(Theorem of three perpendiculars, dihedral angles). Chapter 3: Polyhedra (Prisms, pyramids, regular polyhedra).
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: Features detailed text solutions for every problem in the textbook, covering editions from 2013 to 2025. (Theorem of three perpendiculars, dihedral angles)
The solutions typically follow the standard curriculum structure found in the Proveshchenie textbook : (Theorem of three perpendiculars