Q.

Let T be the set of all triangles in the Euclidean plane and let a relation R on T be defined as aRb if a is congruent to b for all a,b∈T, then R is:

1 reflexive but not symmetric  
2 transitive but not symmetric  
3 equivalence  
4 neither symmetric nor transitive  

Ans.

(3)

Ans.     Equivalence

Explanation:

Each triangle is congruent to itself.

∴   Relation is reflexive.

        Suppose  ∆ABC≅∆PQR

        then         ∆PQR≅∆ABC

∴  Relation is symmetric.

       Suppose   ∆ABC≅∆PQR,

       and           ∆PQR≅∆XYZ

       then          ∆ABC≅∆XYZ

∴  Relation is transitive.

∴  Relation is an equivalence relation.