Belongs to, and the mathematical symbol is "∈", indicating the relationship between elements and sets. If a is an element of set A, it is said that A belongs to set A, marked as A ∈ A; If a is not an element in set a, say that a does not belong to set a, and record it as a? Answer.
For example, a represents the set of "all prime numbers in 1~20", so there is 3 ∈ a.
Belong to ∈ related extension:
Does not belong to:? .
For example, a ∈ r: a is a∈R:a number; Answer? N: a is not a natural number.
In solid geometry, the symbol "∈" is used to represent the positional relationship between points, lines and surfaces.
Example:
A∈l means that point a is on a straight line L.
A∈α means that point A is on plane α.
Real number set (set of all real numbers) R={x | x is a real number}.