 Hello and welcome to the session. Let us understand the following question which says, show that the relations are defined in the set A of all polygons as r is equal to p1 and p2 such that p1 and p2 have same number of sides is an equivalence relation. What is the set of all elements in A related to the right angle triangle T with sides 3, 4 and 5. Now let's proceed on to the solution. We have A is equal to set of all polygons r is equal to p1 and p2 such that p1 and p2 have same number of sides. Now let us check for reflexivity. P and p belongs to r for all p belongs to A. Thus r is reflexive check for symmetry and p2 belongs to r then number of polygon p1 is equal to number of sides equal to number of sides in p1 also belongs to r check for transitivity belongs to r p3 belongs to r p2 and p3 belongs to r p3 belongs to r as both p1 and p3 have same number of sides. Therefore equivalence relation, relation defined in the set of polygons to polygons related to the right angle will be required. I hope you understood this question. Bye and have a nice day.