Exercise 1.1

Show that the relation R defined in the set A of all polygons as R = {(P1, P2) :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?

solution: Case I: R = {(P1, P2) :P1 and P2 have same number of sides} Check for reflexive: P1 and P1 have same number of sides, So R is reflexive. Check for symmetric: P1 and P2 have same number of...

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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?

solution: Case I: T1, T2 are triangle. R = {(T1, T2): T1 is like T2} Check for reflexive: As We realize that every triangle is like itself, so (T1, T1) ∈ R is reflexive. Check for symmetric:...

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Show that the relation R in the set A of points in a plane given by R = {(P, Q) : distance of the point P from the origin is same as the distance of the point Q from the origin}, is an equivalence relation. Further, show that the set of all points related to a point P ≠ (0, 0) is the circle passing through P with origin as centre.

solution: R = {(P, Q): distance of the point P from the beginning is equivalent to the distance of the point Q from the origin} Say "O" is beginning Point. Since the distance of the point P from the...

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Show that each of the relation R in the set A = {x ∈ Z : 0 ≤ x ≤ 12}, given by R = {(a, b) : |a – b| is a multiple of 4} ;R = {(a, b) : a = b} is an equivalence relation. Find the set of all elements related to 1 in each case.

solution: (I) A = {x ∈ Z : 0 ≤ x ≤ 12} In this way, A = {0, 1, 2, 3, … … , 12} Presently R = {(a, b) : |a – b| is a different of 4} R = {(4, 0), (0, 4), (5, 1), (1, 5), (6, 2), (2, 6), ….., (12, 9),...

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Show that the relation R in the set A = {1, 2, 3, 4, 5} given by = {(a, b) : |a – b| is even}, is an equivalence relation. Show that all the elements of {1, 3, 5} are related to each other and all the elements of {2, 4} are related to each other. But no element of {1, 3, 5} is related to any element of {2, 4}

Solution:A = {1, 2, 3, 4, 5} and R = {(a, b) : |a – b| is even} We get, R = {(1, 3), (1, 5), (3, 5), (2, 4)} For (a, a), |a – b| = |a – a| = 0 is even. Therfore, R is reflexive. If |a – b| is even,...

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