Alternate Exterior Angles Dynamic Demonstration

① This example dynamically demonstrates the equality of alternate exterior angles formed when two lines are cut by a transversal, helping students intuitively understand the properties of parallel lines. ② The core mathematical concept is the alternate exterior angles theorem in parallel line properties: when two lines are parallel, the alternate exterior angles formed by a transversal are equal; conversely, if alternate exterior angles are equal, the lines are parallel. ③ Construction details: using GeoGebra commands Line to create lines f, g, and transversal h, Intersect to obtain intersection points C, D, E, Point to mark key points A, B, F, G, H, and Angle to measure alternate exterior angles α and β, with a button1 added for toggling or resetting the demonstration. ④ Suitable for middle school geometry teaching or self-study, especially for interactive classroom demonstrations of parallel line properties and criteria, as well as introductory geometric construction practice.