Theorem monsect 17788

Description: If 𝐹 is a monomorphism and 𝐺 is a section of 𝐹, then 𝐺 is an inverse of 𝐹 and they are both isomorphisms. This is also stated as "a monomorphism which is also a split epimorphism is an isomorphism". (Contributed by Mario Carneiro, 3-Jan-2017.)

Hypotheses

Ref	Expression
sectmon.b	⊢ 𝐵 = (Base‘𝐶)
sectmon.m	⊢ 𝑀 = (Mono‘𝐶)
sectmon.s	⊢ 𝑆 = (Sect‘𝐶)
sectmon.c	⊢ (𝜑 → 𝐶 ∈ Cat)
sectmon.x	⊢ (𝜑 → 𝑋 ∈ 𝐵)
sectmon.y	⊢ (𝜑 → 𝑌 ∈ 𝐵)
monsect.n	⊢ 𝑁 = (Inv‘𝐶)
monsect.1	⊢ (𝜑 → 𝐹 ∈ (𝑋𝑀𝑌))
monsect.2	⊢ (𝜑 → 𝐺(𝑌𝑆𝑋)𝐹)

Assertion

Ref	Expression
monsect	⊢ (𝜑 → 𝐹(𝑋𝑁𝑌)𝐺)

Proof of Theorem monsect

Step	Hyp	Ref	Expression
1		monsect.2	. . . . . . . 8 ⊢ (𝜑 → 𝐺(𝑌𝑆𝑋)𝐹)
2		sectmon.b	. . . . . . . . 9 ⊢ 𝐵 = (Base‘𝐶)
3		eqid 2752	. . . . . . . . 9 ⊢ (Hom ‘𝐶) = (Hom ‘𝐶)
4		eqid 2752	. . . . . . . . 9 ⊢ (comp‘𝐶) = (comp‘𝐶)
5		eqid 2752	. . . . . . . . 9 ⊢ (Id‘𝐶) = (Id‘𝐶)
6		sectmon.s	. . . . . . . . 9 ⊢ 𝑆 = (Sect‘𝐶)
7		sectmon.c	. . . . . . . . 9 ⊢ (𝜑 → 𝐶 ∈ Cat)
8		sectmon.y	. . . . . . . . 9 ⊢ (𝜑 → 𝑌 ∈ 𝐵)
9		sectmon.x	. . . . . . . . 9 ⊢ (𝜑 → 𝑋 ∈ 𝐵)
10	2, 3, 4, 5, 6, 7, 8, 9	issect 17758	. . . . . . . 8 ⊢ (𝜑 → (𝐺(𝑌𝑆𝑋)𝐹 ↔ (𝐺 ∈ (𝑌(Hom ‘𝐶)𝑋) ∧ 𝐹 ∈ (𝑋(Hom ‘𝐶)𝑌) ∧ (𝐹(⟨𝑌, 𝑋⟩(comp‘𝐶)𝑌)𝐺) = ((Id‘𝐶)‘𝑌))))
11	1, 10	mpbid 234	. . . . . . 7 ⊢ (𝜑 → (𝐺 ∈ (𝑌(Hom ‘𝐶)𝑋) ∧ 𝐹 ∈ (𝑋(Hom ‘𝐶)𝑌) ∧ (𝐹(⟨𝑌, 𝑋⟩(comp‘𝐶)𝑌)𝐺) = ((Id‘𝐶)‘𝑌)))
12	11	simp3d 1153	. . . . . 6 ⊢ (𝜑 → (𝐹(⟨𝑌, 𝑋⟩(comp‘𝐶)𝑌)𝐺) = ((Id‘𝐶)‘𝑌))
13	12	oveq1d 7396	. . . . 5 ⊢ (𝜑 → ((𝐹(⟨𝑌, 𝑋⟩(comp‘𝐶)𝑌)𝐺)(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑌)𝐹) = (((Id‘𝐶)‘𝑌)(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑌)𝐹))
14	11	simp2d 1152	. . . . . 6 ⊢ (𝜑 → 𝐹 ∈ (𝑋(Hom ‘𝐶)𝑌))
15	11	simp1d 1151	. . . . . 6 ⊢ (𝜑 → 𝐺 ∈ (𝑌(Hom ‘𝐶)𝑋))
16	2, 3, 4, 7, 9, 8, 9, 14, 15, 8, 14	catass 17690	. . . . 5 ⊢ (𝜑 → ((𝐹(⟨𝑌, 𝑋⟩(comp‘𝐶)𝑌)𝐺)(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑌)𝐹) = (𝐹(⟨𝑋, 𝑋⟩(comp‘𝐶)𝑌)(𝐺(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑋)𝐹)))
17	2, 3, 5, 7, 9, 4, 8, 14	catlid 17687	. . . . . 6 ⊢ (𝜑 → (((Id‘𝐶)‘𝑌)(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑌)𝐹) = 𝐹)
18	2, 3, 5, 7, 9, 4, 8, 14	catrid 17688	. . . . . 6 ⊢ (𝜑 → (𝐹(⟨𝑋, 𝑋⟩(comp‘𝐶)𝑌)((Id‘𝐶)‘𝑋)) = 𝐹)
19	17, 18	eqtr4d 2790	. . . . 5 ⊢ (𝜑 → (((Id‘𝐶)‘𝑌)(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑌)𝐹) = (𝐹(⟨𝑋, 𝑋⟩(comp‘𝐶)𝑌)((Id‘𝐶)‘𝑋)))
20	13, 16, 19	3eqtr3d 2795	. . . 4 ⊢ (𝜑 → (𝐹(⟨𝑋, 𝑋⟩(comp‘𝐶)𝑌)(𝐺(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑋)𝐹)) = (𝐹(⟨𝑋, 𝑋⟩(comp‘𝐶)𝑌)((Id‘𝐶)‘𝑋)))
21		sectmon.m	. . . . 5 ⊢ 𝑀 = (Mono‘𝐶)
22		monsect.1	. . . . 5 ⊢ (𝜑 → 𝐹 ∈ (𝑋𝑀𝑌))
23	2, 3, 4, 7, 9, 8, 9, 14, 15	catcocl 17689	. . . . 5 ⊢ (𝜑 → (𝐺(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑋)𝐹) ∈ (𝑋(Hom ‘𝐶)𝑋))
24	2, 3, 5, 7, 9	catidcl 17686	. . . . 5 ⊢ (𝜑 → ((Id‘𝐶)‘𝑋) ∈ (𝑋(Hom ‘𝐶)𝑋))
25	2, 3, 4, 21, 7, 9, 8, 9, 22, 23, 24	moni 17741	. . . 4 ⊢ (𝜑 → ((𝐹(⟨𝑋, 𝑋⟩(comp‘𝐶)𝑌)(𝐺(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑋)𝐹)) = (𝐹(⟨𝑋, 𝑋⟩(comp‘𝐶)𝑌)((Id‘𝐶)‘𝑋)) ↔ (𝐺(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑋)𝐹) = ((Id‘𝐶)‘𝑋)))
26	20, 25	mpbid 234	. . 3 ⊢ (𝜑 → (𝐺(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑋)𝐹) = ((Id‘𝐶)‘𝑋))
27	2, 3, 4, 5, 6, 7, 9, 8, 14, 15	issect2 17759	. . 3 ⊢ (𝜑 → (𝐹(𝑋𝑆𝑌)𝐺 ↔ (𝐺(⟨𝑋, 𝑌⟩(comp‘𝐶)𝑋)𝐹) = ((Id‘𝐶)‘𝑋)))
28	26, 27	mpbird 259	. 2 ⊢ (𝜑 → 𝐹(𝑋𝑆𝑌)𝐺)
29		monsect.n	. . 3 ⊢ 𝑁 = (Inv‘𝐶)
30	2, 29, 7, 9, 8, 6	isinv 17765	. 2 ⊢ (𝜑 → (𝐹(𝑋𝑁𝑌)𝐺 ↔ (𝐹(𝑋𝑆𝑌)𝐺 ∧ 𝐺(𝑌𝑆𝑋)𝐹)))
31	28, 1, 30	mpbir2and 721	1 ⊢ (𝜑 → 𝐹(𝑋𝑁𝑌)𝐺)

