Where A and B are sets of numbers:
C
(A
U
B) = C
(A) 
C
(B)
The complement of (A
union B) equals the complement of (A)
intersected with the complement of (B)
This law states that the complement of the union of
two sets is the intersection of the complements.
C
(A
B) = C
(A)
U
C (B)
The complement of (A intersection B)
equals complement of (A) united with
the complement of (B)
This law states that the complement of the intersection of two sets is the
union of the complements.