| Step | Hyp | Ref | Expression | 
						
							| 1 |  | sdomdom | ⊢ ( 𝐴  ≺  𝐵  →  𝐴  ≼  𝐵 ) | 
						
							| 2 |  | brdomi | ⊢ ( 𝐴  ≼  𝐵  →  ∃ 𝑓 𝑓 : 𝐴 –1-1→ 𝐵 ) | 
						
							| 3 | 1 2 | syl | ⊢ ( 𝐴  ≺  𝐵  →  ∃ 𝑓 𝑓 : 𝐴 –1-1→ 𝐵 ) | 
						
							| 4 |  | relsdom | ⊢ Rel   ≺ | 
						
							| 5 | 4 | brrelex1i | ⊢ ( 𝐴  ≺  𝐵  →  𝐴  ∈  V ) | 
						
							| 6 | 5 | adantr | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  𝐴  ∈  V ) | 
						
							| 7 |  | vex | ⊢ 𝑓  ∈  V | 
						
							| 8 | 7 | rnex | ⊢ ran  𝑓  ∈  V | 
						
							| 9 | 8 | a1i | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ran  𝑓  ∈  V ) | 
						
							| 10 |  | f1f1orn | ⊢ ( 𝑓 : 𝐴 –1-1→ 𝐵  →  𝑓 : 𝐴 –1-1-onto→ ran  𝑓 ) | 
						
							| 11 | 10 | adantl | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  𝑓 : 𝐴 –1-1-onto→ ran  𝑓 ) | 
						
							| 12 |  | f1of1 | ⊢ ( 𝑓 : 𝐴 –1-1-onto→ ran  𝑓  →  𝑓 : 𝐴 –1-1→ ran  𝑓 ) | 
						
							| 13 | 11 12 | syl | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  𝑓 : 𝐴 –1-1→ ran  𝑓 ) | 
						
							| 14 |  | f1dom2g | ⊢ ( ( 𝐴  ∈  V  ∧  ran  𝑓  ∈  V  ∧  𝑓 : 𝐴 –1-1→ ran  𝑓 )  →  𝐴  ≼  ran  𝑓 ) | 
						
							| 15 | 6 9 13 14 | syl3anc | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  𝐴  ≼  ran  𝑓 ) | 
						
							| 16 |  | sdomnen | ⊢ ( 𝐴  ≺  𝐵  →  ¬  𝐴  ≈  𝐵 ) | 
						
							| 17 | 16 | adantr | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ¬  𝐴  ≈  𝐵 ) | 
						
							| 18 |  | ssdif0 | ⊢ ( 𝐵  ⊆  ran  𝑓  ↔  ( 𝐵  ∖  ran  𝑓 )  =  ∅ ) | 
						
							| 19 |  | simplr | ⊢ ( ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  ∧  𝐵  ⊆  ran  𝑓 )  →  𝑓 : 𝐴 –1-1→ 𝐵 ) | 
						
							| 20 |  | f1f | ⊢ ( 𝑓 : 𝐴 –1-1→ 𝐵  →  𝑓 : 𝐴 ⟶ 𝐵 ) | 
						
							| 21 | 20 | frnd | ⊢ ( 𝑓 : 𝐴 –1-1→ 𝐵  →  ran  𝑓  ⊆  𝐵 ) | 
						
							| 22 | 19 21 | syl | ⊢ ( ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  ∧  𝐵  ⊆  ran  𝑓 )  →  ran  𝑓  ⊆  𝐵 ) | 
						
							| 23 |  | simpr | ⊢ ( ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  ∧  𝐵  ⊆  ran  𝑓 )  →  𝐵  ⊆  ran  𝑓 ) | 
						
							| 24 | 22 23 | eqssd | ⊢ ( ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  ∧  𝐵  ⊆  ran  𝑓 )  →  ran  𝑓  =  𝐵 ) | 
						
							| 25 |  | dff1o5 | ⊢ ( 𝑓 : 𝐴 –1-1-onto→ 𝐵  ↔  ( 𝑓 : 𝐴 –1-1→ 𝐵  ∧  ran  𝑓  =  𝐵 ) ) | 
						
							| 26 | 19 24 25 | sylanbrc | ⊢ ( ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  ∧  𝐵  ⊆  ran  𝑓 )  →  𝑓 : 𝐴 –1-1-onto→ 𝐵 ) | 
						
							| 27 |  | f1oen3g | ⊢ ( ( 𝑓  ∈  V  ∧  𝑓 : 𝐴 –1-1-onto→ 𝐵 )  →  𝐴  ≈  𝐵 ) | 
						
							| 28 | 7 26 27 | sylancr | ⊢ ( ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  ∧  𝐵  ⊆  ran  𝑓 )  →  𝐴  ≈  𝐵 ) | 
						
							| 29 | 28 | ex | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( 𝐵  ⊆  ran  𝑓  →  𝐴  ≈  𝐵 ) ) | 
						
							| 30 | 18 29 | biimtrrid | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( ( 𝐵  ∖  ran  𝑓 )  =  ∅  →  𝐴  ≈  𝐵 ) ) | 
						
							| 31 | 17 30 | mtod | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ¬  ( 𝐵  ∖  ran  𝑓 )  =  ∅ ) | 
						
