Features: The scenery is described in the form of text narration.
Applicable object: a collection of concrete or abstract objects with certain properties.
Second, the description method:
Features: A set is represented by the same features of the elements contained in the * * * set.
Applicable object: the elements in the collection have the same characteristics.
Third, the enumeration method:
Features: when the number of elements is limited, the elements of the set are listed one by one; When the number of elements is infinite, their changing rules are expressed.
Applicable object: the number of elements is more or less, and there is an obvious set of rules between elements.
Extended data:
Four representations of a set:
1, enumeration method
Enumeration is a method of enumerating the elements of a collection one by one. For example, there are four seasons in a year, which can be represented by a collection {spring, summer, autumn and winter}.
Enumeration also includes the case that the elements of a set can not be enumerated one by one, but their changing rules can be expressed. For example, the set of positive integers N+ can be expressed as n+= {1, 2, 3, ..., n, ...}
Step 2 describe the method
The description method is in the form of {representing element | satisfying attribute}. Let the set S consist of all elements with a certain property p, then the set can be expressed by describing the common properties of the elements in the set: S={x|P(x)}.
3. Wayne diagram method (Webster diagram method)
It is a method of representing a set with a set of points on a two-dimensional plane. A set is generally represented by a rectangle or a circle on a plane, which is an intuitive graphical representation of the set.
4. Symbolic method
Some sets can be represented by some special symbols, such as:
N: non-negative integer set or natural number set {0, 1, 2, 3, …}
N* or N+: positive integer set {1, 2,3, …}
Z: integer set {…,-1, 0, 1, …}
Q: Rational number set
Q+: Set of Positive Rational Numbers
Q-: set of negative rational numbers
R: set of real numbers (including rational numbers and irrational numbers)
R+: positive real number set
R-: negative real number set
C: complex set
: empty set (a set without any elements)
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