Theorem pimltpnf2 42998

Description: Given a real-valued function, the preimage of an open interval, unbounded below, with upper bound +∞, is the whole domain. (Contributed by Glauco Siliprandi, 26-Jun-2021.)

Hypotheses

Ref	Expression
pimltpnf2.1	⊢ Ⅎ𝑥𝐹
pimltpnf2.2	⊢ (𝜑 → 𝐹:𝐴⟶ℝ)

Assertion

Ref	Expression
pimltpnf2	⊢ (𝜑 → {𝑥 ∈ 𝐴 ∣ (𝐹‘𝑥) < +∞} = 𝐴)

Distinct variable group:   𝑥,𝐴

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

Proof of Theorem pimltpnf2

Dummy variable 𝑦 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		nfcv 2979	. . . 4 ⊢ Ⅎ𝑥𝐴
2		nfcv 2979	. . . 4 ⊢ Ⅎ𝑦𝐴
3		nfv 1915	. . . 4 ⊢ Ⅎ𝑦(𝐹‘𝑥) < +∞
4		pimltpnf2.1	. . . . . 6 ⊢ Ⅎ𝑥𝐹
5		nfcv 2979	. . . . . 6 ⊢ Ⅎ𝑥𝑦
6	4, 5	nffv 6682	. . . . 5 ⊢ Ⅎ𝑥(𝐹‘𝑦)
7		nfcv 2979	. . . . 5 ⊢ Ⅎ𝑥 <
8		nfcv 2979	. . . . 5 ⊢ Ⅎ𝑥+∞
9	6, 7, 8	nfbr 5115	. . . 4 ⊢ Ⅎ𝑥(𝐹‘𝑦) < +∞
10		fveq2 6672	. . . . 5 ⊢ (𝑥 = 𝑦 → (𝐹‘𝑥) = (𝐹‘𝑦))
11	10	breq1d 5078	. . . 4 ⊢ (𝑥 = 𝑦 → ((𝐹‘𝑥) < +∞ ↔ (𝐹‘𝑦) < +∞))
12	1, 2, 3, 9, 11	cbvrabw 3491	. . 3 ⊢ {𝑥 ∈ 𝐴 ∣ (𝐹‘𝑥) < +∞} = {𝑦 ∈ 𝐴 ∣ (𝐹‘𝑦) < +∞}
13	12	a1i 11	. 2 ⊢ (𝜑 → {𝑥 ∈ 𝐴 ∣ (𝐹‘𝑥) < +∞} = {𝑦 ∈ 𝐴 ∣ (𝐹‘𝑦) < +∞})
14		nfv 1915	. . 3 ⊢ Ⅎ𝑦𝜑
15		pimltpnf2.2	. . . 4 ⊢ (𝜑 → 𝐹:𝐴⟶ℝ)
16	15	ffvelrnda 6853	. . 3 ⊢ ((𝜑 ∧ 𝑦 ∈ 𝐴) → (𝐹‘𝑦) ∈ ℝ)
17	14, 16	pimltpnf 42991	. 2 ⊢ (𝜑 → {𝑦 ∈ 𝐴 ∣ (𝐹‘𝑦) < +∞} = 𝐴)
18	13, 17	eqtrd 2858	1 ⊢ (𝜑 → {𝑥 ∈ 𝐴 ∣ (𝐹‘𝑥) < +∞} = 𝐴)

Syntax hints:   → wi 4   = wceq 1537  Ⅎwnfc 2963  {crab 3144   class class class wbr 5068  ⟶wf 6353  ‘cfv 6357  ℝcr 10538  +∞cpnf 10674   < clt 10677

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1796  ax-4 1810  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2116  ax-9 2124  ax-10 2145  ax-11 2161  ax-12 2177  ax-ext 2795  ax-sep 5205  ax-nul 5212  ax-pow 5268  ax-pr 5332  ax-un 7463  ax-cnex 10595

This theorem depends on definitions:  df-bi 209  df-an 399  df-or 844  df-3an 1085  df-tru 1540  df-ex 1781  df-nf 1785  df-sb 2070  df-mo 2622  df-eu 2654  df-clab 2802  df-cleq 2816  df-clel 2895  df-nfc 2965  df-ral 3145  df-rex 3146  df-rab 3149  df-v 3498  df-sbc 3775  df-dif 3941  df-un 3943  df-in 3945  df-ss 3954  df-nul 4294  df-if 4470  df-pw 4543  df-sn 4570  df-pr 4572  df-op 4576  df-uni 4841  df-br 5069  df-opab 5131  df-id 5462  df-xp 5563  df-rel 5564  df-cnv 5565  df-co 5566  df-dm 5567  df-rn 5568  df-iota 6316  df-fun 6359  df-fn 6360  df-f 6361  df-fv 6365  df-pnf 10679  df-xr 10681  df-ltxr 10682

This theorem is referenced by:  smfpimltxr  43031