Theorem cocnv1ssid 38204

Description: Characterizing when the composition of a converse with a class is included in the identity relation. The instance where the two classes are equal gives a characterization of injectivity (see df-f1 6569). (Contributed by BJ, 22-Oct-2026.)

Assertion

Ref	Expression
cocnv1ssid	⊢ ((◡𝐵 ∘ 𝐴) ⊆ I ↔ ∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑧𝐵𝑦) → 𝑥 = 𝑧))

Distinct variable groups:   𝑥,𝐴,𝑦,𝑧   𝑥,𝐵,𝑦,𝑧

Proof of Theorem cocnv1ssid

Step	Hyp	Ref	Expression
1		cocnv1ss 38203	. 2 ⊢ ((◡𝐵 ∘ 𝐴) ⊆ I ↔ ∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑧𝐵𝑦) → 𝑥 I 𝑧))
2		vex 3458	. . . . 5 ⊢ 𝑧 ∈ V
3	2	ideq 5838	. . . 4 ⊢ (𝑥 I 𝑧 ↔ 𝑥 = 𝑧)
4	3	imbi2i 339	. . 3 ⊢ (((𝑥𝐴𝑦 ∧ 𝑧𝐵𝑦) → 𝑥 I 𝑧) ↔ ((𝑥𝐴𝑦 ∧ 𝑧𝐵𝑦) → 𝑥 = 𝑧))
5	4	3albii 1854	. 2 ⊢ (∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑧𝐵𝑦) → 𝑥 I 𝑧) ↔ ∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑧𝐵𝑦) → 𝑥 = 𝑧))
6	1, 5	bitri 278	1 ⊢ ((◡𝐵 ∘ 𝐴) ⊆ I ↔ ∀𝑥∀𝑦∀𝑧((𝑥𝐴𝑦 ∧ 𝑧𝐵𝑦) → 𝑥 = 𝑧))

This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∧ wa 401  ∀wal 1568   ⊆ wss 3900   class class class wbr 5106   I cid 5550  ^◡ccnv 5655   ∘ ccom 5660

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 1945  ax-6 2002  ax-7 2043  ax-8 2149  ax-9 2157  ax-ext 2735  ax-sep 5253  ax-pr 5396

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1813  df-sb 2102  df-clab 2742  df-cleq 2755  df-clel 2839  df-ral 3081  df-rex 3091  df-rab 3417  df-v 3456  df-ss 3901  df-dif 4050  df-in 4094  df-un 4154  df-nul 4282  df-if 4486  df-sn 4589  df-pr 4591  df-op 4839  df-br 5107  df-opab 5172  df-id 5551  df-xp 5662  df-rel 5663  df-cnv 5664  df-co 5665

This theorem is used by: (None)