let l, n, k be Nat; :: thesis: for K being Field
for a being Element of K
for A being Matrix of n,K st l in dom (1. K,n) & k in dom (1. K,n) holds
(RLineXS (1. K,n),l,k,a) * A = RLineXS A,l,k,a

let K be Field; :: thesis: for a being Element of K
for A being Matrix of n,K st l in dom (1. K,n) & k in dom (1. K,n) holds
(RLineXS (1. K,n),l,k,a) * A = RLineXS A,l,k,a

let a be Element of K; :: thesis: for A being Matrix of n,K st l in dom (1. K,n) & k in dom (1. K,n) holds
(RLineXS (1. K,n),l,k,a) * A = RLineXS A,l,k,a

let A be Matrix of n,K; :: thesis: ( l in dom (1. K,n) & k in dom (1. K,n) implies (RLineXS (1. K,n),l,k,a) * A = RLineXS A,l,k,a )
assume that
A1: l in dom (1. K,n) and
A2: k in dom (1. K,n) ; :: thesis: (RLineXS (1. K,n),l,k,a) * A = RLineXS A,l,k,a
set B = RLineXS (1. K,n),l,k,a;
A3: len (RLineXS (1. K,n),l,k,a) = n by MATRIX_1:25;
A4: len A = n by MATRIX_1:25;
dom (1. K,n) = Seg (len (1. K,n)) by FINSEQ_1:def 3
.= Seg (len A) by A4, MATRIX_1:25
.= dom A by FINSEQ_1:def 3 ;
then A5: len (RLineXS A,l,k,a) = len A by A2, Def3;
A6: ( len ((RLineXS (1. K,n),l,k,a) * A) = n & width ((RLineXS (1. K,n),l,k,a) * A) = n ) by MATRIX_1:25;
A7: width A = n by MATRIX_1:25;
A8: len (RLineXS (1. K,n),l,k,a) = len (1. K,n) by A2, Def3;
then A9: l in Seg n by A1, A3, FINSEQ_1:def 3;
A10: width (RLineXS (1. K,n),l,k,a) = n by MATRIX_1:25;
A11: width (RLineXS (1. K,n),l,k,a) = width (1. K,n) by Th1;
then A12: l in Seg (width (1. K,n)) by A1, A8, A3, A10, FINSEQ_1:def 3;
then A13: [l,l] in Indices (1. K,n) by A1, ZFMISC_1:106;
A14: Indices ((RLineXS (1. K,n),l,k,a) * A) = [:(Seg n),(Seg n):] by MATRIX_1:25;
A15: k in Seg (width (1. K,n)) by A2, A8, A11, A3, A10, FINSEQ_1:def 3;
then A16: [k,k] in Indices (1. K,n) by A2, ZFMISC_1:106;
A17: for i, j being Nat st j in Seg n & i in dom (1. K,n) & i = l holds
((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j
proof
let i, j be Nat; :: thesis: ( j in Seg n & i in dom (1. K,n) & i = l implies ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j )
assume that
A18: j in Seg n and
i in dom (1. K,n) ; :: thesis: ( not i = l or ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j )
thus ( i = l implies ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j ) :: thesis: verum
proof
A19: ( (Line (1. K,n),l) . l = 1_ K & ( for t being Nat st t in dom (Line (1. K,n),l) & t <> l holds
(Line (1. K,n),l) . t = 0. K ) )
proof
thus (Line (1. K,n),l) . l = 1_ K by A13, MATRIX_3:17; :: thesis: for t being Nat st t in dom (Line (1. K,n),l) & t <> l holds
(Line (1. K,n),l) . t = 0. K

