Theorem bj-df-ifc 37281

Description: Candidate definition for the conditional operator for classes. This is in line with the definition of a class as the extension of a predicate in df-clab 2739. We reprove the current df-if 4483 from it in bj-dfif 37282. (Contributed by BJ, 20-Sep-2019.) (Proof modification is discouraged.)

Assertion

Ref	Expression
bj-df-ifc	⊢ if(𝜑, 𝐴, 𝐵) = {𝑥 ∣ if-(𝜑, 𝑥 ∈ 𝐴, 𝑥 ∈ 𝐵)}

Distinct variable groups:   𝜑,𝑥   𝑥,𝐴   𝑥,𝐵

Proof of Theorem bj-df-ifc

Step	Hyp	Ref	Expression
1		df-if 4483	. 2 ⊢ if(𝜑, 𝐴, 𝐵) = {𝑥 ∣ ((𝑥 ∈ 𝐴 ∧ 𝜑) ∨ (𝑥 ∈ 𝐵 ∧ ¬ 𝜑))}
2		ancom 466	. . . . 5 ⊢ ((𝑥 ∈ 𝐴 ∧ 𝜑) ↔ (𝜑 ∧ 𝑥 ∈ 𝐴))
3		ancom 466	. . . . 5 ⊢ ((𝑥 ∈ 𝐵 ∧ ¬ 𝜑) ↔ (¬ 𝜑 ∧ 𝑥 ∈ 𝐵))
4	2, 3	orbi12i 928	. . . 4 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝜑) ∨ (𝑥 ∈ 𝐵 ∧ ¬ 𝜑)) ↔ ((𝜑 ∧ 𝑥 ∈ 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 ∈ 𝐵)))
5		df-ifp 1079	. . . 4 ⊢ (if-(𝜑, 𝑥 ∈ 𝐴, 𝑥 ∈ 𝐵) ↔ ((𝜑 ∧ 𝑥 ∈ 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 ∈ 𝐵)))
6	4, 5	bitr4i 281	. . 3 ⊢ (((𝑥 ∈ 𝐴 ∧ 𝜑) ∨ (𝑥 ∈ 𝐵 ∧ ¬ 𝜑)) ↔ if-(𝜑, 𝑥 ∈ 𝐴, 𝑥 ∈ 𝐵))
7	6	abbii 2827	. 2 ⊢ {𝑥 ∣ ((𝑥 ∈ 𝐴 ∧ 𝜑) ∨ (𝑥 ∈ 𝐵 ∧ ¬ 𝜑))} = {𝑥 ∣ if-(𝜑, 𝑥 ∈ 𝐴, 𝑥 ∈ 𝐵)}
8	1, 7	eqtri 2783	1 ⊢ if(𝜑, 𝐴, 𝐵) = {𝑥 ∣ if-(𝜑, 𝑥 ∈ 𝐴, 𝑥 ∈ 𝐵)}

This proof depends on syntax axioms:  ¬ wn 3   ∧ wa 401   ∨ wo 861  if-wif 1078   = wceq 1570   ∈ wcel 2145  {cab 2738  ifcif 4482

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-9 2155  ax-ext 2732

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-ifp 1079  df-ex 1813  df-sb 2100  df-clab 2739  df-cleq 2752  df-if 4483

This theorem is used by:  bj-dfif  37282  bj-ififc  37283