Theorem subtr2 36543

Description: Transitivity of implicit substitution into a wff. (Contributed by Jeff Hankins, 19-Sep-2009.) (Proof shortened by Mario Carneiro, 11-Dec-2016.)

Hypotheses

Ref	Expression
subtr.1	⊢ Ⅎ𝑥𝐴
subtr.2	⊢ Ⅎ𝑥𝐵
subtr2.3	⊢ Ⅎ𝑥𝜓
subtr2.4	⊢ Ⅎ𝑥𝜒
subtr2.5	⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓))
subtr2.6	⊢ (𝑥 = 𝐵 → (𝜑 ↔ 𝜒))

Assertion

Ref	Expression
subtr2	⊢ ((𝐴 ∈ 𝐶 ∧ 𝐵 ∈ 𝐷) → (𝐴 = 𝐵 → (𝜓 ↔ 𝜒)))

Proof of Theorem subtr2

Step	Hyp	Ref	Expression
1		subtr.1	. . 3 ⊢ Ⅎ𝑥𝐴
2		subtr.2	. . . . 5 ⊢ Ⅎ𝑥𝐵
3	1, 2	nfeq 2914	. . . 4 ⊢ Ⅎ𝑥 𝐴 = 𝐵
4		subtr2.3	. . . . 5 ⊢ Ⅎ𝑥𝜓
5		subtr2.4	. . . . 5 ⊢ Ⅎ𝑥𝜒
6	4, 5	nfbi 1910	. . . 4 ⊢ Ⅎ𝑥(𝜓 ↔ 𝜒)
7	3, 6	nfim 1903	. . 3 ⊢ Ⅎ𝑥(𝐴 = 𝐵 → (𝜓 ↔ 𝜒))
8		eqeq1 2743	. . . 4 ⊢ (𝑥 = 𝐴 → (𝑥 = 𝐵 ↔ 𝐴 = 𝐵))
9		subtr2.5	. . . . 5 ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓))
10	9	bibi1d 344	. . . 4 ⊢ (𝑥 = 𝐴 → ((𝜑 ↔ 𝜒) ↔ (𝜓 ↔ 𝜒)))
11	8, 10	imbi12d 345	. . 3 ⊢ (𝑥 = 𝐴 → ((𝑥 = 𝐵 → (𝜑 ↔ 𝜒)) ↔ (𝐴 = 𝐵 → (𝜓 ↔ 𝜒))))
12		subtr2.6	. . 3 ⊢ (𝑥 = 𝐵 → (𝜑 ↔ 𝜒))
13	1, 7, 11, 12	vtoclgf 3513	. 2 ⊢ (𝐴 ∈ 𝐶 → (𝐴 = 𝐵 → (𝜓 ↔ 𝜒)))
14	13	adantr 481	1 ⊢ ((𝐴 ∈ 𝐶 ∧ 𝐵 ∈ 𝐷) → (𝐴 = 𝐵 → (𝜓 ↔ 𝜒)))

Syntax hints:   → wi 4   ↔ wb 207   ∧ wa 396   = wceq 1547  Ⅎwnf 1790   ∈ wcel 2119  Ⅎwnfc 2886

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1802  ax-4 1816  ax-5 1917  ax-6 1974  ax-7 2015  ax-8 2121  ax-9 2129  ax-10 2152  ax-11 2168  ax-12 2189  ax-ext 2711

This theorem depends on definitions:  df-bi 208  df-an 397  df-or 854  df-tru 1550  df-ex 1787  df-nf 1791  df-sb 2074  df-clab 2718  df-cleq 2731  df-clel 2814  df-nfc 2888  df-v 3433

This theorem is referenced by: (None)