Theorem exintrbi 1686

Description: Add/remove a conjunct in the scope of an existential quantifier. (Contributed by Raph Levien, 3-Jul-2006.)

Assertion

Ref	Expression
exintrbi	⊢ (∀𝑥(𝜑 → 𝜓) → (∃𝑥𝜑 ↔ ∃𝑥(𝜑 ∧ 𝜓)))

Proof of Theorem exintrbi

Step	Hyp	Ref	Expression
1		pm4.71 393	. . 3 ⊢ ((𝜑 → 𝜓) ↔ (𝜑 ↔ (𝜑 ∧ 𝜓)))
2	1	albii 1523	. 2 ⊢ (∀𝑥(𝜑 → 𝜓) ↔ ∀𝑥(𝜑 ↔ (𝜑 ∧ 𝜓)))
3		exbi 1657	. 2 ⊢ (∀𝑥(𝜑 ↔ (𝜑 ∧ 𝜓)) → (∃𝑥𝜑 ↔ ∃𝑥(𝜑 ∧ 𝜓)))
4	2, 3	sylbi 121	1 ⊢ (∀𝑥(𝜑 → 𝜓) → (∃𝑥𝜑 ↔ ∃𝑥(𝜑 ∧ 𝜓)))

This proof depends on syntax axioms:   → wi 4   ∧ wa 104   ↔ wb 105  ∀wal 1400  ∃wex 1545

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1500  ax-gen 1502  ax-ie1 1546  ax-ie2 1547  ax-4 1563  ax-ial 1587

This proof depends on definitions:  df-bi 117

This theorem is used by:  exintr  1687