Reflections: Mirror Images of Polygons and Circles

①This GeoGebra example dynamically demonstrates the reflection of a triangle (polygon) across a median line, along with the corresponding images of a circle and segments, visually illustrating mirror symmetry in the plane. ②Core mathematical concepts include reflection (axial symmetry), the properties of a symmetry axis (median line), corresponding points and segments, distance preservation, and the mapping of real-number coordinates. ③Construction highlights: the Polygon command creates triangle ABC, the Line command defines the median as the axis of symmetry, reflection tools generate corresponding points D, E and the reflected figure f, while circle c and segments a, b are included, with text1 labeling key elements to show congruence before and after reflection. ④Suitable for middle and high school students learning geometric transformations, and for teachers demonstrating symmetry properties in class, helping learners understand that reflection preserves size and shape while changing position and orientation.