If A and B are two given sets, then A∩(A∩B)c is equal to
A
B
ϕ
A∩Bc
A∩(A∩B)c=A∩Ac∪Bc (∵ by De-Morgan's law )=A∩Ac∪A∩Bc=ϕ∪A∩Bc=A∩Bc