1. The problem statement, all variables and given/known data -sin pi/4 , give the exact value? -1/root 2 is the answer according to the book? How in the world do they get that result. What do you to make that happen? 2. Relevant equations 3. The attempt at a solution Also, is this how to do the problem? Find pi/4 on the unit circle, it's root 2 / 2, that doesn't seem to get the right answer even though that's was supposed to be the method?