let t be Nat; :: thesis: ( t in dom (Line (1. K,n),l) & t <> l implies (Line (1. K,n),l) . t = 0. K )
assume that
A20: t in dom (Line (1. K,n),l) and
A21: t <> l ; :: thesis: (Line (1. K,n),l) . t = 0. K
t in Seg (len (Line (1. K,n),l)) by A20, FINSEQ_1:def 3;
then t in Seg (width (1. K,n)) by MATRIX_1:def 8;
then [l,t] in Indices (1. K,n) by A1, ZFMISC_1:106;
hence (Line (1. K,n),l) . t = 0. K by A21, MATRIX_3:17; :: thesis: verum
end;
reconsider q = Col A,j as Element of (width A) -tuples_on the carrier of K by A4, MATRIX_1:25;
A22: len (Col A,j) = len A by MATRIX_1:def 9;
k in Seg n by A2, A8, A3, FINSEQ_1:def 3;
then A23: k in dom (Col A,j) by A4, A22, FINSEQ_1:def 3;
len (Line (1. K,n),k) = width (1. K,n) by MATRIX_1:def 8;
then A24: k in dom (Line (1. K,n),k) by A15, FINSEQ_1:def 3;
l in Seg n by A1, A8, A3, FINSEQ_1:def 3;
then A25: l in dom (Col A,j) by A4, A22, FINSEQ_1:def 3;
len (Line (1. K,n),l) = width (1. K,n) by MATRIX_1:def 8;
then A26: l in dom (Line (1. K,n),l) by A12, FINSEQ_1:def 3;
reconsider p2 = Line (1. K,n),l as Element of (width A) -tuples_on the carrier of K by Th1;
A27: len q = width A by FINSEQ_1:def 18;
reconsider p1 = Line (1. K,n),k as Element of (width A) -tuples_on the carrier of K by Th1;
A28: ( len (a * p1) = width A & len p2 = width A ) by FINSEQ_1:def 18;
A29: ( (Line (1. K,n),k) . k = 1_ K & ( for t being Nat st t in dom (Line (1. K,n),k) & t <> k holds
(Line (1. K,n),k) . t = 0. K ) )
proof
thus (Line (1. K,n),k) . k = 1_ K by A16, MATRIX_3:17; :: thesis: for t being Nat st t in dom (Line (1. K,n),k) & t <> k holds
(Line (1. K,n),k) . t = 0. K

let t be Nat; :: thesis: ( t in dom (Line (1. K,n),k) & t <> k implies (Line (1. K,n),k) . t = 0. K )
assume that
A30: t in dom (Line (1. K,n),k) and
A31: t <> k ; :: thesis: (Line (1. K,n),k) . t = 0. K
t in Seg (len (Line (1. K,n),k)) by A30, FINSEQ_1:def 3;
then t in Seg (width (1. K,n)) by MATRIX_1:def 8;
then [k,t] in Indices (1. K,n) by A2, ZFMISC_1:106;
hence (Line (1. K,n),k) . t = 0. K by A31, MATRIX_3:17; :: thesis: verum
end;
A32: dom (1. K,n) = Seg (len (1. K,n)) by FINSEQ_1:def 3
.= Seg (len A) by A4, MATRIX_1:25
.= dom A by FINSEQ_1:def 3 ;
then (Col A,j) . k = A * k,j by A2, MATRIX_1:def 9;
then consider a1 being Element of K such that
A33: a1 = (Col A,j) . k ;
A34: (Col A,j) . l = A * l,j by A1, A32, MATRIX_1:def 9;
then consider a2 being Element of K such that
A35: a2 = (Col A,j) . l ;
assume A36: i = l ; :: thesis: ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j
then [i,j] in Indices ((RLineXS (1. K,n),l,k,a) * A) by A9, A14, A18, ZFMISC_1:106;
then ((RLineXS (1. K,n),l,k,a) * A) * i,j = (Line (RLineXS (1. K,n),l,k,a),i) "*" (Col A,j) by A10, A4, MATRIX_3:def 4
.= Sum (mlt ((a * p1) + p2),q) by A1, A2, A36, Th5
.= Sum ((mlt (a * p1),q) + (mlt p2,q)) by A28, A27, MATRIX_4:56
.= Sum ((a * (mlt p1,q)) + (mlt p2,q)) by FVSUM_1:83
.= (Sum (a * (mlt p1,q))) + (Sum (mlt p2,q)) by FVSUM_1:95
.= (a * (Sum (mlt (Line (1. K,n),k),(Col A,j)))) + (Sum (mlt (Line (1. K,n),l),(Col A,j))) by FVSUM_1:92
.= (a * a1) + (Sum (mlt (Line (1. K,n),l),(Col A,j))) by A24, A23, A29, A33, MATRIX_3:19
.= (a * a1) + a2 by A26, A25, A19, A35, MATRIX_3:19
.= (a * (A * k,j)) + (A * l,j) by A2, A32, A33, A34, A35, MATRIX_1:def 9
.= (RLineXS A,l,k,a) * i,j by A1, A2, A7, A18, A36, A32, Def3 ;
hence ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j ; :: thesis: verum
end;
end;
A37: for i, j being Nat st j in Seg n & i in dom (1. K,n) & i <> l holds
((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j
proof
let i, j be Nat; :: thesis: ( j in Seg n & i in dom (1. K,n) & i <> l implies ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j )
assume that
A38: j in Seg n and
A39: i in dom (1. K,n) ; :: thesis: ( not i <> l or ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j )
A40: i in Seg n by A8, A3, A39, FINSEQ_1:def 3;
then A41: [i,i] in Indices (1. K,n) by A11, A10, A39, ZFMISC_1:106;
thus ( i <> l implies ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j ) :: thesis: verum
proof
A42: ( (Line (1. K,n),i) . i = 1_ K & ( for t being Nat st t in dom (Line (1. K,n),i) & t <> i holds
(Line (1. K,n),i) . t = 0. K ) )
proof
thus (Line (1. K,n),i) . i = 1_ K by A41, MATRIX_3:17; :: thesis: for t being Nat st t in dom (Line (1. K,n),i) & t <> i holds
(Line (1. K,n),i) . t = 0. K

