Theorem orsird 38055

Description: A lemma for not-or-not elimination, in deduction form. (Contributed by Giovanni Mascellani, 15-Sep-2017.)

Hypothesis

Ref	Expression
orsird.1	⊢ (𝜑 → ¬ (𝜓 ∨ 𝜒))

Assertion

Ref	Expression
orsird	⊢ (𝜑 → ¬ 𝜒)

Proof of Theorem orsird

Step	Hyp	Ref	Expression
1		orsird.1	. . 3 ⊢ (𝜑 → ¬ (𝜓 ∨ 𝜒))
2		ioran 985	. . 3 ⊢ (¬ (𝜓 ∨ 𝜒) ↔ (¬ 𝜓 ∧ ¬ 𝜒))
3	1, 2	sylib 218	. 2 ⊢ (𝜑 → (¬ 𝜓 ∧ ¬ 𝜒))
4	3	simprd 495	1 ⊢ (𝜑 → ¬ 𝜒)

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 395   ∨ wo 847

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 848

This theorem is referenced by: (None)