
theorem Th47:
Sum digits(160,10) = 7
proof
  thus Sum digits(160,10) = Sum <%0,6%>+Sum <%1%> by Th46,AFINSQ_2:55
  .= (0 + 6) + Sum <%1%> by AFINSQ_2:54
  .= 6 + 1 by AFINSQ_2:53
  .= 7;
end;