							| 32 |  | neq0 | ⊢ ( ¬  ( 𝐵  ∖  ran  𝑓 )  =  ∅  ↔  ∃ 𝑤 𝑤  ∈  ( 𝐵  ∖  ran  𝑓 ) ) | 
						
							| 33 | 31 32 | sylib | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ∃ 𝑤 𝑤  ∈  ( 𝐵  ∖  ran  𝑓 ) ) | 
						
							| 34 |  | snssi | ⊢ ( 𝑤  ∈  ( 𝐵  ∖  ran  𝑓 )  →  { 𝑤 }  ⊆  ( 𝐵  ∖  ran  𝑓 ) ) | 
						
							| 35 |  | vex | ⊢ 𝑤  ∈  V | 
						
							| 36 |  | en2sn | ⊢ ( ( 𝐴  ∈  V  ∧  𝑤  ∈  V )  →  { 𝐴 }  ≈  { 𝑤 } ) | 
						
							| 37 | 6 35 36 | sylancl | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  { 𝐴 }  ≈  { 𝑤 } ) | 
						
							| 38 | 4 | brrelex2i | ⊢ ( 𝐴  ≺  𝐵  →  𝐵  ∈  V ) | 
						
							| 39 | 38 | adantr | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  𝐵  ∈  V ) | 
						
							| 40 |  | difexg | ⊢ ( 𝐵  ∈  V  →  ( 𝐵  ∖  ran  𝑓 )  ∈  V ) | 
						
							| 41 |  | ssdomg | ⊢ ( ( 𝐵  ∖  ran  𝑓 )  ∈  V  →  ( { 𝑤 }  ⊆  ( 𝐵  ∖  ran  𝑓 )  →  { 𝑤 }  ≼  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 42 | 39 40 41 | 3syl | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( { 𝑤 }  ⊆  ( 𝐵  ∖  ran  𝑓 )  →  { 𝑤 }  ≼  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 43 |  | endomtr | ⊢ ( ( { 𝐴 }  ≈  { 𝑤 }  ∧  { 𝑤 }  ≼  ( 𝐵  ∖  ran  𝑓 ) )  →  { 𝐴 }  ≼  ( 𝐵  ∖  ran  𝑓 ) ) | 
						
							| 44 | 37 42 43 | syl6an | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( { 𝑤 }  ⊆  ( 𝐵  ∖  ran  𝑓 )  →  { 𝐴 }  ≼  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 45 | 34 44 | syl5 | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( 𝑤  ∈  ( 𝐵  ∖  ran  𝑓 )  →  { 𝐴 }  ≼  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 46 | 45 | exlimdv | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( ∃ 𝑤 𝑤  ∈  ( 𝐵  ∖  ran  𝑓 )  →  { 𝐴 }  ≼  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 47 | 33 46 | mpd | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  { 𝐴 }  ≼  ( 𝐵  ∖  ran  𝑓 ) ) | 
						
							| 48 |  | disjdif | ⊢ ( ran  𝑓  ∩  ( 𝐵  ∖  ran  𝑓 ) )  =  ∅ | 
						
							| 49 | 48 | a1i | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( ran  𝑓  ∩  ( 𝐵  ∖  ran  𝑓 ) )  =  ∅ ) | 
						
							| 50 |  | undom | ⊢ ( ( ( 𝐴  ≼  ran  𝑓  ∧  { 𝐴 }  ≼  ( 𝐵  ∖  ran  𝑓 ) )  ∧  ( ran  𝑓  ∩  ( 𝐵  ∖  ran  𝑓 ) )  =  ∅ )  →  ( 𝐴  ∪  { 𝐴 } )  ≼  ( ran  𝑓  ∪  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 51 | 15 47 49 50 | syl21anc | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( 𝐴  ∪  { 𝐴 } )  ≼  ( ran  𝑓  ∪  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 52 |  | df-suc | ⊢ suc  𝐴  =  ( 𝐴  ∪  { 𝐴 } ) | 
						
							| 53 | 52 | a1i | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  suc  𝐴  =  ( 𝐴  ∪  { 𝐴 } ) ) | 
						
							| 54 |  | undif2 | ⊢ ( ran  𝑓  ∪  ( 𝐵  ∖  ran  𝑓 ) )  =  ( ran  𝑓  ∪  𝐵 ) | 
						
							| 55 | 21 | adantl | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ran  𝑓  ⊆  𝐵 ) | 
						
							| 56 |  | ssequn1 | ⊢ ( ran  𝑓  ⊆  𝐵  ↔  ( ran  𝑓  ∪  𝐵 )  =  𝐵 ) | 
						
							| 57 | 55 56 | sylib | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  ( ran  𝑓  ∪  𝐵 )  =  𝐵 ) | 
						
							| 58 | 54 57 | eqtr2id | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  𝐵  =  ( ran  𝑓  ∪  ( 𝐵  ∖  ran  𝑓 ) ) ) | 
						
							| 59 | 51 53 58 | 3brtr4d | ⊢ ( ( 𝐴  ≺  𝐵  ∧  𝑓 : 𝐴 –1-1→ 𝐵 )  →  suc  𝐴  ≼  𝐵 ) | 
						
							| 60 | 3 59 | exlimddv | ⊢ ( 𝐴  ≺  𝐵  →  suc  𝐴  ≼  𝐵 ) |