Relation of One Set to Another

Relation R is a subset of a cartesian product of A ⊗ B i.e.  RAxB . R' which is a subset of BxA is called an inverse relation denoted by R-1
Example: Set A={1,2,3} and Set B ={1,3,5} Then K=AxB ={(1,1),(1,3),(1,5),(2,1),(2,3),(2,5),(3,1),(3,3),(3,5)}
Set M ={(1,1),(1,3),(3,1),(3,3)} is subset of K and therefore a relation of A →B
If a Relation is defined between two sets, it is called a Binary Relation.
A relation  R is said to be Reflexive if   aRa holds true for ∀a M . M is a reflexive relation because of (1,1) & (3,3)
A relation  R  is said to be symmetric  if aRb bRa ∀a,b M. Here, (1,3) & (3,1) both belong to M. M is a symmetric relation because of (1,1) & (3,1)
A relation is said to be transitive if aRb, bRc aRc ∀a,b,c M . Here M is not a transitive relation.
A relation which is reflexive, symmetric as well as transitive is called an Equivalent Relation.
A relation which is reflexive, anti-symmetric as well as transitive is called an Partial Ordered Relation.
Relation Matrix: In a binary relation, matrix elements mij = 1 iff aiRaj holds good, otherwise  mij = 0. If R AxA, then relation matrix is a square matrix of the same order as that of A. Otherwise, it is a rectangular matrix of m rows and n columns where m is the order of A and n is the order of B.
Example: Suppose R consists of ordered set of integers (x,y) such that (x,y) ∈ R & x2 + y2 =25 . Then R={(-5,0),(0,-5),(0.5),(5,0),(3,4),(4,3),(-3,4),(4,-3),(-4,3),(3,-4),(-3,-4),(-4,-3)} and A= {-5,-4,-3,0,3,4,5} . Order of A is 7 and therefore no. of elements of relation matrix will be 49.
The diagonal elements m11,m22,m33,m4,m55,m66,m77 are equal to zero. m14=m41=1, m23=m32=1, m25=m52=1,m36=m63=1, m47=m74=1,m56=m65=1. Rest are all zero. Here R=R-1
It is a symmetric matrix if both set A and B have the same cardinality, otherwise it is a rectangular matrix.
  Working- Put 2 sets of same cardinality. write the relations. click 1. Then click the image of any relation and then click-3. repeat this for all images. The images u have finished will be yellow.


cardinality A: cardinality B: cardinality A ⊗ B        
set A
set B
matrice mij --            
Relation Set ---1 ---2 ---3 ---4 ---5 ---6 ---7
Elements ---8 ---9 ---10 ---11 ---12 ---13 ---14
  ---15 ---16 ---17 ---18 ---19 ---20 ---21
  ---22 ---23 ---24 ---25 ---26 ---27 ---28