I am working on finding the trig rations of angles that go through a set of x-and-y coordinates ( x , y ). I was doing pretty well; doing the problems, then confirming my answer with the back of the book answers. Then I got to the point ( -10/3 , 4/3 ). X and Y are obvious as they are given as coordinates. But this is where I differ from the text. My answer for the distance, or r, is 2*sqrt(29)/3. And with that number, the sin of angle theta was 2*sqrt(29)/29. The book gave the same answer, but it was negative. I don't see where this negative came from. Can anyone point out my mistake for me?