We need to remember first that negative has nothing to do with the size of something, just the direction it goes in.
I explain that best by talking about calling your parents for a ride. when they ask how to get to you you can't say I'm 5 miles from home, pick me up! you have to use words like east west left or right. negative is the equivalent of these words in math.
I can walk positive 10 feet or negative 10 feet along the x axis. Same distance, different directions. a positive angle starts from an initial side and moves clockwise to its terminal side. A negative angle starts from an initial side and moves counterclockwise to its terminal side.
You can draw an angle in standard position by positioning its vertex at the origin and one "ray" on the positive x-axis. The ray on the x-axis is called the initial side and the other ray is called the terminal side.
An angle is then measured POSITIVE for a counterclockwise rotation and NEGATIVE for a clockwise rotation:
When two angles have the same initial and terminal sides, they are said to be coterminal angles.
Angles of −315° and 45° are coterminal angles.