Theorem mob2 2986

Description: Consequence of "at most one". (Contributed by NM, 2-Jan-2015.)

Hypothesis

Ref	Expression
moi2.1	⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓))

Assertion

Ref	Expression
mob2	⊢ ((𝐴 ∈ 𝐵 ∧ ∃*𝑥𝜑 ∧ 𝜑) → (𝑥 = 𝐴 ↔ 𝜓))

Distinct variable groups:   𝑥,𝐴   𝜓,𝑥

Allowed substitution hints:   𝜑(𝑥)   𝐵(𝑥)

Proof of Theorem mob2

Dummy variable 𝑦 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		simp3 1025	. . 3 ⊢ ((𝐴 ∈ 𝐵 ∧ ∃*𝑥𝜑 ∧ 𝜑) → 𝜑)
2		moi2.1	. . 3 ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜓))
3	1, 2	syl5ibcom 155	. 2 ⊢ ((𝐴 ∈ 𝐵 ∧ ∃*𝑥𝜑 ∧ 𝜑) → (𝑥 = 𝐴 → 𝜓))
4		nfs1v 1992	. . . . . . . 8 ⊢ Ⅎ𝑥[𝑦 / 𝑥]𝜑
5		sbequ12 1819	. . . . . . . 8 ⊢ (𝑥 = 𝑦 → (𝜑 ↔ [𝑦 / 𝑥]𝜑))
6	4, 5	mo4f 2140	. . . . . . 7 ⊢ (∃*𝑥𝜑 ↔ ∀𝑥∀𝑦((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))
7		sp 1559	. . . . . . 7 ⊢ (∀𝑥∀𝑦((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦) → ∀𝑦((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))
8	6, 7	sylbi 121	. . . . . 6 ⊢ (∃*𝑥𝜑 → ∀𝑦((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦))
9		nfv 1576	. . . . . . . . . 10 ⊢ Ⅎ𝑥𝜓
10	9, 2	sbhypf 2853	. . . . . . . . 9 ⊢ (𝑦 = 𝐴 → ([𝑦 / 𝑥]𝜑 ↔ 𝜓))
11	10	anbi2d 464	. . . . . . . 8 ⊢ (𝑦 = 𝐴 → ((𝜑 ∧ [𝑦 / 𝑥]𝜑) ↔ (𝜑 ∧ 𝜓)))
12		eqeq2 2241	. . . . . . . 8 ⊢ (𝑦 = 𝐴 → (𝑥 = 𝑦 ↔ 𝑥 = 𝐴))
13	11, 12	imbi12d 234	. . . . . . 7 ⊢ (𝑦 = 𝐴 → (((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦) ↔ ((𝜑 ∧ 𝜓) → 𝑥 = 𝐴)))
14	13	spcgv 2893	. . . . . 6 ⊢ (𝐴 ∈ 𝐵 → (∀𝑦((𝜑 ∧ [𝑦 / 𝑥]𝜑) → 𝑥 = 𝑦) → ((𝜑 ∧ 𝜓) → 𝑥 = 𝐴)))
15	8, 14	syl5 32	. . . . 5 ⊢ (𝐴 ∈ 𝐵 → (∃*𝑥𝜑 → ((𝜑 ∧ 𝜓) → 𝑥 = 𝐴)))
16	15	imp 124	. . . 4 ⊢ ((𝐴 ∈ 𝐵 ∧ ∃*𝑥𝜑) → ((𝜑 ∧ 𝜓) → 𝑥 = 𝐴))
17	16	expd 258	. . 3 ⊢ ((𝐴 ∈ 𝐵 ∧ ∃*𝑥𝜑) → (𝜑 → (𝜓 → 𝑥 = 𝐴)))
18	17	3impia 1226	. 2 ⊢ ((𝐴 ∈ 𝐵 ∧ ∃*𝑥𝜑 ∧ 𝜑) → (𝜓 → 𝑥 = 𝐴))
19	3, 18	impbid 129	1 ⊢ ((𝐴 ∈ 𝐵 ∧ ∃*𝑥𝜑 ∧ 𝜑) → (𝑥 = 𝐴 ↔ 𝜓))

Syntax hints:   → wi 4   ∧ wa 104   ↔ wb 105   ∧ w3a 1004  ∀wal 1395   = wceq 1397  [wsb 1810  ∃*wmo 2080   ∈ wcel 2202

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-ext 2213

This theorem depends on definitions:  df-bi 117  df-3an 1006  df-tru 1400  df-nf 1509  df-sb 1811  df-eu 2082  df-mo 2083  df-clab 2218  df-cleq 2224  df-clel 2227  df-nfc 2363  df-v 2804

This theorem is referenced by:  moi2  2987  mob  2988