The meaning of expression: subset

For two sets A and B, if any element of set A is an element of set B, we say that set A is contained in set B, or set B contains set A, which means that set A is a subset of set B. ..

For example, b contains a, and it is recorded as a? B, which means that A is a subset of B; Or pronounced a is included in B.

2、? (Really included in)

Meaning: proper subset.

If any element of set A is an element of set B, and at least one element of set B does not belong to set A, then set A is called proper subset of set B, remember the same as above;

Solution:

Look at the symbol "on". The set opposite to the opening contains many elements to distinguish who is a subset of whom, and then distinguish whether it is a subset or a proper subset according to the similarities and differences of symbols.

Extended data:

The setup operation includes the following parts:

(1) intersection: the intersection of topological elements of a shape participating in the operation, and the order of intersection is from low-dimensional elements to high-dimensional elements. The intersection element is divided into some sub-elements by the new elements generated by the intersection result (the dimension is lower than that of the elements involved in the intersection).

2) Ring formation: the surface of the original object is divided by intersecting lines to form some new surface rings.

(3) Classification: for each topological element in the generated topological element set, take a representative point on it, determine the position relationship of the point relative to another entity according to the point/volume classification principle, and consider the type (i.e. dimension) of the topological element represented by the point to determine the classification relationship of the topological element relative to another entity.

(4) Selection: according to the types of topological elements and their classification relationship with another entity, and according to the operator requirements of set operation, it is decided whether to keep or discard topological elements; The reserved topological elements form a reserved set.

(5) Merging: Merging topological elements of the same type in the reserved set, including the merging of faces and edges.

(6) Mosaic: Taking the shared boundary of topological elements as its connection sign, the classified topological elements are collected in turn from high dimension to low dimension to form the boundary representation data structure of the result body? .

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