简单性质 (1)对任意公式a和指派,a∈{0,1} (2)(3)7和(3→)的值如下表: a|0(a→6) 00 01 10 011 0 1101 与、→的真值表相同。(1) α σ, ασ ∈ {0, 1}. (2) (¬β)σ (β→γ)σ : ασ (¬ α)σ 0 1 1 0 ασ βσ (α→β)σ 0 0 1 0 1 1 1 0 0 1 1 1 ¬ ✓→ ✒ 5