I am confused on a homework problem. It states that the Arg(z1z2) = Arg (z1) + Arg (z2) if -90 < z1 >/= 90 , and -90 < z2 >/= 90 , describe the set of points that meet this criteria? I am not sure how to answer this, I'm not sure I know entirely what they are asking. I haven't taken a math course in 3 years so I'm out of practice. Please help!!