Theorem bj-nnfe1 37469

Description: See nfe1 2188. (Contributed by BJ, 12-Aug-2023.) (Proof modification is discouraged.)

Assertion

Ref	Expression
bj-nnfe1	⊢ Ⅎ'𝑥∃𝑥𝜑

Proof of Theorem bj-nnfe1

Step	Hyp	Ref	Expression
1		bj-modal4e 37401	. 2 ⊢ (∃𝑥∃𝑥𝜑 → ∃𝑥𝜑)
2		hbe1 2181	. 2 ⊢ (∃𝑥𝜑 → ∀𝑥∃𝑥𝜑)
3		df-bj-nnf 37411	. 2 ⊢ (Ⅎ'𝑥∃𝑥𝜑 ↔ ((∃𝑥∃𝑥𝜑 → ∃𝑥𝜑) ∧ (∃𝑥𝜑 → ∀𝑥∃𝑥𝜑)))
4	1, 2, 3	mpbir2an 724	1 ⊢ Ⅎ'𝑥∃𝑥𝜑

This proof depends on syntax axioms:   → wi 4  ∀wal 1568  ∃wex 1812  Ⅎ'wnnf 37410

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-10 2179  ax-12 2216

This proof depends on definitions:  df-bi 210  df-an 402  df-ex 1813  df-bj-nnf 37411

This theorem is used by: (None)