关系的运算(2) 口与定义域和值域有关的运算 a dom r={x|3y(x,∈R} d ran r={y|彐x(x∈R fldR=domR∪ranR RA={(x)|x∈ AAxRyCR restriction也记作R个A,RA 口R[4]={y|丑x(x∈A∧(x∈}=ran( Crane 口例 口A={1,234,5},B={1356},A上关系R R={1,2),(1,4),(2,3),3,5),(5,2)}, 求R↑B、RB]关系的运算(2)  与定义域和值域有关的运算  dom R = {x | y (x,y)R}  ran R = {y | x (x,y)R}  fld R = dom R  ran R  R A = {(x,y) | xA xRy}  R restriction 也记作 𝑅 ↾ 𝐴, 𝑅|𝐴  R[A] = {y | x (xA  (x,y)R)}= ran(RA)  ranR  例：  A={1,2,3,4,5}, B={1,3,5,6}, A上关系R： R={(1,2), (1,4),(2,3),(3,5),(5,2)}, 求 RB、R[B] 10