Q.11 Show that the relation R defined in the set A of all triangles as , is equivalence relation. Consider three right-angled triangles: T1 with sides 3, 4, and 5, T2 with sides 5, 12, and 13, and T3 with sides 6, 8, and 10. Which triangles among T1, T2, and T3 are related?
All triangles are similar to itself, so it is reflexive.
Let,
i.e.T1 is similar to T2
T1 is similar to T2; T2 is similar to T1, i.e.
Hence, it is symmetric.
Let,
and i.e. T1 is similar to T2 and T2 is similar toT3 .
T1 is similar toT3 i.e.
Hence, it is transitive,
Thus, , is equivalence relation.
Now , we see ratio of sides of triangle T1 and T3 as shown
i.e. ratios of sides of T1 and T3 are equal.Hence, T1 and T3 are related.