| Step | Hyp | Ref | Expression | 
						
							| 1 |  | oveq2 | ⊢ ( 𝑥  =  ∅  →  ( 𝐴  +o  𝑥 )  =  ( 𝐴  +o  ∅ ) ) | 
						
							| 2 |  | oveq2 | ⊢ ( 𝑥  =  ∅  →  ( 𝐵  +o  𝑥 )  =  ( 𝐵  +o  ∅ ) ) | 
						
							| 3 | 1 2 | sseq12d | ⊢ ( 𝑥  =  ∅  →  ( ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 )  ↔  ( 𝐴  +o  ∅ )  ⊆  ( 𝐵  +o  ∅ ) ) ) | 
						
							| 4 | 3 | imbi2d | ⊢ ( 𝑥  =  ∅  →  ( ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) )  ↔  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  ∅ )  ⊆  ( 𝐵  +o  ∅ ) ) ) ) | 
						
							| 5 | 4 | imbi2d | ⊢ ( 𝑥  =  ∅  →  ( ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) ) )  ↔  ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  ∅ )  ⊆  ( 𝐵  +o  ∅ ) ) ) ) ) | 
						
							| 6 |  | oveq2 | ⊢ ( 𝑥  =  𝑦  →  ( 𝐴  +o  𝑥 )  =  ( 𝐴  +o  𝑦 ) ) | 
						
							| 7 |  | oveq2 | ⊢ ( 𝑥  =  𝑦  →  ( 𝐵  +o  𝑥 )  =  ( 𝐵  +o  𝑦 ) ) | 
						
							| 8 | 6 7 | sseq12d | ⊢ ( 𝑥  =  𝑦  →  ( ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 )  ↔  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) ) ) | 
						
							| 9 | 8 | imbi2d | ⊢ ( 𝑥  =  𝑦  →  ( ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) )  ↔  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) ) ) ) | 
						
							| 10 | 9 | imbi2d | ⊢ ( 𝑥  =  𝑦  →  ( ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) ) )  ↔  ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) ) ) ) ) | 
						
							| 11 |  | oveq2 | ⊢ ( 𝑥  =  suc  𝑦  →  ( 𝐴  +o  𝑥 )  =  ( 𝐴  +o  suc  𝑦 ) ) | 
						
							| 12 |  | oveq2 | ⊢ ( 𝑥  =  suc  𝑦  →  ( 𝐵  +o  𝑥 )  =  ( 𝐵  +o  suc  𝑦 ) ) | 
						
							| 13 | 11 12 | sseq12d | ⊢ ( 𝑥  =  suc  𝑦  →  ( ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 )  ↔  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) ) | 
						
							| 14 | 13 | imbi2d | ⊢ ( 𝑥  =  suc  𝑦  →  ( ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) )  ↔  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) ) ) | 
						
							| 15 | 14 | imbi2d | ⊢ ( 𝑥  =  suc  𝑦  →  ( ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) ) )  ↔  ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) ) ) ) | 
						
							| 16 |  | oveq2 | ⊢ ( 𝑥  =  𝐶  →  ( 𝐴  +o  𝑥 )  =  ( 𝐴  +o  𝐶 ) ) | 
						
							| 17 |  | oveq2 | ⊢ ( 𝑥  =  𝐶  →  ( 𝐵  +o  𝑥 )  =  ( 𝐵  +o  𝐶 ) ) | 
						
							| 18 | 16 17 | sseq12d | ⊢ ( 𝑥  =  𝐶  →  ( ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 )  ↔  ( 𝐴  +o  𝐶 )  ⊆  ( 𝐵  +o  𝐶 ) ) ) | 
						
							| 19 | 18 | imbi2d | ⊢ ( 𝑥  =  𝐶  →  ( ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) )  ↔  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝐶 )  ⊆  ( 𝐵  +o  𝐶 ) ) ) ) | 
						
