InterviewSolution
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Three relations R1, R2 and R3 are defined on a set A = {a, b, c} as follows: R1 = {(a, a), (a, b), (a, c), (b, b), (b, c), (c, a), (c, b), (c, c)}R2 = {(a, a)}R3 = {(b, c)}R4 = {(a, b), (b, c), (c, a)}.Find whether or not each of the relations R1, R2, R3, R4 on A is(i) reflexive (ii) symmetric and (iii) transitive. |
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Answer» (i) Consider as R1 Given that R1 = {(a, a), (a, b), (a, c), (b, b), (b, c), (c, a), (c, b), (c, c)} Now let us check R1 is reflexive, symmetric and transitive Reflexive: Given (a, a), (b, b) and (c, c) ∈ R1 Clearly, R1 is reflexive. Symmetric: We see that the ordered pairs obtained by interchanging the components of R1 are also in R1. So, R1 is symmetric. Transitive: Here, (a, b) ∈ R1, (b, c) ∈ R1 and also (a, c) ∈ R1 So, R1 is transitive. (ii) Consider as R2 Given that R2 = {(a, a)} Reflexive: Clearly (a, a) ∈ R2. So, R2 is reflexive. Symmetric: Clearly (a, a) ∈ R ⇒ (a, a) ∈ R. So, R2 is symmetric. Transitive: R2 is clearly a transitive relation, since there is only one element in it. (iii) Consider as R3 Given that R3 = {(b, c)} Reflexive: Here,(b, b) ∉ R3 neither (c, c) ∉ R3 Clearly, R3 is not reflexive. Symmetric: Here, (b, c) ∈ R3, but (c, b) ∉ R3 So, R3 is not symmetric. Transitive: Here, R3 has only two elements. Hence, R3 is transitive. (iv) Consider as R4 Given that R4 = {(a, b), (b, c), (c, a)}. Reflexive: Here, (a, a) ∉ R4, (b, b) ∉ R4 (c, c) ∉ R4 Clearly, R4 is not reflexive. Symmetric: Here, (a, b) ∈ R4, but (b, a) ∉ R4. So, R4 is not symmetric Transitive: Here, (a, b) ∈ R4, (b, c) ∈ R4, but (a, c) ∉ R4 Clearly, R4 is not transitive. |
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