| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ov2gf.a | ⊢ Ⅎ 𝑥 𝐴 | 
						
							| 2 |  | ov2gf.c | ⊢ Ⅎ 𝑦 𝐴 | 
						
							| 3 |  | ov2gf.d | ⊢ Ⅎ 𝑦 𝐵 | 
						
							| 4 |  | ov2gf.1 | ⊢ Ⅎ 𝑥 𝐺 | 
						
							| 5 |  | ov2gf.2 | ⊢ Ⅎ 𝑦 𝑆 | 
						
							| 6 |  | ov2gf.3 | ⊢ ( 𝑥  =  𝐴  →  𝑅  =  𝐺 ) | 
						
							| 7 |  | ov2gf.4 | ⊢ ( 𝑦  =  𝐵  →  𝐺  =  𝑆 ) | 
						
							| 8 |  | ov2gf.5 | ⊢ 𝐹  =  ( 𝑥  ∈  𝐶 ,  𝑦  ∈  𝐷  ↦  𝑅 ) | 
						
							| 9 |  | elex | ⊢ ( 𝑆  ∈  𝐻  →  𝑆  ∈  V ) | 
						
							| 10 | 4 | nfel1 | ⊢ Ⅎ 𝑥 𝐺  ∈  V | 
						
							| 11 |  | nfmpo1 | ⊢ Ⅎ 𝑥 ( 𝑥  ∈  𝐶 ,  𝑦  ∈  𝐷  ↦  𝑅 ) | 
						
							| 12 | 8 11 | nfcxfr | ⊢ Ⅎ 𝑥 𝐹 | 
						
							| 13 |  | nfcv | ⊢ Ⅎ 𝑥 𝑦 | 
						
							| 14 | 1 12 13 | nfov | ⊢ Ⅎ 𝑥 ( 𝐴 𝐹 𝑦 ) | 
						
							| 15 | 14 4 | nfeq | ⊢ Ⅎ 𝑥 ( 𝐴 𝐹 𝑦 )  =  𝐺 | 
						
							| 16 | 10 15 | nfim | ⊢ Ⅎ 𝑥 ( 𝐺  ∈  V  →  ( 𝐴 𝐹 𝑦 )  =  𝐺 ) | 
						
							| 17 | 5 | nfel1 | ⊢ Ⅎ 𝑦 𝑆  ∈  V | 
						
							| 18 |  | nfmpo2 | ⊢ Ⅎ 𝑦 ( 𝑥  ∈  𝐶 ,  𝑦  ∈  𝐷  ↦  𝑅 ) | 
						
							| 19 | 8 18 | nfcxfr | ⊢ Ⅎ 𝑦 𝐹 | 
						
							| 20 | 2 19 3 | nfov | ⊢ Ⅎ 𝑦 ( 𝐴 𝐹 𝐵 ) | 
						
							| 21 | 20 5 | nfeq | ⊢ Ⅎ 𝑦 ( 𝐴 𝐹 𝐵 )  =  𝑆 | 
						
							| 22 | 17 21 | nfim | ⊢ Ⅎ 𝑦 ( 𝑆  ∈  V  →  ( 𝐴 𝐹 𝐵 )  =  𝑆 ) | 
						
							| 23 | 6 | eleq1d | ⊢ ( 𝑥  =  𝐴  →  ( 𝑅  ∈  V  ↔  𝐺  ∈  V ) ) | 
						
							| 24 |  | oveq1 | ⊢ ( 𝑥  =  𝐴  →  ( 𝑥 𝐹 𝑦 )  =  ( 𝐴 𝐹 𝑦 ) ) | 
						
							| 25 | 24 6 | eqeq12d | ⊢ ( 𝑥  =  𝐴  →  ( ( 𝑥 𝐹 𝑦 )  =  𝑅  ↔  ( 𝐴 𝐹 𝑦 )  =  𝐺 ) ) | 
						
							| 26 | 23 25 | imbi12d | ⊢ ( 𝑥  =  𝐴  →  ( ( 𝑅  ∈  V  →  ( 𝑥 𝐹 𝑦 )  =  𝑅 )  ↔  ( 𝐺  ∈  V  →  ( 𝐴 𝐹 𝑦 )  =  𝐺 ) ) ) | 
						
							| 27 | 7 | eleq1d | ⊢ ( 𝑦  =  𝐵  →  ( 𝐺  ∈  V  ↔  𝑆  ∈  V ) ) | 
						
							| 28 |  | oveq2 | ⊢ ( 𝑦  =  𝐵  →  ( 𝐴 𝐹 𝑦 )  =  ( 𝐴 𝐹 𝐵 ) ) | 
						
							| 29 | 28 7 | eqeq12d | ⊢ ( 𝑦  =  𝐵  →  ( ( 𝐴 𝐹 𝑦 )  =  𝐺  ↔  ( 𝐴 𝐹 𝐵 )  =  𝑆 ) ) | 
						
							| 30 | 27 29 | imbi12d | ⊢ ( 𝑦  =  𝐵  →  ( ( 𝐺  ∈  V  →  ( 𝐴 𝐹 𝑦 )  =  𝐺 )  ↔  ( 𝑆  ∈  V  →  ( 𝐴 𝐹 𝐵 )  =  𝑆 ) ) ) | 
						
							| 31 | 8 | ovmpt4g | ⊢ ( ( 𝑥  ∈  𝐶  ∧  𝑦  ∈  𝐷  ∧  𝑅  ∈  V )  →  ( 𝑥 𝐹 𝑦 )  =  𝑅 ) | 
						
							| 32 | 31 | 3expia | ⊢ ( ( 𝑥  ∈  𝐶  ∧  𝑦  ∈  𝐷 )  →  ( 𝑅  ∈  V  →  ( 𝑥 𝐹 𝑦 )  =  𝑅 ) ) | 
						
							| 33 | 1 2 3 16 22 26 30 32 | vtocl2gaf | ⊢ ( ( 𝐴  ∈  𝐶  ∧  𝐵  ∈  𝐷 )  →  ( 𝑆  ∈  V  →  ( 𝐴 𝐹 𝐵 )  =  𝑆 ) ) | 
						
							| 34 | 9 33 | syl5 | ⊢ ( ( 𝐴  ∈  𝐶  ∧  𝐵  ∈  𝐷 )  →  ( 𝑆  ∈  𝐻  →  ( 𝐴 𝐹 𝐵 )  =  𝑆 ) ) | 
						
							| 35 | 34 | 3impia | ⊢ ( ( 𝐴  ∈  𝐶  ∧  𝐵  ∈  𝐷  ∧  𝑆  ∈  𝐻 )  →  ( 𝐴 𝐹 𝐵 )  =  𝑆 ) |