Noticethat the valueofrdependson the coordinatesof the givenpoint.You can alwaysfind the valueofr
usingthe PythagoreanTheorem.However, oftenwe look at anglesin a circlewith radius1. As you will see
next,doingthis allowsus to simplifythe definitionsof the functions.
The Unit Circle
Consideran anglein standardposition,suchthat the point(x, y) on the terminalside of the angleis a point
on a circlewith radius1.