Definition(Function) RC Ax B is a function from A to B if a∈A:3b∈B:(a,b)∈f. 4口￥0,43，t夏，里Q0 Hengeng Wei thkweionjn.edu.cn 1-10 Set Theory (II):Functions 2019 12 10 6/40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Definition (Function) R ⊆ A × B is a function from A to B if ∀a ∈ A : ∃!b ∈ B : (a, b) ∈ f. f : A → B dom(f) = A cod(f) = B ran(f) = f(A) ⊆ B f : a 7→ b f(a) ≜ b Hengfeng Wei (hfwei@nju.edu.cn) 1-10 Set Theory (III): Functions 2019 年 12 月 10 日 6 / 40