let k, x, n be Nat; ( n >= 1 implies DigA ((DecSD ((x mod ((Radix k) |^ n)),n,k)),n) = DigA ((DecSD (x,n,k)),n) )
set xn = x mod ((Radix k) |^ n);
assume
n >= 1
; DigA ((DecSD ((x mod ((Radix k) |^ n)),n,k)),n) = DigA ((DecSD (x,n,k)),n)
then
n <> 0
;
then A1:
n in Seg n
by FINSEQ_1:3;
then DigA ((DecSD ((x mod ((Radix k) |^ n)),n,k)),n) =
DigitDC ((x mod ((Radix k) |^ n)),n,k)
by RADIX_1:def 9
.=
DigitDC (x,n,k)
by NAT_D:73
.=
DigA ((DecSD (x,n,k)),n)
by A1, RADIX_1:def 9
;
hence
DigA ((DecSD ((x mod ((Radix k) |^ n)),n,k)),n) = DigA ((DecSD (x,n,k)),n)
; verum