Theorem bnj1101 35415

Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011.) (New usage is discouraged.)

Hypotheses

Ref	Expression
bnj1101.1	⊢ ∃𝑥(𝜑 → 𝜓)
bnj1101.2	⊢ (𝜒 → 𝜑)

Assertion

Ref	Expression
bnj1101	⊢ ∃𝑥(𝜒 → 𝜓)

Proof of Theorem bnj1101

Step	Hyp	Ref	Expression
1		bnj1101.1	. . 3 ⊢ ∃𝑥(𝜑 → 𝜓)
2		pm3.42 499	. . 3 ⊢ ((𝜑 → 𝜓) → ((𝜒 ∧ 𝜑) → 𝜓))
3	1, 2	bnj101 35354	. 2 ⊢ ∃𝑥((𝜒 ∧ 𝜑) → 𝜓)
4		bnj1101.2	. . . . 5 ⊢ (𝜒 → 𝜑)
5	4	pm4.71i 569	. . . 4 ⊢ (𝜒 ↔ (𝜒 ∧ 𝜑))
6	5	imbi1i 352	. . 3 ⊢ ((𝜒 → 𝜓) ↔ ((𝜒 ∧ 𝜑) → 𝜓))
7	6	exbii 1880	. 2 ⊢ (∃𝑥(𝜒 → 𝜓) ↔ ∃𝑥((𝜒 ∧ 𝜑) → 𝜓))
8	3, 7	mpbir 234	1 ⊢ ∃𝑥(𝜒 → 𝜓)

This proof depends on syntax axioms:   → wi 4   ∧ wa 401  ∃wex 1811

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1827  ax-4 1841

This proof depends on definitions:  df-bi 210  df-an 402  df-ex 1812

This theorem is used by:  bnj1110  35612  bnj1128  35620  bnj1145  35623