| Step | Hyp | Ref | Expression | 
						
							| 1 |  | onelon | ⊢ ( ( 𝐵  ∈  On  ∧  𝐴  ∈  𝐵 )  →  𝐴  ∈  On ) | 
						
							| 2 | 1 | ex | ⊢ ( 𝐵  ∈  On  →  ( 𝐴  ∈  𝐵  →  𝐴  ∈  On ) ) | 
						
							| 3 | 2 | adantr | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  𝐴  ∈  On ) ) | 
						
							| 4 |  | oewordri | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ↑o  𝐶 )  ⊆  ( 𝐵  ↑o  𝐶 ) ) ) | 
						
							| 5 | 4 | 3adant1 | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ↑o  𝐶 )  ⊆  ( 𝐵  ↑o  𝐶 ) ) ) | 
						
							| 6 |  | oecl | ⊢ ( ( 𝐴  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ↑o  𝐶 )  ∈  On ) | 
						
							| 7 | 6 | 3adant2 | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ↑o  𝐶 )  ∈  On ) | 
						
							| 8 |  | oecl | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐵  ↑o  𝐶 )  ∈  On ) | 
						
							| 9 | 8 | 3adant1 | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐵  ↑o  𝐶 )  ∈  On ) | 
						
							| 10 |  | simp1 | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  𝐴  ∈  On ) | 
						
							| 11 |  | omwordri | ⊢ ( ( ( 𝐴  ↑o  𝐶 )  ∈  On  ∧  ( 𝐵  ↑o  𝐶 )  ∈  On  ∧  𝐴  ∈  On )  →  ( ( 𝐴  ↑o  𝐶 )  ⊆  ( 𝐵  ↑o  𝐶 )  →  ( ( 𝐴  ↑o  𝐶 )  ·o  𝐴 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 ) ) ) | 
						
							| 12 | 7 9 10 11 | syl3anc | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( ( 𝐴  ↑o  𝐶 )  ⊆  ( 𝐵  ↑o  𝐶 )  →  ( ( 𝐴  ↑o  𝐶 )  ·o  𝐴 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 ) ) ) | 
						
							| 13 | 5 12 | syld | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐴  ↑o  𝐶 )  ·o  𝐴 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 ) ) ) | 
						
							| 14 |  | oesuc | ⊢ ( ( 𝐴  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ↑o  suc  𝐶 )  =  ( ( 𝐴  ↑o  𝐶 )  ·o  𝐴 ) ) | 
						
							| 15 | 14 | 3adant2 | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ↑o  suc  𝐶 )  =  ( ( 𝐴  ↑o  𝐶 )  ·o  𝐴 ) ) | 
						
							| 16 | 15 | sseq1d | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ↔  ( ( 𝐴  ↑o  𝐶 )  ·o  𝐴 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 ) ) ) | 
						
							| 17 | 13 16 | sylibrd | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 ) ) ) | 
						
							| 18 |  | ne0i | ⊢ ( 𝐴  ∈  𝐵  →  𝐵  ≠  ∅ ) | 
						
							| 19 |  | on0eln0 | ⊢ ( 𝐵  ∈  On  →  ( ∅  ∈  𝐵  ↔  𝐵  ≠  ∅ ) ) | 
						
							| 20 | 18 19 | imbitrrid | ⊢ ( 𝐵  ∈  On  →  ( 𝐴  ∈  𝐵  →  ∅  ∈  𝐵 ) ) | 
						
							| 21 | 20 | adantr | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ∅  ∈  𝐵 ) ) | 
						
							| 22 |  | oen0 | ⊢ ( ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  ∧  ∅  ∈  𝐵 )  →  ∅  ∈  ( 𝐵  ↑o  𝐶 ) ) | 
						
							| 23 | 22 | ex | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( ∅  ∈  𝐵  →  ∅  ∈  ( 𝐵  ↑o  𝐶 ) ) ) | 
						
							| 24 | 21 23 | syld | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ∅  ∈  ( 𝐵  ↑o  𝐶 ) ) ) | 
						
