Sine on the Unit Circle in Radians

①This example dynamically illustrates the sine function defined on the unit circle using radian measure, linking the angle, arc length, and sine value through an interactive geometric construction. ②Core mathematical concepts include the unit circle, radians, sine function, right triangles, coordinate representation, and the translation and step-function characteristics of the sine graph. ③Construction highlights: using GeoGebra commands such as Intersect, Rotate, Angle, Segment, OrthogonalLine, Polygon, Point, Line, and Vector to build the circle, rotating angle, perpendicular lines, triangles, and corresponding points on the sine curve, with dynamic control via sliders or angle animation. ④Suitable for high school and introductory college students learning trigonometry, radian measure, and function graphing, as well as for classroom demonstrations or self-study to grasp the periodicity and geometric meaning of sine.