Set and Set OperationsIntroductionNotationMore on NotationSet – Builder NotationSpecial Sets of NumbersUniversal Set and SubsetsThe Empty SetIntersection of setsMutually Exclusive SetsUnion of setsComplement of a SetCardinal NumberSet and Set OperationsSection 2.1Introduction•A set is a collection of objects.•The objects in a set are called elements of the set.•A well – defined set is a set in which we know for sure if an element belongs to that set.•Example:– The set of all movies in which John Cazale appears is well – defined. (Name the movies, and what do they have in common? There are only 5.)–The set of all movie serials made by Republic Pictures is well – defined.–The set of best TV shows of all time is not well – defined. (It is a matter of opinion.)Notation•When talking about a set we usually denote the set with a capital letter.•Roster notation is the method of describing a set by listing each element of the set.•Example: Let C = The set of all movies in which John Cazale appears. The Roster notation would be C={The Godfather, The Conversation, The Godfather II, Dog Day Afternoon, The Deer Hunter }. (All 5 of these movies were nominated for Best Picture by the Motion Picture Academy.)•Example: Let set A = The set of odd numbers greater than zero, and less than 10. The roster notation of A={1, 3, 5, 7, 9}More on Notation•Sometimes we can’t list all the elements of a set. For instance, Z Z = The set of integer numbers. We can’t write out all the integers, there infinitely many integers. So we adopt a convention using dots …•The dots mean continue on in this pattern forever and ever.•Z Z = { …-3, -2, -1, 0, 1, 2, 3, …}•WW = {0, 1, 2, 3, …} = This is the set of whole numbers.Set – Builder Notation•When it is not convenient to list all the elements of a set, we use a notation the employs the rules in which an element is a member of the set. This is called set – builder notation. •V = { people | citizens registered to vote in Maricopa County}•A = {x | x > 5} = This is the set A that has all real numbers greater than 5. •The symbol | is read as such that.Special Sets of Numbers•NN = The set of natural numbers. = {1, 2, 3, …}.•WW = The set of whole numbers. ={0, 1, 2, 3, …}•ZZ = The set of integers. = { …, -3, -2, -1, 0, 1, 2, 3, …}•QQ = The set of rational numbers. ={x| x=p/q, where p and q are elements of Z and Z and q q ≠ 0≠ 0 }•HH = The set of irrational numbers.•RR = The set of real numbers.•C = The set of complex numbers.Universal Set and Subsets•The Universal Set denoted by U is the set of all possible elements used in a problem.•When every element of one set is also an element of another set, we say the first set is a subset. •Example A={1, 2, 3, 4, 5} and B={2, 3}We say that B is a subset of A. The notation we use is B A.•Let S={1,2,3}, list all the subsets of S.•The subsets of S are , {1}, {2}, {3}, {1,2}, {1,3}, {2,3}, {1,2,3}.The Empty Set•The empty set is a special set. It contains no elements. It is usually denoted as { } or .•The empty set is always considered a subset of any set.•Do not be confused by this question:•Is this set {0} empty? •It is not empty! It contains the element zero.Intersection of sets•When an element of a set belongs to two or more sets we say the sets will intersect.•The intersection of a set A and a set B is denoted by A ∩ B. •A ∩ B = {x| x is in A and x is in B}•Note the usage of and. This is similar to conjunction. A ^ B.•Example A={1, 3, 5, 7, 9} and B={1, 2, 3, 4, 5}•Then A ∩ B = {1, 3, 5}. Note that 1, 3, 5 are in both A and B.Mutually Exclusive Sets•We say two sets A and B are mutually exclusive if A ∩ B = . •Think of this as two events that can not happen at the same time.Union of sets•The union of two sets A, B is denoted by A U B.•A U B = {x| x is in A or x is in B}•Note the usage of or. This is similar to disjunction A v B. •Using the set A and the set B from the previous slide, then the union of A, B is A U B = {1, 2, 3, 4, 5, 7, 9}.•The elements of the union are in A or in B or in both. If elements are in both sets, we do not repeat them.Complement of a Set•The complement of set A is denoted by A’ or by AC. •A’ = {x| x is not in set A}.•The complement set operation is analogous to the negation operation in logic. •Example Say U={1,2,3,4,5}, A={1,2}, then A’ = {3,4,5}.Cardinal Number•The Cardinal Number of a set is the number of elements in the set and is denoted by n(A). •Let A={2,4,6,8,10}, then n(A)=5.•The Cardinal Number formula for the union of two sets is n(A U B)=n(A) + n(B) – n(A∩B).•The Cardinal number formula for the complement of a set is n(A) +
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