Relationships Between Lines in 3D: Problem #1

This GeoGebra example demonstrates how to visualize and analyze the positional relationships between two lines in three-dimensional space, including intersecting, parallel, or skew lines. The core mathematical concepts involve parametric equations of lines, direction vectors, coplanarity tests, and determining intersections or parallelism. The construction uses the Line command to create lines B, C, f, and g, with points A and D, intersection objects int_1 and int_2, and auxiliary object h to mark key elements, providing an interactive 3D view. This is suitable for high school or early college courses in solid geometry and coordinate geometry, as well as for practicing spatial vector applications and line equation analysis.