							| 20 | 19 | imbi2d | ⊢ ( 𝑥  =  𝐶  →  ( ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑥 )  ⊆  ( 𝐵  +o  𝑥 ) ) )  ↔  ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝐶 )  ⊆  ( 𝐵  +o  𝐶 ) ) ) ) ) | 
						
							| 21 |  | nnon | ⊢ ( 𝐴  ∈  ω  →  𝐴  ∈  On ) | 
						
							| 22 |  | nnon | ⊢ ( 𝐵  ∈  ω  →  𝐵  ∈  On ) | 
						
							| 23 |  | oa0 | ⊢ ( 𝐴  ∈  On  →  ( 𝐴  +o  ∅ )  =  𝐴 ) | 
						
							| 24 | 23 | adantr | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  →  ( 𝐴  +o  ∅ )  =  𝐴 ) | 
						
							| 25 |  | oa0 | ⊢ ( 𝐵  ∈  On  →  ( 𝐵  +o  ∅ )  =  𝐵 ) | 
						
							| 26 | 25 | adantl | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  →  ( 𝐵  +o  ∅ )  =  𝐵 ) | 
						
							| 27 | 24 26 | sseq12d | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  →  ( ( 𝐴  +o  ∅ )  ⊆  ( 𝐵  +o  ∅ )  ↔  𝐴  ⊆  𝐵 ) ) | 
						
							| 28 | 27 | biimprd | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  ∅ )  ⊆  ( 𝐵  +o  ∅ ) ) ) | 
						
							| 29 | 21 22 28 | syl2an | ⊢ ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  ∅ )  ⊆  ( 𝐵  +o  ∅ ) ) ) | 
						
							| 30 |  | nnacl | ⊢ ( ( 𝐴  ∈  ω  ∧  𝑦  ∈  ω )  →  ( 𝐴  +o  𝑦 )  ∈  ω ) | 
						
							| 31 | 30 | ancoms | ⊢ ( ( 𝑦  ∈  ω  ∧  𝐴  ∈  ω )  →  ( 𝐴  +o  𝑦 )  ∈  ω ) | 
						
							| 32 | 31 | adantrr | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( 𝐴  +o  𝑦 )  ∈  ω ) | 
						
							| 33 |  | nnon | ⊢ ( ( 𝐴  +o  𝑦 )  ∈  ω  →  ( 𝐴  +o  𝑦 )  ∈  On ) | 
						
							| 34 |  | eloni | ⊢ ( ( 𝐴  +o  𝑦 )  ∈  On  →  Ord  ( 𝐴  +o  𝑦 ) ) | 
						
							| 35 | 32 33 34 | 3syl | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  Ord  ( 𝐴  +o  𝑦 ) ) | 
						
							| 36 |  | nnacl | ⊢ ( ( 𝐵  ∈  ω  ∧  𝑦  ∈  ω )  →  ( 𝐵  +o  𝑦 )  ∈  ω ) | 
						
							| 37 | 36 | ancoms | ⊢ ( ( 𝑦  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐵  +o  𝑦 )  ∈  ω ) | 
						
							| 38 | 37 | adantrl | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( 𝐵  +o  𝑦 )  ∈  ω ) | 
						
							| 39 |  | nnon | ⊢ ( ( 𝐵  +o  𝑦 )  ∈  ω  →  ( 𝐵  +o  𝑦 )  ∈  On ) | 
						
							| 40 |  | eloni | ⊢ ( ( 𝐵  +o  𝑦 )  ∈  On  →  Ord  ( 𝐵  +o  𝑦 ) ) | 
						
							| 41 | 38 39 40 | 3syl | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  Ord  ( 𝐵  +o  𝑦 ) ) | 
						
							| 42 |  | ordsucsssuc | ⊢ ( ( Ord  ( 𝐴  +o  𝑦 )  ∧  Ord  ( 𝐵  +o  𝑦 ) )  →  ( ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 )  ↔  suc  ( 𝐴  +o  𝑦 )  ⊆  suc  ( 𝐵  +o  𝑦 ) ) ) | 
						
