1, absorption rate: Let A and B be sets, then A ∨( A∩B)= A, A ∩ (A ∪ B) = A;

2. There are many symmetric and antisymmetric relations on the, for example:

I = { & lt 1， 1 & gt； ，& lt2，2 & gt； ，& lt3，3 & gt； There are both symmetry and antisymmetry;

3. There are five different divisions on A, R 1={{ 1}, {2}, {3}}, R2 = {{ 1, 2}, {3}}, R3 = {{ 1, 3}.

4、

P Q R P→(P∧Q)

F F F T

F F T T

F T F T

F T T T

T F F F

Pass, pass, pass.

T T F F

T T T T

5. In the predicate formula, if all quantifiers appear in front of the formula and their scope is the whole formula, the formula is called toe-in paradigm.