let K be Field; :: thesis: for a, b, c, d, e, f, g, h, i being Element of K
for M being Matrix of 3,K st M = <*<*a,b,c*>,<*d,e,f*>,<*g,h,i*>*> holds
Per M = ((((((a * e) * i) + ((c * e) * g)) + ((a * f) * h)) + ((b * f) * g)) + ((b * d) * i)) + ((c * d) * h)

reconsider rid3 = Rev () as Element of Permutations 3 by Th4;
let a, b, c, d, e, f, g, h, i be Element of K; :: thesis: for M being Matrix of 3,K st M = <*<*a,b,c*>,<*d,e,f*>,<*g,h,i*>*> holds
Per M = ((((((a * e) * i) + ((c * e) * g)) + ((a * f) * h)) + ((b * f) * g)) + ((b * d) * i)) + ((c * d) * h)

let M be Matrix of 3,K; :: thesis: ( M = <*<*a,b,c*>,<*d,e,f*>,<*g,h,i*>*> implies Per M = ((((((a * e) * i) + ((c * e) * g)) + ((a * f) * h)) + ((b * f) * g)) + ((b * d) * i)) + ((c * d) * h) )
assume A1: M = <*<*a,b,c*>,<*d,e,f*>,<*g,h,i*>*> ; :: thesis: Per M = ((((((a * e) * i) + ((c * e) * g)) + ((a * f) * h)) + ((b * f) * g)) + ((b * d) * i)) + ((c * d) * h)
reconsider a3 = <*1,3,2*>, a4 = <*2,3,1*>, a5 = <*2,1,3*>, a6 = <*3,1,2*> as Element of Permutations 3 by Th27;
reconsider id3 = idseq 3 as Permutation of (Seg 3) ;
reconsider Id3 = idseq 3 as Element of Permutations 3 by MATRIX_1:def 12;
reconsider B1 = {.Id3,rid3,a3.}, B2 = {.a4,a5,a6.} as Element of Fin () ;
set r = PPath_product M;
A2: () . id3 = the multF of K \$\$ (Path_matrix (Id3,M)) by Def1
.= the multF of K \$\$ <*a,e,i*> by
.= (a * e) * i by Th26 ;
A3: () . a6 = the multF of K \$\$ (Path_matrix (a6,M)) by Def1
.= the multF of K \$\$ <*c,d,h*> by
.= (c * d) * h by Th26 ;
A4: () . a5 = the multF of K \$\$ (Path_matrix (a5,M)) by Def1
.= the multF of K \$\$ <*b,d,i*> by
.= (b * d) * i by Th26 ;
A5: () . a4 = the multF of K \$\$ (Path_matrix (a4,M)) by Def1
.= the multF of K \$\$ <*b,f,g*> by
.= (b * f) * g by Th26 ;
now :: thesis: for x being object st x in B1 holds
x in B1 \ B2
let x be object ; :: thesis: ( x in B1 implies x in B1 \ B2 )
assume A6: x in B1 ; :: thesis: x in B1 \ B2
then ( x = Id3 or x = rid3 or x = a3 ) by ENUMSET1:def 1;
then not x in B2 by ;
hence x in B1 \ B2 by ; :: thesis: verum
end;
then A7: B1 c= B1 \ B2 by TARSKI:def 3;
for x being object st x in B1 \ B2 holds
x in B1 by XBOOLE_0:def 5;
then B1 \ B2 c= B1 by TARSKI:def 3;
then B1 \ B2 = B1 by ;
then A8: B1 misses B2 by XBOOLE_1:83;
set F = the addF of K;
id3 in Permutations 3 by MATRIX_1:def 12;
then reconsider r1 = () . id3, r2 = () . rid3, r3 = () . a3, r4 = () . a4, r5 = () . a5, r6 = () . a6 as Element of K by FUNCT_2:5;
Permutations 3 in Fin () by FINSUB_1:def 5;
then In ((),(Fin ())) = Permutations 3 by SUBSET_1:def 8;
then reconsider X = {Id3,rid3,a3,a4,a5,a6} as Element of Fin () by ;
A9: ( the addF of K \$\$ (B1,()) = (r1 + r2) + r3 & the addF of K \$\$ (B2,()) = (r4 + r5) + r6 ) by ;
A10: () . rid3 = the multF of K \$\$ (Path_matrix (rid3,M)) by Def1
.= the multF of K \$\$ <*c,e,g*> by
.= (c * e) * g by Th26 ;
A11: () . a3 = the multF of K \$\$ (Path_matrix (a3,M)) by Def1
.= the multF of K \$\$ <*a,f,h*> by
.= (a * f) * h by Th26 ;
( In ((),(Fin ())) = X & X = {Id3,rid3,a3} \/ {a4,a5,a6} ) by ;
then Per M = the addF of K . (( the addF of K \$\$ (B1,())),( the addF of K \$\$ (B2,()))) by
.= ((r1 + r2) + r3) + (r4 + (r5 + r6)) by
.= (((r1 + r2) + r3) + r4) + (r5 + r6) by RLVECT_1:def 3
.= ((((((a * e) * i) + ((c * e) * g)) + ((a * f) * h)) + ((b * f) * g)) + ((b * d) * i)) + ((c * d) * h) by ;
hence Per M = ((((((a * e) * i) + ((c * e) * g)) + ((a * f) * h)) + ((b * f) * g)) + ((b * d) * i)) + ((c * d) * h) ; :: thesis: verum