1.5.1
Sets
Sets of Objects
Sets of Objects


Sets
Sets
- Sets are collections of objects.
- The objects in a set are called its elements.
- A set is written using curly brackets:
- {2,3,4} is the set containing 2,3,4
- {positive even numbers below 5} = {2,4}


Universal set
Universal set
- The symbol ξ is used for the universal set: the set that contains everything.
- On a Venn diagram, ξ is everything inside the rectangle.
- The "complement of a set A" is written as A’
- It is the set of all the things that aren’t in A.


Empty set
Empty set
- The symbol ∅ is used to the empty set: the set that contains no elements.


Notation
Notation
- If an element e is in a set A, we use the following notation:
- If an element d is not in A, we use the following notation:


Number of elements
Number of elements
- The number of elements in a set A is written as n(A).
- In the example shown here, n({2,3,4}) = 3.
Subsets
Subsets
As we have seen previously, the universal set contains all elements, and can also contain sets. We say that these sets are subsets of the universal set.


Subsets
Subsets
- Subsets are sets contained within other sets.
- The set A is a subset of set B if all of the elements in A are also elements in B.
- For example the set A = {2, 3, 4} has the following subsets:
- {2, 3}, {3, 4}, {2, 4}, {2}, {3}, {4}, {2,3,4}
- Every set is its own subset.


Notation
Notation
- If A is a subset of B, we write:
- A ⊂ B
- If C is not a subset of B, we write:
- C ⊄ B
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
Jump to other topics
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
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