Syntax hints:   → wi 4   ∧ w3a 1095   = wceq 1550   ∈ wcel 2132  ⟨cop 4578   class class class wbr 5090  ‘cfv 6506  (class class class)co 7381  Basecbs 17217  Hom chom 17269  compcco 17270  Catccat 17668  Idccid 17669  Monocmon 17733  Sectcsect 17749  Invcinv 17750

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1805  ax-4 1819  ax-5 1920  ax-6 1977  ax-7 2018  ax-8 2134  ax-9 2142  ax-10 2165  ax-11 2181  ax-12 2202  ax-ext 2724  ax-rep 5217  ax-sep 5236  ax-nul 5246  ax-pow 5312  ax-pr 5380  ax-un 7703

This theorem depends on definitions:  df-bi 209  df-an 399  df-or 857  df-3an 1097  df-tru 1553  df-fal 1563  df-ex 1790  df-nf 1794  df-sb 2081  df-mo 2556  df-eu 2586  df-clab 2731  df-cleq 2744  df-clel 2827  df-nfc 2901  df-ne 2948  df-ral 3067  df-rex 3077  df-rmo 3357  df-reu 3358  df-rab 3405  df-v 3446  df-sbc 3736  df-csb 3844  df-dif 3898  df-un 3900  df-in 3902  df-ss 3912  df-nul 4277  df-if 4471  df-pw 4547  df-sn 4573  df-pr 4575  df-op 4579  df-uni 4856  df-iun 4941  df-br 5091  df-opab 5153  df-mpt 5172  df-id 5531  df-xp 5642  df-rel 5643  df-cnv 5644  df-co 5645  df-dm 5646  df-rn 5647  df-res 5648  df-ima 5649  df-iota 6462  df-fun 6508  df-fn 6509  df-f 6510  df-f1 6511  df-fo 6512  df-f1o 6513  df-fv 6514  df-riota 7338  df-ov 7384  df-oprab 7385  df-mpo 7386  df-1st 7955  df-2nd 7956  df-cat 17672  df-cid 17673  df-mon 17735  df-sect 17752  df-inv 17753

This theorem is referenced by:  episect  17790