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?