
theorem Th1128:
Sum digits(1125,10) = 9
proof
  thus Sum digits(1125,10) = Sum <%5,2,1%>+Sum <%1%> by Th1127,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%1%> + Sum <%1%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%1%> + Sum <%1%> by AFINSQ_2:54
  .= (5 + 2 + 1) + Sum <%1%> by AFINSQ_2:53
  .= 8 + 1 by AFINSQ_2:53
  .= 9;
end;
