Lecture
This lecture covers the concept of modern symmetry in geometry, focusing on the decomposition of compositions of three axial reflections in the plane into a translation and an axial reflection. The importance of 'glided reflection' as a distinct isometry is highlighted, preserving only a specific line unlike translations. The lecture also delves into spatial symmetry, true angle measurements, and various operations related to symmetry. Practical examples and visualizations are used to illustrate the theoretical concepts.