Question

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

Answer 1

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