| Step | Hyp | Ref | Expression | 
						
							| 1 |  | invfval.b | ⊢ 𝐵  =  ( Base ‘ 𝐶 ) | 
						
							| 2 |  | invfval.n | ⊢ 𝑁  =  ( Inv ‘ 𝐶 ) | 
						
							| 3 |  | invfval.c | ⊢ ( 𝜑  →  𝐶  ∈  Cat ) | 
						
							| 4 |  | invfval.x | ⊢ ( 𝜑  →  𝑋  ∈  𝐵 ) | 
						
							| 5 |  | invfval.y | ⊢ ( 𝜑  →  𝑌  ∈  𝐵 ) | 
						
							| 6 |  | invss.h | ⊢ 𝐻  =  ( Hom  ‘ 𝐶 ) | 
						
							| 7 |  | eqid | ⊢ ( Sect ‘ 𝐶 )  =  ( Sect ‘ 𝐶 ) | 
						
							| 8 | 1 2 3 4 5 7 | invfval | ⊢ ( 𝜑  →  ( 𝑋 𝑁 𝑌 )  =  ( ( 𝑋 ( Sect ‘ 𝐶 ) 𝑌 )  ∩  ◡ ( 𝑌 ( Sect ‘ 𝐶 ) 𝑋 ) ) ) | 
						
							| 9 |  | inss1 | ⊢ ( ( 𝑋 ( Sect ‘ 𝐶 ) 𝑌 )  ∩  ◡ ( 𝑌 ( Sect ‘ 𝐶 ) 𝑋 ) )  ⊆  ( 𝑋 ( Sect ‘ 𝐶 ) 𝑌 ) | 
						
							| 10 | 8 9 | eqsstrdi | ⊢ ( 𝜑  →  ( 𝑋 𝑁 𝑌 )  ⊆  ( 𝑋 ( Sect ‘ 𝐶 ) 𝑌 ) ) | 
						
							| 11 |  | eqid | ⊢ ( comp ‘ 𝐶 )  =  ( comp ‘ 𝐶 ) | 
						
							| 12 |  | eqid | ⊢ ( Id ‘ 𝐶 )  =  ( Id ‘ 𝐶 ) | 
						
							| 13 | 1 6 11 12 7 3 4 5 | sectss | ⊢ ( 𝜑  →  ( 𝑋 ( Sect ‘ 𝐶 ) 𝑌 )  ⊆  ( ( 𝑋 𝐻 𝑌 )  ×  ( 𝑌 𝐻 𝑋 ) ) ) | 
						
							| 14 | 10 13 | sstrd | ⊢ ( 𝜑  →  ( 𝑋 𝑁 𝑌 )  ⊆  ( ( 𝑋 𝐻 𝑌 )  ×  ( 𝑌 𝐻 𝑋 ) ) ) |