cocanss1 - Mathbox for Eric Schmidt

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Theorem cocanss1 46185

Description: Cancellation law for composition. Suggested by BJ. (Contributed by Eric Schmidt, 30-Sep-2026.)

**Hypotheses**
Ref	Expression
cocan1g.1	⊢ (𝜑 → Fun ^◡𝐹)
cocan1g.2	⊢ (𝜑 → Rel 𝐻)
cocan1g.3	⊢ (𝜑 → ran 𝐻 ⊆ dom 𝐹)

**Assertion**
Ref	Expression
cocanss1	⊢ (𝜑 → ((𝐹 ∘ 𝐻) ⊆ (𝐹 ∘ 𝐾) ↔ 𝐻 ⊆ 𝐾))

**Proof of Theorem cocanss1**
Step	Hyp	Ref	Expression
1		cocan1g.1	. . 3 ⊢ (𝜑 → Fun ^◡𝐹)
2		relcnv 6118	. . . 4 ⊢ Rel ^◡𝐻
3	2	a1i 11	. . 3 ⊢ (𝜑 → Rel ^◡𝐻)
4		cocan1g.3	. . . 4 ⊢ (𝜑 → ran 𝐻 ⊆ dom 𝐹)
5		df-rn 5669	. . . 4 ⊢ ran 𝐻 = dom ^◡𝐻
6		dfdm4 5889	. . . 4 ⊢ dom 𝐹 = ran ^◡𝐹
7	4, 5, 6	3sstr3g 3965	. . 3 ⊢ (𝜑 → dom ^◡𝐻 ⊆ ran ^◡𝐹)
8	1, 3, 7	cocanss2 46183	. 2 ⊢ (𝜑 → ((^◡𝐻 ∘ ^◡𝐹) ⊆ (^◡𝐾 ∘ ^◡𝐹) ↔ ^◡𝐻 ⊆ ^◡𝐾))
9		relco 6122	. . . . 5 ⊢ Rel (𝐹 ∘ 𝐻)
10		cnvssb 6207	. . . . 5 ⊢ (Rel (𝐹 ∘ 𝐻) → ((𝐹 ∘ 𝐻) ⊆ (𝐹 ∘ 𝐾) ↔ ^◡(𝐹 ∘ 𝐻) ⊆ ^◡(𝐹 ∘ 𝐾)))
11	9, 10	ax-mp 5	. . . 4 ⊢ ((𝐹 ∘ 𝐻) ⊆ (𝐹 ∘ 𝐾) ↔ ^◡(𝐹 ∘ 𝐻) ⊆ ^◡(𝐹 ∘ 𝐾))
12		cnvco 5879	. . . . 5 ⊢ ^◡(𝐹 ∘ 𝐻) = (^◡𝐻 ∘ ^◡𝐹)
13		cnvco 5879	. . . . 5 ⊢ ^◡(𝐹 ∘ 𝐾) = (^◡𝐾 ∘ ^◡𝐹)
14	12, 13	sseq12i 3943	. . . 4 ⊢ (^◡(𝐹 ∘ 𝐻) ⊆ ^◡(𝐹 ∘ 𝐾) ↔ (^◡𝐻 ∘ ^◡𝐹) ⊆ (^◡𝐾 ∘ ^◡𝐹))
15	11, 14	bitri 278	. . 3 ⊢ ((𝐹 ∘ 𝐻) ⊆ (𝐹 ∘ 𝐾) ↔ (^◡𝐻 ∘ ^◡𝐹) ⊆ (^◡𝐾 ∘ ^◡𝐹))
16	15	a1i 11	. 2 ⊢ (𝜑 → ((𝐹 ∘ 𝐻) ⊆ (𝐹 ∘ 𝐾) ↔ (^◡𝐻 ∘ ^◡𝐹) ⊆ (^◡𝐾 ∘ ^◡𝐹)))
17		cocan1g.2	. . 3 ⊢ (𝜑 → Rel 𝐻)
18		cnvssb 6207	. . 3 ⊢ (Rel 𝐻 → (𝐻 ⊆ 𝐾 ↔ ^◡𝐻 ⊆ ^◡𝐾))
19	17, 18	syl 18	. 2 ⊢ (𝜑 → (𝐻 ⊆ 𝐾 ↔ ^◡𝐻 ⊆ ^◡𝐾))
20	8, 16, 19	3bitr4d 314	1 ⊢ (𝜑 → ((𝐹 ∘ 𝐻) ⊆ (𝐹 ∘ 𝐾) ↔ 𝐻 ⊆ 𝐾))

Colors of variables: wff setvar class

This proof depends on syntax axioms: → wi 4 ↔ wb 209 ⊆ wss 3900 ^◡ccnv 5657 dom cdm 5658 ran crn 5659 ∘ ccom 5662 Rel wrel 5663 Fun wfun 6560

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-12 2216 ax-ext 2735 ax-sep 5255 ax-pr 5398

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 4841 df-br 5109 df-opab 5174 df-id 5553 df-xp 5664 df-rel 5665 df-cnv 5666 df-co 5667 df-dm 5668 df-rn 5669 df-res 5670 df-fun 6568

This theorem is used by: cocan1g 46186

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