Let R and R’ be two symmetric relations on a set A.
Let a, b ∈ A such that (a, b) ∈ R ∪ R’
∴ Either (a, b) ∈ R or (a, b) ∈ R’
If (a, b) ∴ R then (b, a) ∴ R (∵ R is symmetric)
∴ (b, a) ∈ R ∪ R’ (since R ⊆ R⊆ R’)
Similarly we can prove that (a, b) ∈ R’ ∈ (b, a) ∈ R ∪ R’
In both the cases (b, a) ∈ R ∪ R’
∴ R ∪ R’ is a symmetric relation on A.
Let R be the relation in the set N given by R = {(a, b) : a = b – 2, b > 6}.
Choose the correct answer.
(A) (2. 4) ∈ R (B) (3, 8) ∈ R (C) (6,8) ∈ R (D)(8,7) ∈ R
Let A = {1, 2, 3}. Then number of relations containing (1, 2) and (1, 3) which are reflexive and symmetric but not transitive is
(A) 1 (B) 2 (C) 3 (D) 4