1.5.1
Sets
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Sets of Objects

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

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
- The number of elements in a set A is written as n(A).
- In the example shown here, n({2,3,4}) = 3.
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 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
- 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
Practice questions on Sets
Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.
- 1What is the symbol for the universal set?Multiple choice
- 2
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