ABSTRACT
Many aspects of set theory relate very closely to the propositional logic and quantifier logic. This chapter provides an informal introduction to set theory and presents formal definitions of subsets and set operations. It discusses the union of two sets and intersection of two sets. The chapter provides proofs that illustrate both the subset proof template and the subset knowledge template. Informally, a set is a collection of objects called the members of the set. With this intuition, it seems reasonable to say that two sets should be equal if they have precisely the same members. The chapter develops two new ways for proving IFF-statements, the circle proof method and the chain proof method, that can help prove set equalities and other biconditional statements. It introduces the concept of an ordered pair. Ordered pairs are used in analytic geometry and calculus to represent points in the plane.
