Angle Tool

Located at the top of the tool bar, you will see a hand holding an Angle.  Click on it.  You have 3 different Angle Types: 2 Points, 3 Points and 4 Points.  If you select 2 Points, you will get the angle between the 2 points and the X-axis.  If you pick 3 Points or 4 Points, you will get the angle between the 2 vectors.  Give it a try.  Remember, if you want to change the background color for the a=, go to: Tools, Options, Angles, Color and select a Background color.