Download Lesson 2

Lesson 2.1
Basic Set Concepts
• A set is a collection of objects whose contents
can be clearly determined.
• Elements, or members, - the objects in a set
• Capital letters are used to name sets.
• Methods to name sets: 1) word description
2) roster method
3) set builder notation
• Roster method lists all elements in braces { }
• Write a word description for the set.
L = {a, b, c, d, e}
• Set builder notation
– Lets express days of the week in s.b.n
W = {x| x is a day of the week
• Express in roster and set builder notation.
• M is the set of all months beginning with the
letter M.
• The empty set, or null set, contains no
elements. Represented by { } or ø.
– {x|x is greater than 8 and less than 2
• The symbol is used to indicate that an
object is an element of a set.
• True or false
• v {a, b, c … z )
-3
• The set of Natural numbers
N = {1,2,3,4 ……}
{1, 2, 3, ….}
• The number of elements in a set is called the
cardinal number, or cardinality, of the set.
• L = {a,e,i,o,u} has cardinality of 5
• Symbol n(L) is read “n of L.”
• Repeating Elements in a set does not add to
the cardinality of a set.
• If set A is equivalent to set B, then set A and B
contain the same number of elements.
n(A) = n(B)
Example
If set A is equal to set B then, A and B contain
exactly the same elements, regardless of order
or possible repetition.
A=B
example
• Finite set – has a definite number of elements
• Infinite set – doesn't have a set number of
elements
• Examples