Reflections: Mirroring a Polygon Across a Line

① This example demonstrates the reflection (mirror) transformation in plane geometry, using a line as the axis of symmetry to map a polygon and its vertices to symmetric positions, visually showing the symmetry of shapes about a line. ② Core mathematical concepts include reflection transformation, axis of symmetry, corresponding vertices and edges, and the property that the original and reflected figures are congruent. ③ Construction highlights: using GeoGebra commands Polygon to create the original polygon poly1, Line to define the mirror line, and Mirror to generate the reflected polygon poly1' with corresponding vertices A', B', C', D', E', while keeping both original and mirrored objects for easy comparison. ④ Suitable for middle school to high school students learning geometric transformations, and for teachers to demonstrate in class, helping students understand the geometric meaning and coordinate changes of reflection.