Area of Triangles with Same Base and Same Height

① This applet dynamically demonstrates that triangles sharing the same base and having the same height always have equal areas. ② The core mathematical concept is the triangle area formula (Area = base × height ÷ 2), emphasizing that when the base length and corresponding height are fixed, moving the vertex along a line parallel to the base keeps the area constant. ③ Construction highlights: Using GeoGebra commands such as Line, OrthogonalLine, Point, Intersect, Segment, Polygon, Rotate, Angle, and Distance, the applet constructs a base AB, parallel lines, perpendiculars, multiple triangles (poly1, poly2, etc.), and distance measurements (distanceDF, distanceAB). Sliders or draggable points allow changing the vertex position while the area is displayed in real time. ④ This is suitable for middle school geometry teaching, helping students understand the invariant area property of triangles with equal base and height, and can also be used to explore relationships between area, base, and height, or as an interactive demonstration.