基本定律 1. 交换律： 　 A ∪ B = B∪A， A ∩ B = B ∩ A2. 结合律：　 (A ∪ B) ∪ C = A ∪ (B∪C) = A ∪ B∪C(A ∩ B) ∩ C = A ∩ (B ∩ C) = A ∩ B ∩ C3. 分配律： (A ∩ B) ∪C = (A∪C) ∩ (B∪C)(A∪B) ∩ C = (A ∩ C) ∪(B ∩ C)4. 德摩根