Mathematical set of symbols 1, n: non-negative integer set or natural number set {0, 1, 2, 3, …}.
2, N* or N+: positive integer set {1, 2, 3, ...}
3, z: integer set {…,-1, 0, 1, …}
4. Q: Rational number set
5.Q+: Positive Rational Number Set
6.Q-: set of negative rational numbers
7.r: set of real numbers (including rational numbers and irrational numbers)
8.R+: positive real number set
9.R-: negative real number set
10, c: complex set
1 1、? : empty set (a set without any elements)
What are the types of union? A set with elements belonging to A or B is called the union of A and B, marked as A∪B (or B∪A) and pronounced as A and B (or B and A), that is, A ∪ B = {x | x ∈ A
Intersection: The set with elements belonging to A and B is called the intersection (set) of A and B, marked as A∩B (or B∩A), and read as "A crosses B" (or "B crosses A"), that is, A∩B={x|x∈A, X ∩.
Infinite set: Definition: A set containing infinite elements in a set is called an infinite set.
Finite set: let N+ be a positive integer, Nn={ 1, 2,3, ..., n}. If there is a positive integer n that makes the set A correspond to NN one by one, then A is called a finite set.
Difference: The set of elements belonging to A but not to B is called the difference between A and B (set).
Complement set: A set consisting of elements belonging to the complete set U but not to the set A is called the complement set of the set A, and is denoted as CuA, that is, CuA={x|x∈U, and x does not belong to A}.