What is the Sentry Theorem? A Dynamic Geometry Illustration

①This GeoGebra example dynamically illustrates the Sentry Theorem, a geometric result often involving polygons, angles, and rotational symmetry. ②Core mathematical concepts include polygon interior angles, rotation, symmetry, and relationships among rays and segments; the original tags also mention parabola, conditional probability, median line, and parametric curves, suggesting a rich multi-topic context. ③Construction details: the commands Polygon, Ray, Angle, Segment, and Rotate are used to create points A, B, C, D, E, polygon poly1, multiple segments and rays (a–j), angle variables (α–κ), and a text label text1, with rotations generating symmetric configurations. ④Suitable for high school or undergraduate geometry courses, this example helps students visualize and explore the theorem's statement and proof, and can serve as a teacher demonstration or a student inquiry tool.