Assuming that R intersects S, R-S is equivalent to subtracting the intersection of RS (the intersection is R∩S), adding a minus sign in front of it, and returning to the intersection of RS, which is set to T (t =-(R-S)); The sum of t and r is the intersection with t and r, and the intersection part R∩S is found.
Set has unparalleled special importance in the field of mathematics. The foundation of set theory was laid by German mathematician Cantor in the 1970s of 19. After the efforts of a large number of outstanding scientists for half a century, it has established its basic position in the theoretical system of modern mathematics in the 1920s, and the achievements of all branches of modern mathematics are almost based on strict set theory.
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 ∩.
Properties of sets
1. Certainty: Every object can determine whether it is an element of a set. Without certainty, it cannot be a set. For example, "tall classmates" and "small numbers" cannot form a set. This property is mainly used to judge whether a set can constitute a set.
2. Relevance: Any two elements in the set are different objects. If written as {1, 1, 2}, it is equivalent to {1, 2}. Being different from each other makes the elements in the collection not repeat. When two identical objects are in the same set, they can only be counted as an element of this set.
3. Disorder: {a, b, c}{c, b, a} are the same set.
4. Purity: The purity of the so-called set is represented by an example. Set a = {x | x
5, integrity: still use the above example, all in line with X.