How Do You Solve Arg(z1z2) in Complex Numbers?

[becka12]

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!

 

[fourier jr]

can you post exactly what the problem says? i don't understand the -90 < z1 >/= 90 stuff. it looks like it could mean arg(z1) is in some range of degrees but it's not clear.

 

[becka12]

That is what the book says except the book uses radians instead of degrees

 

[HallsofIvy]

Then don't covert to degrees. That just confuses the issue.

The further problem is that "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? " says nothing about what "criteria" are being referred to!