Current location - Training Enrollment Network - Mathematics courses - The set theory of discrete mathematics on scum is distracted. Let me ask you a question. For example, a stands for set, so what do these two operations mean?
The set theory of discrete mathematics on scum is distracted. Let me ask you a question. For example, a stands for set, so what do these two operations mean?
∪ and ∩ are symbols of union and intersection respectively.

In the general set problem, the concepts of set and element are distinguished. The above two symbols are binary operators, and their usage is as follows:

A ∪ b: the set of all elements in a and b; For example, if a = {1, 2} and b = {2,3}, then a ∪ b = {1, 2,3};

A ∩ b: the set of the same elements in A and B; For example, a and b above, a ∩ b = {2};

In professional set theory, everything is a set, and the elements of the set are also sets. Therefore, these two symbols can be regarded as unary operators:

∪A:A: the union of all elements in a; For example, if A={a 1, a2, a3}, then ∪ a = a1∪ a2 ∪ a3;

∩ the intersection of all elements in a: a: a;