Solution R is reflexive, since every triangle is congruent to itself Further,
(T1, T2) ∈ R ⇒ T1 is congruent to T2 ⇒ T2 is congruent to T1 ⇒ (T2, T1) ∈ R Hence,
R is symmetric Moreover, (T1, T2), (T2, T3) ∈ R ⇒ T1 is  congruent to T2 and T2 is
congruent to T3 ⇒ T1 is congruent to T3 ⇒ (T1, T3) ∈ R