
theorem Th53:
Sum digits(190,10) = 10
proof
  thus Sum digits(190,10) = Sum <%0,9%>+Sum <%1%> by Th52,AFINSQ_2:55
  .= (0 + 9) + Sum <%1%> by AFINSQ_2:54
  .= 9 + 1 by AFINSQ_2:53
  .= 10;
end;
