Let U ={1,2,3,4,5,6,7,8,9}
A = {1, 2, 3, 4}, B = {2, 4, 6, 8}, C = {3, 4, 5, 6}
Find (a) A' (b) B' (c)(A ∪ C)' (d) (A ∪ B)' (e) (A')' (f) (B-C)'
Fill in the blanks to make each of the following a true statement : (i) A ∪ A′ = . . . (ii) φ′ ∩ A = . . . (iii) A ∩ A′ = . . . (iv) U′ ∩ A = . . .
(a) A ∪ A′ = U             [By complement law]
(b) φ′ ∩ A = U ∪ A = A       [By complement law]
(c) A ∩ A' = φ              [By complement law]
(d) U′ ∩ A = φ′ ∩ A = φ       [By complement law]
Id U = {1, 2, 3, 4, 5, 7, 8, 9}, A = {2, 4, 6, 8} Â , B ={2, 3, 5, 7} verify De Morgan's laws:
Taking the set of natural numbers as the universal set, write down the complements of the following sets :
(i) {x : x is an even natural number} Â Â Â Â Â Â (ii) {x : x is an odd natural number}
(iii) {x : x is a positive multiple of 3} Â Â Â Â Â Â (iv) {x : x is a prime number}
(v) {x : x is a natural number divisible by 3 and 5} Â
(vi) {x : x is a perfect square} Â Â Â Â Â Â Â Â Â (vii) {x : x is a perfect cube}
(viii) { x : x + 5 = 8 } Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â (ix) { x : 2x + 5 = 9}
(x) { x : x ≥ 7 }                    (xi) {x : x ∈ N and 2x + 1 > 10}