| Step | Hyp | Ref | Expression | 
						
							| 1 |  | submat1n.a |  |-  A = ( ( 1 ... N ) Mat R ) | 
						
							| 2 |  | submat1n.b |  |-  B = ( Base ` A ) | 
						
							| 3 |  | fzdif2 |  |-  ( N e. ( ZZ>= ` 1 ) -> ( ( 1 ... N ) \ { N } ) = ( 1 ... ( N - 1 ) ) ) | 
						
							| 4 |  | nnuz |  |-  NN = ( ZZ>= ` 1 ) | 
						
							| 5 | 3 4 | eleq2s |  |-  ( N e. NN -> ( ( 1 ... N ) \ { N } ) = ( 1 ... ( N - 1 ) ) ) | 
						
							| 6 | 5 | adantr |  |-  ( ( N e. NN /\ M e. B ) -> ( ( 1 ... N ) \ { N } ) = ( 1 ... ( N - 1 ) ) ) | 
						
							| 7 | 6 | adantr |  |-  ( ( ( N e. NN /\ M e. B ) /\ i e. ( ( 1 ... N ) \ { N } ) ) -> ( ( 1 ... N ) \ { N } ) = ( 1 ... ( N - 1 ) ) ) | 
						
							| 8 |  | eqid |  |-  ( N ( subMat1 ` M ) N ) = ( N ( subMat1 ` M ) N ) | 
						
							| 9 |  | elfz1end |  |-  ( N e. NN <-> N e. ( 1 ... N ) ) | 
						
							| 10 | 9 | biimpi |  |-  ( N e. NN -> N e. ( 1 ... N ) ) | 
						
							| 11 | 10 | adantr |  |-  ( ( N e. NN /\ M e. B ) -> N e. ( 1 ... N ) ) | 
						
							| 12 | 11 9 | sylibr |  |-  ( ( N e. NN /\ M e. B ) -> N e. NN ) | 
						
							| 13 | 12 | adantr |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> N e. NN ) | 
						
							| 14 | 13 10 | syl |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> N e. ( 1 ... N ) ) | 
						
							| 15 |  | eqid |  |-  ( Base ` R ) = ( Base ` R ) | 
						
							| 16 | 1 15 2 | matbas2i |  |-  ( M e. B -> M e. ( ( Base ` R ) ^m ( ( 1 ... N ) X. ( 1 ... N ) ) ) ) | 
						
							| 17 | 16 | ad2antlr |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> M e. ( ( Base ` R ) ^m ( ( 1 ... N ) X. ( 1 ... N ) ) ) ) | 
						
							| 18 |  | simprl |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> i e. ( ( 1 ... N ) \ { N } ) ) | 
						
							| 19 |  | nnz |  |-  ( N e. NN -> N e. ZZ ) | 
						
							| 20 |  | fzoval |  |-  ( N e. ZZ -> ( 1 ..^ N ) = ( 1 ... ( N - 1 ) ) ) | 
						
							| 21 | 19 20 | syl |  |-  ( N e. NN -> ( 1 ..^ N ) = ( 1 ... ( N - 1 ) ) ) | 
						
							| 22 | 21 5 | eqtr4d |  |-  ( N e. NN -> ( 1 ..^ N ) = ( ( 1 ... N ) \ { N } ) ) | 
						
							| 23 | 13 22 | syl |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> ( 1 ..^ N ) = ( ( 1 ... N ) \ { N } ) ) | 
						
							| 24 | 18 23 | eleqtrrd |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> i e. ( 1 ..^ N ) ) | 
						
							| 25 |  | simprr |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> j e. ( ( 1 ... N ) \ { N } ) ) | 
						
							| 26 | 25 23 | eleqtrrd |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> j e. ( 1 ..^ N ) ) | 
						
							| 27 | 8 13 13 14 14 17 24 26 | smattl |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> ( i ( N ( subMat1 ` M ) N ) j ) = ( i M j ) ) | 
						
							| 28 | 27 | eqcomd |  |-  ( ( ( N e. NN /\ M e. B ) /\ ( i e. ( ( 1 ... N ) \ { N } ) /\ j e. ( ( 1 ... N ) \ { N } ) ) ) -> ( i M j ) = ( i ( N ( subMat1 ` M ) N ) j ) ) | 
						
							| 29 | 6 7 28 | mpoeq123dva |  |-  ( ( N e. NN /\ M e. B ) -> ( i e. ( ( 1 ... N ) \ { N } ) , j e. ( ( 1 ... N ) \ { N } ) |-> ( i M j ) ) = ( i e. ( 1 ... ( N - 1 ) ) , j e. ( 1 ... ( N - 1 ) ) |-> ( i ( N ( subMat1 ` M ) N ) j ) ) ) | 
						
							| 30 |  | simpr |  |-  ( ( N e. NN /\ M e. B ) -> M e. B ) | 
						
							| 31 |  | eqid |  |-  ( ( 1 ... N ) subMat R ) = ( ( 1 ... N ) subMat R ) | 
						
							| 32 | 1 31 2 | submaval |  |-  ( ( M e. B /\ N e. ( 1 ... N ) /\ N e. ( 1 ... N ) ) -> ( N ( ( ( 1 ... N ) subMat R ) ` M ) N ) = ( i e. ( ( 1 ... N ) \ { N } ) , j e. ( ( 1 ... N ) \ { N } ) |-> ( i M j ) ) ) | 
						
							| 33 | 30 11 11 32 | syl3anc |  |-  ( ( N e. NN /\ M e. B ) -> ( N ( ( ( 1 ... N ) subMat R ) ` M ) N ) = ( i e. ( ( 1 ... N ) \ { N } ) , j e. ( ( 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 e. NN /\ M e. B ) -> ( N ( subMat1 ` M ) N ) e. ( 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 ) e. ( Base ` ( ( 1 ... ( N - 1 ) ) Mat R ) ) -> ( N ( subMat1 ` M ) N ) = ( i e. ( 1 ... ( N - 1 ) ) , j e. ( 1 ... ( N - 1 ) ) |-> ( i ( N ( subMat1 ` M ) N ) j ) ) ) | 
						
							| 38 | 35 37 | syl |  |-  ( ( N e. NN /\ M e. B ) -> ( N ( subMat1 ` M ) N ) = ( i e. ( 1 ... ( N - 1 ) ) , j e. ( 1 ... ( N - 1 ) ) |-> ( i ( N ( subMat1 ` M ) N ) j ) ) ) | 
						
							| 39 | 29 33 38 | 3eqtr4rd |  |-  ( ( N e. NN /\ M e. B ) -> ( N ( subMat1 ` M ) N ) = ( N ( ( ( 1 ... N ) subMat R ) ` M ) N ) ) |