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 . Then R is
(A) reflexive but not transitive (B) transitive but not symmetric
(C) equivalence (D) none of these
(C) equivalence
Here aRb, if a is congruent to b,
So, in aRa, a is congruent to a. This must always be true.
Therefore, R is reflexive.
Say,
Therefore, R is symmetric.
Say, aRb and bRc
Therefore, R is transitive.
Therefore, R is an equivalence relation.