left\{ \tan{(n - 1)\alpha\tan{(n + 1)\alpha}} \right\}\tan{n\alpha}$
$= \left\{ \tan{\alpha\tan\left( \frac{\pi}{2} - \alpha \right)} \right\}\left\{ \tan{2\alpha\tan\left( \frac{\pi}{2} - 2\alpha \right)} \right\}\ldots\tan\frac{\pi}{4}\ \ \left( \because n\alpha = \frac{\pi}{4} \right)$
$= 1$