Dynamic Isosceles Triangle with Adjustable Apex Angle

① This GeoGebra example demonstrates an isosceles triangle where the apex angle can be changed interactively while the triangle remains isosceles. ② Core math concepts include the definition and properties of isosceles triangles: equal legs, equal base angles, and the relationship between the apex angle and base angles. ③ Construction details: uses Point to define vertices, Rotate to generate symmetric points, Angle to measure angles, Line and Intersect to construct sides and intersections, and Polygon to form the triangle; objects include angles α, β, δ, ε, points A, B, C, D', E', segments a, b, c, d, e, polygon poly2, and multiple text labels. ④ Suitable for middle school geometry lessons to explore triangle properties dynamically, and as an introductory example for dynamic geometry software.