12. Show that the relation R defined in the set A of all triangles as R={(T1,T2):T1 is similar to T2}, is equivalence relation. Consider three right angle triangles T1 with sides 3,4,5,T2 with sides 5,12,13 and T3 with sides 6,8,10. Which triangles among T1,T2 and T3 are related?