for D being non empty set
for m, n, m9, n9 being Nat
for A9 being Matrix of n9,m9,D
for mt being Element of m -tuples_on NAT
for F being FinSequence of D
for i being Nat
for nt being Element of n -tuples_on NAT st not i in rng nt & [:(rng nt),(rng mt):] c= Indices A9 holds
Segm (A9,nt,mt) = Segm ((RLine (A9,i,F)),nt,mt)