| ⊢ (f ∧ g) ≡ f ∧ g | BfAndEqv |
Proof:
1 | (f ∧ g) ⊃ f | |
2 | (f ∧ g) ⊃ f | |
3 | (f ∧ g) ⊃ g | |
4 | (f ∧ g) ⊃ g | |
5 | f ⊃ (g ⊃ (f ∧ g)) | |
6 | f ⊃ (g ⊃ (f ∧ g)) | |
7 | (g ⊃ (f ∧ g)) ⊃ ( g ⊃ (f ∧ g)) | |
8 | f ∧ g ⊃ (f ∧ g) | |
9 | (f ∧ g) ≡ f ∧ g |
qed