B^c := X\B
a) B\C = B∩C^c
(x: x∈B ∧ x∉C) = B ∩ (X\C)
B ⊂ X = (x: x∈B ∧ x∈X ∧ x∉C)
(x: x∈B ∧ x∈X ∧ x∉C)
b) (B∩C)^c = B^c U C^c
(x: x∈X ∧ (x∉B ∨ x∉C)) = B^c U C^c
(x: (x∈B^c ∨ x∈C^c)) = B^c U C^c
(x: x∈(B^c U C^c)) = B^c U C^c
B^c U C^c = B^c U C^c
Soweit korrekt?
