Calculate tg a if a belongs to interval (pi, 3pi/2) and sin a = -4/5? Posted on November 1, 2016 Calculate tg a if a belongs to interval (pi, 3pi/2) and sin a = -4/5? Calculate tg a if a belongs to interval (pi, 3pi/2) and sin a = -4/5? Calculate tg a if a belongs to interval (pi, 3pi/2) and sin a = -4/5?