25.2.1 Any Angle: The Angle as a Rotation
Core ideaPicture a pointer sweeping around a center — it can swing half a turn, several turns, forward or backward — so an angle is no longer trapped inside a right triangle.
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.