1.

The relation “is parallel to” on a set S of all straight lines in a plane is :(a) Symmetric only (b) Reflexive and Transitive only (c) Transitive only (d) An equivalence relation

Answer»

(d) An equivalence relation

Let R = {(x, y) : line x is parallel to line y, x y ∈ set of coplanar straight lines}. 

• Every line is parallel to itself. So, if x ∈S, then (x, x) ∈R 

⇒ R is reflexive 

• If (x, y) ∈R ⇒ x | | y ⇒ y | | x ⇒ (y, x) ∈R 

⇒ R is symmetric 

• (x, y) ∈R and (y, z) ∈R 

⇒ x | | y and y | | z 

⇒ x | | z ⇒ (x, z) ∈R 

⇒ R is transitive 

∴ R being reflexive, symmetric and transitive, it is an equivalence relation.



Discussion

No Comment Found

Related InterviewSolutions