Theorem 19.17 1861

Description: Theorem 19.17 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)

Hypothesis

Ref	Expression
19.17.1	⊢ Ⅎxψ

Assertion

Ref	Expression
19.17	⊢ (∀x(φ ↔ ψ) → (∀xφ ↔ ψ))

Proof of Theorem 19.17

Step	Hyp	Ref	Expression
1		albi 1564	. 2 ⊢ (∀x(φ ↔ ψ) → (∀xφ ↔ ∀xψ))
2		19.17.1	. . 3 ⊢ Ⅎxψ
3	2	19.3 1785	. 2 ⊢ (∀xψ ↔ ψ)
4	1, 3	syl6bb 252	1 ⊢ (∀x(φ ↔ ψ) → (∀xφ ↔ ψ))

Syntax hints:   → wi 4   ↔ wb 176  ∀wal 1540  Ⅎwnf 1544

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-11 1746

This theorem depends on definitions:  df-bi 177  df-ex 1542  df-nf 1545

This theorem is referenced by: (None)