Perpendicular Lines and Planes

This lecture covers the concept of perpendicular lines and planes in descriptive geometry. It starts by defining the conditions for two lines or a line and a plane to be perpendicular. The conservation theorem of the right angle is discussed, emphasizing the orthogonality between lines and planes. Through examples and constructions, the instructor illustrates how to determine the intersection points of perpendicular lines and planes. The lecture also explores the use of auxiliary planes to simplify geometric constructions and projections. Additionally, the lecture delves into the properties of orthogonal lines and their relationship with coplanar elements.