| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ndmaov.1 | ⊢ dom  𝐹  =  ( 𝑆  ×  𝑆 ) | 
						
							| 2 | 1 | eleq2i | ⊢ ( 〈  (( 𝐴 𝐹 𝐵 ))  ,  𝐶 〉  ∈  dom  𝐹  ↔  〈  (( 𝐴 𝐹 𝐵 ))  ,  𝐶 〉  ∈  ( 𝑆  ×  𝑆 ) ) | 
						
							| 3 |  | opelxp | ⊢ ( 〈  (( 𝐴 𝐹 𝐵 ))  ,  𝐶 〉  ∈  ( 𝑆  ×  𝑆 )  ↔  (  (( 𝐴 𝐹 𝐵 ))   ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 4 | 2 3 | bitri | ⊢ ( 〈  (( 𝐴 𝐹 𝐵 ))  ,  𝐶 〉  ∈  dom  𝐹  ↔  (  (( 𝐴 𝐹 𝐵 ))   ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 5 |  | aovvdm | ⊢ (  (( 𝐴 𝐹 𝐵 ))   ∈  𝑆  →  〈 𝐴 ,  𝐵 〉  ∈  dom  𝐹 ) | 
						
							| 6 | 1 | eleq2i | ⊢ ( 〈 𝐴 ,  𝐵 〉  ∈  dom  𝐹  ↔  〈 𝐴 ,  𝐵 〉  ∈  ( 𝑆  ×  𝑆 ) ) | 
						
							| 7 |  | opelxp | ⊢ ( 〈 𝐴 ,  𝐵 〉  ∈  ( 𝑆  ×  𝑆 )  ↔  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆 ) ) | 
						
							| 8 | 6 7 | bitri | ⊢ ( 〈 𝐴 ,  𝐵 〉  ∈  dom  𝐹  ↔  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆 ) ) | 
						
							| 9 |  | df-3an | ⊢ ( ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 )  ↔  ( ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆 )  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 10 | 9 | simplbi2 | ⊢ ( ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆 )  →  ( 𝐶  ∈  𝑆  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) | 
						
							| 11 | 8 10 | sylbi | ⊢ ( 〈 𝐴 ,  𝐵 〉  ∈  dom  𝐹  →  ( 𝐶  ∈  𝑆  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) | 
						
							| 12 | 5 11 | syl | ⊢ (  (( 𝐴 𝐹 𝐵 ))   ∈  𝑆  →  ( 𝐶  ∈  𝑆  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) | 
						
							| 13 | 12 | imp | ⊢ ( (  (( 𝐴 𝐹 𝐵 ))   ∈  𝑆  ∧  𝐶  ∈  𝑆 )  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 14 | 4 13 | sylbi | ⊢ ( 〈  (( 𝐴 𝐹 𝐵 ))  ,  𝐶 〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 15 |  | ndmaov | ⊢ ( ¬  〈  (( 𝐴 𝐹 𝐵 ))  ,  𝐶 〉  ∈  dom  𝐹  →   ((  (( 𝐴 𝐹 𝐵 ))  𝐹 𝐶 ))   =  V ) | 
						
							| 16 | 14 15 | nsyl5 | ⊢ ( ¬  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 )  →   ((  (( 𝐴 𝐹 𝐵 ))  𝐹 𝐶 ))   =  V ) | 
						
							| 17 | 1 | eleq2i | ⊢ ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  ↔  〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  ( 𝑆  ×  𝑆 ) ) | 
						
							| 18 |  | opelxp | ⊢ ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  ( 𝑆  ×  𝑆 )  ↔  ( 𝐴  ∈  𝑆  ∧   (( 𝐵 𝐹 𝐶 ))   ∈  𝑆 ) ) | 
						
							| 19 | 17 18 | bitri | ⊢ ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  ↔  ( 𝐴  ∈  𝑆  ∧   (( 𝐵 𝐹 𝐶 ))   ∈  𝑆 ) ) | 
						
							| 20 |  | aovvdm | ⊢ (  (( 𝐵 𝐹 𝐶 ))   ∈  𝑆  →  〈 𝐵 ,  𝐶 〉  ∈  dom  𝐹 ) | 
						
							| 21 | 1 | eleq2i | ⊢ ( 〈 𝐵 ,  𝐶 〉  ∈  dom  𝐹  ↔  〈 𝐵 ,  𝐶 〉  ∈  ( 𝑆  ×  𝑆 ) ) | 
						
							| 22 |  | opelxp | ⊢ ( 〈 𝐵 ,  𝐶 〉  ∈  ( 𝑆  ×  𝑆 )  ↔  ( 𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 23 | 21 22 | bitri | ⊢ ( 〈 𝐵 ,  𝐶 〉  ∈  dom  𝐹  ↔  ( 𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 24 |  | 3anass | ⊢ ( ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 )  ↔  ( 𝐴  ∈  𝑆  ∧  ( 𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) | 
						
							| 25 | 24 | biimpri | ⊢ ( ( 𝐴  ∈  𝑆  ∧  ( 𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) )  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 26 | 25 | a1d | ⊢ ( ( 𝐴  ∈  𝑆  ∧  ( 𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) )  →  ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) | 
						
							| 27 | 26 | expcom | ⊢ ( ( 𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 )  →  ( 𝐴  ∈  𝑆  →  ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) ) | 
						
							| 28 | 23 27 | sylbi | ⊢ ( 〈 𝐵 ,  𝐶 〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  →  ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) ) | 
						
							| 29 | 20 28 | syl | ⊢ (  (( 𝐵 𝐹 𝐶 ))   ∈  𝑆  →  ( 𝐴  ∈  𝑆  →  ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) ) | 
						
							| 30 | 29 | impcom | ⊢ ( ( 𝐴  ∈  𝑆  ∧   (( 𝐵 𝐹 𝐶 ))   ∈  𝑆 )  →  ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) | 
						
							| 31 | 19 30 | sylbi | ⊢ ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) ) | 
						
							| 32 | 31 | pm2.43i | ⊢ ( 〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 ) ) | 
						
							| 33 |  | ndmaov | ⊢ ( ¬  〈 𝐴 ,   (( 𝐵 𝐹 𝐶 ))  〉  ∈  dom  𝐹  →   (( 𝐴 𝐹  (( 𝐵 𝐹 𝐶 ))  ))   =  V ) | 
						
							| 34 | 32 33 | nsyl5 | ⊢ ( ¬  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 )  →   (( 𝐴 𝐹  (( 𝐵 𝐹 𝐶 ))  ))   =  V ) | 
						
							| 35 | 16 34 | eqtr4d | ⊢ ( ¬  ( 𝐴  ∈  𝑆  ∧  𝐵  ∈  𝑆  ∧  𝐶  ∈  𝑆 )  →   ((  (( 𝐴 𝐹 𝐵 ))  𝐹 𝐶 ))   =   (( 𝐴 𝐹  (( 𝐵 𝐹 𝐶 ))  ))  ) |