The meaning of the collection symbol encyclopedia

A collection is a collective of concrete or abstract objects of a particular nature called the elements of the collection.

∪ and

∩

⊂ 　A⊂B， A属于B

⊃ 　A⊃B， A包括B

∈ a∈A, a is the element of A

⊆ A⊆B, A is no greater than B

⊇ A⊇B, A is not less than B

Φ Empty set

R real number

N natural number

Z integer

Z+ positive integer

Z- Negative integer

1, the meaning of the set: some of the specified objects set together to become a set, each of which is called an element.

2. Three characteristics of the elements in the set:

(1) certainty of the elements;

(2) the heterogeneity of elements;

(3) The disorder of the elements

Related knowledge:

1) For a given set, the elements in the set are deterministic, and any object is either or not an element of the given set.

2. In any given set, any two elements are different objects, and when the same object is grouped into a collection, only one element is counted.

3, the elements in the set are equal, there is no order, so to determine whether the two sets are the same, only need to compare whether their elements are the same, do not need to examine whether the order of arrangement is the same.

Classification of collections:

1. Finite set A set of finite elements

2. Infinite set A collection of infinite elements

3、 Empty set A set without any elements Example: {x|x2=-5}

How to represent the collection:

1. Enumeration method: list the elements in the set one by one, and then enclose them in a large bracket.

2. Descriptive method: Describe the common attributes of the elements in the collection and write the method of representing the collection in curly braces. A method that uses a deterministic condition to indicate whether certain objects belong to this collection.

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