Vertical Angles Discovery: Ex. 10 (GeoGebra Beginner)

① This example demonstrates the property that vertical angles are equal when two lines intersect, using an interactive GeoGebra construction for discovery learning. ② The core mathematical concept is vertical angles and their congruence, a fundamental property in plane geometry. ③ Construction-wise, based on the summary, it uses basic GeoGebra objects such as points, lines, and angle measurement tools, allowing users to drag the lines or intersection point to observe that vertical angles remain equal. ④ It is suitable for middle school geometry beginners, serving as an introductory GeoGebra exercise or a classroom exploration activity to foster observation and reasoning skills.