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7 marks Long answer
Define a Lattice. Draw the Hasse diagram of (D₃₆, /) and Show that it is a lattice.
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A lattice is a partially ordered set where every two elements have a unique supremum and infimum; the Hasse diagram must show these relationships.
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7 marks Long answer
If A = {1, 2, 3}, B = {4, 5} and C = {1, 2, 3, 4, 5}. Find (i) A × B (ii) C × B (iii) B × B. Hence prove that: (C × B) - (A × B) = B × B.
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A × B = {(1,4), (1,5), (2,4), (2,5), (3,4), (3,5)}; C × B = {(1,4), (1,5), (2,4), (2,5), (3,4), (3,5), (4,4), (4,5), (5,4), (5,5)}; B × B = {(4,4), (4,5), (5,4), (5,5)}.
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6 marks Long answer
Identify whether the each of the following relation defined on the set A = {1, 2, 3} are reflexive relation, symmetric relation, anti-symmetric relation and transitive relation. R₁ = {(1, 1), (1, 2), (2, 1), (2, 2), (2, 3), (3, 3)} R₂ = Universal Relation.
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R₁ is reflexive, symmetric, and transitive; R₂ is reflexive, symmetric, anti-symmetric, and transitive.
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5 marks Long answer
Let R = {(1, 2), (2, 3), (3, 1)} and A = {1, 2, 3} find the reflexive, symmetric and transitive closure of R using composition of relation R.
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The reflexive closure adds (1,1), (2,2), (3,3); the symmetric closure adds (2,1), (3,2), (1,3); the transitive closure adds (1,3), (2,1), (3,2).
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5 marks Long answer
Use Warshall's algorithm to find the transitive closure of the following relation on the set A = {1, 2, 3}. R = {(1, 2), (2, 3), (3, 1)}
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Applying Warshall's algorithm yields the transitive closure R* = {(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)}.
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5 marks Long answer
Let X = {1, 2, 3, 4, 5, 6, 7} and R = {(x, y) | (x-y) is divisible by 3}, then prove that R is an equivalence relation.
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R is reflexive, symmetric, and transitive, thus proving it is an equivalence relation.
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5 marks Long answer
If R and S are equivalence relation on the set A, prove that R ∩ S is an equivalence relation.
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R ∩ S is reflexive, symmetric, and transitive, hence it is an equivalence relation.
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4 marks Medium answer
Define Power set. Let A = {Ø, b} construct the following set: (i) A - Ø (ii) A ∩ P(A).
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The power set of A is the set of all subsets of A; A - Ø = A and A ∩ P(A) = {Ø, {Ø}, {b}, {Ø, b}}.
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4 marks Medium answer
Let P and Q be the multisets where P = {5.a, 7.b, 8.c} and Q = {3.a, 5.b, 9.c}. Find: (i) P U Q (ii) Q - P.
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P U Q = {5.a, 7.b, 8.c, 3.a, 5.b, 9.c} and Q - P = {3.a, 5.b, 9.c}.
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2 marks Short answer
Differentiate between proper subset and superset.
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A proper subset is a subset that is not equal to the original set, while a superset contains all elements of the subset.
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2 marks Short answer
Define Greatest element and Least element in Hasse diagram.
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The greatest element is the topmost element in a Hasse diagram, while the least element is the bottommost element.
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2 marks Short answer
Let A = {1, 2, 3, 4} and B = {a, b, c, d, e}. Compute the total number of possible relations from A to B.
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The total number of possible relations from A to B is $2^{|A| imes |B|} = 2^{4 imes 5} = 2^{20} = 1048576$.
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