							| 43 | 35 41 42 | syl2anc | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 )  ↔  suc  ( 𝐴  +o  𝑦 )  ⊆  suc  ( 𝐵  +o  𝑦 ) ) ) | 
						
							| 44 | 43 | biimpa | ⊢ ( ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  ∧  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) )  →  suc  ( 𝐴  +o  𝑦 )  ⊆  suc  ( 𝐵  +o  𝑦 ) ) | 
						
							| 45 |  | nnasuc | ⊢ ( ( 𝐴  ∈  ω  ∧  𝑦  ∈  ω )  →  ( 𝐴  +o  suc  𝑦 )  =  suc  ( 𝐴  +o  𝑦 ) ) | 
						
							| 46 | 45 | ancoms | ⊢ ( ( 𝑦  ∈  ω  ∧  𝐴  ∈  ω )  →  ( 𝐴  +o  suc  𝑦 )  =  suc  ( 𝐴  +o  𝑦 ) ) | 
						
							| 47 | 46 | adantrr | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( 𝐴  +o  suc  𝑦 )  =  suc  ( 𝐴  +o  𝑦 ) ) | 
						
							| 48 |  | nnasuc | ⊢ ( ( 𝐵  ∈  ω  ∧  𝑦  ∈  ω )  →  ( 𝐵  +o  suc  𝑦 )  =  suc  ( 𝐵  +o  𝑦 ) ) | 
						
							| 49 | 48 | ancoms | ⊢ ( ( 𝑦  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐵  +o  suc  𝑦 )  =  suc  ( 𝐵  +o  𝑦 ) ) | 
						
							| 50 | 49 | adantrl | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( 𝐵  +o  suc  𝑦 )  =  suc  ( 𝐵  +o  𝑦 ) ) | 
						
							| 51 | 47 50 | sseq12d | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 )  ↔  suc  ( 𝐴  +o  𝑦 )  ⊆  suc  ( 𝐵  +o  𝑦 ) ) ) | 
						
							| 52 | 51 | adantr | ⊢ ( ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  ∧  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) )  →  ( ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 )  ↔  suc  ( 𝐴  +o  𝑦 )  ⊆  suc  ( 𝐵  +o  𝑦 ) ) ) | 
						
							| 53 | 44 52 | mpbird | ⊢ ( ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  ∧  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) )  →  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) | 
						
							| 54 | 53 | ex | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 )  →  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) ) | 
						
							| 55 | 54 | imim2d | ⊢ ( ( 𝑦  ∈  ω  ∧  ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω ) )  →  ( ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) ) ) | 
						
							| 56 | 55 | ex | ⊢ ( 𝑦  ∈  ω  →  ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) ) ) ) | 
						
							| 57 | 56 | a2d | ⊢ ( 𝑦  ∈  ω  →  ( ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝑦 )  ⊆  ( 𝐵  +o  𝑦 ) ) )  →  ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  suc  𝑦 )  ⊆  ( 𝐵  +o  suc  𝑦 ) ) ) ) ) | 
						
							| 58 | 5 10 15 20 29 57 | finds | ⊢ ( 𝐶  ∈  ω  →  ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝐶 )  ⊆  ( 𝐵  +o  𝐶 ) ) ) ) | 
						
							| 59 | 58 | com12 | ⊢ ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω )  →  ( 𝐶  ∈  ω  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝐶 )  ⊆  ( 𝐵  +o  𝐶 ) ) ) ) | 
						
							| 60 | 59 | 3impia | ⊢ ( ( 𝐴  ∈  ω  ∧  𝐵  ∈  ω  ∧  𝐶  ∈  ω )  →  ( 𝐴  ⊆  𝐵  →  ( 𝐴  +o  𝐶 )  ⊆  ( 𝐵  +o  𝐶 ) ) ) |