This is the professional way to do this problem.
We have to convert from rectangular to polar coordinates.
In the first example in the book, the point to convert is (2,3)
We get r=sqrt(13) and theta=tan^(-1) (3/2), making the point (3.6, .98) I get that.
But then the next point is (4,-7), we get r=sqrt(65) and theta=tan^(-1)(-7/4)=2pi-1.05, and they give the point as (8.1,5.2). My question is, could I just put it as (8.1,-1.05) or do you need to put 2pi-1.05?