let D be non empty set ; for f being FinSequence of D
for k2 being Element of NAT st len f <= k2 holds
smid f,1,k2 = f
let f be FinSequence of D; for k2 being Element of NAT st len f <= k2 holds
smid f,1,k2 = f
let k2 be Element of NAT ; ( len f <= k2 implies smid f,1,k2 = f )
assume A1:
len f <= k2
; smid f,1,k2 = f
thus smid f,1,k2 =
f | k2
by Th5
.=
f
by A1, FINSEQ_1:79
; verum