theorem Th25: :: MATRIX13:25

for D being non empty set
for i, j, m, n being Nat
for A being Matrix of D
for nt being Element of n -tuples_on NAT
for mt being Element of m -tuples_on NAT st i in Seg n & j in Seg n & nt . i = nt . j holds
Line ((Segm (A,nt,mt)),i) = Line ((Segm (A,nt,mt)),j)