GeoGebra Orthocenter: Intersection of Triangle Altitudes

① This GeoGebra example dynamically demonstrates the geometric fact that the three altitudes (perpendicular lines from each vertex to the opposite side) of any triangle intersect at a single point, known as the orthocenter. ② Core mathematical concepts include the definition of altitudes, concurrency of three lines, and how the orthocenter's position varies with triangle type (acute, right, obtuse). ③ Construction details: The triangle is created using the Polygon command with vertices A, B, C; perpendicular lines are drawn using OrthogonalLine from each vertex to the opposite side (objects f, g, h); the orthocenter D is obtained via the Intersect command on these lines. Auxiliary objects (t1, b, a, c) may label sides or altitudes. ④ Suitable for middle and high school geometry classes, this interactive tool helps students understand the orthocenter's definition, construction, and relationship to triangle shape, and can serve as a dynamic exploration resource for triangle center properties.