(A∩B∩C)∪(A∩~B∩C)∪(~A∩B∩C)=(A∩B∩C)∪(A∩B∩C)∪(A∩~B∩C)∪(~A∩B∩C)=[(A∩B∩C)∪(A∩~B∩C)]∪[(A∩B∩C)∪(~A∩B∩C)]=(A∩C)∪(B∩C)=(A∪B)∩C