1. Lesson 2.1
Basic Set Concepts

2. 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 { }

3. 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

4. Express in roster and set builder notation.
M is the set of all months beginning with the letter M.

5. The symbol is used to indicate that an object is an element of a set.
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.

6. True or false
v {a, b, c … z ) {1, 2, 3, ….}
The set of Natural numbers
N = {1,2,3,4 ……}

7. 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.

8. If set A is equivalent to set B, then set A and B contain the same number of elements.
n(A) = n(B)
Example

9. 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

10. Finite set – has a definite number of elements
Infinite set – doesn't have a set number of elements
Examples