Theorem iunxsnf 45058

Description: A singleton index picks out an instance of an indexed union's argument. (Contributed by Glauco Siliprandi, 17-Aug-2020.)

Hypotheses

Ref	Expression
iunxsnf.1	⊢ Ⅎ𝑥𝐶
iunxsnf.2	⊢ 𝐴 ∈ V
iunxsnf.3	⊢ (𝑥 = 𝐴 → 𝐵 = 𝐶)

Assertion

Ref	Expression
iunxsnf	⊢ ∪ 𝑥 ∈ {𝐴}𝐵 = 𝐶

Distinct variable group:   𝑥,𝐴

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

Proof of Theorem iunxsnf

Step	Hyp	Ref	Expression
1		iunxsnf.2	. 2 ⊢ 𝐴 ∈ V
2		iunxsnf.1	. . 3 ⊢ Ⅎ𝑥𝐶
3		iunxsnf.3	. . 3 ⊢ (𝑥 = 𝐴 → 𝐵 = 𝐶)
4	2, 3	iunxsngf 5056	. 2 ⊢ (𝐴 ∈ V → ∪ 𝑥 ∈ {𝐴}𝐵 = 𝐶)
5	1, 4	ax-mp 5	1 ⊢ ∪ 𝑥 ∈ {𝐴}𝐵 = 𝐶

Syntax hints:   → wi 4   = wceq 1540   ∈ wcel 2109  Ⅎwnfc 2876  Vcvv 3447  {csn 4589  ∪ ciun 4955

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1795  ax-4 1809  ax-5 1910  ax-6 1967  ax-7 2008  ax-8 2111  ax-9 2119  ax-10 2142  ax-12 2178  ax-ext 2701

This theorem depends on definitions:  df-bi 207  df-an 396  df-3an 1088  df-tru 1543  df-ex 1780  df-nf 1784  df-sb 2066  df-clab 2708  df-cleq 2721  df-clel 2803  df-nfc 2878  df-rex 3054  df-v 3449  df-sbc 3754  df-sn 4590  df-iun 4957

This theorem is referenced by:  fiiuncl  45059  iunp1  45060  sge0iunmptlemfi  46411