Straight-Line Distance on Earth (Chord Length on a Sphere)

This GeoGebra example models Earth as a 3D sphere, drawing the equator, prime meridian, and latitude/longitude grid. It selects two points A and B on the sphere's surface and demonstrates how to calculate the straight-line chord distance between them. Using commands like Sphere, Circle, and Sequence to construct the Earth model, it employs Segment and distance formulas to visualize the Euclidean distance between two points in three-dimensional space. The applet helps students understand the relationship between spherical coordinates and spatial vectors, showing how the chord through the interior of the sphere differs from the curved arc along the surface. Students can drag points A and B to explore how the distance changes, reinforcing key concepts in solid geometry and vector mathematics. The interactive design makes it an effective teaching tool for geometry and vector courses, allowing learners to see the direct connection between coordinate calculations and spatial visualization.