Question

$tg(pi/2+a)*tg(2pi-a)/sin(-a)$

Answer 1

$\frac{tg(\frac{\pi }{2}+a)\cdot tg(2\pi -a)}{sin(-a)}=\frac{-ctga\cdot tg(-a)}{-sina}=\frac{ctga\cdot (-tga)}{sina}=\frac{-1}{sina}=-coseca$