25.2.2 Quadrant Angles and Coterminal Angles
Core ideaWherever the pointer comes to rest tells you which quadrant the angle is in, and spinning whole extra turns lands you right back, so those angles differ by whole multiples of 360°.
Module goal. We break free of the 'angles only run from 0° to 90°' limit, letting angles spin any number of turns and carry a sign, and we bring in radians — a unit better suited to functions — to set the stage for the unit-circle definition.