Therefore, R is
symmetric Further, (a, b) ∈ R and (b, c) ∈ R ⇒ f (a) = f (b) and f(b) = f (c) ⇒ f (a)
= f(c) ⇒ (a, c) ∈ R, which implies that R is transitive Hence, R is an equivalence
relation Example 22 Find the number of all one-one functions from set A = {1, 2, 3} to itself