Hence, R is an equivalence
relation Example 22 Find the number of all one-one functions from set A = {1, 2, 3} to itself Solution One-one function from {1, 2, 3} to itself is simply a permutation on three
symbols 1, 2, 3 Therefore, total number of one-one maps from {1, 2, 3} to itself is
same as total number of permutations on three symbols 1, 2, 3 which is 3