| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							marep01ma.a | 
							 |-  A = ( N Mat R )  | 
						
						
							| 2 | 
							
								
							 | 
							marep01ma.b | 
							 |-  B = ( Base ` A )  | 
						
						
							| 3 | 
							
								
							 | 
							marep01ma.r | 
							 |-  R e. CRing  | 
						
						
							| 4 | 
							
								
							 | 
							marep01ma.0 | 
							 |-  .0. = ( 0g ` R )  | 
						
						
							| 5 | 
							
								
							 | 
							marep01ma.1 | 
							 |-  .1. = ( 1r ` R )  | 
						
						
							| 6 | 
							
								
							 | 
							eqid | 
							 |-  ( Base ` R ) = ( Base ` R )  | 
						
						
							| 7 | 
							
								1 2
							 | 
							matrcl | 
							 |-  ( M e. B -> ( N e. Fin /\ R e. _V ) )  | 
						
						
							| 8 | 
							
								7
							 | 
							simpld | 
							 |-  ( M e. B -> N e. Fin )  | 
						
						
							| 9 | 
							
								3
							 | 
							a1i | 
							 |-  ( M e. B -> R e. CRing )  | 
						
						
							| 10 | 
							
								
							 | 
							crngring | 
							 |-  ( R e. CRing -> R e. Ring )  | 
						
						
							| 11 | 
							
								6 5
							 | 
							ringidcl | 
							 |-  ( R e. Ring -> .1. e. ( Base ` R ) )  | 
						
						
							| 12 | 
							
								3 10 11
							 | 
							mp2b | 
							 |-  .1. e. ( Base ` R )  | 
						
						
							| 13 | 
							
								6 4
							 | 
							ring0cl | 
							 |-  ( R e. Ring -> .0. e. ( Base ` R ) )  | 
						
						
							| 14 | 
							
								3 10 13
							 | 
							mp2b | 
							 |-  .0. e. ( Base ` R )  | 
						
						
							| 15 | 
							
								12 14
							 | 
							ifcli | 
							 |-  if ( l = I , .1. , .0. ) e. ( Base ` R )  | 
						
						
							| 16 | 
							
								15
							 | 
							a1i | 
							 |-  ( ( M e. B /\ k e. N /\ l e. N ) -> if ( l = I , .1. , .0. ) e. ( Base ` R ) )  | 
						
						
							| 17 | 
							
								
							 | 
							simp2 | 
							 |-  ( ( M e. B /\ k e. N /\ l e. N ) -> k e. N )  | 
						
						
							| 18 | 
							
								
							 | 
							simp3 | 
							 |-  ( ( M e. B /\ k e. N /\ l e. N ) -> l e. N )  | 
						
						
							| 19 | 
							
								
							 | 
							id | 
							 |-  ( M e. B -> M e. B )  | 
						
						
							| 20 | 
							
								19 2
							 | 
							eleqtrdi | 
							 |-  ( M e. B -> M e. ( Base ` A ) )  | 
						
						
							| 21 | 
							
								20
							 | 
							3ad2ant1 | 
							 |-  ( ( M e. B /\ k e. N /\ l e. N ) -> M e. ( Base ` A ) )  | 
						
						
							| 22 | 
							
								1 6
							 | 
							matecl | 
							 |-  ( ( k e. N /\ l e. N /\ M e. ( Base ` A ) ) -> ( k M l ) e. ( Base ` R ) )  | 
						
						
							| 23 | 
							
								17 18 21 22
							 | 
							syl3anc | 
							 |-  ( ( M e. B /\ k e. N /\ l e. N ) -> ( k M l ) e. ( Base ` R ) )  | 
						
						
							| 24 | 
							
								16 23
							 | 
							ifcld | 
							 |-  ( ( M e. B /\ k e. N /\ l e. N ) -> if ( k = H , if ( l = I , .1. , .0. ) , ( k M l ) ) e. ( Base ` R ) )  | 
						
						
							| 25 | 
							
								1 6 2 8 9 24
							 | 
							matbas2d | 
							 |-  ( M e. B -> ( k e. N , l e. N |-> if ( k = H , if ( l = I , .1. , .0. ) , ( k M l ) ) ) e. B )  |