let t be Nat; :: thesis: ( t in dom (Line (1. K,n),i) & t <> i implies (Line (1. K,n),i) . t = 0. K )
assume that
A43: t in dom (Line (1. K,n),i) and
A44: t <> i ; :: thesis: (Line (1. K,n),i) . t = 0. K
t in Seg (len (Line (1. K,n),i)) by A43, FINSEQ_1:def 3;
then t in Seg (width (1. K,n)) by MATRIX_1:def 8;
then [i,t] in Indices (1. K,n) by A39, ZFMISC_1:106;
hence (Line (1. K,n),i) . t = 0. K by A44, MATRIX_3:17; :: thesis: verum
end;
len (Col A,j) = len A by MATRIX_1:def 9;
then A45: i in dom (Col A,j) by A4, A40, FINSEQ_1:def 3;
A46: dom (1. K,n) = Seg (len (1. K,n)) by FINSEQ_1:def 3
.= Seg (len A) by A4, MATRIX_1:25
.= dom A by FINSEQ_1:def 3 ;
len (Line (1. K,n),i) = width (1. K,n) by MATRIX_1:def 8;
then A47: i in dom (Line (1. K,n),i) by A11, A10, A40, FINSEQ_1:def 3;
assume A48: i <> l ; :: thesis: ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j
[i,j] in Indices ((RLineXS (1. K,n),l,k,a) * A) by A14, A38, A40, ZFMISC_1:106;
then ((RLineXS (1. K,n),l,k,a) * A) * i,j = (Line (RLineXS (1. K,n),l,k,a),i) "*" (Col A,j) by A10, A4, MATRIX_3:def 4
.= Sum (mlt (Line (1. K,n),i),(Col A,j)) by A1, A2, A39, A48, Th5
.= (Col A,j) . i by A47, A45, A42, MATRIX_3:19
.= A * i,j by A39, A46, MATRIX_1:def 9
.= (RLineXS A,l,k,a) * i,j by A2, A7, A38, A39, A48, A46, Def3 ;
hence ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j ; :: thesis: verum
end;
end;
A49: for i, j being Nat st [i,j] in Indices ((RLineXS (1. K,n),l,k,a) * A) holds
((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j
proof
let i, j be Nat; :: thesis: ( [i,j] in Indices ((RLineXS (1. K,n),l,k,a) * A) implies ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j )
assume [i,j] in Indices ((RLineXS (1. K,n),l,k,a) * A) ; :: thesis: ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j
then A50: ( i in Seg n & j in Seg n ) by A14, ZFMISC_1:106;
dom (1. K,n) = Seg (len (1. K,n)) by FINSEQ_1:def 3
.= Seg n by MATRIX_1:25 ;
hence ((RLineXS (1. K,n),l,k,a) * A) * i,j = (RLineXS A,l,k,a) * i,j by A17, A37, A50; :: thesis: verum
end;
width (RLineXS A,l,k,a) = width A by Th1;
hence (RLineXS (1. K,n),l,k,a) * A = RLineXS A,l,k,a by A4, A7, A6, A5, A49, MATRIX_1:21; :: thesis: verum