| Step | Hyp | Ref | Expression | 
						
							| 1 |  | submat1n.a | ⊢ 𝐴  =  ( ( 1 ... 𝑁 )  Mat  𝑅 ) | 
						
							| 2 |  | submat1n.b | ⊢ 𝐵  =  ( Base ‘ 𝐴 ) | 
						
							| 3 |  | fzdif2 | ⊢ ( 𝑁  ∈  ( ℤ≥ ‘ 1 )  →  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  =  ( 1 ... ( 𝑁  −  1 ) ) ) | 
						
							| 4 |  | nnuz | ⊢ ℕ  =  ( ℤ≥ ‘ 1 ) | 
						
							| 5 | 3 4 | eleq2s | ⊢ ( 𝑁  ∈  ℕ  →  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  =  ( 1 ... ( 𝑁  −  1 ) ) ) | 
						
							| 6 | 5 | adantr | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  =  ( 1 ... ( 𝑁  −  1 ) ) ) | 
						
							| 7 | 6 | adantr | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) )  →  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  =  ( 1 ... ( 𝑁  −  1 ) ) ) | 
						
							| 8 |  | eqid | ⊢ ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 )  =  ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 ) | 
						
							| 9 |  | elfz1end | ⊢ ( 𝑁  ∈  ℕ  ↔  𝑁  ∈  ( 1 ... 𝑁 ) ) | 
						
							| 10 | 9 | biimpi | ⊢ ( 𝑁  ∈  ℕ  →  𝑁  ∈  ( 1 ... 𝑁 ) ) | 
						
							| 11 | 10 | adantr | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  𝑁  ∈  ( 1 ... 𝑁 ) ) | 
						
							| 12 | 11 9 | sylibr | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  𝑁  ∈  ℕ ) | 
						
							| 13 | 12 | adantr | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  𝑁  ∈  ℕ ) | 
						
							| 14 | 13 10 | syl | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  𝑁  ∈  ( 1 ... 𝑁 ) ) | 
						
							| 15 |  | eqid | ⊢ ( Base ‘ 𝑅 )  =  ( Base ‘ 𝑅 ) | 
						
							| 16 | 1 15 2 | matbas2i | ⊢ ( 𝑀  ∈  𝐵  →  𝑀  ∈  ( ( Base ‘ 𝑅 )  ↑m  ( ( 1 ... 𝑁 )  ×  ( 1 ... 𝑁 ) ) ) ) | 
						
							| 17 | 16 | ad2antlr | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  𝑀  ∈  ( ( Base ‘ 𝑅 )  ↑m  ( ( 1 ... 𝑁 )  ×  ( 1 ... 𝑁 ) ) ) ) | 
						
							| 18 |  | simprl | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) | 
						
							| 19 |  | nnz | ⊢ ( 𝑁  ∈  ℕ  →  𝑁  ∈  ℤ ) | 
						
							| 20 |  | fzoval | ⊢ ( 𝑁  ∈  ℤ  →  ( 1 ..^ 𝑁 )  =  ( 1 ... ( 𝑁  −  1 ) ) ) | 
						
							| 21 | 19 20 | syl | ⊢ ( 𝑁  ∈  ℕ  →  ( 1 ..^ 𝑁 )  =  ( 1 ... ( 𝑁  −  1 ) ) ) | 
						
							| 22 | 21 5 | eqtr4d | ⊢ ( 𝑁  ∈  ℕ  →  ( 1 ..^ 𝑁 )  =  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) | 
						
							| 23 | 13 22 | syl | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  ( 1 ..^ 𝑁 )  =  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) | 
						
							| 24 | 18 23 | eleqtrrd | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  𝑖  ∈  ( 1 ..^ 𝑁 ) ) | 
						
							| 25 |  | simprr | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) | 
						
							| 26 | 25 23 | eleqtrrd | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  𝑗  ∈  ( 1 ..^ 𝑁 ) ) | 
						
