Theorem pm4.53r 741

Description: One direction of theorem *4.53 of [WhiteheadRussell] p. 120. The converse also holds in classical logic. (Contributed by Jim Kingdon, 27-Jul-2018.)

Assertion

Ref	Expression
pm4.53r	⊢ ((¬ 𝜑 ∨ 𝜓) → ¬ (𝜑 ∧ ¬ 𝜓))

Proof of Theorem pm4.53r

Step	Hyp	Ref	Expression
1		pm4.52im 740	. 2 ⊢ ((𝜑 ∧ ¬ 𝜓) → ¬ (¬ 𝜑 ∨ 𝜓))
2	1	con2i 617	1 ⊢ ((¬ 𝜑 ∨ 𝜓) → ¬ (𝜑 ∧ ¬ 𝜓))

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 103   ∨ wo 698

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 604  ax-in2 605  ax-io 699

This theorem depends on definitions:  df-bi 116

This theorem is referenced by:  undif3ss  3383