set d = <%3,6%>;
set e = <%(3 * (10 |^ 0)),(6 * (10 |^ 1))%>;
A1: Sum <%(3 * (10 |^ 0)),(6 * (10 |^ 1))%> = (3 * (10 |^ 0)) + (6 * (10 |^ 1)) by AFINSQ_2:54
.= (3 * 1) + (6 * (10 |^ 1)) by NEWTON:4
.= 3 + (6 * 10) by NEWTON:5 ;
A2: dom <%3,6%> = 2 by AFINSQ_1:38
.= dom <%(3 * (10 |^ 0)),(6 * (10 |^ 1))%> by AFINSQ_1:38 ;

now :: thesis: for i being Nat st i in dom <%3,6%> holds
<%(3 * (10 |^ 0)),(6 * (10 |^ 1))%> . i = (<%3,6%> . i) * (10 |^ i)

let i be Nat; :: thesis: ( i in dom <%3,6%> implies <%(3 * (10 |^ 0)),(6 * (10 |^ 1))%> . i = (<%3,6%> . i) * (10 |^ i) )
assume i in dom <%3,6%> ; :: thesis: <%(3 * (10 |^ 0)),(6 * (10 |^ 1))%> . i = (<%3,6%> . i) * (10 |^ i)
then i in 2 by AFINSQ_1:38;
then i in {0,1} by CARD_1:50;
then ( i = 0 or i = 1 ) by TARSKI:def 2;
hence <%(3 * (10 |^ 0)),(6 * (10 |^ 1))%> . i = (<%3,6%> . i) * (10 |^ i) ; :: thesis: verum

end;

then A3: value (<%3,6%>,10) = 63 by A1, A2, NUMERAL1:def 1;
(len <%3,6%>) - 1 = 2 - 1 by AFINSQ_1:38;
then A4: <%3,6%> . ((len <%3,6%>) - 1) <> 0 ;

now :: thesis: for i being Nat st i in dom <%3,6%> holds
( 0 <= <%3,6%> . i & <%3,6%> . i < 10 )

let i be Nat; :: thesis: ( i in dom <%3,6%> implies ( 0 <= <%3,6%> . i & <%3,6%> . i < 10 ) )
assume i in dom <%3,6%> ; :: thesis: ( 0 <= <%3,6%> . i & <%3,6%> . i < 10 )
then i in 2 by AFINSQ_1:38;
then i in {0,1} by CARD_1:50;
then ( i = 0 or i = 1 ) by TARSKI:def 2;
hence ( 0 <= <%3,6%> . i & <%3,6%> . i < 10 ) ; :: thesis: verum

end;

hence digits (63,10) = <%3,6%> by A3, A4, NUMERAL1:def 2; :: thesis: verum