Theorem dfiota3 4371

Description: The ℩ operation using the if operator. (Contributed by Scott Fenton, 6-Oct-2017.)

Assertion

Ref	Expression
dfiota3	⊢ (℩xφ) = if(∃!xφ, ∪{x ∣ φ}, ∅)

Proof of Theorem dfiota3

Step	Hyp	Ref	Expression
1		iotauni 4352	. . 3 ⊢ (∃!xφ → (℩xφ) = ∪{x ∣ φ})
2		iftrue 3669	. . 3 ⊢ (∃!xφ → if(∃!xφ, ∪{x ∣ φ}, ∅) = ∪{x ∣ φ})
3	1, 2	eqtr4d 2388	. 2 ⊢ (∃!xφ → (℩xφ) = if(∃!xφ, ∪{x ∣ φ}, ∅))
4		iotanul 4355	. . 3 ⊢ (¬ ∃!xφ → (℩xφ) = ∅)
5		iffalse 3670	. . 3 ⊢ (¬ ∃!xφ → if(∃!xφ, ∪{x ∣ φ}, ∅) = ∅)
6	4, 5	eqtr4d 2388	. 2 ⊢ (¬ ∃!xφ → (℩xφ) = if(∃!xφ, ∪{x ∣ φ}, ∅))
7	3, 6	pm2.61i 156	1 ⊢ (℩xφ) = if(∃!xφ, ∪{x ∣ φ}, ∅)

Syntax hints:  ¬ wn 3   = wceq 1642  ∃!weu 2204  {cab 2339  ∅c0 3551   ifcif 3663  ∪cuni 3892  ℩cio 4338

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-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-eu 2208  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2479  df-ne 2519  df-ral 2620  df-rex 2621  df-v 2862  df-sbc 3048  df-nin 3212  df-compl 3213  df-in 3214  df-un 3215  df-dif 3216  df-ss 3260  df-nul 3552  df-if 3664  df-sn 3742  df-pr 3743  df-uni 3893  df-iota 4340

This theorem is referenced by: (None)