2. Exclude the set of 0 from the set of non-negative integers, also known as the set of positive integers, and express it as N+ (or N*).
3. The set of all integers is usually called the integer set, and is denoted as z..
4. The set of all rational numbers is usually referred to as rational number set for short, and is recorded as Q..
5. The set of all real numbers is usually referred to as the set of real numbers for short, and recorded as r.
6. the complex set is counted as C.
Extended data
First, the operation of the collection:
1, set the switching rule:
A∩B=B∩A
A∪B=B∪A
2, set associative law:
(A∩B)∩C=A∩(B∩C)
(A∪B)∪C=A∪(B∪C)
3, set the distribution law:
A∩(B∪C)=(A∪B)∩(A∪C)
A ∪( B∪C)=(A∪B)∪( A∪C)
2. Representation methods of sets: enumeration method and description method are commonly used.
1. enumeration: usually used to represent a finite set. All the elements in the collection are listed one by one and enclosed in braces. This method of representing a set is called enumeration. { 1,2,3,……}
2. Description: It is often used to represent an infinite set. The public * * * attribute of the elements in the collection is described by words, symbols or expressions and enclosed in braces. This method of representing a set is called description. {x|P}(x is the general form of the elements of this set, and p is the * * * same property of the elements of this set) For example, a set composed of positive real numbers less than π is expressed as {x | 0.
3. Schema Method (venn diagram): In order to visually represent a set, we often draw a closed curve (or circle) and use its interior to represent a set.
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