交换律：$A cup B = B cup A，A cap B = B cap A$
结合律：$(A cup B) cup C = A cup (B cup C)，(A cap B) cap C = A cap (B cap C)$
分配律：$(A cup B) cap C = (A cap C) cup (B cap C)，(A cap B) cup C = (A cup C) cap (B cup C)$
对偶律：$(A cup B)^c = A^c cap B^c，(A cap B)^c = A^c cup B^c$