Torstan

摘要： function: let A and B be noempty sets. A function f from A to B is an assignment of exactly one element of B to each element of A. We write f(a)=b if b is the unique element of B assigned by the function f to the element a of A. If f is a function from A to B, we write f: A->B, (we also call it f 阅读全文

摘要： key conceptset: a set is an unordered collection of objects. (It is not part of a formal theory of sets)This intuitive notation will lead to paradoxes, or logical inconsistencies.naive set theory: not develop an axiomatic version of set theory.set builder: the defination of belonging symboltwo sets 阅读全文