| Step | Hyp | Ref | Expression | 
						
							| 1 |  | mapsncnv.s | ⊢ 𝑆  =  { 𝑋 } | 
						
							| 2 |  | mapsncnv.b | ⊢ 𝐵  ∈  V | 
						
							| 3 |  | mapsncnv.x | ⊢ 𝑋  ∈  V | 
						
							| 4 |  | mapsnf1o3.f | ⊢ 𝐹  =  ( 𝑦  ∈  𝐵  ↦  ( 𝑆  ×  { 𝑦 } ) ) | 
						
							| 5 |  | eqid | ⊢ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) )  =  ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) | 
						
							| 6 | 1 2 3 5 | mapsnf1o2 | ⊢ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) : ( 𝐵  ↑m  𝑆 ) –1-1-onto→ 𝐵 | 
						
							| 7 |  | f1ocnv | ⊢ ( ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) : ( 𝐵  ↑m  𝑆 ) –1-1-onto→ 𝐵  →  ◡ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) : 𝐵 –1-1-onto→ ( 𝐵  ↑m  𝑆 ) ) | 
						
							| 8 | 6 7 | ax-mp | ⊢ ◡ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) : 𝐵 –1-1-onto→ ( 𝐵  ↑m  𝑆 ) | 
						
							| 9 | 1 2 3 5 | mapsncnv | ⊢ ◡ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) )  =  ( 𝑦  ∈  𝐵  ↦  ( 𝑆  ×  { 𝑦 } ) ) | 
						
							| 10 | 4 9 | eqtr4i | ⊢ 𝐹  =  ◡ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) | 
						
							| 11 |  | f1oeq1 | ⊢ ( 𝐹  =  ◡ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) )  →  ( 𝐹 : 𝐵 –1-1-onto→ ( 𝐵  ↑m  𝑆 )  ↔  ◡ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) : 𝐵 –1-1-onto→ ( 𝐵  ↑m  𝑆 ) ) ) | 
						
							| 12 | 10 11 | ax-mp | ⊢ ( 𝐹 : 𝐵 –1-1-onto→ ( 𝐵  ↑m  𝑆 )  ↔  ◡ ( 𝑥  ∈  ( 𝐵  ↑m  𝑆 )  ↦  ( 𝑥 ‘ 𝑋 ) ) : 𝐵 –1-1-onto→ ( 𝐵  ↑m  𝑆 ) ) | 
						
							| 13 | 8 12 | mpbir | ⊢ 𝐹 : 𝐵 –1-1-onto→ ( 𝐵  ↑m  𝑆 ) |