							| 27 | 8 13 13 14 14 17 24 26 | smattl | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  ( 𝑖 ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 ) 𝑗 )  =  ( 𝑖 𝑀 𝑗 ) ) | 
						
							| 28 | 27 | eqcomd | ⊢ ( ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  ∧  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ∧  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ) )  →  ( 𝑖 𝑀 𝑗 )  =  ( 𝑖 ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 ) 𝑗 ) ) | 
						
							| 29 | 6 7 28 | mpoeq123dva | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ,  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ↦  ( 𝑖 𝑀 𝑗 ) )  =  ( 𝑖  ∈  ( 1 ... ( 𝑁  −  1 ) ) ,  𝑗  ∈  ( 1 ... ( 𝑁  −  1 ) )  ↦  ( 𝑖 ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 ) 𝑗 ) ) ) | 
						
							| 30 |  | simpr | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  𝑀  ∈  𝐵 ) | 
						
							| 31 |  | eqid | ⊢ ( ( 1 ... 𝑁 )  subMat  𝑅 )  =  ( ( 1 ... 𝑁 )  subMat  𝑅 ) | 
						
							| 32 | 1 31 2 | submaval | ⊢ ( ( 𝑀  ∈  𝐵  ∧  𝑁  ∈  ( 1 ... 𝑁 )  ∧  𝑁  ∈  ( 1 ... 𝑁 ) )  →  ( 𝑁 ( ( ( 1 ... 𝑁 )  subMat  𝑅 ) ‘ 𝑀 ) 𝑁 )  =  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ,  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ↦  ( 𝑖 𝑀 𝑗 ) ) ) | 
						
							| 33 | 30 11 11 32 | syl3anc | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  ( 𝑁 ( ( ( 1 ... 𝑁 )  subMat  𝑅 ) ‘ 𝑀 ) 𝑁 )  =  ( 𝑖  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } ) ,  𝑗  ∈  ( ( 1 ... 𝑁 )  ∖  { 𝑁 } )  ↦  ( 𝑖 𝑀 𝑗 ) ) ) | 
						
							| 34 |  | eqid | ⊢ ( Base ‘ ( ( 1 ... ( 𝑁  −  1 ) )  Mat  𝑅 ) )  =  ( Base ‘ ( ( 1 ... ( 𝑁  −  1 ) )  Mat  𝑅 ) ) | 
						
							| 35 | 1 2 34 8 12 11 11 30 | smatcl | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 )  ∈  ( Base ‘ ( ( 1 ... ( 𝑁  −  1 ) )  Mat  𝑅 ) ) ) | 
						
							| 36 |  | eqid | ⊢ ( ( 1 ... ( 𝑁  −  1 ) )  Mat  𝑅 )  =  ( ( 1 ... ( 𝑁  −  1 ) )  Mat  𝑅 ) | 
						
							| 37 | 36 34 | matmpo | ⊢ ( ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 )  ∈  ( Base ‘ ( ( 1 ... ( 𝑁  −  1 ) )  Mat  𝑅 ) )  →  ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 )  =  ( 𝑖  ∈  ( 1 ... ( 𝑁  −  1 ) ) ,  𝑗  ∈  ( 1 ... ( 𝑁  −  1 ) )  ↦  ( 𝑖 ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 ) 𝑗 ) ) ) | 
						
							| 38 | 35 37 | syl | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 )  =  ( 𝑖  ∈  ( 1 ... ( 𝑁  −  1 ) ) ,  𝑗  ∈  ( 1 ... ( 𝑁  −  1 ) )  ↦  ( 𝑖 ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 ) 𝑗 ) ) ) | 
						
							| 39 | 29 33 38 | 3eqtr4rd | ⊢ ( ( 𝑁  ∈  ℕ  ∧  𝑀  ∈  𝐵 )  →  ( 𝑁 ( subMat1 ‘ 𝑀 ) 𝑁 )  =  ( 𝑁 ( ( ( 1 ... 𝑁 )  subMat  𝑅 ) ‘ 𝑀 ) 𝑁 ) ) |