3tg(п/7)-9tg(13п/7)/-2ctg(33п/14)

Решите задачу:

$\frac{3tg\frac{\pi}{7}-9tg\frac{13\pi}{7}}{-2ctg\frac{33\pi}{14}}=\frac{3tg\frac{\pi}{7}-9tg(2\pi -\frac{\pi}{7})}{-2ctg(2\pi +\frac{5\pi}{14})}=\frac{3tg\frac{\pi}{7}+9tg\frac{\pi}{7}}{-2ctg\frac{5\pi}{14}}=-6\frac{tg\frac{\pi}{7}}{ctg{\frac{5\pi}{14}}}=\\=-6\frac{{{sin\frac{\pi}{7}\;sin\frac{5\pi}{14}}}}{cos\frac{5\pi}{14}cos\frac{\pi}{7}}=-6\frac{cos\frac{3\pi}{14}-cos\frac{\pi}{2}}{cos\frac{\pi}{2}+cos\frac{3\pi}{14}}=-6\frac{cos\frac{3\pi}{14}}{cos\frac{3\pi}{14}}=-6$