Theorem pm2.63 763

Description: Theorem *2.63 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.63	⊢ ((φ ∨ ψ) → ((¬ φ ∨ ψ) → ψ))

Proof of Theorem pm2.63

Step	Hyp	Ref	Expression
1		pm2.53 362	. 2 ⊢ ((φ ∨ ψ) → (¬ φ → ψ))
2		idd 21	. 2 ⊢ ((φ ∨ ψ) → (ψ → ψ))
3	1, 2	jaod 369	1 ⊢ ((φ ∨ ψ) → ((¬ φ ∨ ψ) → ψ))

This proof depends on syntax axioms:  ¬ wn 3   → wi 4   ∨ wo 357

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This proof depends on definitions:  df-bi 177  df-or 359

This theorem is used by: (None)