: The theorem of three perpendiculars and angles between planes.
The following textbooks are the most widely used in 10th-grade curricula, each with dedicated GDZ resources available on platforms like GDZ.ru and SkySmart :
: Many solutions include "Self-Control" sections that mirror tasks found on the Unified State Exam (EGE).
: Properties of prisms, pyramids, and their surface areas. How to Use GDZ Effectively
: Since stereometry requires 3D visualization, use GDZ diagrams to understand how to draw spatial figures on a 2D page.
: Basic axioms and their consequences.