							| 25 |  | omordi | ⊢ ( ( ( 𝐵  ∈  On  ∧  ( 𝐵  ↑o  𝐶 )  ∈  On )  ∧  ∅  ∈  ( 𝐵  ↑o  𝐶 ) )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) ) | 
						
							| 26 | 8 25 | syldanl | ⊢ ( ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  ∧  ∅  ∈  ( 𝐵  ↑o  𝐶 ) )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) ) | 
						
							| 27 | 26 | ex | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( ∅  ∈  ( 𝐵  ↑o  𝐶 )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) ) ) | 
						
							| 28 | 27 | com23 | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( ∅  ∈  ( 𝐵  ↑o  𝐶 )  →  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) ) ) | 
						
							| 29 | 24 28 | mpdd | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) ) | 
						
							| 30 | 29 | 3adant1 | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) ) | 
						
							| 31 |  | oesuc | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐵  ↑o  suc  𝐶 )  =  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) | 
						
							| 32 | 31 | 3adant1 | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐵  ↑o  suc  𝐶 )  =  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) | 
						
							| 33 | 32 | eleq2d | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 )  ↔  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐵 ) ) ) | 
						
							| 34 | 30 33 | sylibrd | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) | 
						
							| 35 | 17 34 | jcad | ⊢ ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∧  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) ) | 
						
							| 36 | 35 | 3expa | ⊢ ( ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∧  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) ) | 
						
							| 37 |  | onsucb | ⊢ ( 𝐶  ∈  On  ↔  suc  𝐶  ∈  On ) | 
						
							| 38 |  | oecl | ⊢ ( ( 𝐴  ∈  On  ∧  suc  𝐶  ∈  On )  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  On ) | 
						
							| 39 |  | oecl | ⊢ ( ( 𝐵  ∈  On  ∧  suc  𝐶  ∈  On )  →  ( 𝐵  ↑o  suc  𝐶 )  ∈  On ) | 
						
							| 40 |  | ontr2 | ⊢ ( ( ( 𝐴  ↑o  suc  𝐶 )  ∈  On  ∧  ( 𝐵  ↑o  suc  𝐶 )  ∈  On )  →  ( ( ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∧  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) )  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) | 
						
							| 41 | 38 39 40 | syl2an | ⊢ ( ( ( 𝐴  ∈  On  ∧  suc  𝐶  ∈  On )  ∧  ( 𝐵  ∈  On  ∧  suc  𝐶  ∈  On ) )  →  ( ( ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∧  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) )  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) | 
						
							| 42 | 41 | anandirs | ⊢ ( ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  ∧  suc  𝐶  ∈  On )  →  ( ( ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∧  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) )  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) | 
						
							| 43 | 37 42 | sylan2b | ⊢ ( ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  ∧  𝐶  ∈  On )  →  ( ( ( 𝐴  ↑o  suc  𝐶 )  ⊆  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∧  ( ( 𝐵  ↑o  𝐶 )  ·o  𝐴 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) )  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) | 
						
							| 44 | 36 43 | syld | ⊢ ( ( ( 𝐴  ∈  On  ∧  𝐵  ∈  On )  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) | 
						
							| 45 | 44 | exp31 | ⊢ ( 𝐴  ∈  On  →  ( 𝐵  ∈  On  →  ( 𝐶  ∈  On  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) ) ) | 
						
							| 46 | 45 | com4l | ⊢ ( 𝐵  ∈  On  →  ( 𝐶  ∈  On  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ∈  On  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) ) ) | 
						
							| 47 | 46 | imp | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ∈  On  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) ) | 
						
							| 48 | 3 47 | mpdd | ⊢ ( ( 𝐵  ∈  On  ∧  𝐶  ∈  On )  →  ( 𝐴  ∈  𝐵  →  ( 𝐴  ↑o  suc  𝐶 )  ∈  ( 𝐵  ↑o  suc  𝐶 ) ) ) |