集合的运算律

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：$(A \cup B)^c = A^c \cap B^c，(A \cap B)^c = A^c \cup B^c$