Theorem pm2.81 987

Description: Theorem *2.81 of [WhiteheadRussell] p. 108. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.81	⊢ ((𝜓 → (𝜒 → 𝜃)) → ((𝜑 ∨ 𝜓) → ((𝜑 ∨ 𝜒) → (𝜑 ∨ 𝜃))))

Proof of Theorem pm2.81

Step	Hyp	Ref	Expression
1		orim2 983	. 2 ⊢ ((𝜓 → (𝜒 → 𝜃)) → ((𝜑 ∨ 𝜓) → (𝜑 ∨ (𝜒 → 𝜃))))
2		pm2.76 945	. 2 ⊢ ((𝜑 ∨ (𝜒 → 𝜃)) → ((𝜑 ∨ 𝜒) → (𝜑 ∨ 𝜃)))
3	1, 2	syl6 36	1 ⊢ ((𝜓 → (𝜒 → 𝜃)) → ((𝜑 ∨ 𝜓) → ((𝜑 ∨ 𝜒) → (𝜑 ∨ 𝜃))))

This proof depends on syntax axioms:   → wi 4   ∨ wo 861

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

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862

This theorem is used by: (None)