11映射与函数 Mappings and functions
September, 2004 1.1 映射与函数 Mappings and functions
集合(Set) 1.集合概念 2.集合的运算 September. 2004
September, 2004 一、集合 (Set) 1.集合概念 2. 集合的运算
A与B的直积 Direct product A×B={(a,b)a∈ A and b∈B AxB B 直积也称为笛卡儿积 Cartesian product September. 2004
September, 2004 A B a b a A b B = {( , ) | and } B A A B A与B 的直积 b ( , ) a b a Direct product 直积也称为笛卡儿积 (Cartesian product)
例设 A=a,b,c B=x, yi 求A×B、B×A,B×B 解 A×B={(a,x),(a,y),(b,x),(b,y),(c,x),(c,y)} B×A=(x,a),(y,a,(x,b),(y,b),(x,c),(Jy,c)} B×B={(x,x),(x,y,、(y,x)(y,y)} September. 2004
September, 2004 A B, 例 设 A a b c ={ , , } B x = { , }y 求 B A, B B 解 A B = {( , ), a x ( , ), a y ( , ), b x ( , ), b y ( , ), c x ( , )} c y B A= {( , ), x a ( , ), y a ( , ), x b ( , ), y b ( , ), x c ( , )} y c B B = {( , ), x x ( , ), x y ( , ), y x ( , )} y y
R2=R× r the real plane the set of all pairs(a, b)of real numbers R2={(a,b)|a,b∈R} RERXR September. 2004
September, 2004 2 R R R = the real plane the set of all pairs (a, b) of real numbers 2 R {( , ) | , R} = a b a b 2 R R R = ( , ) a b a b