Theorem difeq 33168

Description: Rewriting an equation with class difference, without using quantifiers. (Contributed by Thierry Arnoux, 24-Sep-2017.)

Assertion

Ref	Expression
difeq	⊢ ((𝐴 ∖ 𝐵) = 𝐶 ↔ ((𝐶 ∩ 𝐵) = ∅ ∧ (𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵)))

Proof of Theorem difeq

Step	Hyp	Ref	Expression
1		ineq1 4112	. . . 4 ⊢ ((𝐴 ∖ 𝐵) = 𝐶 → ((𝐴 ∖ 𝐵) ∩ 𝐵) = (𝐶 ∩ 𝐵))
2		disjdifr 4429	. . . 4 ⊢ ((𝐴 ∖ 𝐵) ∩ 𝐵) = ∅
3	1, 2	eqtr3di 2813	. . 3 ⊢ ((𝐴 ∖ 𝐵) = 𝐶 → (𝐶 ∩ 𝐵) = ∅)
4		uneq1 4162	. . . 4 ⊢ ((𝐴 ∖ 𝐵) = 𝐶 → ((𝐴 ∖ 𝐵) ∪ 𝐵) = (𝐶 ∪ 𝐵))
5		undif1 4432	. . . 4 ⊢ ((𝐴 ∖ 𝐵) ∪ 𝐵) = (𝐴 ∪ 𝐵)
6	4, 5	eqtr3di 2813	. . 3 ⊢ ((𝐴 ∖ 𝐵) = 𝐶 → (𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵))
7	3, 6	jca 521	. 2 ⊢ ((𝐴 ∖ 𝐵) = 𝐶 → ((𝐶 ∩ 𝐵) = ∅ ∧ (𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵)))
8		disj3 4409	. . . . 5 ⊢ ((𝐶 ∩ 𝐵) = ∅ ↔ 𝐶 = (𝐶 ∖ 𝐵))
9		eqcom 2770	. . . . 5 ⊢ (𝐶 = (𝐶 ∖ 𝐵) ↔ (𝐶 ∖ 𝐵) = 𝐶)
10	8, 9	bitri 278	. . . 4 ⊢ ((𝐶 ∩ 𝐵) = ∅ ↔ (𝐶 ∖ 𝐵) = 𝐶)
11	10	birani 509	. . 3 ⊢ (((𝐶 ∩ 𝐵) = ∅ ∧ (𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵)) → (𝐶 ∖ 𝐵) = 𝐶)
12		difeq1 4058	. . . . . 6 ⊢ ((𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵) → ((𝐶 ∪ 𝐵) ∖ 𝐵) = ((𝐴 ∪ 𝐵) ∖ 𝐵))
13		difun2 4439	. . . . . 6 ⊢ ((𝐶 ∪ 𝐵) ∖ 𝐵) = (𝐶 ∖ 𝐵)
14		difun2 4439	. . . . . 6 ⊢ ((𝐴 ∪ 𝐵) ∖ 𝐵) = (𝐴 ∖ 𝐵)
15	12, 13, 14	3eqtr3g 2821	. . . . 5 ⊢ ((𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵) → (𝐶 ∖ 𝐵) = (𝐴 ∖ 𝐵))
16	15	eqeq1d 2765	. . . 4 ⊢ ((𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵) → ((𝐶 ∖ 𝐵) = 𝐶 ↔ (𝐴 ∖ 𝐵) = 𝐶))
17	16	adantl 487	. . 3 ⊢ (((𝐶 ∩ 𝐵) = ∅ ∧ (𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵)) → ((𝐶 ∖ 𝐵) = 𝐶 ↔ (𝐴 ∖ 𝐵) = 𝐶))
18	11, 17	mpbid 235	. 2 ⊢ (((𝐶 ∩ 𝐵) = ∅ ∧ (𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵)) → (𝐴 ∖ 𝐵) = 𝐶)
19	7, 18	impbii 212	1 ⊢ ((𝐴 ∖ 𝐵) = 𝐶 ↔ ((𝐶 ∩ 𝐵) = ∅ ∧ (𝐶 ∪ 𝐵) = (𝐴 ∪ 𝐵)))

This proof depends on syntax axioms:   ↔ wb 209   ∧ wa 401   = wceq 1569   ∖ cdif 4047   ∩ cin 4091   ∪ cun 4151  ∅c0 4280

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1827  ax-4 1841  ax-5 1944  ax-6 2001  ax-7 2042  ax-8 2148  ax-9 2156  ax-ext 2735

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-tru 1572  df-fal 1582  df-ex 1812  df-sb 2101  df-clab 2742  df-cleq 2755  df-clel 2838  df-ral 3080  df-rab 3416  df-v 3455  df-ss 3900  df-dif 4049  df-in 4093  df-un 4153  df-nul 4281

This theorem is used by:  difioo  33427