Definitions I forgot to mention:

• co-terminal angles
  • angles that share the same initial and terminal side.
  • the terminal ray can be any integer number of full rotations.
    (one full rotation being 360 degrees or 2pi radians)
    • positive co-terminal is in counterclockwise direction and adds rotations
    • negative co-terminal is clockwise and subtracts rotations

Course Hub– Lessons 18-20
Video Links– Lessons 18-20
Textbook– Lectures 15-16