Sets and Functions - math.ucdavis.edu

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Chapter 1. sets and Functions We understand a set to be any collection M of certain distinct objects of our thought or intuition (called the elements of M ) into a whole. (Georg Cantor, 1895). In mathematics you don't understand things. You just get used to them. (Attributed to John von Neumann). In this chapter, we define sets , Functions , and relations and discuss some of their general properties. This material can be referred back to as needed in the subsequent chapters. sets A set is a collection of objects, called the elements or members of the set. The objects could be anything (planets, squirrels, characters in Shakespeare's plays, or other sets ) but for us they will be mathematical objects such as numbers, or sets of numbers. We write x X if x is an element of the set X and x / X if x is not an element of X. If the definition of a set as a collection seems circular, that's because it is.

1.1. Sets A set is a collection of objects, called the elements or members of the set. The objects could be anything (planets, squirrels, characters in Shakespeare’s plays, or other sets) but for us they will be mathematical objects such as numbers, or sets of numbers. We write x2Xif xis an element of the set Xand x=2Xif xis not an element of X.

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