Lagrange Theorem: Equivalence Relations

This lecture covers Lagrange's theorem in commutative groups, focusing on finding the order of elements and equivalence relations. It explains the concept of equivalence classes and their role in partitioning sets. The instructor uses examples to illustrate the application of Lagrange's theorem and the construction of equivalence relations. The lecture concludes with a detailed proof demonstrating the relationship between equivalence classes and the cardinality of a group. Through a series of examples, students learn how to apply these concepts in group theory.